Utilization of fly ashes from the coal burning processes to produce

Subscriber access provided by UNIV OF NEWCASTLE

Article

Utilization of fly ashes from the coal burning processes to produce effective low- cost sorbents Agnieszka Adamczuk, and Dorota Ko#ody#ska Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02921 • Publication Date (Web): 03 Jan 2017 Downloaded from http://pubs.acs.org on January 7, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

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

Energy & Fuels

UTILIZATION OF FLY ASHES FROM THE COAL BURNING PROCESSES TO PRODUCE EFFECTIVE LOW- COST SORBENTS

Agnieszka Adamczuk and Dorota Kołodyńska* Department of Inorganic Chemistry, Faculty of Chemistry, Maria Curie Skłodowska University, Maria Curie Skłodowska Sq. 2, 20-031 Lublin, Poland

Abstract The paper presents a novel method to produce sorbents from fly ash (FAI) based on modification by chitosan for zinc(II) removal from aqueous solutions. It also describes a study of the effectiveness of Zn(II) sorption onto the sorbents prepared from FA by thermal activation (from FAI-373 to FAI-1173) as well as by thermal activation and chemical modification using chitosan (from FAICS-373 to FAICS-1173). Serial batch kinetics and static tests were conducted in order to investigate the effects of some important parameters such as the initial concentration, the phase contact time, the pH value of the solution, the obtained sorbent amount as well as the temperature. The kinetic process was described using the pseudo first order (PFO), pseudo second order (PSO) and intraparticle diffusion (IPD) models. The experimental data were analyzed using the Langmuir, Freundlich and Temkin isotherm models in order to study adsorption mechanisms. The correlation coefficient values show that for the FAICS the sorption process can be well defined by the Langmuir isotherm model, while for the FAI sorbent by the Freundlich isotherm one. The maximum adsorption capacities were equal to 21.41 mg/g for FAI and 29.59 mg/g for FAICS-773. The results showed higher efficiency of Zn(II) removal onto FAI modified by temperature and CS compared with FAI. In addition, the determined thermodynamic parameters (such as entropy, enthalpy and free energy of the process) indicate that the process was spontaneous, favourable and endothermic in 1

ACS Paragon Plus Environment

Energy & Fuels

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

nature. The kinetic data were well fitted by the pseudo second kinetic model. On the basis of the present study it can be concluded that production of sorbents by modification of fly ash using chitosan (CS) could become an effective and low-cost technology for Zn(II) ions removal from aqueous solution.

Keywords: fly ash, zinc, adsorption, chitosan, hybrid materials, low-cost, modification

*

Corresponding author: Tel.: +48 81 5375770; Fax:+48 81 5333348

E-mail address: [email protected] (D. Kołodyńska)

1. Introduction Despite greater and greater popularity of technology to obtain energy from renewable sources, burning of conventional fuels is still its main source. Fly ashes (FAs) are one of the products formed in the coal burning process. Some attempts of multidirectional economic applications of these wastes have been made for many years. Their enormous amounts are produced, among others, by thermal-electric power stations and electric power stations, in production of cement and concrete [1-3], in ceramic industry [4] as well as highway engineering [3], agriculture [5-7] and underground mining [8]. Modification: Literature reports that FA is an efficient adsorbent for heavy metal removal [9-11] and for removal of such contaminants as: phosphates [12], fluorides [13], pesticides [14], phenols [15], humic acids [16], dyes [17] as well as to CO2 sequestration [18]. It can be also used for zeolites synthesis [19,20] and as a resource for rare earth elements [21]. Rare earth elements (REEs) are critical and strategic materials in the defense, energy, electronics, and automotive industries. The recovery of REEs from coal combustion fly ash has been proposed as a way to supplement REE mining [22, 23]. 2


Page 2 of 31

Page 3 of 31

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

Energy & Fuels

However, their application for rendering various types of sewages harmless is still insufficient. FA can be physically and chemically modified which can result in changes of specific surface area size, pore size and structure as well as in surface groups structure [24]. One of the physical methods of FA modification is thermal one which causes changes in surface morphology and mineral composition of FA, which, in turn, affects sorption capacity towards heavy metal ions [25, 26]. It was found that activation temperature causes the increase in SiO2, Al2O3, Fe2O3 contents and the decrease in MgO, CaO, TiO2, Na2O and K2O contents. There is also observed the formation on various crystalline phases such as quartz, mullite and hematite which increase FA crystallinity [26]. FA can be also activated by organic and inorganic compounds of various compositions and concentrations. Xu et al. [27] studied FA modification using H2SO4 then their application for phosphate(V) removal from aqueous solutions. FA specific surface area increased four times after modification which increased their sorption capability compared to that of phosphate(V). Shawabkeh et al. [28] used H2SO4 combined with HNO3 for modification of FA specific surface area. The observed increase of specific surface area was from 7.53 to 157.76 m2/g. The changes in the specific surface area and pores structure after FA modification were also described by Sarbak and KramerWachowiak [24]. NaOH, NaOH combined with NH4HCO3, EDTA (ethylenediaminetetraacetic acid) and HCl were applied in modification. The largest increase of specific surface area was observed with the use of HCl but the largest increase of pores volume using EDTA.

Penilla et al. [29] carried out studies on zeolites synthesis due to FA

modification using NaOH and high temperature. Almost twofold increase in the specific surface area was observed. The studies on FA modification using NaOH were also described in [30]. The studies of mineral composition of the obtained sorbent showed that due to modification there were formed new crystalline phases-hydroxysodalite, zeolite Pc and zeolite Na-A [31]. The studies carried out by Yaumi et al. [32] proved that due to 3


Energy & Fuels

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

modification using NH4OH the diameter and pores volume also increased and the sorbents prepared in this way can be applied for selective sorption of CO2 from CO2/N2 mixture. Modification of fly ash can be also made using polymers [33]. There are only few papers describing application of the biodegradable polymer chitosan for modification of fly ash [34, 35]. Wen et al. [34] studied the process of Cr(VI) ions removal from aqueous solution by means of modified FA. Before the modification with chitosan, FA was activated using H2SO4 at 303 K. It was found that sorption capacity for Cr(VI) ions is larger in the case of composite than chitosan and increases with the increasing temperature. Application of FA combined with CS as an effective sorbent for removal of dyes was described by Chen and Sun [36]. FA activation before modification with CS was conducted at 573 K. It was proved that pH as well as chitosan and FA ratio have greatest effect on dyes removal from wastewaters. There are also some examples of zeolites modification with chitosan and their further application for removal of contaminants from waters and wastewaters. The research results obtained by Xie et al. [37] confirmed that the zeolitization process increased the specific surface area BET almost a hundred times compared to that of fly ash used for its preparation. After modification an increase in sorption capacity of zeolites for phosphates(V) as well as humic acids was observed. It was found that negative charge of zeolite pores interior, the presence of CaO, Al2O3 and Fe2O3 in the fractions which did not undergo zeolitization as well as chitosan monolayer on the zeolite surface are responsible for retention of phosphates(V) and organic humic acids. Ngah et al. [38] prepared the CS-zeolite and CS–zeolite combined with epichlorohydrin as well as CS-zeolite with tripolyphosphate(V) to study Cu(II) ions removal efficiency. Of the above mentioned materials, zeolite modified with only chitosan was characterized by the largest specific surface area. Zinc is microelement necessary not only for life of humans and animals but also of all living organisms. It lack makes proper development and functioning impossible. Demand 4


