Recent Developments in Membrane Treatment of Spent Cutting-Oils

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RECENT DEVELOPMENTS IN MEMBRANE TREATMENT OF SPENT CUTTING-OILS: A REVIEW Janja Križan, Arnela Muri#, Irena Petrinic, and Marjana Simonic Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie4003552 • Publication Date (Web): 25 Apr 2013 Downloaded from http://pubs.acs.org on May 5, 2013

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Industrial & Engineering Chemistry Research

RECENT DEVELOPMENTS IN MEMBRANE TREATMENT OF SPENT CUTTING-OILS: A REVIEW Janja Križan, Arnela Murić, Irena Petrinić, Marjana Simonič University of Maribor, Faculty of Chemistry and Chemical Engineering, Smetanova 17, SI-2000 Maribor KEYWORDS. Oily wastewater, conventional treatment, membrane filtration, fouling, cleaning.

ABSTRACT. Throughout the metal-working industry cutting-oil emulsions are used as lubricants and coolants. However, they have to be discarded after a certain time due to losing their functional properties. Hence, they need to be treated in order to separate any oil before disposal. Conventional methods have their advantages, but none are effective enough. Therefore, membrane technology appears to be a promising alternative. The aim of this work was to study the membrane treatment of spent metal-working fluids. The main drawback of membranes is flux-decline due to fouling and concentration-polarization. The complexes of cutting-oils, containing membrane filtration systems demand complementary studies on issues relating to fouling control and its reduction, and membrane cleaning after fouling. Important conclusions were therefore formed about achievements in the field of fouling control and membrane cleaning.

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INTRODUCTION During metal-working processes cutting fluids or metal-working fluids (MWFs) are used where cooling, lubrication, and rust control are important at the tool-work pieces' interfaces during operations such as cutting, grinding or rolling. MWFs help to improve the lifecycle and function of the tool and may account for up to 15% of the machining process cost.1 After being used, the fluids become less effective because of thermal degradation and contamination by substances during suspension and, therefore, need to be replaced periodically. One of these contaminants is a generated waste-stream called spent cutting-oil. Spent cutting-oil emulsions are one of the larger volumes regarding oily wastewater within metal-working industries (Table 1). Table 1. Sources of oily effluents in metal-working industries.2 Metal-working process

Oil concentration (mg/L)

Metal processing and finishing

100-20000

Aluminium rolling

5000-50000

Copper Wire-drawing

1000-10000

Steel-rolling mill

7200

These fluids may be classified into three broad categories (Figure 1)1: OIL-IN-WATER (O/W) EMULSIONS Oil-in-water emulsions are commonly known as ‘water soluble oils’, even though they are not completely soluble in water. They are obtained by mixing a mineral oil with an aqueous phase containing an emulsifier (surfactant). They also contain additives for improving their lubricating properties. SYNTHETIC FLUIDS


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Sometimes referred to as chemical fluids which contain no mineral oil, these comprise mixtures of several water soluble compounds, such as emulsifiers, anti-corrosion agents or defoamers. They form a clear or translucent solution in water and often provide the best cooling performance amongst all MWFs. SEMISYNTHETIC FLUIDS These are a combination of O/W emulsions and synthetic fluids, and have properties common to both types.

Figure 1. Classification of MWFs and their compositions before being dispersed in water (adapted from Coca et al.1). MWFs are a complex mixture of chemicals but their identities and proportions depend on a number of factors, mostly manufacturers’ and users’ requirements. Base-oils are more commonly mineral oils, which are typically hydrogenated petroleum distillates. The majority of additives are organic by nature and they differ in terms of hydrophobicity and polarity, as well in their usages (emulsifiers, lubricants, corrosion inhibitors etc.). Water-based MWFs are now widely used throughout the industry, resulting in an increasing requirement for the disposal of large


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quantities of oily wastewater. Typical limits for oil and grease discharges range from10–15 mg/L for mineral and synthetic oils and 100–150 mg/L for those of animal and vegetable origin.1 The disposal of this waste effluent through a sewer is not a cost-effective solution, and furthermore it is not suitable because of the high associated biocide content and heavy chemical oxygendemand (COD) causing environmental pollution. A solution for the disposal of this sort of waste is to contract the task to a commercial waste-disposal company; the charge for disposal being linked to the volume of waste to be removed. Bearing this in mind, onsite treatment is generally a more cost effective way of solving the disposal problem; as is also recognized as good environmental practice.3 Indeed, manufacturing industries are under increasing pressure from regulators to take more responsibility for their own waste; this pressure, coupled with an increase in the cost of waste disposal, has made the development of on-site processes for the disposal of waste-fluids an increasingly important issue.4,5 Due to the complex compositions of spent cutting-oil emulsions, conventional chemical destabilization methods (gravity, flotation, skimming, coagulation and flocculation) are ineffective for the treatment of oily wastewaters, and thus alternative methods need to be applied.6 Therefore, membrane technology appears to be a promising method for providing several possibilities regarding different materials, modules, process parameters etc. This literature review aims at presenting the principles of treatment systems regarding spent MWFs, and also for reporting on any research that has been carried-out on the application of membrane technology within the area of spent cutting-oils, with special emphasis on fouling control and membrane cleaning. TREATMENT SYSTEMS


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The removal of oily wastewater can probably be accomplished by means of several wellknown and widely-accepted techniques. The performance of any given separation technique mainly depends on the condition of the oily wastewater’s mixture.7 Straight-oils do not normally require any extensive treatment in contrast to emulsifiable (soluble) oils, which are more complex due to separations during both the water and oil-phases. Semisynthetic and synthetic oils have powerful emulsifying chemistries that require polymer methods for chemical separation.7 Conventional approaches to treating oily wastewaters include gravity separations and skimming, dissolved air-flotation (DAF), de-emulsion coagulation and flocculation, coalescence separation, etc. The oil that adheres to the surfaces of solid particles could effectively be removable sedimentation.8 These approaches are effective when removing free oil; however, they are ineffective particularly when the oil-droplets are finely dispersed and the concentration is very low. Reports say that these techniques can reduce oil concentration to barely 1 % by volume of the total wastewater. Systems based on chemical and physical principles cannot provide an absolute guarantee in terms of separation efficiency and effluent quality. Several disadvantages have been reported with these methods, including high capital and operating costs, customization for each individual site, high susceptibility to changes, safety issues, contamination and degradation, mechanical parts’ aging, etc.9 In addition, high consumption of chemicals (sulfuric acid, iron and alumina sulfates, etc.) during coagulation makes these processes costly and sometimes even those chemicals that have not reacted are also found within the final wastewaters. Therefore, any water-phase obtained from such treatment generally requires further purification in order to meet the accepted effluent standard for discharge into ground waters.10 Less commonly used are the biological processes, as these kinds of oily wastewaters contain biocides (such as nitrogen compounds) in order to prevent their


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degradation.11. Table 2 presents the advantages and disadvantages of different oily wastewater treatments. Table 2. Advantages and disadvantages of oily wastewater treatments. Treatment

Advantages

Disadvantages

Gravity separation and Effective for removing free Not effective in removing smaller oil droplets and oil and suspended particles skimming 12 emulsions Low cost Dissolved Air Flotation High oil removal efficiency (DAF) 12,13

High investment operating costs

and

Difficult in terms of operation Sludge problem and chemical needed (combined with chemical coagulant) Corrosion problems due to acidification of the influent Chemical coagulation and Low cost and availability of Low efficiency coagulants flocculation 14,15 Corrosion Natural coagulants (e.g. Recontamination problems minerals) Hazardous activated sludge

Easy to handle Coalescence 16

No chemical additives are Presence of emulsifier causes needed to break the emulsion low efficiency Simple device requirement Low investment costs Long operation cycle coalescence materials

of

Increase in suspended solids’ oil concentration decreases the coalesce element’s lifetime

Gradual adsorption of material on the coalescing Without need of power and media - poisoning and loss of external chemicals effectiveness High removal efficiency of oil


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Adsorption 17

No chemical additives are Cannot be used for high oil needed to break the emulsion and emulsifier concentrations Good for remove oil and Difficult in terms of operation emulsifier (less than ppm) Regeneration of spent Low capital costs adsorbent High chemical demand (COD) efficiencies

Biological processes 11,17

Low investment operating costs

oxygen removal and Difficult in terms of operation Oil and biocides inhibits the biological activities Slow process

Membrane Filtration 12

No chemical additives are Sophisticated instrumentation needed to break the emulsion required for backwash Low investment operational costs

and Frequent flushing

backwashing

or

Rarely difficult in term of Membranes suffer from fouling and degradation operation during use - frequent filter Small space occupancy replacement High chemical oxygen demand (COD) and oil removal efficiencies

