Study of PVDF/Si-R hybrid hollow fiber membranes for removal of dissolved organics from produced water by membrane adsorption

Abstract

Abstract Polyvinylidene fluoride (PVDF) and hydrophobic silica sol (Si-R) hybrid hollow fiber membranes were fabricated by dry-jet wet spinning. The morphology and surface roughness of the PVDF/Si-R hybrid membranes were examined by scanning electron microscope (SEM) and atomic force microscopy (AFM), respectively. FTIR and contact angle analysis were used to characterize hydrophobic Si-R particles in the hybrid membrane. The membrane adsorption efficiency for dissolved organics including BETX (benzene, toluene, ethyl benzene and xylene) and two fatty acids: hexanoic acid and octanoic acid, as well as the membrane regeneration ability, were investigated by membrane adsorption experiments under different pressures, feed rates and temperatures. The results revealed that the hybrid hollow fiber membranes showed a microcellular structure rather than the typical asymmetrical structure of neat PVDF hollow fiber membranes. As the membrane collecting velocity increased, the hybrid hollow fiber membranes possessed enhanced surface roughness on both inner and outer surface. The adsorption efficiency of the PVDF/Si-R hybrid hollow fiber membrane was three times higher than that of the neat PVDF membrane. The adsorption efficiency of hybrid hollow fiber membranes increased with the increase of testing pressure; however, it decreased with the increase in feed rate, and was not influenced by temperature in the range of 0–80 °C. With membrane collecting velocity of 424 cm/min, the PVDF/Si-R hybrid membrane exhibited adsorption efficiency of 94.5% and 96.7% for benzene and octanoic acid, with membrane adsorption capacities of 208.1 mg/g and 173.9 mg/g. respectively. The hybrid membrane also showed high regeneration ability with 500 ppm benzene as feed solution. The PVDF/Si-R hollow fiber membrane offers an attractive possibility for the removal of dissolved organics in oilfield produced water.