Abstract
Membrane filtration is considered to be one of the most promising methods for oily wastewater treatment. Because of their hydrophilic surface, ceramic membranes show less fouling compared with their polymeric counterparts. Membrane fouling, however, is an inevitable phenomenon in the filtration process, leading to higher energy consumption and a shorter lifetime of the membrane. It is therefore important to improve the fouling resistance of the ceramic membranes in oily wastewater treatment. In this review, we first focus on the various methods used for ceramic membrane modification, aiming for application in oily wastewater. Then, the performance of the modified ceramic membranes is discussed and compared. We found that, besides the traditional sol-gel and dip-coating methods, atomic layer deposition is promising for ceramic membrane modification in terms of the control of layer thickness, and pore size tuning. Enhanced surface hydrophilicity and surface charge are two of the most used strategies to improve the performance of ceramic membranes for oily wastewater treatment. Nano-sized metal oxides such as TiO2, ZrO2 and Fe2O3 and graphene oxide are considered to be the potential candidates for ceramic membrane modification for flux enhancement and fouling alleviation. The passive antifouling ceramic membranes, e.g., photocatalytic and electrified ceramic membranes, have shown some potential in fouling control, oil rejection and flux enhancement, but have their limitations.
Highlights
Water scarcity is a worldwide problem that threatens the sustainable development of society [1,2]
The performance of the prepared ZrO2/α-Al2O3 composite membrane was compared with three commercial alumina membranes for separating O/W emulsions and the results indicated that the zirconia membrane had the highest stable permeate flux and same oil rejection as γ-Al2O3 membrane despite its higher mean pore size
Xu et al [141] compared the performance of alumina and silicon carbide (SiC) hollow fibre membranes for MF of O/W emulsion, the results indicated that the SiC membrane had a smaller pore size, but gave a higher flux due to a higher hydrophilic surface
Summary
Water scarcity is a worldwide problem that threatens the sustainable development of society [1,2]. It is important to develop a robust, energy-efficient and low-cost technology for sustainable oily wastewater treatment [15]. Membrane separation is considered as one of the most promising methods for oily wastewater treatment, especially for oil/water (O/W) emulsion separation with an oil droplets size smaller than 20 μm [16,17]. Large oil droplets may accumulate on the membrane surface, causing cake layer formation. The membrane pore size can be blocked or plugged by small droplets, leading to internal clogging For both cases, the membrane performance deteriorates. Afterwards, the current status, mechanism, and performance on the state-of-the-art anti-fouling ceramic membranes for the treatment of oily wastewater are presented. Potential opportunities and challenges of using modified ceramic membranes for oily wastewater treatment are highlighted
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