MEMBRANE TECHNOLOGY Past decades have shown that membrane filtration is a clean and effective technology for the treatment of oily wastewaters in order to separate the oil from the water, to reduce the effluent volume, and to improve the quality of the effluent significantly. It has high oil removal efficiency, low energy cost, and a compact design compared with traditional treatments.18 Early investigations into oily wastewater treatment using membrane separation technologies originated in the 1970s. Since then many approaches have been conducted within this field. Membrane


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technology has become a dignified separation technology over the last 30 years and is becoming a promising technology. This technology has numerous advantages (e.g. high-selectivity, easy separation, a mild operation, and a continues, automatic, economic, and fast operation, as well as relatively low capital and on-going investments, ...) including stable effluent quality and small area requirements.8 Moreover, no chemical addition is required. The more common membrane separation methods for the treatment of oily wastewater emulsions are microfiltration (MF) 19-24 and ultrafiltration (UF)10,25-32, while nanofiltration (NF)33,34 is not as widely used. In order to separate the oil from the water by ultrafiltration, an emulsion containing cutting-oil droplets with diameters of less than 5 μm is circulated through an ultra-filter equipped with a water-permeable porous membrane, the pores of which have diameters of approximately 0.1-0.01 m. Treatment processes employing ultrafiltration exhibit undoubted advantages. They consume very little energy, the treatment plants are small in size and, after treatment, the water is free from cuttingoil. In addition, no on-going human maintenance is needed, as in the cases of physicochemical processes, and consequently, they can be easily automated. This is a considerable advantage within the presented context. Most membrane companies recommend using membranes with molecular weight cut-offs of 20,000-50,000 Daltons for the treatment of oily wastewater. There is an unclear demarcation between MF and UF for the treatment of O/W emulsions, since the formation of an oil gel layer on the membrane surface modifies the membrane selectivity, and a MF membrane may behave as a UF membrane.12,35 MF membranes provide higher permeate fluxes but have a higher risk of oil permeation. UF membranes, which have tighter pores, are usually selected in most applications to ensure steady permeate quality. The decline in permeate flux over time is mainly because of concentration- polarization, membrane fouling – due to surfactant or oil adsorption on the pore walls – and gel layer formation or pore-blocking by oil


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droplets. However, most industrial processes operate under constant flux mode and observe increasing transmembrane pressure as membrane fouls. MEMBRANE MATERIALS A membrane is a selective barrier or interphase between two phases that prevents the transport of certain components based on various characteristics. Membranes are very diverse in their natures with the one unifying theme of separation. Membranes can be liquid or solid, homogeneous or heterogeneous, transport can be active or passive. In addition, membranes can be natural or synthetic; they can be classified by morphology or by their structures and ranges of thickness. They can be manufactured to be electrically neutral, positive, negative or bipolar. These different characteristics enable membranes to perform many different separation mechanisms, and hence applications.35 Membrane materials and structures, especially the poresizes and characteristics of the membrane surfaces and support structures (thickness, porosity, wettability, zeta-potential, surface and chemical properties) have an influence on permeate flux and retention properties, as well as on fouling tendencies. The chemical nature of the membrane can have a major effect on the permeability. Membranes can be organic (polymeric) or inorganic (ceramic or metallic), according to their compositions, and their morphology depends on the natures of the materials Polymeric membranes are membranes that take the form of polymeric interphases that can selectively transfer certain chemical species over others. There are several mechanisms that could be deployed during their functioning.36 Mostly, the used polymers for membranes in oily wastewater treatment applications are PVDF (polyvinylidene fluorides), PS (polysulfone), PES (polyethersulfone), PAN (polyacrylonitrile), and regenerated cellulose (RC). Table 3 compares operating conditions and typical results achieved by cutting-oil emulsions using different


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membrane materials. Typical processes achieve oil-removal as high as 95-99 % of the oil within the feed, with residual oil concentrations within the permeate often less than 10 mg/L. Permeate fluxes are reported to range from 10 L/(m2h) to 380 L/(m2h).


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Table 3. Literature review of cutting-oil’s ultrafiltration.

Material

Author

Water flux

MWCO/

(L/(m2h))

pore size

800

100 kDa

700

20 kDa

1000

60 kDa

Polyethersulfone (PES) Hu et al.37

Polyvinylidene fluorid (PVDF)

200 kDa Hilal et al.3 100 kDa

Belkacem et al.25,38

265

50 kDa

Polyacrilonitirile (PAN) Karakulski 47.9 et al.6

70 kDa

Feed (oil Operating concentration) conditions 0.5%

TMP=3bar,

5%

T=20-60°C

0.5%

TMP=2bar,

5%

T=20-60°C

0.5%

TMP=3bar,

5%

T=20-60°C

5%

Retention (%)

90-110 49

20%

TMP=2bar

5%

10 39

20%

6

4%

13

4% + 400 CaCl2/L 124 mg/L emulsion)

mg TMP=1bar (real

TMP=1.5bar, T=38°C

5000

Permeate flux (L/(m2h))

mg/L

156 COD:78/ OIL: 97.9 COD:89/

34 34


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(simulated emulsion)

Acryl

Janknecht et al.39

Lin and Lan40

Polysulfone (PSf)

Benito al.41

et

288

OIL: 99.9

1-30 kDa

5%=38g/L

TMP=3bar, T=22°C

OIL: 99.98 6.2

40-60 kDa

5%=38g/L

TMP=2bar, T=22°C

OIL: 99.98

6.6

30 kDa

3% real emulsion

TMP=1.7bar, T=30°C

COD:91.4

4.8

TMP=1bar, T=20°C

10 kDa 500 mg/L

545

30 kDa

TMP=1.5bar, T=20°C

OIL: 99.9

90

1-50 kDa

TMP=7bar, T=22°C

OIL: 99.99

273

40-60 kDa

TMP=2bar, T=22°C

OIL: 99.99

9.8

1-15 kDa

TMP=5bar, T=22°C

OIL: 99.99

45

TMP=3.5bar, T=22°C

OIL: 99.99

6.65

TMP=1.7bar,

COD:89.1

10.2

T=30°C

COD:89.4

8.4

5%=38g/L

Fluouropolymer

Janknecht et al.39

Cellulose

15-30 kDa

Lin and Cellulose acetate Lan40 (CA)

100 kDa

Karakulski 37.9

70

30 kDa 70 kDa

5%=38g/L

3% real emulsion 124

mg/L

(real TMP=1.5bar,

COD:89.8/ 24


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et al.6

emulsion) 5000 (simulated emulsion)

Hesampour 345 et al.42,43 Regenerated cellulose (RC)

Polyvinyl chloride (PVC)

ZrO2/TiO2

Benito al.41

et

35 243

Karakulski 75 et al.6

Benito al.44

et

T=38°C mg/L

OIL: 99.1 COD:91/ OIL: 99.9

100 kDa

pH=11,T=40°, 0.5% + 100 mg TMP=3.5bar, OIL: 85 NaCl/L CVF=3.2m/s,

10 kDa

2500 mg/L

TMP=2bar, T=20°C

500 mg/L

TMP=2bar, T=20°C

30 kDa

124 mg/L emulsion) 110 kDa

50 kDa

5000 (simulated emulsion)

TMP=1.5bar, mg/L T=38°C

oil+different surfactantsanionic,cationic and non-ionic

388

40 OIL: 99.9 110 COD:72.5/

(real

10

OIL: 97.4 COD:85/ OIL: 99.9

TMP = 0.5- COD: 3.5bar to 100

up

54

53

10 - 200

COD: ZrO2

Faibish et 26.3. 10-6 m/s 45 al.

