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Designing injection water for enhancing oil recovery from kaolinite laden hydrocarbon reservoirs: A spectroscopic approach for understanding molecular level interaction during saline water flooding. Saheli Sanyal, Uttam Kumar Bhui, Sashi Saurabh Kumar, and Dileep Balaga Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b01648 • Publication Date (Web): 26 Sep 2017 Downloaded from http://pubs.acs.org on October 1, 2017

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Designing injection water for enhancing oil recovery from

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kaolinite laden hydrocarbon reservoirs: A spectroscopic

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approach for understanding molecular level interaction during

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saline water flooding.

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Saheli Sanyal*, Uttam K. Bhui, Sashi Saurabh Kumar and Dileep Balaga

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School of Petroleum Technology, Pandit Deendayal Petroleum University, Raisan, Gandhinagar, Gujarat 382007, India.

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* Corresponding author. Mob. No: +91 9836999636 E-mail address: [email protected] (Saheli Sanyal)

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Abstract

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Numerous experiments were performed to understand the mechanism(s) behind incremental

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oil recovery from hydrocarbon reservoirs during low saline water flooding (LSWF). Yet, the

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exact mechanism(s) are still doubtful. It is believed that the role of clay minerals present in

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the hydrocarbon reservoir rocks and the salt concentration in the injected water have a

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significant effect on the oil recovery during LSWF. Yet, the exact interaction mechanism (s)

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are still doubtful for designing the injection fluids for enhancing oil recovery from subsurface

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reservoirs. For understanding the interaction between reservoir components explicitly,

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kaolinite and the crude oil and the interaction between reservoir components and injection

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saline water, three dead crude oil samples collected from different reservoirs of Cambay

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basin, India, and two kaolinite powder samples were used in this study. The kaolinites are

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different on the basis of their exchangeable cations, Fe3+ substitution in octahedral site and

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cation exchange capacity (CEC) values. The three crude oils show differences regarding

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asphaltene content and the abundance of polycyclic aromatic hydrocarbon in asphatenes. The

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interaction between reservoir components particularly, kaolinite and crude oil was

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demonstrated by keeping both the kaolinite and crude oil mixtures for two months. Detail

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analysis of X-ray diffraction pattern, Fourier transform infrared (FTIR) spectra, and cation

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exchange capacity (CEC) values indicated that the polar oil components are adsorbed on to

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the interlayer surfaces of kaolinite, making it oil wet and the interaction depends highly upon

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the composition of kaolinite and crude oil. The oil removal capacity of three brine

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concentrations of 500 ppm (low saline), 3000 ppm (intermediate saline) and 8000 ppm (high

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saline) of NaCl, CaCl2, and MgCl2 from oil adsorbed kaolinites was investigated using UV-

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visible and fluorescence spectroscopy technique. The present study demonstrated that low

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saline water (500 ppm) rich in Na+ ion is more capable of desorbing the maximum amount of

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4-6 ring size PAH components from kaolinites interlayer surfaces with respect to Ca++ and 2 ACS Paragon Plus Environment

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Mg++ ions. The composition of polar oil components, particularly, asphaltenes enrich with 4-

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6 ring polycyclic aromatic hydrocarbon (PAH) greatly influences the recovery of oil from

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mixed wet to oil wet kaolinite laden hydrocarbon reservoir during saline water flooding.

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Thus, apart from the concentration level of the saline water, the type of cation present in the

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saline water is playing the major role during LSWF. The kaolinite composition and their

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crystallinity, and ring size of PAH in asphaltene present inside hydrocarbon reservoir are also

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influencing the enhanced oil recovery (EOR). These molecular level insights are valuable for

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designing of effective injection fluid for enhancing oil recovery during LSWF in kaolinite

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laden hydrocarbon reservoir.

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Keywords: Kaolinite, low saline water flooding (LSWF), asphaltenes, polycyclic

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aromatic hydrocarbon (PAH), UV-visible spectroscopy, fluorescence spectroscopy.

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1. Introduction

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The worldwide increase in petroleum demand has resulted in the development of new or

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modified, economically viable enhanced oil recovery (EOR) techniques from subsurface

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hydrocarbon reservoirs. Low saline water flooding (LSWF) into the hydrocarbon reservoir is

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one of such techniques that has gained importance because of its low cost and minimal

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adversity towards the environment. Literature survey shows that different cations and their

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salinities in the flooding fluid are the key factors for the enhancement of oil recovery in

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sandstone and carbonate reservoir rocks 1–7. There are several existing mechanisms that can

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explain how low salinity water (LSW) works better for oil recovery from reservoirs. These

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mechanisms are clay particle (fine) migration 8, osmosis 9, increased pH and reduced

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interfacial tension (IFT) similar to the alkaline flooding 10, multi-component ion exchange

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(MIE) 11–14, expansion of the double layer 12,15,16, mineral dissolution 17, salting-in effect 18,

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salting out effect 19. Numerous core flooding experiments in sandstone rocks 6–9 have proved

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that LSWF has good potential to enhance oil recovery but the suitable range of salinity,

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preferable cations, their contributions, and most importantly the type of crude oil components

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released by the saline water are still debatable.

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It has been proved that presence of clay minerals in reservoir rock is necessary for successful

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implementation of LSWF for EOR 9,20. A number of studies have shown that most sandstone

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reservoir rocks are rich in different types of clay minerals, predominantly kaolinite 21,22. It is

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negatively charged particle 23 having a high affinity for polar fractions 24–27 of crude oils.

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According to Soraya et al.28, the polar crude oil components are adsorbed by negatively

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charged clay particles through cation exchange. Moreover, the polar resins and asphaltenes

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are adsorbed parallel to the layers of the kaolinites predominantly by van der Waals energy

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with the smaller contribution of electrostatic energy and H-bonding energy 29,30. Thus the

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adsorption of these heavy polar components of crude oil onto the kaolinite layer surfaces

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generates oil wet to mixed wet reservoir system 8,31. During LSWF the cations present in the

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LSW would replace the adsorbed crude oil components from kaolinite making the reservoir

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water wet 28. Fogden 32 demonstrated that crude oil with asphaltenes (stable or unstable)

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altered the kaolinites from water wet to oil wet during migration of crude oil in the reservoir

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rocks, while the LSW flushed out the adsorbed crude oil components flipping kaolinite to

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more water wet resulting enhanced oil recovery. According to the extended- Derjagui-

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Landau- Verwey- Overbeek (DLVO) theory the colloidal interaction between polar oil

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components and kaolinite was mainly due to the change in salinity and pH of the flushing

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solutions 33,34 which ultimately desorbed the oil components from kaolinite. A direct

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relationship between oil recovery and the presence of kaolinite was claimed by few

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researchers 7,28,35–37. However, Austad et al.6 and Pu et al. 17 showed a negligible role of

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kaolinite during LSWF. Thus, the effectiveness of LSWF is very controversial for kaolinite

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laden hydrocarbon reservoir which required molecular level understanding for designing

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customized injection fluid for EOR.


