Enhanced demulsification from aqueous media by using magnetic chitosan-based flocculant

Sources, colloidal characteristics, and separation technologies for highly hazardous waste nanoemulsions

Nanoemulsions play a crucial role in various industries. However, their application often results in hazardous waste, posing significant risks to human health and the environment. Effective management and separation of waste nanoemulsions requires special attention and effort. This review provides a comprehensive understanding of waste nanoemulsions, covering their sources, characteristics, and suitable treatment technologies, intending to mitigate their environmental impact. This study examines the evolution of nanoemulsions from beneficial products to hazardous wastes, provides an overview of the production processes, fate, and hazards of waste nanoemulsions, and highlights the critical characteristics that affect their stability. The latest advancements in separating waste nanoemulsions for recovering oil and reusable water resources are also presented, providing a comprehensive comparison and evaluation of the current treatment techniques. This review addresses the significant challenges in nanoemulsion treatment, provides insights into future research directions, and offers valuable implications for the development of more effective strategies to mitigate the hazards associated with waste nanoemulsions.

Fluorinated polyether-coated Fe3O4-functionalized oxidized carbon nanotubes as a recyclable demulsifier for crude oil emulsion treatment

Based on the excellent adsorption properties of carbon materials, a new magnetic nanodemulsifier was prepared in this study. First, carbon nanotubes were oxidized using a solvothermal method. Then, Fe3O4 was combined with oxidized carbon nanotubes using a one-pot method, and then grafted onto fluorine-containing polyether to prepare a magnetic composite demulsifier (Fe3O4@C-F) with good demulsification properties. The surface morphology of the composite demulsifier was analyzed using scanning electron microscopy (SEM). The structure of the composite demulsifier was characterized using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectrometry (XPS). The stability of the composite demulsifier was characterized using thermogravimetric analysis (TGA). Results showed that the oxidized carbon nanotubes and fluorinated polyether were successfully attached to Fe3O4. The experimental objective was to obtain a self-made crude oil emulsion. The demulsification test and recovery performance test were then performed, and the main factors affecting the demulsification performance of the demulsifier were investigated. Results showed that when the dosage was 800 mg L-1, the temperature was 65 °C, the demulsification time was 90 min, and the pH value was 6. The demulsification effect of the Fe3O4@C-F magnetic composite demulsifier was the best, whereby the demulsification rate could reach 91.68%, and the oil-water interface was clear. Fe3O4@C-F had a magnetic response and could be recycled from the two-phase system six times under the action of an external magnetic field. Fe3O4@C-F is an efficient and environmentally friendly demulsifier that has important application value for enriching demulsification technology systems.

Natural-based coagulants/flocculants as sustainable market-valued products for industrial wastewater treatment: a review of recent developments

Industrial wastewater is categorized as a voracious consumer of fresh water and a high-strength source of pollution. Coagulation-flocculation is a simple and cost-effective technique for removing organic/inorganic compounds and colloidal particles from industrial effluents. Despite the outstanding natural properties, biodegradability, and efficacy of natural coagulants/flocculants (NC/Fs) in industrial wastewater treatment, their significant potential to remediate such effluents is underappreciated, particularly in commercial scale applications. Most reviews on NC/Fs focused on the possible application of plant-based sources such as plant seeds, tannin, certain vegetables/fruit peels, and their lab-scale potential. Our review expands the scope by examining the feasibility of using natural materials from other sources for industrial effluent decontamination. By analyzing the latest data on NC/Fs, we identify the most promising preparation techniques for making these materials stable enough to compete with traditional options in the marketplace. An interesting presentation of the results of various recent studies has also been highlighted and discussed. Additionally, we highlight the recent success of using magnetic-natural coagulants/flocculants (M-NC/Fs) in treating diverse industrial effluents, and discuss the potential for reprocessing spent materials as a renewable resource. The review also offers different concepts for suggested large-scale treatment systems used by MN-CFs.