Page 4 of 31

Page 5 of 31

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

Energy & Fuels

of organism of zinc is rather small (less than 100 mg per day). However, its excess results in toxicity in the organism, disturbing metabolism and absorption of other important elements such as copper or iron. Therefore it is essential not to introduce its large amounts into the environment as it can take place in the case of waters and wastewaters. The objective of this work was to find out if production of sorbents by modification of FA using CS could become an effective and low-cost technology for Zn(II) ions removal from aqueous solution. The influence of parameters such as initial concentration, pH, contact time, temperature and adsorbent dosage was examined to optimize the sorption. The kinetic and isotherm studies of Zn(II) sorption onto the obtained sorbent were carried out.

2. Experimental section Materials and chemicals Chitosan powder (denoted as CS) (degree of deacetylation 76%, molecular mass 3.52×105 kDa, viscosity 261 cP) was purchased from Sigma-Aldrich. The coal fly ash (denoted as FAI) was collected from the Heat and Power Generating Plant Kozienice, Poland. Following ASTM [39], FAI can be classified as class F because it contents of SiO2, Fe2O3 and Al2O3 is more than 70% and content of CaO is less than 10%. The zinc solution was prepared by dissolving ZnCl2 in deionized water. The solution pH was adjusted to a given value (pH=2.0) by adding either 0.1 M H2SO4 (to avoid CS dissolution) and 0.1 M NaOH. All the chemicals used in this research were purchased from POCH (Poland) and were analytical grade. Preparation of FAI and FAICS sorbents FAI was prepared by the thermal activation method in a muffle furnace at 373, 773, 973, 1173 K for 1h and sieved. The obtained samples were denoted as FAI-373, FAI-773, FAI-973, FAI-1173. Powder of CS (without further pretreatment) was initially dissolved in 5


Energy & Fuels

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

aqueous solution of acetic acid (under stirring until completely dissolved at 1000 rpm for 24 h at room temperature). The activated by temperature FAI was added to the CS solution (the ratios of FAI to CS was 4:1). In the next step pH of the mixture was adjusted to 9. After this procedure the suspension was kept under stirring for 30 min and next it was filtered and washed by using distilled water until pH of supernatant was 7. Finally sorbents (abbreviated as FAICS-373, FAICS-773, FAICS-973, FAICS-1173) were obtained by drying the solid for 48 h in an oven at 323 K and next were sieved. It should be mentioned that fly ash as a waste is available free of cost. Production of proposed sorbents is the sum of cost terms representing: fly ash transportation (depending on the distance transportation), electricity usage of magnetic stirrer and a muffle furnace (depending on the activation temperature), cost of chemicals (acetic acid and small amount of NaOH for pH adjustment) – all of these costs are low and almost negligible. In the case of FAICS there is additional cost of chitosan (10-20 $/kg), hence the production expenditure of 1 kg of FAICS is mainly cost of chitosan which is equal about 2-4 $. What is more, using fly ash makes savings due to fly ash utilization (cost of 1 ton of fly ash storage in Poland in 2015 was approximately 30 $). As it can be seen the cost of preparation of both FAI and FAICS sorbents is low, hence these materials can be classified as low-cost sorbents. Methods of investigation of fly ash For determination of specific surface area, pores size and their volume, the nitrogen sorption/desorption method was used. To achieve the aim ASAP 2040 (Micromeritics) analyzer was applied. Scanning electron microscopy images of chitosan, FA and composite were obtained using Quanta 3D FEG microscope (FEI). The structural properties of the studied materials were characterized using the nitrogen adsorption/desorption isotherms measured at 77 K. Before the measurements the samples were degassed. The specific surface area was determined based on the linear 6


Page 6 of 31

Page 7 of 31

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

Energy & Fuels

form of the BET equation in the area of relative pressures at the p/p0 value between 0.05 and 0.2. The pore volume (Vp) was determined from that of adsorbed N2 at the pressure p/p0 0.98. Pore diameters (Dp), assuming their cylindrical shape, were calculated according to the Eq.1: Dp =

4Vp

(1)

SBET

where: SBET is the BET surface area, Vp is the pore volume. X-ray diffraction method (XRD) was obtained using the X-ray diffractometry PANalytical (Empyrean, Netherlands). Methods of sorption experiments The kinetic sorption study was conducted by contacting 20 cm3 of the zinc solution (pH =2,0) with 0.2 g of FAICS (temperature 293 K, shaking speed 180) and mixture was shaken using the laboratory shaker type 357 (Elpin Plus). In the next step the suspension was filtered and the concentration of Zn(II) in the filtrate was determined. FAICS sorption capacity was calculated taking into account the variation of the zinc concentration (1×10-3 M - 3×10-3 M) and fixed time of shaking (1, 3, 5, 10, 15, 20, 60, 120, 180 min.). The pH was measured using a pH meter (Elmetron). The concentrations of Zn(II) ions were measured with the AAS spectrometer SpectrAA-FS 240 (Varian). Equilibrium studies were also carried out by mixing 0.2g of sorbent with 20 cm3 zinc solution and shaken, but the concentration of Zn(II) was 1×10-3 M–2.5×10-2 M. After shaking the solution was filtered and the filtrate was analyzed to determine the concentration of Zn(II) as previously. In this case FAICS sorption capacity was calculated taking into account the variation of temperature (293, 313, 333 K). Adsorbent dosage dependency studies were conducted by shaking 20 cm3 of Zn (II) solution (concentrations 1×10-3 M–3×10-3 M) with fixed dosages of adsorbent (0.05-0.3 g) for 180 min. The shaking speed was kept at 180 rpm and the temperature at 293 K as

7


Energy & Fuels

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 8 of 31

previously. Finally after filtering of the suspensions the concentration of zinc ions was determined. The Zn(II) removal efficiency was calculated using Eq.2: S% =

( c0 - c e ) ×100% c0

(2)

The equilibrium adsorption capacity of FAICS qe (mg/g) was calculated using Eq.2: q e = ( c0 - c e ) ×

V m

(3)

The Zn(II) sorption capacity for FAICS at any time t, qt (mg/g) was calculated using Eq.4: q t = ( c0 - ct ) ×

V m

(4)

where: c0 is the initial concentration of Zn(II) ion in the aqueous phase (mg/dm3); ct is the concentration of Zn(II) ion in the aqueous phase at time t (mg/dm3); ce is the concentration of metal ion in the aqueous phase at equilibrium (mg/dm3); V is the volume of the solution (dm3); m is the mass of the sorbent (g).