15 kDa

TMP = 0.372-90/ Model cutting oil 0.7bar, solution OIL: T=20°C 74.3–94.8

5.51–22.6 . 10-6 m/s


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COD: 13.3. 10-6 m/s

74.3–94.8/ 3.35–12.1. 10-6 m/s OIL:

PVP-grafted ZrO2

95.5-98.6

α- Al2O3

Wang al.46

γ-ZrO2/α-Al2O3 α -ZrO2/α-Al2O3 α -ZrO2/α-Al2O3 ZrO2/α-Al2O3

Yang al.47

et

0.1-0.2 μm 0.1-0.2 μm

Symmetric Al2O3 0.01 μm support: 0.2 μm et 400 , 1.0 μm Asymmetric Al2O3 support: 0.2 μm 1500

1-5% (1000 mg/L) TMP=0.8bar, 1-5% (1000 mg/L) T=30°C

5000 g/L

TMP = 1.5bar

1-

OIL: 99.9

100

OIL:99.8

43

OIL: 99.8

18

OIL: 99.9

22

OIL: 94.3

27

OIL: 99.8

93


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Hydrophobic membrane material such as polysulfone is often used for ultrafiltration membranes. Its properties exhibit excellent chemical and thermal stability but, because of its hydrophobic properties in nature, fouling is the critical problem for polysulfone membranes. For example, free oils can coat hydrophobic membranes resulting in poor flux. Hydrophilic membranes preferentially attract water rather than the oil, resulting in much higher flux. Hydrophobic membranes can be used, but usually within a tubular configuration that allows for a high degree of turbulence (cross-flow velocity) to be maintained in order to minimize oil-wetting of the membrane.12 Benito et al.41 compared the filtration performances of polymeric membranes made of regenerated cellulose and polysulfone. As a result of the low fouling characteristic and the higher permeate flux, the regenerated cellulose membranes appear to be better choices than polysulfone membranes for applications when treating cutting-oils. Polysulfone membranes are less hydrophilic than regenerated cellulose membranes, so they are easily wetted by the surfactants present in the oily emulsion, and fouled. Lipp et al.32 also found similar results from direct observation of the four polymeric membranes (regenerated cellulose, polysulfone, polyacrilic, and polyamide). The reversibility of gel layers by simple cleaning was strongly dependent on membrane type. A regenerated cellulose membrane was the least affected and the more easily cleaned, while a polysulfone membrane was the more irreversibly fouled. On the membrane market, polymeric membranes are dominant and non-polymeric membranes are mainly used only in special cases where polymeric membranes cannot be used. Such membranes include inorganic membranes (for example metal, ceramic, carbon, and zeolites), and liquid-membranes. The ceramic-membrane is the final layer of the porous ceramic filtration element that is in direct contact with the feed-stream. It is composed of ceramic particles having


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a well-defined size, to create a filtering layer of a well-defined pore size, and usually of just a few microns’ thickness. Ceramic ultrafilters have been developed within the industry for 20 years and widely-used in oily wastewater treatment. Research on ceramic membranes was initially directed towards the preparation of alumina membranes. The important features of inorganic-membranes are their interactions with aqueous media. The hydration mechanism of the alumina walls leads to an amphoteric dissociation of the surface groups Al – OH-. Then, water molecules, hydrated ions, and organic compounds can develop strong interactions with the alumina surface. This phenomenon explains why an alumina membrane retains various substances that modify the pore-volumes and pore-sizes. Therefore, membrane performance and selectivity are also affected.48 Nowadays, many porous membrane materials that have been applied to develop the ceramic membrane include alumina, zirconia, titanium, and silica. Among them zirconia is a very interesting material for inorganic membranes. The outstanding qualities of zirconia membranes are their high chemical resistance that allows for steam sterilization and cleaning procedures within the pH range 0–14, good pure water permeability, high membrane flux during separation and filtration due to their specific surface properties, and high thermal stability which is very attractive for catalytic membrane reactors at high temperatures.2 Numerous research works have focused on the synthesis of zirconia microfiltration membranes and their applications in oily-wastewater. Yang et al.47 used zirconia membranes and three different alumina membranes in order to separate oil–water emulsion emitted from steelworks when evaluating the permeability and separation characteristics. The results showed mostly the same oil rejection efficiency but the flux of zirconia was higher than the others. Wang et al.46 compared alumina and zirconia MF membranes for the treatment of waste cutting-emulsion. The


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emulsion had a milky gray appearance and contained 1–5% of oil as well as several kinds of additives and other impurities. The applied transmembrane pressure was 0.08 MPa, cross-flow velocity 2.5 m/s, and temperature 30°C. The results show that the zirconia membranes provided higher flux and rejection efficiencies, 100 L/m2h and 99.9%, respectively. Glass can be considered as well as a ceramic material. Abbasi et al.49 reported that the MF with mullite (silicate mineral) ceramic membranes can be used as an advanced method for the treatment of oily wastewaters. Both polymeric and ceramic membrane materials are used during oily wastewater treatment. Numerous studies have arrived at the conclusion that ceramic-membranes are superior to polymeric-membranes for oily-water separation, as they exhibit better properties such as chemical resistance, stability, and a wider range of pH values.50-54 However, commercial ceramic membrane modules are approximately five times more costly than the polymeric membrane modules. But, their operational life-spans are also in excess of five times those of polymeric membrane modules, which typically last around three to five years. The ability to rapidly backpulse during operations allows the system’s operating expense to be reduced significantly. Furthermore, the ability to use steam and heat-treatments to completely recover membrane performance removes the need for the storage of cleaning chemicals, as well as the disposal of those chemicals. When the above operating expense reductions are taken into account, the reduction in operating expenses by switching to ceramic membranes can be up to 50%.46,55,56 Wang et al.46 compared the performance of the polymeric membrane UF plant, as used in Shanghai Baoshan Steel & Iron Co. (SBSIC), with two different inorganic membranes. This comparison was made at the same throughput rates for the two processes. It was discovered that both inorganic membranes (zirconia and alumina) had several advantages over organic


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membranes when treating the waste cutting-emulsion. First of all, the energy consumptions of the inorganic membranes were much lower than those of the organic membranes. Secondly, the handling of the used cleaning chemicals was easier for the inorganic membranes. Finally, authors claimed that the price of the inorganic membranes per area used in their paper was around fivetimes cheaper than that of the imported organic membranes used in SBSIC. The inorganic microfiltration of waste emulsion has already been adopted by some factories. Recently, a new class of materials was studied and developed, the zeolite membranes. Cui et al. have reported that this material is performing well during the treatment of oily wastewater.53 One of the novelties regarding membrane materials is dynamic-membranes. These are a specific type of membrane that can be formed in situ by filtering a solution containing either inorganic or organic materials through a porous support. The potential benefit of the dynamicmembrane lies in its ability to be formed by a simple filtration process using inexpensive materials. Once the membrane is fouled, the deposited layer can be removed and a new dynamic layer can be deposited. Dynamic-membranes can be classified into two types: self-forming and pre-coated types. Many inorganic or polymeric-materials have been used as supports for dynamic membranes, e.g., porous ceramic and porous stainless-steel tubes, polymeric membranes, and sintered polymer (PVC, PE, etc.) tubes. Wide-ranges of colloidal materials are used to form dynamic-membranes.57 The complete membrane process comprises membrane modules, pressure vessels, pumps, and control instruments. In regard to industrial operations, membranes are commonly packaged into plates and frames, spirals, tubular and hollow fibers, cassettes, and inorganic monolithic modules.12,35 The feed channels within the plate and frame, spiral, and hollow fiber configurations are prone to plugging when treating feeds containing large amounts of particulate


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matter.58 Tubular-configuration is the most suitable for spent cutting-oil treatment application (Figure 2), due to the high concentration of oils and suspended solids in oily wastewater from the metal-working industry.

Figure 2. Tubular module.36 MEMBRANE SYSTEMS FOR THE TREATMENT OF SPENT CUTTING OILS A typical UF-based system for oily wastewaters consists of a feed tank, a pre-treatment stage for removing particles and free oil, a pre-filter, a process tank, and the membrane module (Figure 3). The membrane unit is operated within a semi-batch recycle mode. The retentate containing the oil is recycled to the process tank and the permeate is withdrawn continuously. Fresh oily wastewater is added to the process tank, thus maintaining a constant level. The final concentrate volume may be only 3–5% of the initial oily wastewater volume. The system is then cleaned until the initial permeate flux is restored.1


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Figure 3. Schematic of typical membrane system for the treatment of oily wastes (adapted from Cheryan et al.12). Comparison between the ceramic and polymeric membrane modules’ efficiencies for real spent cutting-oils was carried out at the Hidria Rotomatika Company (Koper, Slovenia), where a plant (Fig. 4) was installed with three polymeric (acrylonitrile) and two ceramic (α-alumina/zirconia) UF membranes. The main parts of the UF plant, as shown in Figure 4, are the equalization tank, process tank, five tubular UF membranes, and a filtrate tank. The oily wastewater within the process tank is pumped to the UF membrane. The feed is separated into permeate and retentate streams. Permeate is re-collected within the filtrate tank. The retentate is returned to the process tank for recycling through the modules.


20

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Figure 4. Schematic representation of the UF plant installed in Hidria Rotomatika (Koper, Slovenia). Figure 5 shows the oily wastewater UF treatment plant in 2008 with three polymeric modules installed. In 2010, the plant was upgraded with two ceramic modules. The modules are connected in sequence, with the option of using either polymeric or ceramic membrane modules separately.