Application of Functionalized Fe3O4 Magnetic Nanoparticles Using CTAB and SDS for Oil Separation from Oil-in-Water Nanoemulsions

Using magnetic nanoparticles (MNPs) for emulsified oil separation from wastewater is becoming increasingly widespread. This study aims to synthesize MNPs using amphiphilic coatings to stabilize the MNPs and prevent their agglomeration for efficiently breaking oil-in-water nanoemulsions. We coat two different sizes of Fe₃O₄ nanoparticles (15-20 and 50-100 nm) using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with surfactant-to-MNP mass ratios of 0.4 and 0.8. We study the effect of various variables on the demulsification performance, including the MNP size and concentration, coating materials, and MNP loading. Based on the oil-water separation analysis, the smaller size MNPs (MNP-S) show a better demulsification performance than the larger ones (MNP-L ) for a 1000 ppm dodecane-in-water emulsion containing nanosized oil droplets (250-300 nm). For smaller MNPs (MNP-S) and at low dosage level of 0.5 g/L, functionalizing with surfactant-to-MNP mass ratio of 0.4, the functionalization increases the separation efficiency (SE) from 57.5% for bare MNP-S to 86.1% and 99.8 for the SDS and CTAB coatings, respectively. The highest SE for MNP-S@CTAB and the zeta potential measurements imply that electrostatic attraction between negatively charged oil droplets (-55.9 ± 2.44 mV) and positively charged MNP-S@CTAB (+35.8 ± 0.34 mV) is the major contributor to a high SE. Furthermore, the reusability tests for MNP-S@CTAB reveal that after 10 cycles, the amount of oil adsorption capacity decreases slightly, from 20 to 19 mg/g, indicating an excellent stability of synthesized nanoparticles. In conclusion, functionalized MNPs with tailored functional groups feature a high oil SE that could be effectively used for oil separation from emulsified oily wastewater streams.

Preparation and Characterization of Magnetic Carbon Nanospheres for the Demulsification of Water-in-Oil Emulsion

In order to reduce the harmful effects of demulsifiers on the environment and provide a green and reusable demulsifier, a magnetic carbon nanosphere demulsifier (Fe₃O₄/CNNs) was prepared in this study. The morphology and structure of the Fe₃O₄/CNNs were characterized by scanning electron microscopy, Fourier transform infrared, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed that the magnetic demulsifier has uniform particles and good dispersibility. In addition, the demulsification experiments showed that the dehydration rate could reach 92% under the optimal demulsification conditions, and the residual water content of Fe₃O₄/CNN magnetic demulsifier increased by 0.11% in 8 cycles of recovery experiments. The demulsification mechanism of the demulsifier was speculated. This work showed that the compounded magnetic demulsifier is friendly to the environment and is an effective material for separating oil and water phases, with broad application prospects.

Demulsification Performance and Mechanism of Tertiary Amine Polymer-Grafted Magnetic Nanoparticles in Surfactant-Free Oil-in-Water Emulsion

Numerous cationic magnetic nanoparticles (MNPs) have previously been developed for demulsifying oil-in-water (O/W) emulsion, and results showed that the cationic MNPs could effectively flocculate and remove the negatively charged oil droplets via charge attraction; however, to the best of our knowledge, there are no research reports regarding the synergetic influence of both the positive charge density and interfacial activity of MNPs on the demulsification performance. In this study, three tertiary amine polymer-grafted MNPs, namely, poly(2-dimethylaminoethyl acrylate)-grafted MNPs (M-PDMAEA), poly(2-dimethylamino)ethyl methacrylate)-grafted MNPs (M-PDMAEMA), and poly(2-diethylaminoethyl methacrylate)-grafted MNPs (M-PDEAEMA), were synthesized and evaluated for their demulsification performance. Results demonstrated that a high positive charge density and superior interfacial activity of MNPs could cause partial oil droplet re-dispersion when excessive MNPs were introduced, leading to a lower magnetic separation efficiency and narrower demulsification window. Herein, a demulsification window is defined as a range of nanoparticle dosages in which the MNPs can effectively demulsify the O/W emulsion under certain conditions. For highly positively charged MNPs, their good interfacial activity could aggravate the formation of a narrower demulsification window. When tertiary amine polymer-grafted MNPs carried a lower positive charge density or weak interfacial activity, that is, M-PDMAEA at pH 4.0, M-PDMAEMA at pH 5.0-9.0, and M-PDEAEMA at pH 9.0-10.0, wide demulsification windows were observed. Additionally, a recycling experiment suggested that MNPs could maintain high demulsification efficiency up to at least five cycles, indicating their satisfactory recyclability. The three tertiary amine polymer-grafted MNPs can be potentially used for efficient demulsification from surfactant-free O/W emulsion in various pH ranges.

