Nanofiltration of synthetic and industrial dye baths: Influence of temperature on rejection and membrane fouling

Abstract

Nanofiltration (NF) has become a widely accepted process not only for producing drinking water but also for recovering wastewater in industrial processes or removing pollutants from industrial wastewater effluent. In the textile industry, the treatment of various dye baths with NF at room temperature have already been studied and was found feasible at lab-scale and pilot scale. The aim of this study was to investigate the effect of temperature on permeate quality and membrane fouling in NF of textile effluents using a range of commercial membranes (Desal 5 DK, Desal 5 DL, N30F, NF PES 10) in a temperature range from 20 ^oC to 70 ^oC. Synthetic dye baths at different salt and/or dye concentrations and real dye baths were used. The performance of the NF membranes was evaluated by measuring the water flux, salt and color rejection. Na₂SO₄ rejection of 15% and color rejection of more than 80% were achieved through the experiments at elevated temperature. Permeate quality was satisfactory enough to recycle these effluents in reactive dyeing for water and energy savings. The fouling effect at elevated temperature on NF membrane increases the Na₂SO₄ and color rejection slightly, but membrane damage was observed for some membranes. There was a correlation between the results of experiments with synthetic solutions and with real wastewater.