Figure 5. UF plant with three polymeric modules installed in Hidria Rotomatika (Koper,


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Slovenia) in 2008. It was discovered that better COD and oil-removal efficiencies were achieved using ceramic membrane modules compared with polymeric ones. The tests showed that the removal efficiencies of COD and oils increased by up to 15 % when using a combination of all five membrane modules. Nowadays, a combination of two or more separation processes (within integrated or hybrid processes) is required in order to reach the most severe discharge standards. Specifically, hybrid membrane processes are the more frequently used for the treatment of oily wastewaters at industrial scale. Integrated processes may reduce total production cost, energy consumption, capital cost, and provide better oil separation efficiency. In regard to the treatment of oily wastewater generated during the manufacture of metal components for pumps within a local company, this treatment was studied in regard to its performance at this plant. This plant, shown in Figure 6, consists of magnetic and mesh filters for solids’ removal, a 1000 L stainless-steel feed holding-tank for storing the oily wastewater and operating in continuous mode, a demulsification/centrifugation stage for emulsion- breaking and the removal of free and demulsified oil, a ceramic membrane UF stage (50 nm pore size, 1.7 m 2 membrane

area)

to

remove

the

remaining

oil

during

the

aqueous

phase

from

demulsification/centrifugation, and a peat bed filter which could be used for the treatment of spent synthetic MWFs (no oil content) or if the permeate obtained during the UF stage has an oil content higher than the limiting standards.


22

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Figure 6. Schematic diagram of the modular pilot plant for the treatment of oil-containing wastewaters.1 The waste emulsion was first passed through the filters to remove the metallic filings. The pretreated emulsion was then pumped into the feed storage tank, where it was mixed with 1000 mg/L of the demulsifying agent. Afterwards, it was fed to a centrifuge. The aqueous phase obtained at this point was fed to the UF unit. In order to obtain a final effluent suitable for discharge, the next treatment stage was filtration using mixed beds of peat and calcium sulfate. More than 99.9% of the oil removal and 90% of COD reduction were achieved using this integrated treatment. The resulting final effluent is suitable for discharging into the sewage system for subsequent treatments within a conventional wastewater treatment plant as the pollutants that could cause operational problems have been removed.1 EFFECTS OF PROCESS PARAMETERS


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During an industrial application of membrane filtration, operational parameters such as transmembrane pressure and fluid temperature may affect the process’ performance. Obviously, pressure and temperature control are vital when optimizing an industrial UF process. Technical and economic aspects would favour pressure-control before temperature regulation. Temperature: The temperature has a double effect on permeation flux. In general, the permeation flux increases with increasing temperature due to lower viscosity, with a high temperature the viscosity and the density of the emulsion decrease, which has a positive effect on the flow. Moreover, an increased temperature results in an increased collision rate between particles and in coalescence for disperse systems. This might increase the oil droplets’ sizes and thus difficulties with fouling and concentration polarization are reduced - and consequently a higher permeate flux can be observed.20,42,43 In contrast, temperature increases reduce the size and reduces permeability because of pore-blocking by oil droplets.46 pH: The pH-value can have a significant influence on the membrane surface-charge and/or emulsion properties. Lobo et al.59 found that permeate flux of ceramic membrane highly depends on pH, which thus influences the zeta potential values of those membrane-active layers formed by metal oxides. However, there have been certain arguments in previous studies regarding the pH effect on the stabilities of the cutting-oil emulsions. Some authors found that the steady-flux decreased as the pH increased within a range of 2–10, because acidic pH causes demulsification of the emulsion.60 In contrast others have reported that maximum permeability was observed at neutral and alkaline pHs.21,43,46 According to Hesampour et al.42 the stability of cutting-oil increases with pH. At higher pH the drops are bigger and, therefore, the free energy is lower and the emulsion becomes more stable.


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Cross-flow velocity (CFV): A higher rate of cross-flow generally increases steady-flux. Any explanation of this fact considers the occurred higher turbulence and higher mass-transfer coefficient, which lower the aggregations of the feed components within the gel-layer formation. As a result the aggregate material on the membrane surface is removed back to the feed and further on the phenomena of concentration-polarization is reduced, and the flux is improved.3,59 In the case of spent cutting-oils this can be interpreted as follows: the extent of accumulation regarding the rejected oil on the membrane surface is decreasing, thus reducing the total resistance. Although high CFV can enhance the permeated flux, forceful turbulence is not recommended during the membrane processes. The main reason is that turbulent flow may consume the TMP of the system, causing a decline in the permeate flux. A recent study

61

showed that an optimal CFV depends on the frictional pressure drop, which is the function of solution viscosity and module configuration. In a normal flow channel a high tangential flow increases turbulence close to the membrane surface, which mitigates the formation of concentration-polarization. Hesampour et al.42,43 used a thin channel during their study, where the flow was at a maximum within the transient region (Reynolds number varied between 2500 and 3000) and the effect of flow velocity was reflected by an increase in the shear tension on the surface of the membrane; due to the produced tension oil was removed from the membrane surface and flux increased. Lobo et al.59 established the optimal CFV based on the pumping cost and improvement in the permeate flux across the membrane. Transmembrane pressure (TMP): The permeate flow-rate depends directly on the applied transmembrane pressure for a given surface area under otherwise uniform conditions.54 The flux of the pure water is linearly pressure-dependent. When the feed solution is more complex and also contains other substances, the flux behavior is more complex. At the beginning the flux


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increases steadily until the critical flux is achieved. Then the flux reaches a constant value because of concentration- polarization. Increasing the TMP causes the bulk to flow towards the membrane to obtain more than the back diffusion from the surface. As the oil is rejected by the membrane, it accumulates near the membrane surface and the concentration gradient causes the flux to decline. Thus, above the critical flux, an increase in pressure does not have any positive effect on the flux; on the contrary it can lead to a decrease in flux due to the compaction of the fouling layers.3,22,42,59 Higher TMP allows droplets (both solvent and solute) to pass rapidly through the membrane pores. However, more cutting-oil droplets accumulate both on the membrane surface and in the membrane pores, leading to membrane fouling.62 Nazzal and Wiesner found that emulsion rejection could be maximized if TMP were below a critical pressure. Also, Chakrabarty et al.10 found that the flux declination was greater, while the oil rejection had a decreasing trend with any increase in pressure. FOULING AND ITS CONTROL During filtration of the spent cutting-oils, any rejection of the dissolved matter (oil, surfactants, co-surfactants or some other organic matter) by the membrane leads to an accumulation of these substances within a mass transfer boundary-layer adjacent to the membrane surface. This phenomenon is called concentration-polarization, which is a natural consequence of membrane selectivity. Thus, a build-up of dissolved molecules at the surface reduces the solvent activity, which generates an osmotic pressure that reduces the solvent-flow through the membrane. This can be represented as a reduction in the effective transmembrane pressure (TMP) driving-force due to an osmotic pressure difference between the filtrate and the feed solution immediately adjacent to the membrane surface. This phenomenon is inevitable, but it is reversible with the elimination of TMP, and hence flux.63


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The adverse effects of concentration-polarization are intensified when a deposition and/or an irreversible adsorption of certain feed constituents occurs at the membrane surface, affecting the hydraulics (decreasing flux (for fixed TMP) or increasing TMP (for a given flux)) over time when all operating parameters, such as pressure, flow-rate, temperature, and feed concentration are kept constant. This phenomenon is referred to as membrane fouling with a consequent increase in energy and membrane replacement costs. Membrane fouling may be the result of concentration-polarization but it may also just be a consequence of adsorption regarding feedsolution constituents at the membrane surface (or on layers that are already adhering to the membrane surface), and also within the membrane structure.58 The fouling problem in the case of cutting-oils’ emulsions is even more serious because the deformable nature of oil-droplets and their sizes may vary with imposed shear, oil concentration, oil-surfactant ratio, and interaction with the membrane.32 Meanwhile, membrane pore-size distribution, membrane nature, as well as operating conditions, are also factors regarding membrane fouling.63 The mechanism of fouling by oil is rather unclear. According to Lee et al. 63 fouling begins by an adsorption of oil drops on the membrane. The adsorption of oil modifies the wettability of the membrane and the effective pore-diameter, thus accelerating the formation of a gel-layer on the surface. The extent of adsorption depends on the different interactions between the oil and the membrane, such as hydrophobic/hydrophilic interactions, Van der Waals forces, hydrogenbonding, and electrostatic forces. Lipp et al.32 stated that fouling followed by gel polarizaton, and film-model behavior, with the oil droplets coalescing into the surface-fouling oil film. Whilst adsorption has been reported as the initial point of fouling, some researchers have claimed that fouling starts with pore-plugging and, as the operational time increases, the