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The use of spectroscopic techniques to characterize different crude oil components is well

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known to literature. Many workers have employed different optical spectroscopic techniques

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to detect oil components as they exhibit excitation at UV-visible light and fluoresce in the

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range of visible wavelength 38–40. But, use of spectroscopic techniques particularly, Fourier

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transform infrared (FTIR) spectroscopy 41, UV-visible absorption spectroscopy 42,43, and

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fluorescence spectroscopy 32 to understand the molecular level interaction among kaolinite,

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crude oil, and injection water during LSWF and thereby designing injection water for

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enhancing oil recovery is very few in literature. Recently, Katika et al. 42, and Sokama-

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Neuyam 43 employed UV-visible spectroscopy to determine the volume of oil fractions

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present in core flood effluents and the polar components present in crude oil sample

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respectively by standard absorption curve. Fogden 32, determined the concentration of

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asphaltene residues on kaolinite after saline water wash, by using fluorescence spectroscopy.

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Bringing all of this literature into account, we adopt spectroscopic techniques for their cost-

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effectiveness and preciseness to understand the molecular-level interaction that takes place

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between kaolinite and crude oil, and between the oil treated kaolinite and saline water. The

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present work is an attempt to categorize the salinity and the ion efficiency of sodium (Na+),

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calcium (Ca++) and magnesium (Mg++) for enhancing oil recovery from oil wet to mixed wet

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kaolinite-rich hydrocarbon reservoirs having different types of crude oils based on the

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spectroscopic studies.

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2. Experimental Section

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2.1. Materials

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2.1.1. Clay samples

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Two types of kaolinite powder samples (purchased from High Purity Laboratory Chemicals,

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Mumbai, India) labeled here as K1 and K2 were used in this study. The samples were oven

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dried at 90°C and characterized using X-ray diffraction (XRD), Fourier transform infrared


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(FTIR) spectroscopy, and energy dispersive X-ray analysis (EDAX). The cation exchange

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capacity (CEC) values for the two kaolinite samples were also measured.

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2.1.2. Crude oil samples

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Three crude oil samples (labeled here as S1, S2, and S3), collected from well heads of three

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different reservoirs of Cambay basin of India, were used in the study. S1 and S2 were kindly

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provided by Oil and Natural Gas Corporation Limited (ONGCL) and S3 was kindly provided

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by Gujarat State Petroleum Corporation (GSPC). The asphaltenes were separated from each

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of the crude oils by ASTM D2007-80 (standard asphaltene separation method from crude

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oil). Crude oils and their asphaltenes are characterized with the help of fluorescence

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spectroscopic analysis by dissolving them in toluene in 1:1000 ratio.

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2.1.3. Salts

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The saline water has been prepared using three types of salts namely, sodium chloride

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(NaCl), calcium chloride (CaCl2) and magnesium chloride (MgCl2), (from Merck, 99%

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purity).

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2.2. Sample preparation & experimental procedures

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An overview of sample preparation and interaction study for a single set of sample (taking

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only K1 and S1) is represented providing a flow chart in Fig. 1. Rest of the sample sets are

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were prepared in a similar way.

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2.2.1. Oil treated clay samples

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The oven dried kaolinite samples (K1, and K2) were soaked separately, with the three crude

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oils (i.e. S1, S2, and S3) and mixed properly by stirring for 15 minutes. The mixture was left

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for 2 months

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The oil treated kaolinite samples were washed repeatedly with n-hexane (Merck, 99% pure),

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followed by distilled water for complete removal of excess surficial oil. The washed samples

44,45

in ambient room temperature (T) and pressure (P) to make them oil wet.


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were then dried and characterized using XRD and FTIR techniques. CEC of the samples were

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also measured.

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2.2.2. Saline water samples

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Saline water samples were prepared by dissolving the desired amount of salts i.e. sodium

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chloride (NaCl), calcium chloride (CaCl2) and magnesium chloride (MgCl2) separately in

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distilled water. Three different salinity of each salt solutions were prepared to investigate the

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interaction study: low salinity (500 ppm), intermediate salinity (3000 ppm) and high salinity

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(8000 ppm) solution.

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2.2.3. Oil treated kaolinite interacted saline water

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1 gm. of each oil treated kaolinite powder samples were taken into three different measuring

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cylinders of 50 ml volume. Saline water of 500 ppm, 3000 ppm, and 8000 ppm were then

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added up to 25 ml volume. The cylinders were then shaken laterally for 10 minutes and

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allowed to settle for next 24hrs at the ambient P-T condition. The mixtures, kept in the

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measuring cylinders, were separated by filtration. UV-visible absorption and fluorescence

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spectroscopic studies were carried out with the filtered out saline water samples while the

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separated clay samples were kept in the sealed glass bottle.

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2.3.Instrumentation

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2.3.1. X-ray diffraction (XRD)

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XRD study was carried out for the oven dried untreated and oil treated powdered kaolinite

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samples. PANalytical X-ray powder diffractometer was used with Ni-filtered CuKα radiation

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employing a range of 10°-60° at a step size of 0.05⁰/2ϴ and a count time of 1.5 seconds per

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step. The mineral identification was done with the standard 2ϴ value from existing literature.

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2.3.2. Fourier transform infrared (FTIR) spectroscopy

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The powdered kaolinite (untreated and oil treated) samples were combined with

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spectroscopic grade KBr (1:20) in an agate mortar and pellets were prepared with a hand held


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KBr press machine. The FTIR spectra of the raw kaolinite samples (K1and K2) and oil

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treated kaolinite samples (K1S1, K1S2, K1S3, K2S1, K2S2, and K3S3) were acquired by

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Perkin Elmer FTIR spectrometer (Spectrum Two model) version 10.4.2 using KBr pellet

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technique. With the same instrument, the infrared spectra of neat crude oil samples (S1, S2,

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and S3) are captured using the ATR mode which is equipped with a diamond crystal having a

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refractive index of 2.4. All the transmittance spectra were taken by considering avg. of 20

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scans from 4000-400 cm-1 wavenumber range at room temperature with a resolution of 4 cm-

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1

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2.3.3. Energy Dispersive X-ray Analysis (EDAX)

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The elemental composition of two kaolinites was evaluated by energy dispersive X-ray

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analysis using a Zeiss, model Ultra 55. The powder clay samples (K1, K2) were sprinkled

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onto adhesive carbon tapes supported on a standard metal stub and subjected to lightly sputter

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with gold for EDAX.