Results and discussion Characteristic of tested materials Application of chitosan as a modifier for preparation of novel sorbents based on zeolite is justified not only by the economical aspect connected with reduction of production costs of mineral sorbents rich in donor nitrogen atoms and accessibility of chitin and chitosan (their resource are renewable owing to growth crustaceans) but also due to proecological aspect. Utilization of large amounts of wastes is vital form the environmental protection point of view. Physicochemical properties of FAI (chemical and mineral composition) and CS (chemical composition, deacetylation degree, molecular mass etc.) were presented in the our previous paper [40]. To acquire better understanding of sorption 8


Page 9 of 31

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

Energy & Fuels

process crystallographic structures of FAI, specific surface area and average pore diameter of FAI, FAI-373, FAI-773, FAI-973, FAI-1173, FAICS-373, FAICS-373, FAICS773, FAICS-973, FAICS-1173 were analyzed in [41]. Analyzing of the nitrogen adsorption/desorption isotherms and pore decomposition functions (Fig.1) it can be stated that the studied FAI are characterized by differential specific surface area, pore shape and volume. The isotherm shape in the area of the relative average pressures with the well-formed hysteresis loop confirms the presence of mesopores in the structure. Isotherms such as these can be classified as type IV (hysteresis loop is associated with capillary condensation taking place in mesopores and the limiting uptake over a range of high p/p0, however, its initial part is connected with the monolayer-multilayer adsorption) according to the IUPAC recommendations. Type IV isotherms are given by many mesoporous industrial adsorbents and are generally associated with mesoporous materials (pore diameters between 1.7 and 50 nm) [42, 43]. It is well known that the shape of the hysteresis loop reflects that of the pore structure. The hysteresis loops of samples FAI are similar to the hysteresis loop type H3 which is connected with the parallel-plate shaped pores (Fig.1). However, the hysteresis loops of samples FAI-373-1173 (type H2) are connected with the ink-bottle shaped ones. As for the surface area and pore volume these two parameters are together correlated. The difference in the width between the adsorption and desorption branches indicates the presence of the ink-bottle pores with large chambers connected with narrow transport pores. Increase in adsorption after exceeding the relative pressure 0.4 p/p0 indicates the homogeneous structure of pores which is also evidenced by narrow functions of pore size distribution. FAI-373-1173 were characterized by decreasing with temperature specific surface area and pore volume (Table 1). Comparing the total pore and mesopore volume it can be stated that mainly mesopores constitute porosity only in the case of FAI. The sizes of the exterior surface are small. The pore diameters change in the range 2.4-14.0 nm. 9


Energy & Fuels

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

The surface morphology of the obtained sorbents was investigated. It can be seen from the SEM images (Figs.2a-d) that FAI and FAICS-373-1173 particles are compact and globular of different sizes and some shapeless fragments of unburnt carbon with small pores. However, spherical particles are have smooth boundary with no pores onto external surface. There are also some smaller particles adhered to larger ones. Typical chemical composition of Class F fly ash was presented in [40]. The mineral composition of FAI was determined by means of powder X-ray diffraction (XRD) using a Philips X’pert APD diffractometer. The analysis of mineral phases of FAI, temperature modified FAI and FAICS samples shows the presence of mullite, quartz, hematite, lime, brookite and rutile. At higher temperatures contents of mullite rises with the increasing temperature. Modification by using CS also caused increase of mullite content, however, decrease of quartz and hematite well as elimination of lime and rutile/brookite without formation of different crystalline phases [44].

Influence of adsorbent dosage It is clear that removal of heavy metal ions is dependent on the adsorbent dosage. The adsorption percentage (%S) for the FAI-Zn(II) system was in the range 2.7-24.3 %, 2.7-13.7 % and 2.9-12.5 % for 1x10-3, 2x10-3, 3x10-3 M concentration, respectively. %S for Zn(II) ions adsorbed onto FAICS-373 were higher than for the FAI samples and equal to 13.5-83.6 %, 5.85-81.8 %, 11.7-84.9 % in the concentration range 1x10-3 M–3x10-3 M, respectively (data not presented) which indicated great improvement. The results shows the best adsorption of Zn(II) when amount of sorbent was equal to 0.3 g. It could be seen that %S for Zn(II) ions increases with the adsorbent mass increasing for all investigated sorbents. This is evident from the fact that with increasing of adsorbent mass the adsorption surface area increases and more active adsorption sites are available [45].

Influence of contact time and initial concentration

10


Page 10 of 31

Page 11 of 31

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

Energy & Fuels

The influence of contact time and initial concentration was investigated as those of the most important factors affecting the adsorption efficiency. The dependence of the phase contact time on sorption effectiveness of Zn(II) ions is shown in Figs.3a-e and 4a-d. The obtained results of the influence of the initial concentration of Zn(II) (1x10-3 M–3x10-3 M) and the phase contact time (1-180 min.) of the solution-sorbent system make it to possible to observe the increase of qt values with the increasing contact time for the FAI samples, while for the FAICS sorbents the increase of the phase contact time does not result in increase of Zn(II) removal from aqueous solutions (%S values are almost stable). This is consistent with the results obtained by Pehlivan et al. [46]. Very rapid sorption can be observed during first few minutes for adsorption using FAICS, while that onto FAI increases not so rapidly during the first 30 min. The adsorption equilibrium was reached rapidly and took less than 20 min. onto FAICS, while for FAI the this contact time was longer (60 min.). The similar results of equilibrium achieved in time less than 20 min. were observed for adsorption of the same initial concentration of Zn(II) onto the same dosage of chitosan (data not presented). What is more it was found that there is no significant influence of initial concentration on equilibrium time.

Kinetic models The most popular kinetic models were selected to analyze the adsorption dynamics and investigate the adsorption mechanism. The kinetic parameters for the adsorption process onto all studied sorbents were determined using the following kinetic equation the pseudo first order model expressed as Eq.5 [46]: log( q1 - qt ) = log q1 -

k1t 2.303

(5)

where: q1 and qt denote the amount of sorption at equilibrium and at time t (mg/g) respectively; k1 is the rate constant of the pseudo first order sorption (1/min). Based on the plot of log (q1-qt) vs. t the kinetic parameters were calculated..

