Ceramic Membrane-Based Treatment of Emulsified Oily Wastewater: A Critical Review of Recent Progress

The oil and gas industry produces enormous quantities of oily wastewater with serious implications for aquatic ecosystems and public health, given its complex composition of dissolved and dispersed oils, heavy metals, radionuclides, surfactants, and treatment chemicals. Conventional separation techniques such as coagulation/flocculation, adsorption, and biological treatment have been widely applied but are often limited by high energy consumption, generation of secondary pollutants, and inadequate removal of emulsified oil droplets. Membrane technology is an attractive alternative because of its high separation efficiency, simple operation, and low energy consumption. Among the membrane materials, ceramic membranes are particularly useful for treating oily wastewater owing to their high chemical inertness, thermal stability, and mechanical durability in harsh industrial environments. This review critically discusses recent advances in treating emulsified oily wastewater by ceramic membrane-based methods. Four main membrane materials, i.e., aluminum oxide (Al2O3), silicon carbide (SiC), zirconia (ZrO2), and titanium dioxide (TiO2), are reviewed based on their separation efficiency, fouling characteristics, and antifouling attributes. Membrane fouling by oil droplet adhesion and pore blocking is recognized as the main barrier to implementation. Fouling mechanisms, including cake filtration, pore blocking, and contaminant adsorption, are discussed in conjunction with the effect of pH, salinity, surfactants, and operating conditions. Strategies for fouling mitigation, including pretreatment, hydraulic backwashing, and chemical cleaning, are described in detail. In addition, surface modification strategies like hydrophilic nanoparticle functionalization, superhydrophilic/underwater superoleophobic coatings, and photocatalytic self-cleaning membranes are assessed for their potential to improve flux recovery and long-term antifouling performance. Finally, this review underlines the significant challenges regarding scalability, standardization, and cost and suggests some future research directions toward sustainable industrial implementation by integrating multifunctional membrane design, low-cost raw materials, and artificial intelligence-driven process optimization.