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2.3.4. Cation exchange capacity (CEC)

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The CEC of untreated and oil treated kaolinite samples were determined according to the

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ASTM C 837-81 (the standard test method for methylene blue index of clay).

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2.3.5. UV-visible spectroscopy

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Optical absorption spectra of the filtered saline water samples after interaction with oil

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treated kaolinites (described earlier in 2.2.3) were recorded using PerkinElmer Lambda 35

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spectrometer employing 200-800 nm wavelength range. Optical quartz cuvettes (10 mm × 10

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mm) were used to hold the sample and reference (neat saline water solutions of same

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concentration) solutions.

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For the control experiment, two raw clay powders (K1and K2) are treated with prepared

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saline waters and then filtered similarly as described in 2.2.3, in the absence of crude oil. The

.


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absorption spectra of the filtered samples were captured for examining the presence of

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unwanted clay fractions.

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2.3.6. Fluorescence spectroscopy:

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Steady-state fluorescence spectra of diluted crude oils and their asphaltenes were measured

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over a wavelength range of 200-700nm, on a PerkinElmer LS55 fluorescence

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spectrophotometer employing 320 nm excitation wavelength. The excitation and emission slit

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width were kept 5/5 nm and scanning speed was 500 nm min-1 for recording the spectra.

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Similarly, the emission spectra of the filtered saline water samples (described earlier in 2.2.3)

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were measured employing 300 nm excitation wavelength. Emission spectra of all the neat

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saline water solutions were also recorded at 300 excitation wavelength.

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3.

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3.1. Kaolinite and crude oil characterization

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3.1.1. Kaolinite characterization

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The XRD pattern of the K1 (Fig. 2.a) and K2 (Fig. 3.a) samples suggest the major mineral

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phase present is kaolinite46 which is depicted by the intense peaks near 7.14 A⁰, 3.56 A⁰, and

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1.48A⁰. In addition to this, a varying proportion of quartz, goethite, anatase and an

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insignificant amount of illite and halloysite46,47 are present in both K1 and K2. The d-space

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values and the symbols of the minerals are given against each respective peak in Fig. 2.a and

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Fig. 3.a. The semi-quantitative mineralogy was estimated from intensity values of the peaks

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against the corresponding 2ϴ values and presented in Table 1. In K1 sample the order of

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mineral abundance is kaolinite>quartz>goethite>anatase>illite>halloysite whereas, where in

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K2

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kaolinite>goethite>quartz>anatase>halloysite>illite.

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FTIR transmission spectra of untreated kaolinite samples are given in Fig. 4 (K1) and Fig. 5

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(K2) and the characteristic transmission bands are presented in Table 2

Results and Discussion

the

abundance

is

slightly


different

with

46,48–51

. Both the

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kaolinite samples (K1, and K2), are showing sharp bands near 3695 cm-1, and 3620 cm-1

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which are accounted for OH stretching vibrations bands. The weak deflection near 939 cm-1

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and sharp band at 912 cm-1 are assigned for OH stretching deformation bands. These bands

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are characteristic of the kaolinite. The relative transmittance values of the two bands found

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near 794 cm-1 and 754 cm-1 for Si-O-Al vibration could be associated with the disordered

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kaolinite

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have been found which are arising due to the stretching and bending vibrations of AlFe3+OH.

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The bands are pointing towards the Fe3+ substitution for Al at the octahedral sheet of kaolinite

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structure

51

235

kaolinite

51

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figure of Fig. 5). Therefore, the crystallinity of K1 is said to be poorer than that of K2 sample.

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EDAX spectra of K1 and K2 (Fig. 6) are showing the major element present in both the

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kaolinite are oxygen, silicon, aluminium. However, the spectrum of K1 reveals the presence

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of iron, sodium, calcium, magnesium, and potassium which is not detected in the EDAX

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spectrum of K2 except iron.

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The CEC values for K1 and K2 samples were measured and presented in Table 3. K1 has 6.5

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meq/100 gm CEC whereas the CEC of K2 is 4 meq/100 gm.

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Based on the XRD, FTIR, EDAX, and CEC results, the K1 and K2 are differentiated in terms

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of their chemical composition and crystallinity. The FTIR spectra of K1 exhibit substitution

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of Fe3+ for Al3+ which is not so prominent in K2. Moreover, the FTIR spectrum of K1 is

246

showing feature of poor crystallinity compared to K2 spectrum. K1 contains more Na, Ca, K,

247

and Mg as exchangeable ions in the interlayer surface compared to K2 as seen from EDAX

248

results. All these facts are explaining the CEC result where K1 is showing higher CEC value

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with respect to K2. It has been reported that CEC is a function of crystallinity

51

. In K1 two weak deflections at 3600 cm-1 and 875 cm-1 (inset figure in Fig. 4)

. This type of substitution is related to the disordered or poorly crystallized

. However, FTIR spectrum of K2 is completely lacking this phenomenon (Inset


52

, as

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crystallinity decreases CEC value increases. The EDAX data also supports the higher CEC

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value for K1 and lower for K2.

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3.1.2. Crude oil characterization

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FTIR spectra of three crude oil are relatively similar as seen from Fig. 4 and Fig. 5. The

254

characteristic transmission bands of the oil samples are presented in Table 2 following

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existing literature 53–55. All the crude oils show most intense bands in three regions near i)

256

2954 cm-1 to 2852 cm-1 which is assigned for C-H antisymmetric and symmetric stretching in

257

aliphatic chains; ii) 1462 cm-1 to 1377 cm-1 is due to CH3 antisymmetric deformation and CH

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symmetric in aliphatic compounds; and iii) 900 cm-1 to 700 cm-1 is attributed to aromatic C-H

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out-of-plane bending mode. In addition to these frequency bands, S2 oil spectrum exhibits a

260

broad peak near 3381 cm-1 which is accounted for O–H and N–H stretching in the crude oil

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components. All the three crude oils show the presence of polar functional groups as

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exhibited by the presence of weak peak near 1700 cm-1 to 1740 cm-1 region. Transmission

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bands near 1600 cm-1 to 1650 cm-1 is featured by aromatic ring vibration which is more

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pronounced in S2 spectrum than S1 and S3. The weak transmission peaks in S1 and S2

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spectra near 1300 cm-1 to 1100 cm-1 exhibits an overlapping zone of aromatic CC stretching

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mode and the aromatic C-H in-plane bending mode 56.