11


Energy & Fuels

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 12 of 31

The second, was the pseudo second order model whose linear form is presented as Eq.6 [47]:

t t 1 = + qt q2 k2 q22

(6)

where: k2 is the rate constant of the pseudo second order sorption (g/mg min). The kinetic parameters were calculated based on the plots of t/qt vs. t. Weber-Morris kinetic equation also known as the intraparticle diffusion model (IPD) [48, 49] given below Eq.7:

qt = ki t1/ 2 + C

(7)

where: ki is the intraparticle diffusion rate constant (mg/g min0.5), C is the intercept which reflects the boundary layer effect. The intraparticle diffusion kinetic model is the mathematical relationship between the concentration of adsorbed ions onto the solid surface. Asfour et al. [50] report the first straight section presents the macropore diffusion and the second one presents the micropore diffusion. The studies of fitting experimental data for the investigated Zn(II)-sorbent system based on the relation log(q1-qt) vs. t for the pseudo first order model, t/qt vs. t for the pseudo second order model and qt vs. t1/2 from the equation of the intraparticle diffusion are presented in Table 2. The values of rate constant k1 are in the range 0.01-1.60 for all studied systems. However, in most cases the rate constant of the pseudo second order sorption k2 decreases and the initial sorption rate h increases when the initial concentration increases for sorption onto all studied sorbents. The values of q2 calculated from the pseudo second order model were higher than those of q1 calculated from the pseudo first order model and they were in good agreement with those obtained from experiment. It should be also mentioned that q2 values increase with the increasing activation temperature for fly ash sorbents, while for the FAICS sorbents no significant difference in q2 values is observed. 12


Page 13 of 31

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

Energy & Fuels

As follows from the obtained results the intraparticle diffusion rate constant ki increases with the increasing initial concentration of Zn(II) ions. It means that the concentration of Zn(II) ions had a strong influence on adsorption diffusion kinetics. Summing up the results of kinetic studies, it can be concluded that the pseudo second order kinetic model describes better the experimental data for all studied systems, which is confirmed by high values of determination coefficient R2 (1.000). Similar results were reported by Li et al. [51] and Papandreou [52].

Thermodynamic studies Temperature is another important parameter influencing sorption effectiveness. Thermodynamic parameters have to be estimated in order to evaluate nature of the adsorption process for example it is spontaneous or not. The value of ∆Go was calculated using Eq.8 [53]: (8)

∆G o = -RT ln K c

where: R is the gas constant (8.314 J/mol K), T is the temperature (K) and KC is the equilibrium constant evaluated by the equation: Kc =

ca ce

(9)

where: ca (mg/dm3) is the amount of solute adsorbed by the adsorbent at equilibrium and ce is the equilibrium concentration (mg/dm3). For Zn(II)-sorbents systems, lnKc was plotted against 1/T. Using these plots entropy change (∆So) and enthalpy change (∆Ho) were calculated. The thermodynamic parameters summarized in Table 3 indicate that for all studied systems the Zn(II)-sorbent process was spontaneous and favourable in nature as confirmed by the negative values of ∆Go (in the range from -10.65 to -6.31 kJ/mol). The obtained results showed positive values of enthalpy ∆Ho (in the range 0.86-3.35 kJ/mol) which indicates that the process was endothermic. Weng at al. [54] also reported the negative values of ∆Go and positive ∆H° for Zn(II) adsorption onto fly ash. 13


Energy & Fuels

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 14 of 31

The values of ∆Ho in the range 2.1-20.9 kJ/mol point out that the process is physical adsorption [55], hence it can be concluded that Zn(II) removal of onto FAI, FAI-973, FAI1173,FAICS-773, FAICS-1173 proceeds according to physical adsorption mechanism. It is worth mentioning that for the other studied sorbents the value of ∆Ho was very close to 2.1 kJ/mol. The negative values of ∆Go higher than -20 kJ/mol also confirm that for all studied systems the process was predominated by physical adsorption [56]. Increase of ∆Go when the temperature increases from 293 to 333 K can be also observed. The negative values of ∆So indicate a decrease in randomness at the solid/liquid interface during Zn(II) sorption onto all studied sorbents. Similar results were also observed by other researchers [57]. It can be found that adsorption capacity increases with the increasing temperature for both Zn(II)-FAI and Zn(II)-FAICS systems. The literature reports that this kind of behaviour takes place when the adsorption process is controlled by the intraparticle transport-pore diffusion process [56]. To sum up the thermodynamic considerations, it can be concluded that the process is spontaneous, favourable and endothermic in nature as indicated by the determined thermodynamic parameters (such as enthalpy, entropy and free energy of process).

Isotherm models In this study three two-parameter isotherm models: Langmuir, Freundlich and Temkin were also applied to describe adsorption, analyze experimental sorption equilibrium data and obtain some important information on the surface properties of the adsorbent and its affinity for the investigated metal ions. The Langmuir model assumes that uptake of metal ions occurs on a homogeneous surface by monolayer adsorption without any interaction between adsorbed ions [58]. This model has a linear expression as shown below: [59]: ce c 1 = + e qe q0 K L q0

(10)

The equilibrium parameter RL which is the essential characteristics of the Langmuir isotherm model [49] was calculated using Eq. 11[60]: 14


Page 15 of 31

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

Energy & Fuels

RL =

1 1 + K Lc0

(11)

where: c0 is the adsorbate initial concentration (mg/L). The Freundlich isotherm model is an empirical equation used for the description of multilayer adsorption with the interactions between the adsorbed molecules [61]. It can be expressed by the linear form described as follows [62]: log qe = log K F +

1 log c e n

(12)

where: q0 is the monolayer sorption capacity of chitosan (mg/g) and KL is a constant related to the free energy sorption (dm3/mg); KF (mg/g)(dm3/mg)1/n) and 1/n are the Freundlich constants, characteristic of the system and the indicators of adsorption capacity and reaction energy, respectively. The Temkin isotherm model is based on the assumption that decline of the heat of sorption as a function of temperature is linear. The model is given by the following equation [63]:

qe =

RT RT lnA+ ln ce b b

(13)

where: A (dm3/g) and B are the Temkin constants, A plot of qe vs. lnce enables the determination of the constants A and B. The constant B is related to the heat of adsorption and is expressed by the equation:

RT =B b

(14)

The adsorption isotherms of FAI-Zn(II) and FAICS-273-1137-Zn(II) systems at 293 K, 313 K and 333 K are shown in Figs.5a-e and 6a-d. The Langmuir and Freundlich constants were calculated from the intercept and the slope of the linear plot of: ce/qe vs. ce (q0 and KL) and logqe vs. logce (KF and 1/n), respectively. The isotherm constants KT and bT were evaluated from the plot of qe vs. lnce. The calculated parameters based on the Langmuir, 15


Energy & Fuels

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

Freundlich and Temkin adsorption models were listed in Table 4. As can be seen from Table 4 the calculated values of dimensionless factor RL are in the range 0-1 which indicates the favourable adsorption of Zn(II) onto all obtained sorbents. What is more, the values of 1/n are in the range 0.48-0.54 for FAICS-273-1137 and 0.07-1.25 for FAI. It can be seen that for Zn(II) sorption onto all sorbents (except FAI) 1/n values are in the range 0.1 < 1/n < 1. If value of 1/n is below 1 it means a normal adsorption, while value of 1/n above 1 indicates cooperative adsorption [64]. Zn(II) adsorption capacities for all studied sorbents increase with the increasing process temperature due to enlargement of pore size or activation of the adsorbent surface [65]. As follows from the values of correlation coefficient for Zn(II) adsorption onto FAICS-273-1137 the Langmuir isotherm model better fits the equilibrium data than the Freundlich isotherm model, while for FAI the experimental data fit well the Freundlich model. Good agreement of the experimental data to the linear equation of Langmuir isotherm model suggests that during Zn(II) sorption onto FAICS the monolayer of ions is created. The parameters obtained from the Temkin model (Table 4) represent poorer fit of experimental data. It can be seen that the values of KT are much larger for FAI than FAICS-373-1173. The Temkin constant, bT, related to heat of sorption is in the range 343.89-505.61 for the studied Zn(II)-sorbent systems.

