Journal of ELECTRONIC MATERIALS, Vol 45, No 7, 2016 DOI: 10.1007/s11664-016-4513-6 Ó 2016 The Minerals, Metals & Materials Society Synthesis of Polymer-Coated Magnetic Nanoparticles from Red Mud Waste for Enhanced Oil Recovery in Offshore Reservoirs T.P NGUYEN,1,2,5 U.T.P LE,3 K.T NGO,1,3 K.D PHAM,1 and L.X DINH4 1.—Institute of Applied Materials Science, Mac Dinh Chi Street, District 1, Ho Chi Minh City, Vietnam 2.—Duy Tan University, K7/25 Quang Trung Street, District Hai Chau, Da Nang, Vietnam 3.—Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam 4.—Institute of Materials Sciences, 18 Hoang Quoc Viet, Cau Giay District, Ha Noi, Vietnam 5.—e-mail: phuongtungng@gmail.com Buried red mud waste from groundwater refineries can cause pollution The aim of this paper is to utilize this mud for the synthesis of Fe3O4 magnetic nanoparticles (MNPs) Then, MNPs are encapsulated by a copolymer of methyl methacrylate and 2-acrylamido-2-methyl-1-propanesulfonate via oleic acid linker MNPs are prepared by a controlled co-precipitation method in the presence of a dispersant and surface-modified agents to achieve a high hydrophobic or hydrophilic surface Mini-emulsion polymerization was conducted to construct a core–shell structure with MNPs as core and the copolymer as shell The core–shell structure of the obtained particles enables them to disperse well in brine and to stabilize at high-temperature environments The chemical structures and morphology of this nanocomposite were investigated by Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy The thermal stability of the nanocomposite was evaluated via a thermogravimetric analysis method for the solid state and an annealing experiment for the liquid state The nanocomposite is about 14 nm, disperses well in brine and is thermally stable in the solid state The blends of synthesized nanocomposite and carboxylate surfactant effectively reduced the interfacial tension between crude oil and brine, and remained thermally stable after 31 days annealed at 100°C Therefore, a nanofluid of copolymer/magnetic nanocomposite can be applied as an enhanced oil recovery agent for harsh environments in offshore reservoirs Key words: Red mud waste, mini-emulsion polymerization, magnetic nanoparticles, core–shell, enhanced oil recovery, offshore INTRODUCTION Global energy demand is expected to increase by 2–3% annually in the coming decades, and the increase is predicted to rise by 50% after 20 years.1 Satisfying this demand is the main challenge for the oil and gas industry With the era of easily accessible and produced oil coming to an end and the increasing difficulty of finding new resources, the traditional oil and gas industry has been directed to (Received December 18, 2015; accepted April 1, 2016; published online April 29, 2016) extract more resources from existing oil fields [enhanced oil recovery (EOR)] and from the fields exposed to extremely harsh environments by using new technologies and solutions Thus, the EOR field is important and urgent in the petroleum industry The typical oil recovery efficiency of 30–40% should be increased to 60–80%.2 Recovery of secondary oil, which is trapped in the pores of reservoir solids, needs a more sophisticated approach Therefore, improved reservoir mapping and advanced production methods are necessary Nanotechnology has recently received considerable attention from the petroleum industry, and a decade’s worth of 3801 3802 Nguyen, Le, Ngo, Pham, and Dinh nanotechnology development is poised to become a reality in the oil field.3,4 Numerous studies that involve EOR in the field of nanotechnology have recently been published SiO2 nanoparticles (SiO2NPs) are commonly used as nanomaterials because of their commercial availability A number of studies that focused on EOR from hard nanoparticles (NPs) engineering have been performed Li et al.,5–7 Moustafa et al.,8 and McElfresh et al.9,10 reported the possibility of using SiO2NPs dispersion fluids as a more robust wettability modifier than the soft ones Hunter et al.11 found that the effects of NPs, especially SiO2NPs, on reducing capillary