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The chemical composition of the three crude oils and their fractionated asphaltenes was

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investigated by steady-state fluorescence emission in terms of the size of aromatic moieties

269

present, particularly, polycyclic aromatic hydrocarbon (PAH). The wt. percentage of

270

separated and measured asphaltenes from S1, S2, and S3 crudes are 3%, 7.5%, and 9.4%

271

respectively. It has been seen from Fig. 7.a that all the spectra of bulk crude oils are showing

272

a broad range of emission from 310 nm- 650 nm. However, a red shift of emission maxima

273

(λmax) has been noticed for S2 crude oil spectrum compared to S1 and S3 (Fig. 7.a). In

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general, the small PAH structures exhibit emission at lower wavelength whereas, large PAH


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structure emit at a higher wavelength 57,58. Thus, it can be inferred from the red shift of S2

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spectrum that the S2 crude oil is rich in larger PAH than S1 and S3 crude oils. A detailed

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analysis exhibits that S1 and S3 crude oils contain 4-7 fused aromatic ring (FAR) with the

278

predominance of 4-5 FAR structures whereas, S2 is mostly rich with 5-7 FAR 56,59,60. The

279

emission spectra of asphaltenes are presented in Fig. 7.b. The S2 asphaltene spectrum is red

280

shifted than S1 and S3 spectra which is very similar to crude oil spectra. However, all the

281

asphaltene spectra are showing emission in a broad range from 310 nm - 670 nm. Thus, it has

282

been found that the nature of PAH in three asphaltenes are likely similar but their abundance

283

is different. Fig. 7.b shows S1 asphaltenes are rich with smaller 4-5 ring PAH 56,59,60 with less

284

amount of large ring (6-7) PAH; S1 and S2 asphaltenes are abundant with the large ring (5-7)

285

PAH 56,59,60.

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Above results suggest that there is a distinct difference lies among the three crude oils (S1,

287

S2, and S3) in terms of chemical composition. S1 oil contains lowest (3 wt. %) fractions of

288

asphaltenes which are rich in mostly 4-5 ring PAH. Moderate asphaltene content (7.5 wt. %)

289

has been found in S2, however, the asphaltenes are dominantly enriched in larger PAH (5-7

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FAR). S3 crude oil is having highest asphaltene content (9.4 wt. %) with a broad range of

291

PAH (5-7 FAR). In S1 and S2, the presence of aromatic moieties is significant than S3 as

292

seen from FTIR spectra of oils (Fig. 4).

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3.2. Characterization of crude oil treated kaolinite

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3.2.1. X-Ray Diffraction (XRD)

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After oil treatment, the intensity of kaolinite peak, near 7.14 A⁰, is decreased slightly

296

(Fig.2.b, and Fig. 3.b) indicating decrease in the stacking order 61 which may be due to crude

297

oil absorption. The oil treated K1 samples are showing more intensity reduction of 7.14 A⁰

298

peak (Fig.2.b) than oil treated K2 samples (Fig. 3.b) exhibiting more oil absorption by K1


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than K2. Further, K1S1 is showing significant reduction in peak (7.14 A⁰) intensity than

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K1S2 and K1S3 proving more S1 oil components absorption by K1 during oil treatment.

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3.2.2. Fourier transform infrared spectroscopy (FTIR)

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FTIR transmission spectra of oil treated kaolinite samples are presented in Fig. 4 (K1

303

samples), and Fig. 5 (K2 samples). All the samples exhibit the presence of new sets of bands

304

near (1) 2954 cm-1, 2918 cm-1, 2850 cm-1 (2) 1473 cm-1, and 1463 cm-1, compared to raw

305

kaolinite. The bands at 2954 cm-1, 2918 cm-1, 2849 cm-1 are attributed to C-H antisymmetric

306

and symmetric stretching in an aliphatic hydrocarbon, and the bands at 1473 cm-1 and 1463

307

cm-1 are of CH3 antisymmetric deformation of hydrocarbon crude (as given in Table 2). For

308

both the S3 oil treated kaolinite samples the intensity of transmittance bands are showing a

309

higher value than other samples. With the addition of the new set of transmission bands, the

310

intensity of surface hydroxyl (OH) groups (3694 cm-1, 3668 cm-1, and 3653 cm-1) of kaolinite

311

samples are reduced, however, the intensity of the constitutional OH (near 3621 cm-1)

312

remains unchanged. These modifications in the spectra suggest that the crude oil components

313

are adsorbed onto the kaolinite interlayer surfaces 62–64 which is evident also from XRD peak

314

(7.14A⁰) reduction. The FTIR spectra of oil treated kaolinite samples reveal that the polar

315

crude oil components adsorbed onto the kaolinite layer surface, are rich with primary

316

aliphatic chains

317

kaolinite affects the hydroxyl groups as evidenced from the reduced OH intensity of the FTIR

318

spectra 63,64 .

319

3.2.3. Cation exchange capacity (CEC)

320

The measured CEC values of kaolinite samples (K1 and K2) before and after oil treatment

321

are presented in Table 3 which shows that the oil treated kaolinite samples were reduced from

322

the original value. This can be explained as a result of adsorption of polar crude oil

323

components onto the interlayer surfaces of kaolinites

25

. Incorporation of the oil components onto the interlayered surface of

25,65,66

. It has been observed that the


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

324

percentage of CEC reduction for oil treated K1 samples is higher than oil treated K2 samples

325

which may be due to higher absorption of polar oil components on to K1 interlayer surface

326

than that of K2. This can be explained on the basis of the compositional difference found

327

between K1 and K2 as seen from EDAX spectra (Fig. 6). The CEC values of the oil treated

328

kaolinite samples infer that the polar oil components of S1 are absorbed more onto the

329

kaolinite interlayer surface than S2 and S3.