Mechanism of sorption As was mentioned the main role of the added chitosan is to coat and bridge the fly ash particles and led to the formation of a more condensed network structure and thus enhances the mechanical behavior of the sorbent. It also provides the functional groups. On the other hand the activation process of fly ash by acids, such as nitric acid can provide of an oxygenation of the particle surface by the nitrate ions. Many studies have observed differences in the sorption mechanisms and/or metal species associated with chitosan under the experimental conditions such as pH, metal concentration and 16


Page 16 of 31

Page 17 of 31

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

Energy & Fuels

metal/ligand ratio. As follows form the literature data in the case of divalent ions, the capacity to sorb Zn(II) ions is higher than for Ca(II). This indicated that the coordination selectivity of chitosan was independent of cation size or ion hardness [66] and their coordination occurs by the the –OH and –NH2 groups.

Future application of the findings Economical and technical conditioning makes necessary to search for new materials whose properties will be suitable for a given application. On the other hand, the solutions beneficial for waste economy rationalization are search for of cheap materials whose sorption properties are favourable there are naturals zeolites, biochars, chitosan, alluminium and iron oxides, industrial wastes etc. [67]. Taking the above into consideration it is essential to apply fly ashes for production of synthetic zeolites or for example, fertilizer carries. Determination of sorption conditions based on the analysis of the parameters such as: pH, initial concentration, value of ionic strength, phase contact time, temperature and substances influencing effectiveness of sorption of such metal ions as: Cu(II), Zn(II), Mn(II) or Fe(II)/(III) is of significant importance from the technological point of view. It enables preparation of fertilizers macro- and microelement carries based on waste materials. The method presented in this work developed a novel low-cost sorbent for the removal of Zn(II) ions. The sorption techniques applying the obtained sorbent can be used inexpensively also for the treatment of other heavy metals ions such as Cu(II), As(V),Cr(III,VI), Cd(II)) which are present in both waters and many aqueous industrial effluents.

Conclusions 1) As follows from the research results adsorption capacity toward Zn(II) ions increased with the increase of contact time, sorbent dosage and initial concentration. For

17


Energy & Fuels

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 18 of 31

all studied Zn(II)-sorbent systems, the obtained results were well described by the pseudo second order model which is confirmed by high values of distribution coefficients. 2) For the FAICS-373-1173 sorbent the sorption process can be well defined by the Langmuir isotherm model, while for FAI the process can be well determined by the Freundlich isotherm model. The maximum adsorption capacity was equal to 21.41 mg/g for FAI and 29.59 mg/g for FAICS-773. The obtained results showed the highest efficiency of Zn(II) removal onto FAICS-273-1137 compared with FAI. 3) In accordance with obtained results it can be concluded that the process was spontaneous, favourable and endothermic in nature as proved by the positive value of ∆Ho and the negative value of ∆Go. 4) The investigations show that effectiveness of Zn(II) ions removal from aqueous solutions is better in the case of FAICS compared with FAI. 5) The use of FAICS sorbent for removal of Zn(II) from water and wastewater can solve the important environmental protection problems such as large amount of fly ash production and environmental contamination with heavy metal ions. The proposed method of producing a low-cost sorbent for Zn(II) removal can be readily applied. The findings suggest that this approach could also be useful for wastewaters.

Acknowledgements: We

acknowledge

the

financial

support

from

NCBiR

within

Project

GEKON

2/O2/266818/1/2015.

References: (1) Nawaz, A.; Julnipitawong, P.; Krammart, P.; Tangtermsirikul, S. Constr. Build. Mater.

2016, 102, 515-530. (2) Hamzaoui, R.; Bouchenafa, O.; Guessasma, S.; Leklou, N.; Bouaziz, A. Mater. Design

2016, 90, 29-37. (3) Arulrajah, A.; Mohammadinia, A.; Horpibulsuk, S.; Samingthong, W. Constr. Build. Mater., 2016, 127, 743-750. 18


Page 19 of 31

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

Energy & Fuels

(4) Baheti, V.; Militky, J.; Mishra, R.; Behera, B. K. Composites Part B 2016, 85, 268-276. (5) Nayak, A. K.; Raja, R.; Rao, K. S.; Shukla, A. K.; Mohanty, S.; Shahid, M.; Tripathi, R.; Panda, B. B.; Bhattacharyya, P.; Kumar, A.; Lal, B.; Sethi, S. K.; Puri, C.; Nayak, D.; Swain, C. K. Ecotoxicol. Environ. Safety 2015, 114, 257-262. (6) Matsi, T.; Keramidas, V. Z Environ. Pollut. 1999, 104, 107-112. (7) Basu, M.; Pande, M.; Bhadoria, P. B. S.; Mahapatra, S. C. Prog. Natural Sci. 2009, 19/10, 1173-1186. (8) Palarski, J.; Plewa, F.; Pierzyna, P. Górnictwo i Geoinżynieria 2005, 29, 129-137. (in Polish) (9) Fu, F.; Wang, Q. J. Environ. Managem. 2011, 92, 407-418. (10) Héquet, V.; Ricou, P.; Lecuyer, I.; Le Cloirec, P. Fuel 200, 80, 851-856. (11) Nascimento, M.; Sérgio P.; Soares M.; Paulo de Souza V. Fuel 2009, 88, 1714-1719. (12) Ragheb, S. M., HBNRC Journal 2013, 9, 270-275. (13) Mohapatra, M.; Anand, S.; Mishra B. K.; Giles, D. E.; Singh, P. Review of fluoride removal from drinking water J. Environ. Manage. 2009, 91, 67-77. (14) Singh, N. J. Hazard. Mater. 2009, 168, 233-237. (15) Chaudhary, N.; Balomajumder, Ch. J. Taiwan Instit. Chem. Eng. 2014, 45, 852-859. (16) An, Ch.; Yang, S.; Huang, G.; Zhao, Sh.; Zhang, P.; Yao, Y. Fuel 2016, 165, 264271. (17) Visa, M; Chelaru, A. M. App. Surface Sci. 2014, 303, 14-22. (18) Majchrzak-Kuceba, I.; Nowak, W. Thermochim. Acta 2005, 437, 67-74. (19) Derkowski, A.; Franus, W.; Beran E.; Czímerová A. Powder Technol. 2006, 166, 4754. (20) Bandura, L.; Franus, M.; Józefaciuk, G.; Franus, W. Fuel 2015, 147, 100-107. (21) Franus, W.; Wiatros-Motyka, M.M.; Wdowin, M. Environ. Sci. Pollut. Res. Int. 2015, 22, 9464-9474. (22) Taggart, R.K.; Hower, J.C.; Dwyer, G.S.; Hsu-Kim, H. Environ. Sci. Technol. 2016, 50, 5919−5926. (23) Kashiwakura, S.; Kumagai, Y.; Kubo, H.; Wagatsuma, K. Open J. Phys. Chem., 2013, 3, 69-75. (24) Sarbak, Z.; Kramer-Wachowiak, M. Powder Technol. 2002, 123, 53-58. (25) Mishra, S. B.; Langwenya, S. P.; Mamba, B. B.; Balakrishnan, M. Phys. Chem. Earth