pressure can be attributed to the specific attraction of NPs to absorb onto the interfaces of water–oil– rock phases and alternate the contact angle NPs can also be absorbed by the surfactants in the surfactant medium Therefore, given the effect of packing, the local surface/capillary pressure is reduced and consequently increases the oil displacement efficiency MNPs surface-modified by different agents have been actively studied for biomedical applications,12–14 and investigation of their potential use in oil exploration, especially EOR, has recently started.15,16 Compared with SiO2NPs, besides the common advantages of nanoscale materials, MNPs can also be easily recovered and reused because of their magnetic responsivity Sanders et al.16 used magnetic shell cross-linked knedel-like nanoparticles in a contaminated aqueous environment to remove hydrophobic contaminants Once loaded, crude oil-absorbed nanoparticles were easily isolated through introducing an external magnetic field The surface of MNPs requires modification to function as an EOR agent The surrounding polymer layer enables the particles to disperse in injected brine, become compatible with oil and be stable at high temperatures, and resist adsorption on the surface of the reservoir rock To date, many major oil fields in Vietnam, such as White Tiger, Dragon, and Dawn, have passed their peak harvesting period and their production is rapidly declining; thus, EOR measures should be considered, including the use of NPs.17,18 To focus on the use of modified MNPs in nanofluids as EOR agents, MNPs must be fabricated at an affordable cost Red mud waste from groundwater refinery stations is currently being buried and becomes a source of solid waste that may contribute to soil and groundwater pollution Therefore, this work used red mud as raw material to synthesize polymercoated MNPs and to evaluate its nanofluid system as an EOR potential agent for offshore high-temperature reservoirs in Vietnam (98%), ammonium hydroxide (NH4OH) (30%), ammonium persulfate ((NH4)2S2O8), and hydrochloric acid (HCl) were purchased from Merck Chemicals Sodium dodecyl sulfate (SDS) and ethanol (C2H5OH) were obtained from Sigma Aldrich Ankylphenolpolyethoxy carboxylate (50% by weight) prepared by our laboratory was used for this research; the ferric salts were prepared from a red mud source containing about 75% ferric oxide (Fe3O4), according to the analyzed result of energy dispersive x-ray spectroscopy (EDS) Procedure for Synthesis of Oleic Acid-Coated MNPs Encapsulated by Copolymer of MMA and AMPS (OMNPs-MMA-co-AMPS) Preparation of Ferric Salts from Red Mud Source Red mud (12 g) was dissolved in a 400-ml beaker containing 200 ml distilled H2O A calculated amount of HCl (30 ml) was then added The reaction mix was stirred vigorously at room temperature for 30 Then, the solution was filtered, and the filtrate, which was ferric salt (FeCl3), was obtained The filtrate was used for the synthesis of iron oxide nanoparticles (MNPs) The relevant chemical reaction can be expressed as follows (Eq 1): FeOHị3 ỵ HCl ! FeCl3 ỵ H2 O: ð1Þ Synthesis of Fe3O4 Magnetic Nanoparticles (MNPs) MNPs were synthesized using the combined method of co-precipitation and microemulsion in the presence of SDS as surfactant FeCl3 (0.5 M, 100 ml) and FeCl2 (0.5 M, 50 ml) (molar ratio 2:1) were premixed in a 500-ml three-necked roundbottom flask, which was equipped with a mechanical stirrer, under nitrogen atmosphere Meanwhile, g of SDS was dissolved into 50 ml of deoxygenated distilled water, which was poured into the mixture of Fe3+ and Fe2+ through a funnel The mixture was then heated gradually to 80°C and maintained at this temperature for h Subsequently, 45 ml of NH4OH (30%) was poured drop by drop (1 drop/s) into the solution Black nanoparticles were precipitated After the reaction, the mixture was stirred vigorously for another h; the nanoparticles were isolated by centrifugation and washed three times with 20 ml of ethanol by magnetic decantation until the pH was neutral The relevant chemical reaction can be expressed as follows (Eq 2): Fe2ỵ ỵ 2Fe3ỵ þ 8OHÀ ! Fe3 O4 þ 4H2 O: ð2Þ EXPERIMENTAL Materials Synthesis of Oleic Acid-Coated MNPs (OMNPs) Methyl methacrylate (MMA), sodium 2-acrylamido-2-methyl-propanesulfonate (AMPS), ferrous chloride tetrahydrate (FeCl2Ỉ4H2O), oleic acid MNPs (3 g) were dispersed into 50 ml of deoxygenated distilled water with the aid of an ultrasound bath, and the solution was heated Synthesis of Polymer-Coated Magnetic Nanoparticles from Red Mud Waste for Enhanced Oil Recovery in Offshore Reservoirs 3803 Fig Synthesized procedure for OMNPs-MMA-co-AMPS (a) (b) Intensity Synthesized Fe3O4 JCPDS 79-0417 (Fe3O4) 20 25 30 35 40 45 50 55 60 65 70 Two theta, degree Fig (a) XRD pattern of MNPs produced from red mud, (b) TEM image of MNPs produced from red mud waste simultaneously at 60°C with vigorous stirring for h Oleic acid (1.5 ml) was added into the dispersion and was vigorously stirred with a mechanical stirrer for h at 80°C Afterward, the mixture was cooled to room temperature and centrifuged (1000 rpm) for 30 The obtained precipitates (OMNPs, 4.52 g) were washed three times with 20 ml of ethanol–distilled water solution (volumetric ratio 1:1) to remove the excess amount of oleic acid Synthesis of OMNPs Encapsulated by Copolymer of MMA and AMPS (OMNPs-MMA-co-AMPS) OMNPs (4.52 g) were added to a three-necked round-bottom flask containing 50 ml of distilled H2O and 40 ml of AMPS–MMA mixture (molar ratio 1:1) The mixture was then sonicated and stirred vigorously for h at room temperature Meanwhile, 1g of ammonium persulfate (NH4)2S2O8 was dissolved in 10 ml of distilled H2O, and surfactant SDS was added This initial solution was sonicated for h with vigorous stirring and then poured into the above solution by using a dropping funnel The obtained polymerization mixture was stirred, heated gradually to 75°C, and then maintained at this temperature for 1.5 h without ultrasonics Afterward, the solution was sonicated for another h at ambient condition The final product was dried in an oven at 50°C overnight to yield 5.07 g of OMNPs-MMA-co-AMPS The 3804 Nguyen, Le, Ngo, Pham, and Dinh Evaluation of Thermal Stability of OMNPsMMA-co-AMPS (Nanocomposite) (a) The thermal stability of nanocomposite in the solid state was evaluated by the TGA method The temperature ranged from 30°C to 800°C with a heating rate of 10°C/min under a dynamic flow of nitrogen by using a DSC (Labsys Evo) The thermal stability of the nanocomposite in solution was evaluated as follows: Transmitance (b) (c) – OMNPs Oleic acid MNPs 4000 3600 3200 – 2800 2400 2000 1600 1200 800 400 – Wavenumber, cm-1 Fig FT–IR spectra of MNPs, oleic acid and OMNPs – (a) Dilute the carboxylic surfactant (50% by weight) in brine to obtain a concentration of 1000 ppm Disperse the nanocomposite in brine to obtain a concentration of 1000 ppm Add the appropriate surfactant solution to an appropriate nanofluid solution to obtain a nanocomposite/surfactant mixture with the desired ratios Put these mixtures into glass heat-resistant ampoules (ACE), deoxygenating with nitrogen, annealing at temperature of 100°C, observing the transparency and measuring the interfacial tension (IFT) of the mixtures before annealing and after every days Transmittance (b) The IFT of the mixtures was measured on a spinning drop interfacial tensiometer model 500 (TEMCO, TX, USA) Crude oil and brine from the White Tiger Oligocene oilfield of Vietnam were used (c) RESULTS AND DISCUSSION (a) OMNPs-MMA-co-AMPS (b) MMA-co-AMPS (c) OMNPs 4000 3600 3200 2800 2400 2000 Synthesis of MNPs and Oleic Acid-Coated MNPs (OMNPs) 1600 1200 800 400 Wavenumber, cm-1 Fig FT–IR spectra comparison of (a) OMNPs, (b) MMA-coAMPS, and (c) OMNPs-MMA-co-AMPS synthetic procedure of OMNPs-MMA-co-AMPS is shown in Fig Characterization of Obtained Compounds The chemical structure of MNPs, OMNPs and OMNPs-MMA-co-AMPS, were characterized by using Fourier transform infrared spectroscopy (FT– IR) with a Brucker Equinox 55 spectrometer in the range of 4000–400 cmÀ1 The morphology of the obtained materials was examined by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) (JSM 7401F).The