Role of Tea Polyphenols in Enhancing the Performance, Sustainability, and Self-Cleaning Capability of Membrane Separation for Water-Soluble Pollutant Removal

Abstract

Tea polyphenols (TPs), such as green tea polyphenol (GTP) and black tea polyphenol (BTP), feature phenolic hydroxyl molecular structures capable of forming coordination and hydrogen bonds. These attributes render them effective in bridging the surface interface between inorganic catalysts and membrane substrates. In this study, TPs were employed as interface agents for the preparation of TPs-modified needle-clustered NiCo-layered double hydroxide/graphene oxide membranes (NiCo-LDH-TPs/GO). The incorporation of porous guest material, NiCo-LDH-TPs, facilitated water channel expansion, enhancing membrane permeability and resulting in the development of high-performance, sustainable self-cleaning membranes. The introduction of TPs through coordination weakened the surface electronegativity of NiCo-LDH, promoting a uniform mixed dispersion with GO and facilitating membrane self-assembly. NiCo-LDH-GTP/GO-5 and NiCo-LDH-BTP/GO-5 membranes demonstrated permeances of 85.98 and 90.76 L m-2 h-1 bar-1, respectively, with rejections of 98.73% and 99.54% for methylene blue (MB). Notably, the NiCo-LDH-BTP/GO-5 membrane maintained a high rejection of 97.11% even after 18 cycles in the catalytic self-cleaning process. Furthermore, the modification of GTP and BTP enhanced MB degradation through PMS activation, resulting in a 0.33% and 0.35% increase in the reaction rate constants of NiCo-LDH, respectively, while reducing metal ion spillover. These findings highlighted the potential of TPs in enhancing the efficiency and sustainability of self-cleaning GO membranes for water purification and separation processes.

Keywords: Tea polyphenols, Membrane separation, LDH, Self-Cleaning, PMS activation, Water-soluble pollutant.