27


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adsorption onto the membrane surface then controls the fouling.64 Koltuniewicz et al.22 and Arnot et al.65 investigated the mechanisms of flux-decline during simultaneous experiments into both dead-end and cross-flow modes through the microfiltration of oil-in-water emulsions, using a general formula by modifying Hermia’s model. They observed that the membranes initially fouled internally (described by a pore-blocking model), and then external fouling began to dominate (described by a cake-filtration model). PREVENTATIVE ANTI-FOULING ACTION AND MEMBRANE CLEANING AFTER FOULING Membrane fouling is a complex phenomenon depending on the characteristic of the feedsolution, membrane-related properties, and process-related factors. Therefore, the pre-treatment, selection of membrane, module, process configuration and conditions are all important, to varying extents, for achieving a high-degree of separation without productivity decline due to polarization and fouling.66 In order to obtain good process performance and to extend membranelife, an integrated-membrane or membrane-based hybrid process may be a suitable alternative.1 The feed-properties can be changed by pre-treatment, which can involve either mechanical or chemical processes. Usually the process starts with the removal of settleable solids and freefloating oil prior to membrane treatment, mainly UF. This can be accomplished in a tank with free-oil removal equipment, such as a skimmer, or by a rotating brush strainer, a pressure or vacuum filter for removing solids, and a centrifugal separator or a hydrocyclone for removing oil and solids. The remaining oily wastewater is then transferred to a process tank and pumped through the UF unit to remove the emulsified oil, obtaining a permeate which can be discharged continuously into the sewage system.1,12 Oily wastes can sometimes be treated by a combination of two membrane processes. Hilal et al.3 used ultrafiltration as pre-treatment prior to


28

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nanofiltration; the use of pre-treatment leads to considerably lower fouling of the nanofiltration membrane and therefore improves the qualities of the final permeates. There are certain processes that use chemical instead of mechanical pretreatment, which consists mainly of a process tank where a coagulation/ flocculation

67,68

takes place prior to the membrane treatment.

According to Hesampour et al.42 feed pH adjustment and the addition of salt, such as CaCl2 mostly affects the stability of oil-in-water emulsions. CaCl2 acts as a coagulant and destabilizes the oil emulsion due to the reduction of the zeta potential.69 The destabilized oil-drops are coalesced by agitation provided by a pump, and by Van der Waals interaction forces.70 Also, Wang et al.46 reported that the pretreatment of waste cutting-emulsion by sodium hydroxide improves flux and permeate qualities. This could be a consequence of the enlargement of the droplets in the emulsion by the pretreatment agent and also the changing of the droplets’ surface wettability from hydrophobic to hydrophilic. The membrane material and structure, especially the pore-sizes and characteristics of the membrane-surface and support-structure (thickness, porosity, wettability, zeta-potential, surface and chemical properties), have an influence on the permeate flux and retention properties as well as on the fouling tendency, largely through the tendency of some materials to adsorb solutes more readily than others. An appropriate choice of membrane material and modification of the membrane surface can lead to looser binding of the solutes to the membrane surfaces, which can have the effect of lessening membrane-solute interaction (such as molecule or particle penetration into the surface pores). This leads to a reduction in membrane permeability, and may also make the solute easier to remove during cleaning. It is known from literature that hydrophilic membranes have a lower fouling tendency compared to hydrophobic membranes.66 These hydrophilic membranes, however, usually have limited chemical and thermal stabilities.


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Therefore, hydrophobic membranes are used, and flux enhancement can be achieved, by modifying the surface properties of the membrane. Various chemical and physical methods have been proposed for modifying membranes in order to reduce membrane-fouling. This surface modification can be either irreversible (e. g. chemical-reaction irradiation

74,75

) or reversible (e. g. adsorption-coating

76

71

, plasma-treatment

72,73

). A limited number of studies

, UV71,77-84

have specifically addressed membrane fouling reduction via membrane surface modification for the treatment of oil-contaminated waste streams. Blending an original polymer with polymers having more suitable properties and the addition of a polymeric layer on the surface of an available membrane, are some examples of the membrane modification approaches. An example for the blending of two polymers and making more fouling resistant membrane for use in oily water filtration has been described by Asatekin et al.81. In their work, a copolymer (composed of a hydrophobic backbone and hydrophilic polyethylene oxide (PEO) side-chain) was added to the casting solution of poly-acrylonitrile (PAN). The developed membrane had a significantly higher flux after 24 hours of filtration, compared with the commercial PAN membrane. The developed membrane could be completely cleaned by physical methods (backwashing) alone. Li et al.80 added poly (ethylene glycol) (PEG) to a cellulose polymer during the preparation of a membrane. A resistant fouling membrane was formed with a remarkably lower total relative flux reduction. The effect of blending a surface by modifying a macromolecule (a mixture of methylene bisphenyl di-isocyanate (MDI), polypropylene diol (PPO) and fluorotelomer intermediate) with the casting solution of polyethersulfone (PES) was studied by Hamza et al.83. The surface active agent rendered the surface of the membrane more hydrophilic. Research using PES membrane modified by amphiphilic copolymer Pluronic F127 showed an improvement in membrane operation as


30

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described by Chen et al.85 A more hydrophilic surface enable a doubling of the fluxes and exhibits antifouling properties of the membrane compared with the non-modified PES membrane. This study showed that when using SDS as the cleaning agent, the flux recovery percentage increased to 93%. The effectiveness of the poly(vinylpyrrolidone) (PVP)modification of a zirconia-based ultrafiltration membrane was investigated by Faibish and Cohen. 45 The native membrane was irreversibly fouled by both the oil-in-water micro-emulsion and the commercial cutting oil emulsion. In contrast, irreversible fouling was not observed for the PVP-modified membrane. McCloskey et al.78 deposited polydopamine (PD) on MF, UF, NF, and RO membranes using an aqueous-based surface modification strategy. This surface treatment not only retained much of the membranes’ intrinsic pure water permeability, but also improved the fouling resistances of all the membranes studied and measured using oil/water emulsion filtration. For example, the flux of a PD-modified PS UF membrane was 125 % higher than that of an non-modified membrane after 1 h of oil emulsion filtration. The extent of membrane fouling can also be limited by optimizing the operational conditions, which may involve maintaining a high cross-flow velocity, limiting transmembrane pressure, periodical hydraulic and/or mechanical cleaning, temperature, choice of cleaning chemicals, and the frequency of cleaning etc. One of the easiest ways to improve fluxes is to increase cross-flow velocity, which requires high-pressure, and a changing of the flow-field within a membrane module from laminar to turbulent-flow. Due to this, the concentration-polarization effects diminish as a result of increased mass-transfer, thus resulting in an improved flux. Turbulentflow can also reduce fouling because of an increase in the wall’s shear-rate at the membrane surface. Backflow techniques, such as backwashing, back-flushing, and pulsing by filtration can increase the permeate flux by removing the formed layer from time to time.18,86-88 A number of


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other methods for flux enhancement have also been used and they include feed-pulsation 12,89-91, two-phase flow

92,93

, rotating and vibrating filters

94

, use of turbulence promoters, additional

force-fields (for example electric and/or ultrasonic) during filtration enhancements such as inserts, baffles and stamped membranes

97

95,96

, hydraulic

, and gas injection

98

. Their

positive effect on flux very much depends on other filtration parameters and should be evaluated case by case. The extent of membrane fouling can also be limited by temperature control. Fouling results essentially from the accumulation of oil on the membrane wall at lower temperatures.99 Although pre-treatment, membrane modification and the introduction of hydrodynamic instabilities within the fluid flow across the membrane surface may reduce any reversible fouling caused by cutting-oil drops and other impurities in the emulsion, irreversible fouling cannot be completely avoided without further chemical cleaning, as can be seen in Figure 7.

Figure 7. Illustration of reversible and irreversible permeate flux decline in membrane UF.45 Complete fouling removal is impossible and has to be tolerated up to a decrease in mass-flux down to 75 % of the original flux.58 The cleaning of irreversibly-fouled membranes requires


32

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harsh chemical and/or high temperature thermal treatments.45 Cleaning solutions are usually circulated with a pressure somewhat lower than that used during filtration, in order to prevent deeper penetration of the foulants into the membrane. Dissolving of the foulants by a chemical agent seems to be the predominant mechanism during chemical cleaning.63,100 There is no priori rule that can be applied for predicting which cleaning technique might be the more successful during any particular application.38,58 Different parameters such as the type of cleaning agent, pH, concentration, temperature and time, have an influence on the cleaning results.100 Mineral foulants should be generally removed by an acidic cleaning agent and organic compounds by an alkaline solution although, for a satisfactory performance, a combination of both methods is sometimes needed. The cleaning of fouled ultrafiltration membranes by oil has been studied since the start-up operations of the first filtration plants. The first filtration devices were simple, consisting just of a feed tank, pump, and UF unit.63,101 A review of some of these studies with an emphasis on cutting-oils is provided in Table 4. In the case of cutting-oils, the layer concentration is independent of the operating conditions; therefore the fouling phenomenon is definitely inevitable, mostly within an irreversible mechanism. Regular chemical cleaning is needed due to the latter and the highly-complex cutting-oil formulations. Table 4. Chemical cleaning of membranes fouled by cutting oil. Membrane material

