Nanofiltration hollow fiber membranes for textile wastewater treatment: Lab-scale and pilot-scale studies

The textile industry is a water intensive industry that generates a vast amount of wastewater. The wastewater generated from the textile industry is generally loaded with pollutants comprising spent textile dyes, suspended solids, mineral oils, electrolytes, surfactants, etc. Therefore, it must be properly treated before disposal or reuse. A systematic study was conducted to evaluate the performance of newly developed polyamide-imide hollow fiber nanofiltration (NF) membrane in various operating conditions such as feed temperature (i.e., 25, 40, 50, 70°C), solute concentration (i.e., 100, 500, 1000ppm) and pH (i.e., 3, 7, 10). The results indicate that the NF membrane has satisfactory rejections (average: >90%) against various dyes at most testing conditions. In addition, more than 80% of NaCl and 90% of Na₂SO₄ permeate through the membrane. As a result, these salts have the potential to be be recovered and reused for the next dyeing process. The robustness of the membrane was proven by showing satisfactory and stable performance under cycles of chemical cleaning during the lab-scale and pilot-scale evaluations.