330

3.3. Characterization of filtered saline water samples from oil treated kaolinites

331

3.3.1. Ultraviolet-visible (UV-visible) spectroscopy

332

Fig. 8 and Fig. 9 represent the absorbance spectra of the filtered low (500 ppm) and high

333

(8000 ppm) salinity water of sodium, calcium and magnesium salts after interaction with oil

334

treated kaolinite samples (K1S1, K1S2, K1S3, K2S1, K2S2 and K2S3) whereas the spectra

335

for filtered 3000 ppm saline water solutions are given separately in supplementary 1. The

336

absorption spectra are showing high absorption value in UV range and low absorption in the

337

visible range. Both the spectra (Fig. 8 and Fig. 9) exhibit intense and broad absorption bands

338

below 320 nm which may be attributed to the presence of π- π * conjugated system of

339

aromatic chromophores 67 in the filtered saline water samples. As kaolinite absorption spectra

340

exhibit peak around 245 nm wavelength 68, the absorption spectra of saline water treated raw

341

kaolinite samples (K1 and K2) were also captured (given in Fig. 10) to see the effect of raw

342

kaolinites on the said absorption curves (Fig. 8 and Fig. 9). The saline water treated raw

343

kaolinite samples are showing a flat type of absorption spectra with some absorbance value at

344

wavelength ˂ 300 nm which may be due to the presence of some submicron and nano-sized

345

clay particles in the sample. However, the absorption value of the filtered sample prepared

346

from oil treated kaolinites is higher than that of filtered samples from raw kaolinites below

347

320 nm wavelength (Fig. 10). This implied that the absorbance in Fig. 8 and Fig. 9 is due to

348

the presence of oil in the filtered samples (prepared from oil treated kaolinites). Furthermore,


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Energy & Fuels

349

a ratio of two spectra of the filtered NaCl (500 ppm) saline water samples (prepared from oil

350

treated and untreated kaolinite) is taken 69 and plotted against corresponding wavelength (Fig.

351

11). The resultant spectrum shows two peaks at 237 nm and 261 nm which further support

352

the presence of alkane and aromatic components respectively 70 in the filtrate from oil treated

353

kaolinite. In, general, the absorbance value at ˃ 320 nm wavelength signifies the presence of

354

different fused rings of polycyclic aromatic hydrocarbons (PAH)

355

wavelength of absorption maximum, the bigger the chromophore structures

356

could be ascertained from the absorption spectra (Fig. 8 and Fig. 9) that the interacted saline

357

water solutions exploit PAH structures 67. These PAH are the crude oil components that are

358

adsorbed onto the kaolinite interlayer surfaces

359

released during the interaction with the saline water. Further, fluorescence emission spectra

360

of the same saline water samples (prepared from oil treated kaolinites) were acquired for the

361

detail investigation of the presence of PAH structures in them and presented in section 3.3.2.

362

The low salinity NaCl salt solution are showing higher absorbance value and well separated

363

from all other saline water solutions for K1S1 and K1S2 samples (Fig. 8). However, it is not

364

so prominent in K1S3 spectra (Fig. 8). The high salinity NaCl solution spectra are mostly

365

overlapping with the MgCl2 and CaCl2 solutions spectra. Maximum absorbance values have

366

been exhibited by filtered low saline NaCl solution though it is not showing any significant

367

separation from spectra of rest saline water solutions (Fig. 9). In the absorption spectra for

368

K2S2 samples, the absorbance value shown by the high salinity water solution and low

369

salinity water solution of NaCl are almost similar (Fig. 9).

370

It has been observed that the interacted saline water solutions are showing higher absorbance

371

value for oil treated K1 samples (K1S1, K1S2, and K1S3) than oil treated K2 (K2S1, K2S2,

372

and K2S3) samples (Fig. 8 and Fig. 9), suggesting higher extraction of polar oil components

373

from K1 than K2. This can be explained in the light of the peak reduction in XRD results and

29

67

. The higher the 71

present. It

during the interaction with oil and are


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

374

reduction of CEC values after oil treatment where it has been found that K1 adsorbed more

375

polar crude oil components than K2. As a consequence, during saline water interaction, the

376

low saline (500 ppm) NaCl solution showed the maximum ability to remove oil components

377

from the oil treated K1 samples.

378

The foregoing discussion endorses that the oil removal from the oil treated kaolinite samples

379

is not only dependent on the salinity but also on the type of cations and composition of

380

kaolinite and crude oils

381

components from kaolinite rather than other salts.

382

3.3.2. Fluorescence Spectroscopy

383

As the fluorescence intensity is directly proportional to the number density of chromophores

384

present in the samples, the oil removing efficiency of different saline water samples from oil

385

treated kaolinite (K1 and K2) can be investigated by the fluorescence spectroscopy method.

386

This method has also been used for the investigation of PAH structures in terms of their

387

number of fused aromatic rings (FAR) 57,73 present in the filtered out saline water.

388

The steady-state emission spectra of the filtered out low (500 ppm) and high (8000 ppm)

389

saline water (from oil treated kaolinites) of sodium, calcium, and magnesium salts are

390

recorded by employing excitation wavelength of 300 nm and presented in Fig. 12 (for K1S1,

391

K1S2, K1S3) and Fig. 13 (K2S1, K2S2, K2S3). Fluorescence spectra for filtered out

392

intermediate saline (3000 ppm) water samples are attached separately in supplementary 2. All

393

the samples are showing an almost similar broad type of emission pattern extending from

394

340-560 nm range. The small deflections in the emission spectra are indicative of the

395

presence of different aromatic moieties i.e. PAH-containing various sizes of FAR within the

396

saline water samples

397

410 nm and 450 nm in the emission spectra indicating the presence of 4-6 ring PAH 56,59,60 in

398

the filtered saline water samples. This range of PAH is very much correlated with the polar

72

. However, LSW of Na salt is most effective to remove oil

58

. The deflections present in the emission spectra at around 385 nm,


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Energy & Fuels

399

asphaltenes of the crude oils where the ring sizes of PAH are varying from 4-7 as seen from

400

Fig. 7.b.

401

For a better understanding of the oil removal efficiency by different saline waters, a column

402

plot is presented in Fig. 14. It is drawn by normalizing the maximum fluorescence intensity

403

(of emission maxima i.e. λmax) depicted by each spectrum of filtered saline water samples

404

with respect to the maximum fluorescence intensity of filtered out 500 ppm NaCl sample

405

from K1S1.