Polymeric membranes

Polyether (PES)

Cleaning agent

Reference

Micellar solution dodecyl sulfone (sodium Lee 1984 63, Hu 2002 37 sulfate (SDS)-nPentanol-water)

Polyvinylidene difluoride (PVDF)

Micellar solution

Belkacem 1995 38

IMPUREX

Gryta 2001 102


33


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Koch Detergent

Reed 1997 103

Ultrasil 11

Koltuniewicz 1995 22

Polyacrilonitrile (PAN)

Micellar solution

Belkacem 1995 38

Cellulose

Ultrasil 110

Hesampour 2008 42,43

Cellulose acetate

NaOH, NaClO

Lin 1998 40

NaOH, NaClO

Lin 1998 40

Derquim+

Benito 200141

Regenerated cellulose

Derquim+

Benito 2001 41

Polypropylene

NaOH, H2SO4

Hlavacek 1995 24

Ultrasil 11

Koltuniewicz 1995 22

NaOH

Faibish 2001 45

Polysulfone

ZrO2

mullite 2SiO2)

(3Al2O3

Ceramic membrane

NaOH, ethylene diamine tetra acetic + acid disodium salt-2Abbasi 2012 49 hydrate (EDTA), sodium dodecyl sulfate (SDS) Lee 2002 88, Hua 2007 Nazzal 1996 23

NaOH HNO3, toluene

α-Al2O3

Zeolit membrane

Liquid

Page 34 of 51

aceton,

,

Lee 2002 88

HCl

Hua 2007 21

ZrO2/TiO2

Derquim+, HNO3

Lobo 2006 59

TiO2/Al2O3

NaOH, H2SO4

Viadero 1999 94

NaA zeolite/ceramic

NAOH

EDTA,

21

Cui 2008 53

CONCLUSIONS


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This paper presented important investigations into the field of spent cutting-fluids. Its treatments were studied and the more important results highlighted. Nowadays, a combination of two or more separation processes is required in order to avoid membrane fouling and to reach the most severe discharge standards. Specifically, hybrid membrane processes are more frequently used for the treatment of oily wastewaters on the industrial scale in order to obtain good process performance, and to extend membrane life integrated-membrane. The numerous advantages of membrane filtration systems for treating such emulsions were confirmed. In comparison to polymeric membranes, ceramic membranes are slower to foul, and can be regenerated using more extreme membrane performance recovery methods, which polymeric membranes are not able to handle due to thermal limitations of polymeric materials. However, commercial ceramic membrane modules are up to five times more costly than the polymeric membrane modules. Membrane surface modification is gaining ground as an attractive route for reducing favorable membrane surface–foulant interactions, thereby reducing fouling and enhancing membrane longevity and performance. Recent studies have shown that improvements in oil rejection up to 100% are possible by proper surface modification. The crucial process parameters are temperature, pH, cross-flow velocity and transmembrane pressure during both the filtration and cleaning modes. The understanding is significant of the possible double-temperature effect, pH influence around the isoelectric point, constant crossflow velocity, and transmembrane pressure. In addition to the filtration part, optimal parameters, such as low-pressure and high-temperature, are equally important when choosing a chemical agent during the cleaning mode.


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Further investigations and innovative approaches will probably offer even better results and even more technologically-improved methods by using, for example, new or modified materials, naturally obtained emulsifiers, etc.

AUTHOR INFORMATION Corresponding Author * Corresponding author: Janja Križan Tel.: ++38622294483 Fax.: ++38622294476 e-mail: [email protected]

ACKNOWLEDGEMENT The authors are grateful to the Slovenian Research Agency for its financial support (P2-0032). REFERENCES (1) Coca, J.; Gutiérrez, G.; Benito, J., Treatment of Oily Wastewater. Water Purification and Management 2011, 1-55.2011 (2) Wang, L. K.; Chen, J. P.; Hung, Y. T.; Shammas, N. K. Membrane and desalination technologies; Humana Press, 2010. (3) Hilal, N.; Busca, G.; Hankins, N.; Mohammad, A. W., The use of ultrafiltration and nanofiltration membranes in the treatment of metal-working fluids. Desalination 2004, 167 (0), 227-238.2004 (4) Eastwood, J., EC Dangerous Preparations Directive–application to metalworking fluids and ingredients. Industrial Lubrication and Tribology 2002, 54 (6), 296-301.2002 (5) Soković, M.; Mijanović, K., Ecological aspects of the cutting fluids and its influence on quantifiable parameters of the cutting processes. Journal of Materials Processing Technology 2001, 109 (1–2), 181-189.2001


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(6) Karakulski, K.; Kozlowski, A.; Morawski, A., Purification of oily wastewater by ultrafiltration. Separations Technology 1995, 5 (4), 197-205.1995 (7) Cozzens, D.; Rao, P.; Olson, W.; Sutherland, J.; Panetta, J. M., An experimental investigation into the effect of cutting fluid conditions on the boring of aluminum alloys. Journal of manufacturing science and engineering 1999, 121 (3), 434-439.1999 (8) Salahi, A.; Gheshlaghi, A.; Mohammadi, T.; Madaeni, S. S., Experimental performance evaluation of polymeric membranes for treatment of an industrial oily wastewater. Desalination 2010, 262 (1), 235-242.2010 (9) Falahati, H.; Tremblay, A., Flux dependent oil permeation in the ultrafiltration of highly concentrated and unstable oil-in-water emulsions. Journal of Membrane Science 2011, 371 (1), 239-247.2011 (10) Chakrabarty, B.; Ghoshal, A.; Purkait, M., Cross-flow ultrafiltration of stable oilin-water emulsion using polysulfone membranes. Journal of Membrane Science 2008, 325, 427-437.2008 (11) Kim, B. R.; Zemla, J. F.; Anderson, S. G.; Stroup, D. P.; Rai, D. N., Anaerobic removal of COD in metal-cutting-fluid wastewater. Water environment research 1992, 216-222.1992 (12) Cheryan, M.; Rajagopalan, N., Membrane processing of oily streams. Wastewater treatment and waste reduction. Journal of Membrane Science 1998, 151 (1), 13-28.1998 (13) Zhou, Y. B.; Tang, X. Y.; Hu, X. M.; Fritschi, S.; Lu, J., Emulsified oily wastewater treatment using a hybrid-modified resin and activated carbon system. Separation and purification technology 2008, 63 (2), 400-406.2008 (14) Ahmad, A. L.; Sumathi, S.; Hameed, B. H., Coagulation of residue oil and suspended solid in palm oil mill effluent by chitosan, alum and PAC. Chemical Engineering Journal 2006, 118 (1–2), 99-105.2006 (15) Yan, L.; Hong, S.; Li, M. L.; Li, Y. S., Application of the Al2O3–PVDF nanocomposite tubular ultrafiltration (UF) membrane for oily wastewater treatment and its antifouling research. Separation and purification technology 2009, 66 (2), 347352.2009 (16) Zhao, H.; Li, G., Application of Fibrous Coalescer in the Treatment of Oily Wastewater. Procedia Environmental Sciences 2011, 10, 158-162.2011 (17)

Tri, P. T., Asian Institute of Technology, 2002.

(18) Schoeman, J. J.; Novhe, O., Evaluation of microfiltration for the treatment of spent cutting-oil. Water SA 2009, 33 (2).2009 (19) Mahdi, S.; Sköld, R., Experimental study of membrane filtration for the recycling of synthetic waterbased metalworking fluids. Tribology international 1991, 24 (6), 389395.1991


