Treatment of textile dyes containing wastewaters with PES/PVA thin film composite nanofiltration membranes

Poly(ether sulfone) (PES) has been widely used in commercial ultrafiltration membranes. In the present work, the commercial PES ultrafiltration membrane is coated with poly(vinyl alcohol) (PVA) to make thin-film nanofiltration membranes by dip-coating method. PVA is a water soluble, hydrophilic polymer with the ability to form ultra thin films. Malic acid is used as the cross-linking agent to enhance thermal and chemical stability. The membrane performance is evaluated by cross-flow filtration of dyes - acid, reactive and disperse, which are commercially used in textile industries. The rejection and fouling characteristics of the membrane towards removal of different types of dyes from synthetic aqueous solutions were studied. Rejection towards salts like NaCl, Na2SO4 and MgSO4 were also studied. The membrane is characterized by FE-SEM, ATR-FTIR, TGA and contact angle measurements. It was observed that the permeate flux was almost same as that of pure water. A flux of 3.06 L/(m2 h atm) was obtained with the membrane with 1 wt% PVA. Maximum dye rejection of about 97.7% was observed for disperse dyes. The influence of operating parameters on the membrane performance was studied. Combined film-theory solution-diffusion model was used to find mass transfer coefficients and solute transport parameters.