The determination of performances of polysulfone (PS) ultrafiltration membranes fabricated at different evaporation temperatures for the pretreatment of textile wastewater

The effects of evaporation temperature on properties and filtration performances of polysulfone membrane were investigated with a series of experiments. Membranes were fabricated by phase inversion process at five different evaporation temperatures (25 ± 0.4, 35 ± 0.6, 45 ± 0.5, 55 ± 0.5 and 65 ± 0.6 °C). The resulted membranes were characterized by water permeability, MWCO (molecular weight cut-off), AFM, porosity, contact angle and SEM analyses and tested for filtration performances by using a model dye solution (reactive orange 16-RO16) and a real dye-bath textile wastewater. The pore size and density onto the membrane surface become smaller and the surface roughness, porosity, permeability and MWCO values of membranes considerably decreased with the increasing of evaporation temperature. At the pretreatment filtration experiments, the flux values of membranes decreased largely with the increase of the evaporation temperature while the removal efficiencies for color, COD and conductivity parameters increased. At the membrane fouling analysis, the flux reduction ratios (FRR), the filtration (R_t) and fouling (R_f) resistances and the reusable performances of membrane changed directly proportional with roughness, porosity and pore size characteristics of membranes. At the nanofiltration step (NF-270 membrane), the moderate color, chemical oxygen demand (COD) and conductivity removal were showed at permeate of PS-65 membrane (the membrane fabricated at 65 ± 0.6 °C).