Experimental Study on Synergistic Demulsification of Microwave-Magnetic Nanoparticles

Owing to the difficulty in the demulsification of heavy oil-in-water (O/W) emulsions, the demulsification rules of magnetic nanoparticles, microwave radiation, and magnetic-nanoparticle-assisted microwaves were investigated in this study. The surface potential and droplet size of the emulsion under different demulsification conditions were investigated by using a ζ potentiometer and polarizing microscopy to reveal the mechanism of demulsification. The results showed that γ-Fe₂O₃ exhibited the best demulsification performance among the six magnetic nanoparticles used for demulsification. With an increase in the concentration of γ-Fe₂O₃, the water separation of the heavy O/W emulsion first increased and then decreased, and with a decrease in pH, the demulsification performance gradually increased. The experimental results showed that microwave demulsification had an optimal power. The demulsification efficiency was significantly improved at the synergistic action between magnetic nanoparticles and the microwave, proving that magnetic nanoparticles had a promoting effect on microwave demulsification. In addition, the recycling experiment results showed that the magnetic nanoparticles exhibited good recyclability and reusability. Finally, a temperature field model of the emulsion under the synergistic effect of microwaves and magnetic nanoparticles was established and evaluated. Both before and after the addition of the magnetic nanoparticles, the theoretical temperature of the heavy O/W emulsion was consistent with the experimental temperature at different microwave powers and radiation times.

Nano-modification of carboxylated polyether for enhanced room temperature demulsification of oil-water emulsions: Synthesis, performance and mechanisms

Oil-water emulsions separation is frequently required considering the production and environmental issues. Herein, a nano-modification strategy has been proposed for carboxylated poly(propylene oxide)-poly(ethylene oxide) block polyether (mANP) using epoxy-functionalized magnetic nanoparticles (Fe₃O₄@SiO₂-GPTMS), achieving the construction of a highly efficient demulsifier (M-mANP). Bottle tests showed that M-mANP could separate over 98.5% of water from the asphaltene-stabilized water-in-oil (W/O) emulsion at mANP concentration of 150 ppm within 2 min at room temperature. The demulsification efficiency for crude oil-in-water emulsion was nearly 100%. According to interfacial tension and wettability tests, the nano-modification endows M-mANP with good amphiphilicity and high interfacial activity, which enables M-mANP to rapidly adsorb at the oil-water interface. Molecular dynamics simulation shows that abundant oxygen-containing groups (hydroxyl, ether bond, ester and carboxyl groups, Fe-O and Si-O bond) in M-mANP could strengthen the interaction with water, facilitating the replacement of asphaltene molecules at interfacial film. Observation of demulsification process by microscope reveals that the nano-size promotes M-mANP to bridge small dispersed droplets, enhancing the flocculation and coalescence of droplets. The nano-modified carboxylated polyether with outstanding demulsification ability shows a promising application for the treatment of different oil-water emulsions.

