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Oilfield produced water (OPW) is one of the most important by-products, resulting from oil and gas exploration. The water contains a complex mixture of organic and inorganic compounds such as grease, dissolved salt, heavy metals as well as dissolved and dispersed oils, which can be toxic to the environment and public health. This article critically reviews the complex properties of OPW and various technologies for its treatment. They include the physico-chemical treatment process, biological treatment process, and physical treatment process. Their technological strengths and bottlenecks as well as strategies to mitigate their bottlenecks are elaborated. A particular focus is placed on membrane technologies. Finally, further research direction, challenges, and perspectives of treatment technologies for OPW are discussed. It is conclusively evident from 262 published studies (1965-2021) that no single treatment method is highly effective for OPW treatment as a stand-alone process however, conventional membrane-based technologies are frequently used for the treatment of OPW with the ultrafiltration (UF) process being the most used for oil rejection form OPW and oily waste water. After membrane treatment, treated effluents of the OPW could be reused for irrigation, habitant and wildlife watering, microalgae production, and livestock watering. Overall, this implies that target pollutants in the OPW samples could be removed efficiently for subsequent use, despite its complex properties. In general, it is however important to note that feed quality, desired quality of effluent, cost-effectiveness, simplicity of process are key determinants in choosing the most suitable treatment process for OPW treatment., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Various treatments of choice are available to overcome contamination of bisphenol A (BPA) in the environment including membrane technologies; however, the treatment still releases contaminants that threaten the human being. Therefore, the present study is conducted to investigate the degradation of BPA by recently developed visible-light-driven photocatalytic nitrogen-doping titanium dioxide (N-doped TiO2) dual-layer hollow fibre (DLHF) membrane and its efficiency in reducing the level of BPA in contaminated water. Fabricated with suitable polymer/photocatalyst (15/7.5 wt.%) via co-extrusion spinning method, the DLHF was characterized morphologically, evaluated for BPA degradation by using submerged photocatalytic membrane reactor under visible light irradiations followed by the investigation of intermediates formed. BPA exposure effects were accessed by immunohistochemistry staining of gastrointestinal sample obtained from animal model. BPA has been successfully degraded up to 72.5% with 2 intermediate products, B1 and B2, being identified followed by total degradation of BPA. BPA exposure leads to the high-intensity IHC staining of Claudin family which indicated the disruption of small intestinal barrier (SIB) integrity. Low IHC staining intensity of Claudin family in treated BPA group demonstrated that reducing the level of BPA by N-doped TiO2 DLHF is capable of protecting the important component of SIB. Altogether, the fabricated photocatalytic DLHF membrane is expected to have an outstanding potential in removing BPA and its health effect for household water treatment to fulfil the public focus on the safety of their household water and their need to consume clean water. [ABSTRACT FROM AUTHOR]

Previous water treatments used are nondestructive and lead to the formation of new type of pollution. Photocatalytic reaction which induced by illumination of semiconductors in suspension was one of the most promising processes for wastewater treatment due to the ability of providing an interface with the aqueous medium and induce an advanced oxidation process. In this study, Malaysian bauxite has been selected as a new potential candidate for photocatalytic degradation. Bauxite powder was undergone heat treatment ranging from 800 to 1000 °C and then was characterized by field emission scanning electron microscope, X-ray diffraction (XRD), Brunauer–Emmett–Teller, ultraviolet–visible–near infrared spectroscopy and suspension absorbance test to determine the existing components and their composition, structure of the powder, band gap energy as well as the photocatalytic efficiency of bauxite in suspension of various concentrations of Reactive Black 5 (RB5) ranging from 5 to 20 ppm. The finding revealed that bauxite possessed slight changes in terms of XRF composition as well as particle size due to thermal process. This is supported by XRD analysis which showed that phase conversion occurred at 800 °C. Heat-treated bauxite possesses low band gap energy (2.04 eV). The photocatalytic activity of raw bauxite suspension was measured after 360 min illumination, and it proved that there was degradation of 67% and 63% from the initial 5 ppm concentration of RB5 using visible and UV lights, respectively. This finding clearly shows that bauxite exhibits good photocatalytic degradation and hence has a promising potential in removing dyes for industrial wastewater. [ABSTRACT FROM AUTHOR]