37


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 51

(20) Hu, B.; Scott, K., Influence of membrane material and corrugation and process conditions on emulsion microfiltration. Journal of Membrane Science 2007, 294 (1), 3039.2007 (21) Hua, F.; Tsang, Y.; Wang, Y.; Chan, S.; Chua, H.; Sin, S., Performance study of ceramic microfiltration membrane for oily wastewater treatment. Chemical Engineering Journal 2007, 128 (2), 169-175.2007 (22) Koltuniewicz, A.; Field, R.; Arnot, T., Cross-flow and dead-end microfiltration of oily-water emulsion. Part I: Experimental study and analysis of flux decline. Journal of Membrane Science 1995, 102, 193-207.1995 (23) Nazzal, F. F.; Wiesner, M. R., Microfiltration of oil-in-water emulsions. Water environment research 1996, 1187-1191.1996 (24) Hlavacek, M., Break-up of oil-in-water emulsions induced by permeation through a microfiltration membrane. Journal of Membrane Science 1995, 102 (0), 1-7.1995 (25) Belkacem, M.; Hadjiev, D.; Aurelle, Y., A model for calculating the steady state flux of organic ultrafiltration membranes for the case of cutting oil emulsions. The Chemical Engineering Journal and The Biochemical Engineering Journal 1995, 56 (2), 27-32.1995 (26) Nyström, M., Ultrafiltration of O/W emulsions stabilized by limiting amounts of tall oil. Colloids and surfaces 1991, 57 (1), 99-114.1991 (27) Mahdi, S. M.; Skoeld, R. O., Ultrafiltration for the recycling of a model waterbased metalworking fluid. Process design considerations. Lubrication engineering 1991, 47 (8), 686-690.1991 (28) Dick, R., Ultrafiltration for oily wastewater treatment. Lubr. Eng. 1982, 38 (4), 219-222.1982 (29) Bailey, P., The treatment of waste emulsified oils by ultrafiltration. Filtration and Separation 1977, 14 (1).1977 (30) Rezvanpour, A.; Roostaazad, R.; Hesampour, M.; Nyström, M.; Ghotbi, C., Effective factors in the treatment of kerosene–water emulsion by using UF membranes. Journal of hazardous materials 2009, 161 (2–3), 1216-1224.2009 (31) Bhattacharyya, D.; Jumawan, A.; Grieves, R.; Harris, L., Ultrafiltration characteristics of oil-detergent-water systems: membrane fouling mechanisms. Separation science and technology 1979, 14 (6), 529-549.1979 (32) Lipp, P.; Lee, C.; Fane, A.; Fell, C., A fundamental study of the ultrafiltration of oil-water emulsions. Journal of Membrane Science 1988, 36, 161-177.1988 (33) Jönsson, C.; Jönsson, A. S., The influence of degreasing agents used at car washes on the performance of ultrafiltration membranes. Desalination 1995, 100 (1), 115123.1995


38

Page 39 of 51

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(34) Park, E.; Barnett, S. M., Oil/water separation using nanofiltration membrane technology. Separation science and technology 2001, 36 (7), 1527-1542.2001 (35)

Mulder, M. Basic principles of membrane technology; Springer, 1996.

(36) Drioli, E.; Giorno, L. Comprehensive membrane science and engineering; Elsevier Science, 2010; Vol. 2. (37) Hu, X.; Bekassy-Molnar, E.; Vatai, G., Study of ultrafiltration behaviour of emulsified metalworking fluids. Desalination 2002, 149 (1), 191-197.2002 (38) Belkacem, M.; Matamoros, H.; Cabassud, C.; Aurelle, Y.; Cotteret, J., New results in metal working wastewater treatment using membrane technology. Journal of Membrane Science 1995, 106 (3), 195-205.1995 (39) Janknecht, P.; Lopes, A. D.; Mendes, A. M., Removal of industrial cutting oil from oil emulsions by polymeric ultra-and microfiltration membranes. Environmental science & technology 2004, 38 (18), 4878-4883.2004 (40) Lin, S. H.; Lan, W. J., Treatment of waste oil/water emulsion by ultrafiltration and ion exchange. Water research 1998, 32 (9), 2680-2688.1998 (41) Benito, J.; Ebel, S.; Gutierrez, B.; Pazos, C.; Coca, J., Ultrafiltration of a waste emulsified cutting oil using organic membranes. Water, Air, & Soil Pollution 2001, 128 (1), 181-195.2001 (42) Hesampour, M.; Krzyzaniak, A.; Nyström, M., Treatment of waste water from metal working by ultrafiltration, considering the effects of operating conditions. Desalination 2008, 222 (1), 212-221.2008 (43) Hesampour, M.; Krzyzaniak, A.; Nyström, M., The influence of different factors on the stability and ultrafiltration of emulsified oil in water. Journal of Membrane Science 2008, 325 (1), 199-208.2008 (44) Benito, J.; Cambiella, A.; Lobo, A.; Gutierrez, G.; Coca, J.; Pazos, C., Formulation, characterization and treatment of metalworking oil-in-water emulsions. Clean Technologies and Environmental Policy 2010, 12 (1), 31-41.2010 (45) Faibish, R. S.; Cohen, Y., Fouling and rejection behavior of ceramic and polymermodified ceramic membranes for ultrafiltration of oil-in-water emulsions and microemulsions. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2001, 191 (1), 27-40.2001 (46) Wang, P.; Xu, N.; Shi, J., A pilot study of the treatment of waste rolling emulsion using zirconia microfiltration membranes. Journal of Membrane Science 2000, 173 (2), 159-166.2000 (47) Yang, C.; Zhang, G.; Xu, N.; Shi, J., Preparation and application in oil–water separation of ZrO< sub> 2/α-Al< sub> 2 O< sub> 3 MF membrane. Journal of Membrane Science 1998, 142 (2), 235-243.1998


39


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 51

(48) Ousman, M.; Bennasar, M., Determination of various hydraulic resistances during cross-flow filtration of a starch grain suspension through inorganic membranes. Journal of Membrane Science 1995, 105 (1), 1-21.1995 (49) Abbasi, M.; Salahi, A.; Mirfendereski, M.; Mohammadi, T.; Rekabdar, F.; Hemmati, M., Oily wastewater treatment using mullite ceramic membrane. Desalination and Water Treatment 2012, 37 (1-3), 21-30.2012 (50) Burggraaf, A. J.; Cot, L. Fundamentals of inorganic membrane science and technology; Elsevier Science, 1996; Vol. 4. (51) Laitinen, N., Development of a ceramic membrane filtration equipment and its applicability for different wastewaters. Acta Universitatis Lappeenrantaensis 2001.2001 (52) Krstić, D. M.; Höflinger, W.; Koris, A. K.; Vatai, G. N., Energy-saving potential of cross-flow ultrafiltration with inserted static mixer: Application to an oil-in-water emulsion. Separation and purification technology 2007, 57 (1), 134-139.2007 (53) Cui, J.; Zhang, X.; Liu, H.; Liu, S.; Yeung, K. L., Preparation and application of zeolite/ceramic microfiltration membranes for treatment of oil contaminated water. Journal of Membrane Science 2008, 325 (1), 420-426.2008 (54) Bhave, R. R. Inorganic membranes: synthesis, characteristics, and applications; Van Nostrand Reinhold, 1991. (55) Panglisch, S. In Proceedings of AWWA Membrane Technology Conference: Memphis, Tennessee, 2009. (56) Mir, L.; Michaels, S.; Goel, V.; Kaiser, R., Crossflow microfiltration: applications, design and cost. Membrane Handbook. New York: Van Nostrand Reinhold 1992.1992 (57) Zhao, Y.; Tan, Y.; Wong, F. S.; Fane, A.; Xu, N., Formation of dynamic membranes for oily water separation by crossflow filtration. Separation and purification technology 2005, 44 (3), 212-220.2005 (58)

Peng, H., University of Ottawa, Canada, 2002.

(59) Lobo, A.; Cambiella, Á.; Benito, J. M.; Pazos, C.; Coca, J., Ultrafiltration of oilin-water emulsions with ceramic membranes: Influence of pH and crossflow velocity. Journal of Membrane Science 2006, 278 (1), 328-334.2006 (60) Zhao, Y.; Xing, W.; Xu, N.; Wong, F.-S., Effects of inorganic salt on ceramic membrane microfiltration of titanium dioxide suspension. Journal of Membrane Science 2005, 254 (1), 81-88.2005 (61) Nordin, A. K.; Jönsson, A. S., Flux decline along the flow channel in tubular ultrafiltration modules. Chemical Engineering Research and Design 2009, 87 (11), 15511561.2009


40

Page 41 of 51

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(62) Hua, F. L.; Tsang, Y. F.; Wang, Y. J.; Chan, S. Y.; Chua, H.; Sin, S. N., Performance study of ceramic microfiltration membrane for oily wastewater treatment. Chemical Engineering Journal 2007, 128 (2–3), 169-175.2007 (63) Lee, S.; Aurelle, Y.; Roques, H., Concentration polarization, membrane fouling and cleaning in ultrafiltration of soluble oil. Journal of Membrane Science 1984, 19 (1), 23-38.1984 (64) Mueller, J.; Cen, Y.; Davis, R. H., Crossflow microfiltration of oily water. Journal of Membrane Science 1997, 129 (2), 221-235.1997 (65) Arnot, T.; Field, R.; Koltuniewicz, A., Cross-flow and dead-end microfiltration of oily-water emulsions: Part II. Mechanisms and modelling of flux decline. Journal of Membrane Science 2000, 169 (1), 1-15.2000 (66) Fane, A.; Fell, C., A review of fouling and fouling control in ultrafiltration. Desalination 1987, 62, 117-136.1987 (67) Gutiérrez, G.; Lobo, A.; Benito, J. M.; Coca, J.; Pazos, C., Treatment of a waste oil-in-water emulsion from a copper-rolling process by ultrafiltration and vacuum evaporation. Journal of hazardous materials 2011, 185 (2), 1569-1574.2011 (68) Benito, J.; Rios, G.; Gutierrez, B.; Pazos, C.; Coca, J., Integrated process for the removal of emulsified oils from effluents in the steel industry. Separation science and technology 1999, 34 (15), 3031-3043.1999 (69) R os, G.; Pazos, C.; Coca, J., Destabilization of cutting oil emulsions using inorganic salts as coagulants. Colloids and Surfaces A: Physicochemical and Engineering Aspects 1998, 138 (2), 383-389.1998 (70) Tansel, B.; Regula, J.; Shalewitz, R., Treatment of fuel oil and crude oil contaminated waters by ultrafiltration membranes. Desalination 1995, 102 (1), 301311.1995 (71) Anderson, G.; Saw, C.; Le, M., Oil/water separation with surface modified membranes. Environmental Technology 1987, 8 (1-12), 121-132.1987 (72)

Howell, B. F.; Venkatachalam, R. S.; Wehrle, J. P.; Google Patents, 1994.