Elimination of microplastics from the aquatic milieu: A dream to achieve

Microplastics (MPs) have become a significant source of concern as they have emerged as a widespread pollutant that harms the aquatic environment. It has become an enormous challenge, having the capacity to biomagnify and eventually affect human health, biodiversity, aquatic animals, and the environment. This review provides in-depth knowledge of how MPs interact with different toxic organic chemicals, antibiotics, and heavy metals in the aquatic environment and its consequences. Membrane technologies like ultrafiltration (UF), nanofiltration (NF), microfiltration (MF), and dynamic membranes can be highly effective techniques for the removal of MPs. Also, hybrid membrane techniques like advanced oxidation processes (AOPs), membrane fouling, electrochemical processes, and adsorption processes can be incorporated for superior efficiency. The review also focuses on the reactor design and performance of several membrane-based filters and bioreactors to develop practical, feasible, and sustainable membrane technologies. The main aim of this work is to throw light on the alarming scenario of microplastic pollution in the aquatic milieu and strategies that can be adopted to tackle it.

Destructing surfactant network in nanoemulsions by positively charged magnetic nanorods to enhance oil-water separation

The separation of ultrafine oil droplets from wasted nanoemulsions stabilized with high concentration of surfactants is precondition for oil reuse and the safe discharge of effluent. However, the double barriers of the interfacial film and network structures formed by surfactants in nanoemulsions significantly impede the oil-water separation. To destroy these surfactant protective layers, we proposed a newly-developed polyethyleneimine micelle template approach to achieve simultaneous surface charge manipulation and morphology transformation of magnetic nanospheres to magnetic nanorods. The results revealed that positively charged magnetic nanospheres exhibited limited separation performance of nanoemulsions, with a maximum chemical oxygen demand (COD) removal of 50%, whereas magnetic nanorods achieved more than 95% COD removal in less than 30 s. The magnetic nanorods were also applicable to wasted nanoemulsions from different sources and exhibited excellent resistance to wide pH changes. Owing to their unique one-dimensional structure, the interfacial dispersion of magnetic nanorods was significantly promoted, leading to the efficient capture of surfactants and widespread destruction of both the interfacial film and network structure, which facilitated droplet merging into the oil phase. The easy-to-prepare and easy-to-tune strategy in this study paves a feasible avenue to simultaneously tailor surface charge and morphology of magnetic nanoparticles, and reveals the huge potential of morphology manipulation for producing high-performance nanomaterials to be applied in complex interfacial interaction process. We believe that the newly-developed magnetic-nanorods significantly contribute to hazardous oily waste remediation and advances technology evolution toward problematic oil-pollution control.

Effective remediation of petrochemical originated pollutants using engineered materials with multifunctional entities

The highly robust, effective, and sustainable remediation of hydrocarbon-contaminated wastewater matrices, which is mainly generated from petroleum and related petrochemical industries, is of supreme interest. Owing to the notable presence of suspended solids, oil, and grease, organic matter, highly toxic elements, high salts, and recalcitrant chemicals, crude oil emulsions, and hydrocarbon-contaminated wastewater are considered a potential threat to the environments, animals, plants, and humans. To effectively tackle this challenging issue, magnetic hybrid materials assembled at nano- and micro-scale with unique structural, chemical, and functional entities are considered robust candidates for demulsification purposes. The current research era on magnetic materials has superwettability, leading to an effective system of superwettability, which is vibrant and promising. The wettability of magnetic and magnetic hybrid materials explaining the theme of superhydrophobicity and superhydrophilicity under the liquid. Herein, we reviewed the applications of magnetic nanoparticles (MNPs) as effective demulsifiers. The demulsifier wettability, dose, pH, salinity, and surface morphology of compelling, magnetic nanoparticles are the main hidden factors in effective demulsifiers. There is a comprehensive discussion on the reuse and recyclability of MNPs after oil, water separation. Furthermore, the main challenges, coupled with the magnetic nanoparticles in the effective separation of emulsions, are intensified in detail. This review will compare the current literature and the utilization of MNPs for the demulsification of oil and water emulsions. This is envisioned that the MNPs would be critical in the petroleum and petrochemical industry to effectively eliminate water from a crude oil emulsion.

