Preparation, characterization, and applications of kaolin/kaolin-based composite membranes in oily wastewater treatment: Recent developments, challenges, and opportunities
Amos Avornyo, Shadi W. Hasan, Fawzi Banat, Constantinos V. Chrysikopoulos
Abstract
Rapid industrialization and the accompanying generation of significant amounts of oily wastewater pose major environmental challenges, which necessitate efficient treatment technologies. Kaolin-based membranes have emerged as a promising option due to their availability, affordability, and effective filtration performance. This review comprehensively analyzes the potential of kaolin for the treatment of oily wastewater. The focus is on the main manufacturing methods such as uniaxial pressing, slip casting, tape casting, phase inversion, and extrusion, as well as modifications that improve the structural integrity of the membrane, and its surface wettability to enhance separation performance. In addition, characterization techniques to evaluate membrane properties such as mechanical strength, thermal and chemical stability, antifouling behavior etc. are discussed. Basically, kaolin can be used as a supporting substrate, as a primary separation layer or as an additive in non-kaolin membranes. In evaluating the oil-water separation performance of kaolin-based membranes, this review highlights important metrics such as oil separation rate, flux, flux recovery, antifouling behavior, and resistance to harsh physical and chemical environments. Articles selected for the review were retrieved from major databases such as EBSCOhost, Scopus, ScienceDirect, Web of Science, and Google Scholar using relevant keywords. Based on the data from these studies, the main advances, challenges, and prospects are highlighted. Although still in the early stages of commercial application, kaolin membranes show significant potential to improve filtration efficiency, mechanical and chemical resistance, and reduce operating costs in industrial oily wastewater treatment systems. • Kaolin membranes are a promising, affordable, and efficient solution for treating oily wastewater. • Kaolin functions as a supportive substrate, primary separation layer, or additive in membranes. • Kaolin membrane fabrication, modifications, characterization, and applications in oily wastewater treatment are examined. • Microfiltration and ultrafiltration are the main membrane-based technologies used for oil-water separation. • Kaolin membranes are currently in the development stage but hold great promise for the future.