406

In K1S1, the maximum fluorescence intensity is shown by 500 ppm NaCl solution (Fig. 12

407

and Fig. 14) and the spectra are slightly red-shifted with respect to other spectra proving

408

maximum incorporation of different ring size (5-6 FAR) PAH structures 73. High saline NaCl

409

solutions are also showing higher fluorescence intensity than the other saline solutions of

410

CaCl2 and MgCl2. In K1S2, the maximum fluorescence intensity is exhibited by high saline

411

(8000 ppm) NaCl water showing maximum emission near 405 nm. However, the

412

fluorescence intensity of low saline (500 ppm) NaCl solution spectrum is overriding the 8000

413

ppm saline water spectrum in higher wavelength (> 430 nm) indicating its compatibility for

414

exploiting larger size PAH component from oil treated K1. The fluorescence spectra of K1S3

415

treated saline water samples reveal similar results where low saline NaCl water shows a sharp

416

peak with maximum intensity. CaCl2 and MgCl2 saline waters are showing the similar

417

capability of removing PAH. Thus, NaCl proved to be the most potential candidate for

418

removing variable ring size (4-6 FAR) PAH structures from the oil treated K1 samples than

419

the other two salts. It has also been observed that the oil removal is higher in K1S1 than

420

K1S2 and K1S3 samples.

421

Low saline (500 ppm) NaCl water for K2S1 and K2S3 samples (Fig. 13) exhibit emission

422

spectra with maximum fluorescence intensity. However, high saline NaCl water shows

423

maximum fluorescence intensity for K2S2 sample (Fig. 13). For S2 oil treated kaolinite


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

424

samples low saline (500 ppm) as well as high saline (8000 ppm) NaCl solution works more or

425

less in a similar way for oil removal. So, high saline (8000 ppm) NaCl water is better than

426

low saline CaCl2 and MgCl2 solutions (Fig. 13 and Fig. 14). Fluorescence intensity of all salt

427

spectra (NaCl, CaCl2, and MgCl2) are showing high value for K2S1 and K2S2 whereas for S3

428

oil treated K2 it is very less. It is revealed (Fig. 13 and Fig. 14) that the saline water samples

429

are able to remove more crude oil from K2S1 than K2S2 and K2S3 samples.

430

It has been observed for both the oil treated kaolinite, that NaCl saline water solutions are

431

playing a key role to remove significant PAH compared to CaCl2, and MgCl2 solutions of

432

similar concentration. A possible reason for explaining the phenomenon would be the ionic

433

strength of salts, which varies with different salts. As the ionic strength of NaCl is less than

434

the ionic strength of CaCl2 and MgCl2, NaCl is showing much efficiency for oil removal

435

from oil treated kaolinites than the other two.

436

Thus, five observations can be made from fluorescence emission spectra (Fig. 12 and Fig. 13)

437

and Fig. 14: (i) low saline (low ionic strength) water samples are most compatible for oil

438

removal from oil treated kaolinite samples than the high saline water samples; (ii) saline

439

water solutions having Na+ ions are much more efficient for oil removal than saline water

440

solutions having Ca++ and Mg++ ions; (iii) saline water solutions show maximum oil

441

recovery from oil treated K1 samples than oil treated K2 samples; (iv) all the saline water

442

solutions are compatible for removing 4-6 ring PAH and (v) as S1 asphaltenes are dominated

443

with 4-6 FAR the saline water removed more oil from S1 treated kaolinite samples compared

444

to other two oil (S2, S3) treated kaolinites.

445

The whole discussion is summarized in Fig. 15.

446

4.

447

The interaction behavior of two kaolinites (K1, and K2) and three different crude oils (S1, S2,

448

and S3) are analyzed in this work followed by a detail discussion on the oil removal

Conclusions


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Energy & Fuels

449

efficiency of saline water solutions (500 ppm, 3000 ppm and 8000 ppm) of different salts

450

(NaCl, CaCl2 and MgCl2) from the oil treated kaolinite.

451

XRD, FTIR, EDAX, and CEC results are clearly showing the difference between two

452

kaolinites (K1 and K2) (i) K1 is poorly crystallized than K2; (ii) K1 have higher amount of

453

exchangeable cations and Fe3+ substitution in octahedral Al site than K2, thus having a higher

454

CEC value than K2. A detailed characterization of the three crudes (S1, S2, and S3) and their

455

fractionated asphaltenes are showing that they are different in their asphaltene content and the

456

nature of PAH in asphaltenes: (i) S1 has 3 wt. % asphaltenes containing predominantly 4-5

457

ring size PAH, (ii) S2 is having 7.5 wt. % of asphaltenes which are rich in PAH of 5-7 FAR,

458

and (iii) S3 has 9.4wt. % of asphaltene content with 5-7 FAR rich PAH.

459

The reduction of peak intensity from XRD, the presence of C-H antisymmetric and

460

symmetric stretching bands and the CH3 antisymmetric deformation in FTIR spectra, and

461

decrease in CEC values of oil treated kaolinites along with the UV-visible absorption spectra

462

and steady-state fluorescence spectra of filtered sample (prepared from oil treated kaolinites)

463

are attesting the fact that oil components particularly the asphaltene components absorbed

464

adsorption onto the interlayer surface of kaolinite. Oil adsorption is higher onto K1 interlayer

465

surfaces which has higher CEC & poor crystallinity than that of K2.

466

The interaction study of oil treated kaolinite and different saline water solution reveals low

467

saline water (500 ppm) rich in Na+ is more compatible to recover 4-6 ring PAH from oil

468

treated kaolinite than low saline water of Ca++ and Mg ++. Thus, the maximum oil recovery

469

doesn’t only depend on salinity but also the type of cation present in the saline water.

470

Moreover, as S1 asphaltenes are predominantly rich with 4-5 FAR, the salt solutions have

471

shown higher oil recovery from S1 treated kaolinite samples. On the contrary, filtered saline

472

water samples, from S2 and S3 treated kaolinites, are showing less oil recovery as S2 and S3

473

asphaltenes are rich in 5-7 FAR. Saline water samples are not so capable to remove PAH >


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

474

6FAR. So, apart from asphaltene percentage, the ring size of PAH present in asphaltene of

475

crude oil has a strong connotation for designing injection fluid for EOR.

476

Thus, Na+ is proved to be the most suitable candidate for low saline water flooding in a

477

kaolinite laden reservoir. However, the oil removal may also vary with the type kaolinite and

478

asphaltene structures of crude oil present inside the subsurface reservoir. The whole

479

discussion is summarized in Fig. 15.

480

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Dandekar, A. Y. Interfacial Tension and Wettability. In: Petroleum Reservoir Rock and Fluid Properties. Taylor & Francis; 2006, 109-141.

587 588

Sokama-neuyam, Y. Retention of Polar Oil Components in Low Salinity Water

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Worasith, N.; Goodman, B. A.; Neampan, J.; Jeyachoke, N. Characterization of

591

modified kaolin from the Ranong deposit Thailand by XRD , XRF , SEM , FTIR and

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EPR techniques. 2011, 539-559.