2010, 35, 811-814. (26) Katara, S.; Kabra, S; Sharma, A; Hada, R.; Rani, A. Internat. Res. J. Pure App. Chem. 2013, 3/4, 299-307. 19


Energy & Fuels

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

(27) Xu, X.; Li, Q.; Cui, H.; Pang, J.; Sun, L.; An, H.; Zhai, J. Desalination 2011, 272, 233239. (28) Shawabkeh, R.; Khan, M.J.; Al-Juhani A. A.; Al-Abdul Wahhabb H.I.; Husseina I. A. App. Surface Sci. 2011, 258, 1643-1650. (29) Penilla P. R.; Bustos A. G.; Elizalde S. G.; Fuel 2006, 85, 823-832. (30) Hsu, T.Ch.; Yu, Ch. Ch.; Yeh, Ch. M. Fuel 2008, 87, 1355-1359. (31) Tanaka, H.; Miyagawa, A.; Eguchi, H.; Hino, R. Ind. Eng. Chem. Res. 2004 43 60906094. (32) Yaumi, A. L.; Hussien, I. A.; Shawabkeh, R. A. App. Surface Sci. 2013, 266, 118-125. (33) Cao, X. Y.; Yue Q. Y.; Song L. Y.; Li, M.; Zhao, Y. C. J. Hazard. Mater. 2007, 147, 133-138. (34) Wen, Y.; Tanga, Z.; Chen, Y.; Gu, Y.; Chem. Eng. J. 2011 175 110-116. (35) Lin, J.; Zhan, Y. Chem. Eng. J. 2012, 200-202, 202-213. (36) Chen, X.; Sun, H.; Chin. J. Oceanol. Limnol. 2009, 2, 875-881. (37) Xie, J.; Li, Ch.; Chi, L.; Wu, D. Fuel 2013, 103, 480-485. (38) Wan Ngah, W. S.; Teong, L. C.; Toh, R. H.; Hanafiah, M. A. K. M., Chem. Eng. J.

2013, 223, 231-238. (39) ASTM standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete (C618-05). In: Annual book of ASTM standards, concrete and aggregates, vol. 04.02. American Society for Testing Materials 2005. (40) Adamczuk, A; Kołodyńska, D. Chem. Eng. J. 2015, 274, 200-212. (41) Adamczuk, A; Kołodyńska, D. 2015 Fly ash coated chitosan as efficient adsorbent for removal of heavy metal ions from waters and wastewaters, Proceedings of International Conference "Industrial waste and wastewater treatment and valorization" 21-23 May, 2015, Athens, Greece. (42) Shirai, H; Ikeda, M.; Tanno, K. Energy Fuels 2011, 25, 5700-5706. (43) Du, X.; Wu, E. J. Phys. Chem. Solids, 2007, 68, 1692-1699. (44) Sing, K. S. W.; Everett, D. H.; Haul, R. A. W.; Moscou, L.; Pierotti, R. A.; Rouquérol, J., Siemieniewska, T. Pure Appl. Chem. 1985, 57, 603-619. (45) Kushwaha, J. P.; Srivastava, V. Ch.; Deo Mall, I. Bioresource Technol. 2010, 101, 3474-3483. (46) Pehlivan, E.; Cetin, S.; Yanik, B. H., J. Hazard. Mater. 2006, B 135, 193-199. (47) Lagergren, S. Kungliga Svenska Vetenskapsakademiens Handlingar 1898, 24, 1-39. (48) Ho, Y. S.; McKay, G. Chem. Eng. J. 1998, 70, 115-124. (49) Weber, W. J.; Morris, J. C.; Eng. Divis. Amer. Soc. Civil Eng. 1963, 89, 31-60. 20


Page 20 of 31

Page 21 of 31

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

Energy & Fuels

(50) Asfour, H. M.; Nassar, M. M., Fadali, O. A.; El-Geundi M. S. J. Chem. Technol. Biotechnol. 1985, 35, 28-35. (51) Li, H.; Bi, S.; Liu, L.; Dong, W.; Wang, X. Desalination 2011, 278, 397-404. (52) Papandreou, A. D.; Stournaras, C. J.; Panias, D. J. Hazard. Mater. 2007, 148, 538– 547 (53) Mahmouda, D.K.; Salleha, M.A.M.; Karima, W.A.W.A.; Idris, A.; Abidina Z.Z.; Chem. Eng. J., 2012, 181–182, 449-457. (54) Weng, Ch. H.; Huang, C. P. Colloids Surfaces A: Physicochem. Eng. Aspects 2004, 247, 137 -143. (55) Wang, S.; Wu, H. J. Hazard. Mater. 2006, 136 482-501. (56) Jaycock, M. J.; Parfitt, G. D. Chemistry of Interfaces; Ellis Horwood; Onichester, 1981; pp. 12-13. (57) Zubair, A.; Bhatti, N. N.; Hanif, M. A.; Shafqat, F. Water Air Soil Pollut. 2008, 191, 305-318. (58) Amuda, O. S.; Adelowo, F. E.; Ologunde, M. O. Kinetics and equilibrium studies of adsorption of chromium(VI) ion from industrial wastewater using Chrysophyllum albidum (Sapotaceae) seed shells Colloids Surfaces B: Biointerfaces, 2009, 68, 184-192. (59) Langmuir, I. J. Am. Chem. Soc. 1916, 38, 2221-2295. (60) Hall, K. R.; Eagleton, L. C.; Acrivos, A.; Vermeulen, T. Ind. Eng. Chem. Fundam.

1966, 5, 212-223. (61) Rangabhashiyam, S.;

Anu, N.; Nandagopal M. S. G.; Selvaraju, N., J. Environ.

Chem. Eng. 2014, 2, 398-414. (62) Nibou, D.; Khemaissia, S.; Amokrane, S.; Barkat, M.; Chegrouche, S.; Mellah, A. Chem. Eng. J. 2011, 172, 296-305. (63) Liu, X.; Zhang, L. Powder Technol. 2015, 277 112-119. (64) Mohan, S.; Karthikeyan, J.; Environ. Pollut. 1997, 97 183-187. (65) Dizge, N.; Aydiner, C.; Demirbas, E.; Kobya, M.; Kara, S. J. Hazard. Mater.

