Magnetically recoverable poly (methyl methacrylate-acrylic acid)/iron oxide magnetic composites nanomaterials with hydrophilic wettability for efficient oil-water separation (2023)

Introduction

Rapid growth in the oil and gas industry has led to the production of thick emulsion and oil spillage, leading to production issues. Also, these stable emulsions and hydrocarbon-contaminated wastewater pose a significant environmental challenge that must be immediately addressed (Zaman et al., 2019; Chen et al., 2021). Common methods of oil-water separation, like coagulation, gravity separation, thermal treatment, etc., have some disadvantages like consumption of high energy, longer separation time, and low separation efficiency (Chen et al., 2021; Xue et al., 2014), which make them commercially unviable.

Magnetic materials possess unique magnetic behavior resulting from complex multiphase structures (Zhang et al., 2015). Magnetic nanoparticles (NPs) have proved dominancy in various industries and research applications like drug delivery, electronics, separation, and purification (Yang et al., 2021a, Yang et al., 2021b; Nawaz et al., 2021; Ali et al., 2015a; Zhang et al., 2013), catalysis (Issaka et al., 2022; Yang et al., 2021a, Yang et al., 2021b; Khan et al., 2021) etc., owing to their strong magnetic domain and easy separation from stable emulsion system through external magnet (Ali et al., 2021; Dzumbira et al., 2021). Magnetite (Fe₃O₄) is considered a perfect candidate due to its minimum cytotoxicity and excellent compatibility (Ali et al., 2014; Nawaz et al., 2021). Evaluating NPs at liquid/liquid interfaces is significant in numerous research and industrial practices, including food processing, crude oil extraction, and mineral flotation (Ali et al., 2015b; Tian et al., 2015). Based on previous experimental and theoretical studies in this field, it is relatively easy to rationally describe the adsorbing phenomena of nanomaterials at liquid/liquid interfaces along with the emulsions stability as well as the formation of the foam resulting from the nanomaterials interface adsorption (Chu et al., 2022; Ali et al., 2019). Among these particles, stimuli-responsive polymers, together with nanoscale inorganic materials, have previously succeeded in the progress of composite materials with solvent, thermal, optical, and electronic characteristics (Hu et al., 2021; Ali et al., 2020; Cui et al., 2021).

The nanoscale inorganic materials hybridized with stimuli-responsive material may be demonstrated to utilize the water/oil interface (Liao et al., 2021). Previously, the integration of nanoscale, inorganic particles was used to fabricate multi-layered composite materials associated with individual nanoscale particle properties (Stefan et al., 2021; Zaman et al., 2019). Moreover, the composite of stimuli-responsive polymer with inorganic NPs have also been used for reversibly regulating the stability of the emulsion within stable oil-water systems through pH or temperature variation (Guo et al., 2022; Xu et al., 2022). In the stable emulsion, the emulsified water droplets are highly attractive regarding the development of facile inorganic NPs, with super hydrophilic wettability because NPs quickly migrate to the water phase in water, oil emulsion. Self-assembly of the inorganic NPs in the stable water, oil emulsion has been used to develop super hydrophilic multi-layered composites that effectively combine the properties of composite material and the individual nanoscale material (Ali et al., 2015c; Wang et al., 2021). Composite material formation by integrating stimuli-responsive polymers with magnetic inorganic NPs has also been used to reduce the emulsion stability via pH and temperature modulation (Zaman et al., 2019; Yue and Rahaman, 2022).

In this study, novel and recyclable magnetic composite NP, containing magnetic (Fe₃O₄) and an organic block copolymer of poly(methyl methacrylate acrylic acid) having strong hydrophilic wettability were developed. The magnetic composite NPs migrate to the emulsified water droplets due to the hydrophilic wettability of poly(methyl methacrylate-acrylic acid), thus efficiently detaching them through an external magnet (Scheme 1). The material is effective at 30°C temperature making 99% separation in about 30min. Furthermore, there is very low sludge formation and oil loss during separation. The prepared magnetic composite NPs can be recovered through external magnetic from the separated emulsion and can be recycled and used 8 times. Also, the treated emulsion is not contaminated with these NPs, presenting their green applications.