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Brindley, G.; Brown, G. Crystal Structures of Clay Minerals and Their Identification. Mineralogical Soceity; 1980.

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(48)

Madejova, J. FTIR techniques in clay mineral studies. 2014, 2031.

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Farmer, V. Infrared Spectroscopy Studies In Clay Mineral. 1968, 373-387.

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Saikia, B. J.; Parthasarathy, G. Fourier Transform Infrared Spectroscopic

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Characterization of Kaolinite from Assam and. J Mod Phys. 2010, 1, 206-210.


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Russell, J. D.; Fraser, A. R. Infrared methods. In: M. J. Wilson, ed. Clay Mineralogy:

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Spectroscopic and Chemical Determinative Methods. Springer Science+Business

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Media Dordrecht; 1994, 11-64.

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Ma, C.; Eggleton, R. A. Cation Exchange Capacity of Kaolinite. 1999, 47, 174-180.

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Barnaji, M. J.; Pourafshary, P.; Rasaie, M. R. Visual investigation of the effects of clay

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minerals on enhancement of oil recovery by low salinity water flooding. Fuel. 2016,

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184, 826-835.

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spectroscopy analysis of crude oils and their fractions. 2014.

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Lambert, J. B.; Shurvell, H. F.; Lightner, D. A.; Cooks, R. G. Organic Structural Spectroscopy Prentice-Hall. Inc New Jersey Google Sch. 1998, 568.

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Gawel, B.; Eftekhardadkhah, M.; Øye, G. An elemental composition and FT-IR

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Merola, M. C.; Carotenuto, C.; Gargiulo, V.; Stanzione, F.; Ciajolo, A.; Minale, M.

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Chemical-physical analysis of rheologically different samples of a heavy crude oil.

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Fuel Process Technol. 2016, 148, 236-247.

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Aromatic Mixtures. Anal Chem. 2004, 76, 2138-2143.

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Kasha, M. Paths of Molecular Excitation. In: Proceedings of a Symposium Sponsored by the U. S. Atomic Energy Commission. New York; 1960.

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Groenzin, H.; Mullins, O. C. Molecular Size and Structure of Asphaltenes from Various Sources. Energy Fuels. 2000, 14, 677-684.

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Apicella, B.; Ciajolo, A.; Tregrossi, A. Fluorescence Spectroscopy of Complex

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Pampanin, D.; Kemppainen, E.; Skogland, K.; Jorgensen, K.; Sydnes, M. Investigation

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of fixed wavelength fluorescence results for biliary metabolites of polycyclic aromatic

621

hydrocarbons formed in Atlantic cod (Gadus morhua). Chemosphere. 2016, 144, 1372-

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1376.

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Sugahara, Y.; Satokawa, S.; Kuroda, K.; Kato, C. Preparation of a Kaolinite-


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Polyacrylamide Intercalation Compound. Clay Miner. 1990, 38, 137-143.

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Lagaly, G.; Ogawa, M. Clay mineral organic interactions ´ ny. 2006, 1, 309-377.

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Komori, Y.; Enoto, H.; Takenawa, R.; Hayashi, S.; Sugahara, Y.; Kuroda, K.

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Modification of the Interlayer Surface of Kaolinite with Methoxy Groups. 2000, 10,

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5506-5508.

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Kaolinite. Clays Clay Miner. 1990, 38, 121-128.

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Dean, K.; James, L.; McATEE, J. Asphaltene adsorption on clay. Appl Clay Sci. 1986, 1, 313-319.

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Clementz, D. Alteration of Rock Properties by Adsorption of Petroleum Heavy Ends: Implications for Enhanced Oil Recovery. Soc Pet Eng. 1982.

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aggregates as studied by near-UV / visible spectroscopy I . Structure of the absorbance

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spectrum. 2003, 37, 135-143.

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Miner. 1973, 21, 59-70.

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Karickhoff, S. W.; Bailey, G. Optical absorption spectra of clay minerals. Clays Clay

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ZnO. Nucl Instruments Methods Phys Res Sect B Beam Interact with Mater Atoms.

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2013,311, 20-26.

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Zhao, X.; Wang, Y.; Ye, Z.; Borthwick, A. G. L.; Ni, J. Oil field wastewater treatment

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in Biological Aerated Filter by immobilized microorganisms. Process Biochem. 2006,

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41, 1475-1483.

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Royal Society of Chemistry; 2004.

647 648

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McMillan, M. D.; Rahnema, H.; Romiluy, J.; Kitty, F. J. Effect of exposure time and


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crude oil composition on low-salinity water flooding. Fuel. 2016, 185, 263-272.

649 650

(73). Berlman, I. Handbook of Fluorescence Spectra of Aromatic Molecules. 2nd ed. Academic Press; 1971.

651 652 653 654 655 656 657 658

Table 1. The mineralogy of K1 and K2 sample. Sample name

Minerals present in percentage (%) Kaolinite

Quartz

Goethite

Anatase

Halloysite

Illite

K1

54.257416

20.90028

9.46

8.96

1.71

4.69

K2

51.986128

16.737806

20.164023

7.1481207

3.1

0.86

659 660 661 662 663 664 665 666 667 668 27 ACS Paragon Plus Environment

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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 46

669

Table 2. FTIR absorption frequencies (cm-1) and their assignments in kaolinite (K1 and

670

K2) and crude oil (S1, S2 and S3) samples.

K1

K2

3695

3695

3668

3667

3652

3653

3620

3621

3600

-

-

Vibration assignment Internal surface–OH stretching vibration OH stretching vibration OH stretching vibration Inner –OH stretching vibration Al-Fe-OH bending vibration

-

S1

S2

S3

Vibration assignment

-

-

-

-

-

-

-

-

-

-

-

-

-

3381

-

O–H and N–H stretching

2954

2954

2954

2920

2920

2918

2852

2851

2852

C-H antisymmetric and symmetric stretching in aliphatic

1739

1737

1700

-

-

-

Stretching of C=O bond in carboxylic acid

-

-

1639

1637

-

-

1604

1634

1604

Stretching of C=C bond in aromatic rings

-

-

1463

1463

1463

CH3 antisymmetric deformation

-

-

1378

1377

1377

CH3 symmetric in aliphatic compounds

1224

1215

-

-

-

-

-

-

-

-

-

839 811

839 -

840 -

720

719

719

-

-

-

1117

1117

1031

1035

1006

1003

936

939

912

912

880 794 754 -

795 754 -

-

-

696

696

533

536

467

467

646

surface water

Si-O bending vibration Al-OH bending vibration Al-Fe-OH bending vibration Si-O-Al compound vibrations

Si-O Quartz Si-O-Al stretching Si-O vibrations

-

-

-

-

-

-

-

-

-


Out of plane bending of C–H bond in aromatic compounds and bending (rocking type) of C–H in CH2

Page 29 of 46

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Energy & Fuels

671 672

Table 3. CEC values of untreated and oil treated kaolinite samples.

CEC value ± 0.25 (meq/100gm)

CEC reducti on (%)

K1S1

6.75 3.25

51.85

K1S2 K1S3

5 4

25.93 40.74

K2S1

4 3.5

12.5

K2S2 K2S3

3.75 3.5

6.25 12.5

Name of the clay samples Untreated samples

Oil treated samples

K1

K2

0.25

673 674

Figure Captions

675

Fig. 1. Flow chart of sample preparation for the interaction study with single set of kaolinite

676

(K1) and Crude oil (S1). All other samples are prepared similarly for kaolinite (K1, and K2)

677

and crude oils (S1, S2, and S3).

678

Fig. 2. a. X-ray diffractogram (XRD) patterns of the untreated K1 and oil treated K1 samples

679

(K1S1, K1S2, and K1S3) used in the experiments. The mineral symbols and d-space values

680

are assigned for corresponding peaks. The assignments of the minerals, K = kaolinite, H =

681

halloysite, Q = quartz, I = illite, and G = goethite, and A = anatase. b. Enlarged view of the

682

primary peak (7.14 A⁰) of kaolinite (K1) before and after oil treatment.

683

Fig. 3. a. X-ray diffractogram (XRD) patterns of the untreated K1 and oil treated K2 samples

684

(K2S1, K2S2, and K2S3) used in the experiments. The mineral symbols and d-space values

685

are assigned for corresponding peaks. The assignments of the minerals, K = kaolinite, H =

686

halloysite, Q = quartz, I = illite, G = goethite, and A = anatase. b. Enlarged view of the

687

primary peak (~ 7.15 A⁰) of kaolinite (K2) before and after oil treatment.


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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

688

Fig. 4. Fourier transform infrared spectroscopy (FTIR) spectra of untreated K1, neat crude

689

oils (S1, S2, and S3) and oil treated K1 samples. The oil treated kaolinite samples exhibit the

690

presence of new sets of bands near 2954 cm-1, 2918 cm-1, 2849 cm-1 and 1473 cm-1, 1463

691

cm-1. The intensity of surface hydroxyl (OH) groups (3695 cm-1, 3668 cm-1 and 3653 cm-1) of

692

kaolinite samples are reduced. Inset figures are showing enlarged view of the marked portion

693

of each spectrum.

694

Fig. 5. FTIR spectra of untreated K2, neat crude oils (S1, S2, and S3) and oil treated K2

695

samples. The oil treated Kaolinite samples exhibit the presence of new sets of bands at 2954

696

cm-1, 2918 cm-1, 2849 cm-1 and 1473 cm-1, 1463 cm-1. The intensity of surface hydroxyl

697

(OH) groups (3694 cm-1, 3668 cm-1, and 3653 cm-1) of kaolinite samples are reduced. Inset

698

figures are showing enlarged view of the marked portion of each spectrum.

699

Fig. 6. EDAX spectra of K1 and K2 kaolinite.

700

Fig. 7.a. Normalized fluorescence spectra of bulk crudes and b. separated asphaltenes at 320

701

nm excitation wavelength.

702

Fig. 8. The absorption spectra for saline waters (low and high salinity water) after interaction

703

with oil treated K1S1, K1S2, and K1S3. The absorption spectra, are showing by high

704

absorption value in UV range and low absorption value in the visible range (see text for

705

details).

706

Fig. 9. The absorption spectra of filtered saline waters (low and high salinity water) after

707

interaction with oil treated K2S1, K2S2, and K2S3. The absorption spectra, are showing by

708

high absorption value in UV range and low absorption value in the visible range (see text for

709

details).

710

Fig. 10. The absorption spectra for neat NaCl saline waters (low and high salinity water),

711

filtered saline waters (low and high salinity water) after interaction with raw kaolinite


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Energy & Fuels

712

samples (K1 and K2), and filtered saline waters (low and high salinity water) after interaction

713

with oil treated kaolinite samples (K1S1, K2S1). See text for details.

714

Fig. 11. UV–visible absorption spectra of 500 ppm NaCl filtered solution treated with K1,

715

and K1S1. The resultant spectrum is also plotted by taking ratio of K1S1 and K1 absorbance

716

values of the study wavelength range.

717

Fig. 12. Fluorescence spectra for filtered saline waters (low and high salinity water) after

718

interaction with oil treated K1S1, K1S2 and K1S3. All the samples are showing almost

719

similar broad emission pattern extending from 340-560 nm range (see text for details).

720

Fig. 13. Fluorescence spectra for filtered saline waters (low and high salinity water) after

721

interaction with oil treated (a) K2S1, (b) K2S2 and (c) K2S3.All the samples are showing

722

almost similar broad emission pattern extending from 340-560 nm range (see text for details).

723

Fig. 14. Column plot for fluorescence intensity values (at emission maxima) of filtered saline

724

water samples considering K1S1 500 ppm NaCl intensity value as 100%.

725

Fig. 15. Summary table of the oil removal capacity of the different cations with their best

726

salinity, from oil (S1, S2, and S3) treated kaolinite samples (K1 and K2).


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Fig. 1 199x197mm (300 x 300 DPI)

ACS Paragon Plus Environment

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Fig. 2 209x185mm (300 x 300 DPI)


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Fig. 3 209x186mm (300 x 300 DPI)


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Fig. 4 201x258mm (300 x 300 DPI)


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Fig. 5 201x258mm (300 x 300 DPI)


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Fig. 6 197x230mm (300 x 300 DPI)


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Fig. 7 258x201mm (300 x 300 DPI)


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Fig. 8 201x258mm (300 x 300 DPI)


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

Fig. 9 201x258mm (300 x 300 DPI)


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Fig. 10 279x197mm (300 x 300 DPI)


Energy & Fuels

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Fig. 11 258x201mm (300 x 300 DPI)


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Fig. 12 201x258mm (300 x 300 DPI)


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Fig. 13 201x258mm (300 x 300 DPI)


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Fig. 14 210x201mm (300 x 300 DPI)


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Fig. 15 278x129mm (300 x 300 DPI)


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Designing Injection Water for Enhancing Oil ... - ACS Publications

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