Biopolymer-based flocculants: a review of recent technologies

Biopolymer-based flocculants have become a potential substitute for inorganic coagulants and synthetic organic flocculants due to their wide natural reserves, environmental friendliness, easy natural degradation, and high material safety. In recent years, with more and more attention to clean technologies, a lot of researches on the modification and application of biopolymer-based flocculants have been carried out. The present paper reviews the latest important information about the base materials of biopolymer-based flocculants, including chitosan, starch, cellulose, and lignin etc. This review also highlights the various modification methods of these base materials according to reaction types in detail. Via the recent researches, the flocculation mechanisms of biopolymer-based flocculants, such as adsorption, bridging, charge neutralization, net trapping, and sweeping, as well as, some other special mechanisms are comprehensively summarized. This paper also focuses on the water treatment conditions, the removal efficiency, and advantages of biopolymer-based flocculants in applications. Further, this review sheds light on the future perspectives of biopolymer-based flocculants, which may make progress in the sources of base materials, modification processes, multi-function, and deepening application researches. We believe that this review can guide the further researches and developments of biopolymer-based flocculants in the future, to develop them with a higher efficiency, a lower cost, more safety, and multi-function for more diversified applications. Graphical abstract.

Application of coagulation/flocculation in oily wastewater treatment: A review

Volumes of oily wastewater are inevitably generated by every walk of life. The removal of oil particles from oil-contaminated wastewater which is characterized as huge amounts, intricate composition, and great threats to human health and the ecological environment is a research hotspot in water treatment fields. Due to high treatment costs and undesirable treatment efficiencies, oily wastewater treatment remains a topical and urgent issue. At present, coagulation/flocculation as an indispensable oily wastewater treatment technology receives much attention because it is very well established, economical, practical and relatively efficient. The influencing factors of oil wastewater treatment by coagulation/flocculation have also been summarized in-depth, like dosage, pH, etc. In consideration of its complex composition and treatment difficulty, this paper will also compare the treatment effects of different coagulants/flocculants used alone and combined effects in oily wastewater treatment: inorganic coagulants, organic synthetic polymeric flocculants, natural flocculants and modified polymeric flocculants. Additionally, in this review, the mechanisms of removing oily substance by coagulation/flocculation are emphasized. Given strict emission standards and the refractory nature of oily wastewater, the combination process with coagulation/flocculation, such as electrocoagulation, coagulation-membrane filtration hybrid process, and coagulation/flocculation-flotation can present better application potential and are discussed in this review. To provide a proper choice in practical application, the operating cost of coagulation and several conventional technologies are also compared. Finally, the existing challenges in the treatment of oily wastewater by coagulation are analyzed, and the feasible research direction is proposed.

Photocatalytic demulsification of oil/water emulsions containing nonionic surfactant

Separation of oil-water (OW) emulsions is investigated using a photocatalytic demulsification approach. Experiments were conducted using two types of photocatalysts, namely, ZnO and TiO₂. The emulsion samples were prepared with oil to water ratios of 1:3, 1:1, and 3:1 and using nonionic surfactant Tween 20 as an emulsifier. The demulsification efficiency was determined using a direct time varying phase separation measurement, while dynamic light scattering (DLS) and microscope imaging (MI) were used to determine the change in emulsion droplets size. The investigation results showed that all the emulsions were destabilized and separated within 30-90 min with demulsification efficiency that ranged from 38 to 90%. On the other hand, untreated control samples remained stable with no phase separation for more than 24 h. For most of the studied experimental conditions, TiO₂ nanoparticles gave better demulsification results than ZnO. Modeling of the batch demulsification kinetics for both systems agreed satisfactorily with the experimental measurements. This could allow its further extension towards design of continuous processes for potential implementation in treatment of industrial oily wastewaters.