2008,150, 737-746. (66) Zhang, L.; Li, B.; Meng, X.; Huang, L.; Wang, D. Environ. Sci. Pollut. Res. 2015, 22, 15104–15112. (67) Franus, W.; Wdowin, M.; Franus, M., Environ. Monit. Assess. 2014, 186, 5721-5729.

21


Energy & Fuels

FAI sorption FAI desorption FAI-373 sorption FAI-373 desorption

1,4

3

Quantity adsorbed [cm /g STP]

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 22 of 31

1,2 1,0 0,8 0,6 0,4 0,2 0,0 0,0

0,2

0,4

0,6

0,8

1,0

Relative pressure [P/P0]

Fig.1. N2 adsorption–desorption isotherm of FAI and FAI-373.

22


Page 23 of 31

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

Energy & Fuels

(a)

(b)

(c)

(d)

Fig.2a-d. SEM images of a) FAI-373 K, b) FAI-1173 K and c) FAICS-373, d) FAICS-1173.

23


Energy & Fuels

(b)

2,5

2,5

2,0

2,0

1,5

1,5 qt [mg/g]

qt [mg/g]

(a)

FAI

1,0

-3 Zn(II) 1x10 M -3 Zn(II) 2x10 M -3 Zn(II) 3x10 M

0,5

0

20

40

60

80

100

120

140

160

180

1,0

FAI-973 -3 Zn(II) 1x10 M -3 Zn(II) 2x10 M -3 Zn(II) 3x10 M

0,5

0,0

0,0

200

0

20

40

60

80

t [min]

120

140

160

180

200

(d) 2,5

2,0

2,0

1,5

1,5 qt [mg/g]

2,5

FAI-773

1,0


0,5

20

40

60

80

100

120

140

160

180

1,0

FAI-973 -3 Zn(II) 1x10 M -3 Zn(II) 2x10 M -3 Zn(II) 3x10 M

0,5

0,0 0

100 t [min]

(c)

qt [mg/g]

0,0

200

0

20

40

60

80

t [min]

100

120

140

160

180

200

t [min]

(e) 2,5

2,0

1,5 qt [mg/g]

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 24 of 31

FAI-1173

1,0


0,5

0,0 0

20

40

60

80

100

120

140

160

180

200

t [min]

Fig.3a-e. Effect of contact time for the adsorption of Zn(II): a) FAI b) FAI-373, c) FAI-773, d) FAI-973, e) FAI-1173 (initial concentration 1x10-3-3x10-3 M, temperature 293 K, contact time 180 min, adsorbent dosage 0.2 g, shaking speed 180 rpm). 24


Page 25 of 31

(b)

10

10

8

8

6

6 qt [mg/g]

qt [mg/g]

(a)

FAICS-373

4


2

0

20

40

60

80

100

120

140

160

180

4

FAICS-773 -3 Zn(II) 1x10 M -3 Zn(II) 2x10 M -3 Zn(II) 3x10 M

2

0

0

200

0

20

40

60

80

t [min]

120

140

160

180

200

(d) 10

8

8

6

6 qt [mg/g]

10

FAICS-973

4


2

20

40

60

80

100

120

140

160

180

FAICS-1173

4


2

0 0

100 t [min]

(c)

qt [mg/g]

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

Energy & Fuels

0

200

0

20

40

t [min]

60

80

100

120

140

160

180

200

t [min]

Fig.4a-d. Effect of contact time for the adsorption of Zn(II): a) FAICS-373, b) FAICS-773, c) FAICS-973, d) FAICS-1173 (initial concentration 1x10-3-3x10-3 M, temperature 293 K, contact time 180 min, adsorbent dosage 0.2 g, shaking speed 180 rpm).

25


Energy & Fuels

(a)

(b)

30

30

FAI-Zn(II) 293 K 313 K 333 K

25

20 q [mg/g] e

q [mg/g] e

20

FAI-373-Zn(II) 293 K 313 K 333 K

25

15

15

10

10

5

5

0 0

200

400

600

800

1000 3 ce [mg/dm ]

1200

1400

0

1600

0

(c)

200

400

600

800 1000 3 ce [mg/dm ]

1200

1400

1600

600

800 1000 3 ce [mg/dm ]

1200

1400

1600

(d)

30

30

FAI-773-Zn(II) 293 K 313 K 333 K

25

20 q [mg/g] e

20

FAI-973-Zn(II) 293 K 313 K 333 K

25

q [mg/g] e

15

15

10

10

5

5

0

0 0

200

400

600

800

1000 3 ce [mg/dm ]

1200

1400

0

1600

200

400

(e) 30 FAI-373-Zn(II) 293 K 313 K 333 K

25 20 q [mg/g] e

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 26 of 31

15 10 5 0 0

200

400

600

800 1000 3 ce [mg/dm ]

1200

1400

1600

Fig.5a-e. The adsorption isotherms of Zn(II) onto: a) FAI, b) FAI-373, c) FAI-773, d) FAI973, e) FAI-1173 in temperature 293 K, 313 K, 333 K.

26


Page 27 of 31

(a)

(b) 30

30 FAICS-373-Zn(II) 293 K 313 K 333 K

25

q [mg/g] e

20

q [mg/g] e

20

FAICS-773-Zn(II) 293 K 313 K 333 K

25

15

15

10

10 5

5

0

0 0

200

400

600

800

1000 3 ce [mg/dm ]

1200

1400

1600

0

(c)

200

400

600

800 1000 3 ce [mg/dm ]

1200

1400

1600

600

800 1000 3 ce [mg/dm ]

1200

1400

1600

(d)

30

30 FAICS-973-Zn(II) 293 K 313 K 333 K

25

20 q [mg/g] e

20

FAICS-1173-Zn(II) 293 K 313 K 333 K

25

q [mg/g] e

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

Energy & Fuels

15

15 10

10

5

5

0

0 0

200

400

600

800

1000 3 ce [mg/dm ]

1200

1400

1600

0

200

400

Fig.6a-d. The adsorption isotherms of Zn(II) onto: a) FAICS-373, b) FAICS-773, c) FAICS973, d) FAICS-1173 in temperature 293 K, 313 K, 333 K.

