PVDF hollow fiber membrane modification for dye wastewater treatment by ozonation membrane contacting process

Abstract

One of the main pollutions from textile wastewater is the dyeing wastewater containing color and organic matters. Among the treatment methods of dye wastewater, ozonation membrane contactor was used as the concept of this research. PVDF membranes were developed by pulse inductively coupled plasma (PICP) and grafted by organosilanes for hydrophobicity enhancement applied for dye wastewater treatment by ozonation membrane contactor. To obtain a stable grafting, the surface of PVDF hollow fiber membrane was activated by the plasma operating condition including two different plasma gases (oxygen and argon), applied voltage and pressure, plasma treatment shot, followed by grafting with four different organosilanes (methyltrichlorosilane (MTCS), trimethylchlorosilane (TMCS),1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS-C8), and 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (FAS-C6), organosilane concentration and different grafting time. The results found that oxygen plasma activation of PVDF membrane was more effective compared to argon plasma. The hydrophobic membrane modified by MTCS and FAS-C8 was increased, while the plasma-activated membranes grafted by TMCS and FAS-C6 did not change. The success of membrane modification was confirmed by the presence of silicon functional group and composition in FTIR and EDX results and the decrease of surface roughness. After activated by oxygen plasma under 10kV/0.3 mbar/2 shots followed by grafting with MTCS for 4h and FAS-C8 for 6h, the water contact angle was greatly increased from 74.7o to 125.3o and 112.7.4o, respectively. The ozone flux of modified membranes was higher and more stable than that of the original PVDF membrane. In addition, PVDF-FAS-C8 membrane gave the highest results in terms of ozone flux and dye removal. Direct Blue 71 (DB 71) and Reactive Red 239 (RR 239) decolorization by PVDF-FAS-C8 membrane were almost complete decolorization. After 90 mins, the COD removals of DB 71 and RR 239 by PVDF-FAS-C8 were 62.5% and 67.5%, respectively. The energy consumption of modified membrane in membrane contactor for dye wastewater was lower than that of original membrane. This study demonstrated that the modified membrane has a potential interest in improving hydrophobicity and membrane contactor applications.