Synthesis and performance evaluation of PES/chitosan membranes coated with polyamide for acid mine drainage treatment

In this article, performance evaluation of PES membrane infused with chitosan and coated with polyamide layer for treatment of acid mine drainage (AMD) is reported. PES/chitosan membranes were fabricated by varying chitosan concentration (0, 0.5, 0.75 and 1 wt%) using phase inversion method. PES/chitosan membranes were coated with polyamide (PA) via co-solvent assisted interfacial polymerization technique (CAIP). Scanning electron microscopy (SEM) and contact angle analysis show that chitosan and polyamide could enhance permeability without affecting rejection of the membrane. The permeability was improved with increasing chitosan content. Atomic absorption spectroscopy (AAS) was used to quantitatively determine cations in the permeate and the sulphate ions were analysed using ultraviolet and visible (UV-VIS) spectrophotometer. Pure water flux of PES/PA membrane was significantly improved from 56 to 93 l/m(2).hr with 1 wt% chitosan addition. Cation rejection (90.4, 88.3, 89.3 and 75.7% for Mn(2+),Fe(2+), Mg(2+) and Ca(2+), respectively) was observed to be higher than anion rejection (56.33% for SO(4)(2−)), when chitosan content was 0.75 wt%. These results indicate that the positively charged membranes under acidic condition had strong repulsive forces with the cations than attractions forces with anions. Polyethersulphone membrane modified with chitosan and coated with polyamide layer displayed potential for application in treatment of AMD.