Dyes removal by composite membrane of sepiolite impregnated polysulfone coated by chemical deposition of tea polyphenols

Abstract

Two multi-amine, metformin (MTM) and polyethyleneimine (PEI), were used to prepare separative layer of composite membrane through chemical deposition with tea polyphenols (Tph), an inexpensive mixture of nature polyphenols, on a hybrid polysulfone (Psf) membrane. The supporting layer was a blend membrane of Psf, coupling agent treated sepiolite and cetyltrimethylammonium bromide (CTAB). Sepiolite and the surfactant improved surface hydrophilicity of membrane. Pure water flux (PWF) of membranes was increased from 33.97 to 611.46Lm−2h−1bar−1. The optimum mass ratio for MTM to Tph and PEI to Tph were 9.4:1 and 2.4:1 in chemical deposition reaction, respectively. MTM-Tph (MT) surface was negative charged while PEI-Tph (PT) was positive charged. Monomer reactivity determined the thickness of functional layer. Both composite membranes showed dyes rejection capacity at 1bar. PT layer was thicker than MT, so did its rejection for dyes. The rejection of PT for 5 dyes were all higher than 98% and remained at 99.3% and 98.6% in 200 h for Congo red (CR) and neutral red (NR). PT membrane displayed the potential in textile waste water treatment.