(73) Ulbricht, M.; Belfort, G., Surface modification of ultrafiltration membranes by low temperature plasma II. Graft polymerization onto polyacrylonitrile and polysulfone. Journal of Membrane Science 1996, 111 (2), 193-215.1996 (74) Pieracci, J.; Crivello, J. V.; Belfort, G., Increasing membrane permeability of UVmodified poly (ether sulfone) ultrafiltration membranes. Journal of Membrane Science 2002, 202 (1), 1-16.2002 (75) Nyström, M.; Järvinen, P., Modification of polysulfone ultrafiltration membranes with UV irradiation and hydrophilicity increasing agents. Journal of Membrane Science 1987, 60 (2), 275-296.1987


41


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 51

(76) Reddy, A. V. R.; Mohan, D. J.; Bhattacharya, A.; Shah, V. J.; Ghosh, P. K., Surface modification of ultrafiltration membranes by preadsorption of a negatively charged polymer: I. Permeation of water soluble polymers and inorganic salt solutions and fouling resistance properties. Journal of Membrane Science 2003, 214 (2), 211221.2003 (77) Su, C.; Xu, Y.; Zhang, W.; Liu, Y.; Li, J., Porous ceramic membrane with superhydrophobic and superoleophilic surface for reclaiming oil from oily water. Applied Surface Science 2011.2011 (78) McCloskey, B. D.; Park, H. B.; Ju, H.; Rowe, B. W.; Miller, D. J.; Freeman, B. D., A bioinspired fouling-resistant surface modification for water purification membranes. Journal of Membrane Science 2012.2012 (79) Ju, H.; McCloskey, B. D.; Sagle, A. C.; Wu, Y. H.; Kusuma, V. A.; Freeman, B. D., Crosslinked poly (ethylene oxide) fouling resistant coating materials for oil/water separation. Journal of Membrane Science 2008, 307 (2), 260-267.2008 (80) Li, H. J.; Cao, Y. M.; Qin, J. J.; Jie, X. M.; Wang, T. H.; Liu, J. H.; Yuan, Q., Development and characterization of anti-fouling cellulose hollow fiber UF membranes for oil–water separation. Journal of Membrane Science 2006, 279 (1), 328-335.2006 (81) Asatekin, A.; Mayes, A. M., Oil industry wastewater treatment with fouling resistant membranes containing amphiphilic comb copolymers. Environmental science & technology 2009, 43 (12), 4487-4492.2009 (82) Castro, R. P.; Cohen, Y.; Monbouquette, H. G., Silica-suported polyvinylpyrrolidone filtration membranes. Journal of Membrane Science 1996, 115 (2), 179-190.1996 (83) Hamza, A.; Pham, V.; Matsuura, T.; Santerre, J., Development of membranes with low surface energy to reduce the fouling in ultrafiltration applications. Journal of Membrane Science 1997, 131 (1), 217-227.1997 (84) Faibish, R. S.; Cohen, Y., Fouling-resistant ceramic-supported polymer membranes for ultrafiltration of oil-in-water microemulsions. Journal of Membrane Science 2001, 185 (2), 129-143.2001 (85) Chen, W.; Peng, J.; Su, Y.; Zheng, L.; Wang, L.; Jiang, Z., Separation of oil/water emulsion using Pluronic F127 modified polyethersulfone ultrafiltration membranes. Separation and purification technology 2009, 66 (3), 591-597.2009 (86) Srijaroonrat, P.; Julien, E.; Aurelle, Y., Unstable secondary oil/water emulsion treatment using ultrafiltration: fouling control by backflushing. Journal of Membrane Science 1999, 159 (1), 11-20.1999 (87) Cakl, J.; Bauer, I.; Doleček, P.; Mikulášek, P., Effects of backflushing conditions on permeate flux in membrane crossflow microfiltration of oil emulsion. Desalination 2000, 127 (2), 189-198.2000


42

Page 43 of 51

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(88) Lee, S. H.; Chung, K. C.; Shin, M. C.; Dong, J. I.; Lee, H. S.; Auh, K. H., Preparation of ceramic membrane and application to the crossflow microfiltration of soluble waste oil. Materials Letters 2002, 52 (4), 266-271.2002 (89) Gupta, B.; Blanpain, P.; Jaffrin, M., Permeate flux enhancement by pressure and flow pulsations in microfiltration with mineral membranes. Journal of Membrane Science 1992, 70 (2), 257-266.1992 (90) Jaffrin, M.; Gupta, B.; Paullier, P., Energy saving pulsatile mode cross flow filtration. Journal of Membrane Science 1994, 86 (3), 281-290.1994 (91) Jones, W. F.; Valentine, R. L.; Rodgers, V., Removal of suspended clay from water using transmembrane pressure pulsed microfiltration. Journal of Membrane Science 1999, 157 (2), 199-210.1999 (92) Mercier-Bonin, M.; Lagane, C.; Fonade, C., Influence of a gas/liquid two-phase flow on the ultrafiltration and microfiltration performances: case of a ceramic flat sheet membrane. Journal of Membrane Science 2000, 180 (1), 93-102.2000 (93) Cheng, T. W.; Yeh, H. M.; Wu, J. H., Effects of gas slugs and inclination angle on the ultrafiltration flux in tubular membrane module. Journal of Membrane Science 1999, 158 (1), 223-234.1999 (94) Viadero Jr, R. C.; Vaughan Jr, R. L.; Reed, B. E., Study of series resistances in high-shear rotary ultrafiltration. Journal of Membrane Science 1999, 162 (1), 199211.1999 (95) Chai, X.; Kobayashi, T.; Fujii, N., Ultrasound effect on cross-flow filtration of polyacrylonitrile ultrafiltration membranes. Journal of Membrane Science 1998, 148 (1), 129-135.1998 (96) Huotari, H. M.; Huisman, I. H.; Trägårdh, G., Electrically enhanced crossflow membrane filtration of oily waste water using the membrane as a cathode. Journal of Membrane Science 1999, 156 (1), 49-60.1999 (97) Broussous, L.; Prouzet, E.; Beque, L.; Larbot, A., An experimental study of helically stamped ceramic microfiltration membranes using bentonite suspensions. Separation and purification technology 2001, 24 (1), 205-221.2001 (98) Um, M. J.; Yoon, S. H.; Lee, C. H.; Chung, K. Y.; Kim, J. J., Flux enhancement with gas injection in crossflow ultrafiltration of oily wastewater. Water research 2001, 35 (17), 4095-4101.2001 (99) Lopez, R. V.; Elmaleh, S.; Ghaffor, N., Cross-flow ultrafiltration of hydrocarbon emulsions. Journal of Membrane Science 1995, 102, 55-64.1995 (100) Lindau, J.; Jönsson, A., Cleaning of ultrafiltration membranes after treatment of oily waste water. Journal of Membrane Science 1994, 87 (1), 71-78.1994


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(101) Goldsmith, R. L.; Roberts, D. A.; Burre, D. L., Ultrafiltration of soluble oil wastes. Journal (Water Pollution Control Federation) 1974, 2183-2192.1974 (102) Gryta, M.; Karakulski, K.; Morawski, A., Purification of oily wastewater by hybrid UF/MD. Water research 2001, 35 (15), 3665-3669.2001 (103) Reed, B. E.; Lin, W.; Dunn, C.; Carriere, P.; Roark, G., Treatment of an oil/grease wastewater using ultrafiltration: pilot-scale results. Separation science and technology 1997, 32 (9), 1493-1511.1997


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Recent Developments in Membrane Treatment of Spent Cutting-Oils

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