Treatment of effluents from textile-rinsing operations by thermally stable nanofiltration membranes

Abstract Thermally stable nanofiltration membranes were used to recover hot water from rinsing effluents from acid and reactive dyeing operations. Two types of flat-sheet membranes, MPF-34 (MWCO 200) and MPF-36 (MWCO 1000), were tested at 60°C and 10 bar. Experiments carried out with the made-up feeds containing acid dye and acetic acid showed that both membranes were able to retain more than 99% of dye. MPF-36 suffered from substantial flux decline due to the dye and acid in the feeds but still provided higher fluxes than MPF-34. Furthermore, reactive dye rejection of MPF-36 was acceptable, ranging from 97 to 99.5%, while the fluxes, 105–140 1/m 2 .h, were exceptionally high. MPF-36 was then further tested with the wastewater from industrial processes. The membrane could recover hot water by removing more than 98% of acid dye and 90% of reactive dyes. Despite severe fouling by acid dye, the membrane was still able to provide 40–50 1/m 2 .h of permeate fluxes. For the reactive dye rinsing effluents, remarkably high fluxes of 120–1501/m2.h were obtained. Chemical cleaning of the used membrane with 0.2% wt. HNO 3 and subsequently 0.5% wt. NaOH recovered 80–100% of the flux.