Polarity of Cationic Lignin Polymers: Physicochemical Behavior in Aqueous Solutions and Suspensions

The structure of cationic monomers can significantly impact the polarity of lignin after polymerization. Cationic hydrolysis lignin (CHL) polymers were produced by polymerizing hydrolysis lignin (HL) with [3-(methacryloylamino)propyl] trimethylammonium chloride (MAPTAC) or [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride (METAC). The METAC monomer has an oxygen atom, with larger electronegativity, in its molecular structure, whereas the MAPTAC monomer contains a nitrogen atom, as well as an extra nonpolar CH₂ group, facilitating investigation into the effects of the polarity of CHLs on their physicochemical performance in an aqueous system. CHL polymers are analyzed and their interactions with clay particles are determined in colloidal systems. CHLs are designed to have similar charge densities (2.1-2.2 mmol g^-1) and molecular weights (55000-60000 g mol^-1 ). The hydrodynamic radius (H_y) and radius of gyration, (R_g) of HL-METAC are larger than those of HL-MAPTAC, implying a more 3-dimensional structure of HL-METAC in aqueous solution. The stability ratio of kaolin particles affirms the better performance of HL-METAC in comparison to HL-MAPTAC, which reflects the better flocculation efficiency of HL-METAC. The results also reveal that salt and urea aqueous solutions affect the H_y, R_g, and configuration of CHL polymers, which alters the flocculation efficiency of HL-METAC and HL-MAPTAC polymers in kaolin suspensions.

Flocculation Performance and Kinetics of Magnetic Polyacrylamide Microsphere under Different Magnetic Field Strengths

In this study, the flocculation performance and kinetics of magnetic cationic polyacrylamide (MCPAM) microspheres, compared with cationic polyacrylamide (CPAM), were systematically investigated under different magnetic field strengths. Flocculation performance was observed by jar test experiment. The density of flocs was estimated by the determination of floc settlement velocity and image analysis. The frequency distribution of floc size was measured with a Malvern Mastersizer instrument. When the diatomite suspension was treated by MCPAM and CPAM, the residual diatomite turbidity was 16.28 NTU and 244.13 NTU, respectively. The maximum turbidity removal efficiency of MCPAM was about 99.65% under 1000 Gauss magnetic field, which was higher than that (94.75%) of CPAM. The synergy of gravitational and magnetic fields for MCPAM promoted the formation of larger flocs with higher growth rates compared with CPAM. The effective density range of flocs in the MCPAM flocculation was increased to 10–252 kg m−3. The kinetic constants were calculated by monitoring the frequency of floc collisions. The increase of kinetic constant (k) to 25.81 × 10−11 s−1 suggested that interaction of contact and collision between magnetic flocs was sufficient. According to the evolution of the size and density of flocs under the synergy of gravitational and magnetic fields, the magnetic flocculation rate equation dN/dt=−1/9μρ−ρlg+ρkmHdH/dXai2−aj2−ai2e9μt/2ai2ρ+aj2e9μt/2aj2ρai+aj2 was derived. The study of magnetic flocculation kinetics can provide theoretical support for magnetic flocculation and is critical for the analysis of solid-liquid separation processes.

Synthesis of Fe3O4 nanocomposites for efficient separation of ultra-small oil droplets from hexadecane-water emulsions

Eco-friendliness and low cost are critical when investigating new oil–water separation agents with high separation efficiencies for the treatment of emulsified oily wastewater in industrial applications, including crude oil exploitation. Treatment methods specifically suited to wastewater containing ultra-small oil droplets are lacking and urgently required. This study investigated the one-pot synthesis of humic acid and polydimethyldiallylammonium chloride coated Fe₃O₄ nanoparticles. A low dosage of the nanoparticles (375 μg mL⁻¹) exhibited excellent separation efficiency (nearly 100%) and reusability when applied to hexadecane–water emulsions containing ultra-small droplets (200–300 nm). Electrostatic interactions and the strong interfacial activity of the nanoparticles played essential roles in achieving oil–water separation. This study provided an efficient extraction material synthesized by a facile and cheap method for separating ultra-small oil droplets from emulsions.

