Fabrication of high permselectivity nanofiltration membranes based on 3,5-dihydroxybenzoic acid for separation of dye/salts

Abstract

The preparation of high permselectivity nanofiltration membranes that can efficiently separate dyes and salts is beneficial to promote the sustainable development of the textile industry. However, the current loose nanofiltration membranes suffer from poor separation of small molecule dyes and salts and unsatisfactory permeance to the dye solution, such as acid fuchsin (AF) and sunset yellow (SY). In this paper, loose polyester nanofiltration membranes were successfully prepared by interfacial polymerization of 3,5-dihydroxybenzoic acid (DHBA) and trimesoyl chloride (TMC) under the catalysis of 4-dimethylaminopyridine (DMAP). The DHBA_2.2-TMC_0.22-DMAP_0.1 membrane showed a permeance of 31.17 ± 1.40 L·m⁻²·h⁻¹·bar⁻¹. It also exhibited a rejection from 95.65 % to 99.90 % for dyes of varying molecular weights from 452.37 to 696.68 Da. The dye/salts separation factors range from 25.39 to 992.85. After five cycles of pollution experiments, the flux reduction rate was only 18 %, and the flux recovery rate reached 89 %. The DHBA_2.2-TMC_0.22-DMAP_0.1 membrane also demonstrated good operational stability in a 96-hour continuous operation experiment and chlorine-resistance performance. The membranes prepared in this work are of great significance for the effective separation of dye/salts in printing and dyeing wastewater.