Removal of bisphenol a from wastewater by adsorption and membrane separation: Performances and mechanisms

Bisphenol A (BPA) is an industrial chemical used in the production of certain plastics and epoxy resins. Due to its widespread distribution, severe toxicity and potential health risks, the need to develop efficient techniques to remove BPA is urgent. Among many potential strategies, adsorption and membrane separation techniques have been widely studied as they are cost-effective and easy to operate for efficient BPA removal. In this review, the performances and mechanisms of BPA adsorption by various adsorbents were summarized, including carbon-based materials (activated carbon, carbon nanotubes, graphene and its derivatives, and biochar), porous materials (MOFs, COFs), natural inorganic minerals (clays and clay minerals, zeolite-based adsorbents), and natural polymers (chitosan and cellulose, cyclodextrins, and molecularly imprinted polymers). Comparative results indicated that modified adsorbents and composite materials have better performances for removing BPA. Furthermore, the influencing factors, the fitted isotherm and adsorption kinetic models, and the application of density functional theory (DFT) and molecular dynamics (MD) in investigating adsorption mechanisms were discussed. The applications of membrane separation processes (microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO)) for the removal of BPA were discussed in terms of membrane flux, membrane materials, mechanisms and influencing factors. The efficiency of BPA rejection decreases in the following order: RO > NF > UF > MF. This review clarified the current state of knowledge and challenges, and compared the adsorption efficiency of various adsorbents and the rejection efficiency of different membrane separation processes, which can provide guidance for future research and development from the aspects of mechanism investigation, methods development and materials functionalization, aiming to promote the advancements in both technologies for the removal of emerging pollutants.