A facile one-pot synthesis of Fe₃O₄ nanoparticles exhibited excellent separation efficiency with a low dosage and reusability when applied to hexadecane–water emulsions containing ultra-small droplets.

The Demulsification Properties of Cationic Hyperbranched Polyamidoamines for Polymer Flooding Emulsions and Microemulsions

Polymer flooding emulsions and microemulsions caused by tertiary oil recovery technologies are harmful to the environment due to their excellent stability. Two cationic hyperbranched polyamidoamines (H-PAMAM), named as H-PAMAM-HA and H-PAMAM-ETA, were obtained by changing the terminal denotation agents to H-PAMAM, which was characterized by 1H NMR, FT-IR, and amine possession, thereby confirmed the modification. Samples (300 mg/L) were added to the polymer flooding emulsion (1500 mg/L oil concentration) at 30 °C for 30 min and the H-PAMAM-HA and H-PAMAM-ETA were shown to perform at 88% and 91% deoil efficiency. Additionally, the increased settling time and the raised temperature enhanced performance. For example, an oil removal ratio of 97.7% was observed after dealing with the emulsion for 30 min at 60 °C, while 98.5% deoil efficiency was obtained after 90 min at 45 °C for the 300 mg/L H-PAMAM-ETA. To determine the differences when dealing with the emulsion, the interfacial tension, ζ potential, and turbidity measurements were fully estimated. Moreover, diametrically different demulsification mechanisms were found when the samples were utilized to treat the microemulsion. The modified demulsifiers showed excellent demulsification efficiency via their obvious electroneutralization and bridge functions, while the H-PAMAM appeared to enhance the stability of the microemulsion.

Removal of Emulsified Oil from Aqueous Environment by Using Polyvinylpyrrolidone-Coated Magnetic Nanoparticles

In recent years, a large amount of emulsified oily wastewaters were produced from petroleum and food industries, resulting in severe environmental problems. In this study, a series of polyvinylpyrrolidone (PVP)-coated Fe3O4 magnetic nanoparticles (MNPs) were prepared via one-step solvothermal method by introducing various amounts or types of PVP. The synthesized MNPs were characterized by multiple techniques, and their demulsification performances were evaluated in petrochemical and vegetable oil wastewaters, respectively. Results showed that the introduction of PVP in solvothermal process could significantly enhance the demulsification efficiency of MNPs, although excessive addition of PVP could not further increase its efficiency. Moreover, the effects of pH, surfactant concentration of wastewater, and the recycle number of MNPs on the demulsification performance were investigated in detail. It was found that the demulsification efficiency decreased with the increase of pH and surfactant concentration, and the synthetic MNPs were still effective after being reused for 5 cycles under acidic and neutral conditions. It is expected that the development of the PVP-coated MNPs can provide a simple and powerful route for the oily wastewater treatment.

Insights of CMNPs in water pollution control

The various toxic contaminants such as dyes, heavy metals, pesticides, rare-earth elements, and hazardous chemicals are the major threats to all the flora and fauna. Owing to the harmful ill effects caused by the toxic contaminants, it is necessary to eliminate these compounds from the authors' ecosystem. The chitosan magnetic nanomaterials (CMNPs) are one of the superior materials used in the wastewater treatment through various conventional technologies. The chitosan is a natural source obtained from the crustacean shells of crabs, prawns etc. The magnetic nanomaterial prepared by the reinforcement of chitosan is highly effective in the removal of heavy metals, dyes, organic matter, and harmful chemicals. It is used in various technologies such as adsorption, flocculation, immobilisation, photocatalytic technology, and bioremediation. This possesses unique surface and magnetic characteristics, Moreover, it is simple, economically feasible, and eco-friendly material used efficiently in wastewater treatment. This review paper depicts the overview of CMNP in the industrial effluent treatment.