size of the nanocomposite OMNPs-MMA-co-AMPS was estimated by using FE-SEM Thermo-gravimetric analysis (TGA) was conducted on both unfilled polymer and polymeric nanocomposite from 30°C to 800°C with a heating rate of 10°C/min under a dynamic flow of nitrogen by using a differential scanning calorimeter (DSC; Labsys Evo) The x-ray diffraction (XRD) pattern (Fig 2a) showed that the obtained materials had a Fe3O4 structure and that the size of these materials was about 14 nm (Fig 2b) Therefore, MNPs were synthesized successfully A correct particle size is required in MNPs preparation to ensure its dispersion capacity in brine medium while preserving good magnetic properties Ferric salt obtained from red mud waste reacted well in the co-precipitation to produce MNPs with tailored sizes depending on the reaction medium The surface of the nonfunctionalized MNPs was modified by reaction with oleic acid to enhance the probability of a core–shell structure performance later in polymerization Oleic acid is known to provide a high affinity with iron oxide through chemical interaction between their –COO– groups and Fe atoms Consequently, the hydrophobic tails of oleic acid molecules face outward and generate a non-polar shell, therefore warranting stability of MNPs suspension in non-polar solvents during the occurrence of mini-emulsion polymerization The presence of oleic acid on the MNPs surface was confirmed through FT-IR (Fig 3) The bands at 2862 cmÀ1 and 2923 cmÀ1 were observed according Synthesis of Polymer-Coated Magnetic Nanoparticles from Red Mud Waste for Enhanced Oil Recovery in Offshore Reservoirs 3805 Fig FE-SEM images of (a) OMNPs coated on the surface layer of MMA-co-AMPS copolymer (not used SDS) and (b) MMA-co-AMPS copolymer-coated OMNPs in the core–shell structure (used SDS) Fig TGA patterns of MMA-co-AMPS copolymer to the stretch modes of –CH2– and –CH3 of oleic acid The stretching vibration of C=O at 1710 cmÀ1 was clearly detected, and the bands at 1438 cmÀ1 and 1518 cmÀ1 were clearly recognized and attributed to the asymmetric and symmetric stretching vibrations of the –COO– functional group This result indicates that the layer of oleic acid was successfully coated onto the MNP surface Furthermore, a band at 587 cmÀ1, corresponding to the vibration of the Fe–O bonds in the Fe3O4 structure, was observed The results corresponded well with previous data Encapsulation of OMNPs by Copolymer of MMA and AMPS Figure shows the presence of the MMA-coAMPS copolymer on the OMNP surface whch was confirmed through FT-IR The bands at 1250 cmÀ1, 659 cmÀ1, 1099 cmÀ1, and 3200–3500 cmÀ1 from the FT-IR spectrum were assigned to S=O, S–O, C–S, and –NH– stretching vibrations, respectively, indicating that the AMPS structure compared with the –CH3, –CH2, and –COONa vibrations in MMA was clearly observed at 1389–2956 cmÀ1, 1502 cmÀ1, 3806 Nguyen, Le, Ngo, Pham, and Dinh Fig TGA pattern of OMNPs-MMA-co-AMPS Table I IFT of MNP-copolymer composite/surfactant mixtures in brine aged at 100°C and crude oil Appearance, IFT (dyne/cm) in time (days) No Sample 0–1000 200–800 400–600 600–400 800–200 1000–0 Appearance IFT Appearance IFT Appearance IFT Appearance IFT Appearance IFT Appearance IFT Start 14 21 31 Clear 0.8554 Dispersed 0.7899 Dispersed 0.9021 Dispersed 1.2320 Dispersed 5.4343 Dispersed 17.6737 Clear 1.3392 Dispersed 0.9235 Dispersed 1.2693 Dispersed 1.8932 Dispersed 6.5342 Dispersed 17.5248 Clear 1.7464 Dispersed 1.4582 Dispersed 1.5790 Dispersed 1.9835 Dispersed 6.9845 Dispersed 17.6345 Clear 1.4663 Dispersed 1.7204 Dispersed 1.9321 Dispersed 2.2436 Dispersed 6.9864 Dispersed 17.4687 Clear 2.1440 Dispersed 1.9889 Dispersed 2.5674 Dispersed 2.8742 Dispersed 7.2465 Dispersed 17.6453 and 1567–1385 cmÀ1, repectively In addition, the absorption bands at 1747 cmÀ1 and 1196 cmÀ1 corresponded to carbonyl (C=O) and asymmetric C–O–C stretching vibrations, repectively, indicating that oleic acid had been coated onto the MNPs’ surface Furthermore, the band at 582 cmÀ1 which belongs to the Fe–O bond in the Fe3O4 structure was still observed Thus, the FT-IR spectrum exhibited