This present study aims to develop a visible-light driven photocatalytic dual layer hollow fiber (DLHF) membrane for photodegradation activity. Nitrogen-doped TiO 2 DLHF membranes with different loadings of N-doped TiO 2 were successfully fabricated via a single step co-extrusion method. The fabricated membranes were characterized for their morphology and properties. The incorporation of N-doped TiO 2 into membrane matrix has shifted the absorption capability into visible light region with lowest band gap energy obtained was 2.63eV. The photocatalytic performance evaluations of the N-doped TiO 2 DLHF reported 75% and 100% of Reactive Black 5 (RB5) removal were achieved after 360 min of visible and UV light illumination respectively. Altogether, N-doped TiO 2 DLHF exhibits excellent photocatalytic degradation activity under visible and UV light irradiation, hence have a promising potential in removing RB5 and other organic contaminants for water treatment. • The fabrication of visible light driven photocatalytic dual layer hollow fiber via co-extrusion technique. • The incorporation of N-doped TiO 2 into membrane surface successfully expand the photoresponse into the visible light region. • Good photocatalytic activity with 75% and 100% removal of RB5 under visible and UV light irradiation, respectively. • Efficient photocatalytic degradation process of visible-light driven N-doped TiO 2 for contaminants present in the water. [ABSTRACT FROM AUTHOR]

[Display omitted] • TiO 2 -WO 3 @GO/PVDF-DLHF photocatalytic membrane with catalytic memory was fabricated. • 3 wt% photocatalyst loaded membrane achieved 98.62% TOC rejection in visible light. • Good anti-fouling and self-cleaning with water flux of 99.51 L/m2h and FRR of 91.35 % • 3 wt% loaded membrane achieved 68.56% TOC rejection for memory catalysis. • Excellent stability after prolonged use with a TOC rejection of 89.76% Oilfield-produced water (OPW) is a complex wastewater that is difficult to treat causing significant harm to the environment. Photocatalytic membranes are emerging for OPW treatment. However, they suffer significant fouling due to the inability to self-clean during prolonged treatment. They also require continuous photo assistance to sustain the catalytic process. This limits their applications in the absence of light referred to as memory catalysis. This work reported the fabrication of a unique ternary photocatalyst TiO 2 -WO 3 @GO/PVDF dual-layer hollow fiber (DLHF) photocatalytic membranes for photodegradation and memory catalysis of total organic carbon (TOC) in OPW. The photocatalytic membranes were fabricated via phase inversion and co-extrusion method varying (0,1,3,5) wt% of the TiO 2 -WO 3 @GO photocatalyst. The membranes were characterized and their performances for TOC removal under visible light and memory catalysis were evaluated. The membranes exhibited excellent TOC degradation, rejection, anti-fouling, self-cleaning, and catalytic memory. The WO 3 was responsible for electron storage within the system and improved the absorptive capacity of TiO 2 in the visible range while the GO promoted the electron-hole transfer creating abundant active sites for photocatalytic reaction. The 3 wt% loaded membrane showed the best TOC rejection of 98.62 % after 6 h of operation, water and permeate fluxes of 99.51 L/m2h, and 76.54 L/m2h respectively. The membrane showed good catalytic memory in the dark with a TOC rejection of 68.56 % after 6 h, OPW flux recovery ratio (FRR), and TOC rejection of 91.35 % and 89.76 % respectively after 5 cycles of operation under visible light. This work is expected to bring a paradigm shift toward the fabrication of memory catalytic membranes for wastewater treatment. [ABSTRACT FROM AUTHOR]