Section snippets

Chemicals

Heavy crude oil sample with diverse physical properties (Table 1) was obtained from the Gansu province Chang Qin oil field. NaAc, FeCl₃·6H₂O, and acrylic acid (AA) were provided by the reagent factory of Tianjin Hongyan Chemicals. Guang Zhou Jin Hua Da Chemical Co. Ltd provided Na₃Cit, while methyl methacrylate (MMA) and ethylene glycol (EG) were provided by Fu Yu chemical reagent Co. Ltd Tianjin supplied by Jin Shan Hua Shi Chengdu chemical. Potassium peroxy sulphate was delivered by Shanghai,

Surface morphology

TEM image of P(MMA-AA) precursor can be seen in Fig. 1. (a) and (b) as well as magnetic composite NPs in Fig. 1. (c) and (d). The TEM image in Fig. 1. (a) and (b) demonstrates the polymeric precursor NPs morphology to be uniform and almost monodisperse sphere-shaped particles having an average diameter of almost 140nm. Whereas images (c) and (d) show that the black Fe₃O₄ were appropriately adsorbed over the grey clour poly (methyl methacrylate-acrylic acid) polymer precursor nanoparticles

Demulsification capability at different concentration

To determine the hydrophilic wettability and demulsification capability of P(MMA-AA)/Fe₃O₄ magnetic composite NPs a number of successive experiments were performed via stable emulsions of crude oil having 24.7 °A PI. Fig. 8 image (a) for sample 01 (24.7 °API) describes the process of hydrophilic wettability and demulsification capability. Variant quantity of naphtha diluted (0.03, 0.04, and 0.05g) magnetic composite NPs had been added in 15mL 7:3 ratios (heavy crude) oil and water emulsion.

Comparison of magnetic composite NPs with commercial demulsifiers

After optimising different separation parameters such as time, temperature, pH, salt content and water content, the magnetic composite NPs were compared with various commercial demulsifiers available in the market (Fig. 13 a and b). Different commercial demulsifiers, i.e., hexyl amine and propylene oxide block copolymer, were used at 30°C for a stable emulsion of 24.7 °API. The separation efficiency for hexyl amine is 10%, and ethylene oxide–propylene oxide block copolymer is 23.3% at 30°C

Recycling test

In contrast to other commercial demulsifiers, the poly(methyl methacrylate acrylic acid)@Iron oxide (Magnetic) composite NPs were observed to increase the coalescence capability of water droplets, their kinetics, and their capacity of reusing after demulsification. Several demulsification trials were performed at 30°C by maintaining the demulsification for 30min to examine the magnetic composite NPs recycling ability. The recycle tests were performed 8 times. Fig. 14 (a) gives the image

Mechanism of demulsification performance of magnetic composite NPs

Two parts in the asymmetrical hybrids structure of P(MMA-AA)/Fe₃O₄ can be seen, one is organic polymer NPs with grey clour, and the other black clour is for inorganic iron oxide, which is appropriately deposited on the surface of the former. To know the water removal procedure from emulsions using P(MMA-AA)/Fe₃O₄ “magnetic composite NPs”, the emulsion system was analyzed through an optical microscope. Fig. 15 (a) confirms the presence of (water) droplets in the system in emulsions with droplets

Separated water physicochemical characterization for reuse

Water separation is the important step when oil is generated to remove replicated (produced) water with a number of organic and inorganic materials from chemicals. It is crucial to carry out the physicochemical characterization of (separated) water in large volumes and their suitable discarding or reuse for vital environmental concerns. Thus, physicochemical testing for the separated water from stable oil, water emulsion was performed through standard ASTM methods to confirm if the synthesized

Conclusion

P(MMA-AA)/Fe₃O₄ magnetic composite NPs with robust hydrophilic wettability and excellent demulsification application was prepared via a facile technique. The hydrophilic wettability of magnetic composite NPs permits them to efficiently move to the emulsified water droplets in emulsions, whereas the strong magnetic domain of Fe₃O₄ imparted quick separation of emulsified water from the heavy oil, water emulsion. The material was checked at different temperatures, time, pH, and salt contents and

Author statement

Hira Zaman, Anwar ul Haq Ali Shah, Nisar Ali: Conceptualization, Formal analysis and curation, Project administration, Supervision, Validation, Writing – original draft, Writing – review & editing. Hira Zaman, Cao Zhou, Adnan Khan: Investigation, Methodology, Formal analysis and curation, Interpretation of results. Farman Ali, Chen Tian Tian: Conceiving and design of analytical methods, Validation, Writing – review & editing. Nisar Ali, Muhammad Bilal: Formal analysis, Formal analysis, Writing

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors acknowledge the support from the International Joint Laboratory on Intelligent Preparation of High-end Mineral Salt Functional Materials, Key Laboratory of Regional Resource Exploitation and Medicinal Research, project numbers LPRK201909 and LPRK202101, National & Local Joint Engineering Research Center for Mineral Salt Deep Utilization, project number SF201801, Jiangsu Province College Students’ Innovation and Entrepreneurship Training program, project number 202111049338 and

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