all the component signals in the core–shell structure of the MMA-co-AMPS copolymer As shown in Fig 5, the FE-SEM images clearly show the differences of our OMNPs coated in MMAco-AMPS copolymer on the surface layer of latex particles or in the core–shell structure TGA for OMNPs-MMA-co-AMPS Thermal stability of the polymer-coated iron oxide nanoparticles and unfilled copolymer MMA-coAMPS was investigated using a thermogravimetric analyzer, and the resultant thermo-diagrams are presented in Figs and The thermo-diagram of the nanocomposite for OMNPs-MMA-co-AMPS shows four steps The first weight-loss process in a temperature range of 30– 185°C is associated with the loss of adsorbed water that constitutes 10–15% of the weight of OMNPsMMA-co-AMPS The second weight-loss process lies in the temperature range of 185–335°C which can be attributed to the loss of the loosely bonded polymer matrix This weight-loss process is Synthesis of Polymer-Coated Magnetic Nanoparticles from Red Mud Waste for Enhanced Oil Recovery in Offshore Reservoirs (a) Before (b) During applying magnetic field applying magnetic field (c) After applying magnetic field 3807 mixture of 200 ppm magnetic nanocomposite and 800 ppm surfactant During the aging period, the IFT of all the tested samples with the nanocomposite increased, which is similar to the surfactant solution (Sample 1) This finding can be explained by the presence of alkylphenolpolyethoxy alcohol (NP-9), a nonionic surfactant precursor of synthesized alkylphenolpolyethoxy carboxylate in a ratio of 50:50 Thermostability of nanocomposites is better than bare MNPs, which is shown by good dispersion of the system, which we can observe in Fig CONCLUSION 16 A nanocomposite of MNPs and encapsulated copolymer of MMA and AMPS was sucessfully synthesized in the core–shell structure with advanced properties such as good dispersion, thermal stability, and reusing capacity The obtained magnetic nanocomposite exhibited a high potential for implementation as an EOR agent for offshore high temperature reservoirs ACKNOWLEDGEMENTS We would like acknowledge Prof Dr N.T.K Thanh (University College London, UK) for her good ideas and other support We also thank Dr Nguyen Hoang Duy (Institute of Applied Materials Science, Vietnam) for his good dicussion of this paper IFT of mixture, dyne/cm Fig Thermal stability of mixture copolymer composite/surfactant mixtures by time 32 0.5 14 21 28 35 Time of aging, days NC-Surf 0-1000 ppm NC-Surf 200-800 ppm NC-Surf 400-600 ppm NC-Surf 600-400 ppm NC-Surf 800-200 ppm NC-Surf 1000-0 ppm Fig Appearance of nanocomposite/surf brine solutions after aging for 25 days at 100°C influenced by the magnetite concentration used for nanocomposite preparation The third (400–600°C) step shows the advanced thermal stability of this nanocomposite to unfilled polymer The fourth (600– 800°C) step is related to iron oxide nanoparticles Figure shows a thermo-diagram of the unfilled copolymer At 350°C, the copolymer lost about half of its mass, and the final degradation happened at 400°C, or at 100°C lower than in the case of polymer-coated MNPs composite (500°C) Thermostability of the Mixtures The interfacial tension (IFT) between the solution of 1000 ppm of MNPs in brine and crude oil was 17.6737 dyne/cm This value was compared with that of sea water and crude oil of 19.1401 dyne/cm This result indicates that nanofluids, as surfactant solutions, cannot reduce IFT As shown in Table I and Fig 8, a slight synergistic effect resulting in IFT reduction appeared in the REFERENCES M.R Haroun, S Alhassan, A.A Ansari, N.A.M.A Kindy, N.A Sayed, B.A.A Kareem, and H.K Sarrma, Abu Dhabi UAE Int Pet Conf Exhib 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(Fig 3) The bands at 2862 cmÀ1 and 2923 cmÀ1 were observed according Synthesis of Polymer-Coated Magnetic Nanoparticles from Red Mud Waste for Enhanced Oil Recovery in Offshore Reservoirs 3805... into 50 ml of deoxygenated distilled water with the aid of an ultrasound bath, and the solution was heated Synthesis of Polymer-Coated Magnetic Nanoparticles from Red Mud Waste for Enhanced Oil