27


Energy & Fuels

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 28 of 31

Table 1. BET surface area as a function of the activation temperature for FA, CS, FAI, FAI-373, FAI-773, FAI-973, FAI-1173 and FAICS-373, FAICS-773, FAICS-973, FAICS1173 [36]. Sample CSflakes CS powder FAI FAI-373 FAI-773 FAI-973 FAI-1173

Sample

BET (m²/g) 0.35 0.64 1.72 1.22 1.37 0.72 0.36

FAICS-373 FAICS-773 FAICS-973 FAICS-1173

28


BET (m²/g) 0.83 0.81 0.63 0.48

Page 29 of 31

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

Energy & Fuels

Table 2. Kinetic parameters for the adsorption of Zn(II) onto FAI, FAI-373, FAI-773, FAI973, FAI-1173, FAICS-373, FAICS-773, FAICS-973, FAICS-1173. The pseudo first order C0 q1 k1 R2 (mg/g)

(M)

(g/mgmin)

The pseudo second order q2 k2 h R2 (mg/g)

-3

1x10 2x10-3 3x10-3

0.29 0.28 0.53

0.02 0.03 0.01

0.93 0.95 0.86

1x10-3 2x10-3 3x10-3

0.30 0.39 0.39

0.02 0.02 0.02

0.98 0.93 0.94

1x10-3 2x10-3 3x10-3

0.52 1.84 0.88

0.01 0.02 0.02

0.95 0.87 0.97

1x10-3 2x10-3 3x10-3

0.58 1.84 0.67

0.02 0.02 0.02

0.99 0.87 0.95

1x10-3 2x10-3 3x10-3

0.45 1.85 1.96

0.01 0.01 0.02

0.87 0.87 0.90

1x10-3 2x10-3 3x10-3

0.94 0.01 0.02

0.03 1.43 1.60

0.93 0.99 0.93

1x10-3 2x10-3 3x10-3

1.11 0.87 0.51

0.02 0.02 0.02

0.99 0.99 0.83

1x10-3 2x10-3 3x10-3

0.31 0.24 0.36

0.04 0.02 0.03

0.99 0.83 0.95

1x10-3 2x10-3 3x10-3

0.48 0.30 0.42

0.02 0.02 0.01

0.90 0.90 0.76

(g/mgmin)

FAI-Zn(II) 0.67 0.29 0.95 0.43 1.24 0.15 FAI-373-Zn(II) 0.66 0.28 1.01 0.21 1.64 0.23 FAI-773-Zn(II) 1.09 0.13 1.45 0.18 2.23 0.10 FAI-973-Zn(II) 0.98 0.12 1.45 0.18 1.82 0.13 FAI-1173-Zn(II) 0.82 0.14 1.04 0.12 1.62 0.18 FAICS-373-Zn(II) 3.47 0.11 6.91 0.06 8.64 0.06 FAICS-773-Zn(II) 3.35 0.08 5.28 0.12 8.08 0.21 FAICS-973-Zn(II) 3.25 0.54 6.12 0.55 8.92 0.38 FAICS-1173-Zn(II) 3.67 0.22 5.39 0.37 8.17 0.19

Intraparticle ki R2 0.5

(mg/g/min)

(mg/gmin )

0.13 0.19 0.22

0.99 0.99 0.99

0.03 0.04 0.05

0.86 0.88 0.90

0.20 0.22 0.62

0.99 0.99 0.99

0.03 0.04 0.04

0.93 0.93 0.92

0.15 0.39 0.47

0.99 0.99 0.99

0.05 0.06 0.08

0.97 0.81 0.94

0.11 0.39 0.43

0.99 0.99 0.99

0.05 0.06 0.06

0.94 0.81 0.93

0.09 0.13 0.47

0.99 0.99 0.99

0.04 0.05 0.05

0.93 0.93 0.87

1.34 2.74 4.66

1.00 1.00 1.00

0.07 0.12 0.15

0.97 1.00 0.92

0.95 3.27 13.87

0.99 1.00 1.00

0.05 0.08 0.10

0.96 0.97 0.73

5.68 20.66 30.30

1.00 1.00 1.00

0.03 0.03 0.03

0.82 0.83 0.86

2.95 10.85 12.44

0.99 1.00 1.00

0.03 0.03 0.05

0.89 0.86 0.90

29


Energy & Fuels

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 30 of 31

Table 3. Thermodynamic data for adsorption of Zn(II) onto FAI, FAI-373, FAI-773, FAI973, FAI-1173, FAICS-373, FAICS-773, FAICS-973, FAICS-1173.

Adsorbent

FAI

FAI-373

FAI-773

FAI-973

FAI-1173

FAICS-373

FAICS-773

FAICS-973

FAICS-1173

Temperature (K)

∆Go (kJ/mol)

293 313 333 293 313 333 293 313 333 293 313 333 293 313 333 293 313 333 293 313 333 293 313 333 293 313 333

-6.51 -7.12 -7.76 -6.70 -7.18 -7.87 -6.49 -7.02 -7.62 -6.31 -6.92 -7.55 -6.39 -7.05 -7.63 -9.13 -9.81 -10.50 -8.77 -9.55 -10.43 -8.77 -9.55 -10.21 -9.07 -9.92 -10.65

∆Ho (kJ/mol)

∆So (kJ/mol K)

R2

2.61

-26.3

1.00

1.83

-28.4

0.79

1.75

-29.3

0.97

2.78

-26.4

1.00

2.73

-26.3

0.98

0.86

-23.3

0.99

3.35

-16.11

0.97

1.81

-21.3

0.93

2.57

-17.7

0.96

30


Page 31 of 31

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

Energy & Fuels

Table 4. Langmuir and Freundlich parameters for adsorption of Zn(II) onto FAI, FAICS373, FAICS-773, FAICS-973, FAICS-1173. T (K)

Langmuir model q0 (mg/g)

KL (dm3/mg)

RL (-)

293 313 333

21.41 30.30 39.06

4.0x10-4 3.4x10-4 3.0x10-4

0.6 0.6 0.6

293 313 333

27.70 29.15 29.41

3.3x10-3 3.1x10-3 3.1x10-3

0.1 0.1 0.1

293 313 333

29.59 28.99 28.65

2.7x10-3 3.1x10-3 3.4x10-3

0.1 0.1 0.1

293 313 333

24.81 25.71 26.11

3.9x10-3 3.9x10-3 4.00x10-3

0.1 0.1 0.1

293 313 333

28.17 28.90 29.50

3.7x10-3 3.8x10-3 3.9x10-3

0.1 0.1 0.1

Freundlich model R2

KF 1/n (mg/g) FAI 0.71 397.56 1.25 0.65 264.48 1.21 0.81 183.23 1.16 FAICS-373 0.99 0.60 0.52 0.98 0.57 0.54 0.98 0.57 0.54 FAICS-773 0.99 1.80 0.56 1.00 0.55 0.54 1.00 0.61 0.53 FAICS-973 0.99 0.73 0.48 0.99 0.69 0.50 0.99 0.73 0.49 FAICS-1173 0.99 0.75 0.50 0.99 0.81 0.49 0.99 0.83 0.49

Temkin model KT b (L/g) (L/mol)

R2

0.99 0.99 0.99

112.9 108.0 106.6

390.35 373.22 343.89

0.8 0.8 0.8

0.97 0.96 0.97

24.30 25.47 9.935

441.20 420.73 419.34

0.9 0.9 0.9

0.96 0.96 0.95

28.32 25.59 23.48

421.25 424.22 427.93

0.9 0.9 0.9

0.94 0.95 0.96

19.71 20.47 19.99

505.61 478.12 474.32

0.9 0.9 0.9

0.96 0.96 0.97

20.52 19.52 19.35

446.58 436.87 428.50

0.9 0.9 0.9

R2

31


Utilization of fly ashes from the coal burning processes to produce

Recommend Documents