Hydrophobic PVDF hollow fiber membrane modified with pulse inductively coupling plasma activation and chloroalkylsilanes for efficient dye wastewater treatment by ozonation membrane contactor

PVDF membranes were modified by pulse inductively coupled plasma (PICP) and followed by grafting by chloroalkylsilanes for hydrophobicity enhancement and applied to dye wastewater treatment by ozonation membrane contactor. Two plasma gases (oxygen and argon), two grafting chloroalkylsilanes (methyltrichlorosilane [MTCS] and trimethylchlorosilane [TMCS]), and a range of grafting times (0.5–4 h) were investigated. Hydrophobicity enhancement was influenced by the modification conditions including the type of plasma gas, the applied voltage and pressure, the number of plasma treatment shots, and the grafting agent and duration. The results revealed that oxygen-plasma activation was more effective than argon plasma for functionalizing MTCS for hydrophobicity enhancement. The hydrophobicity increased with MTCS grafting but not with TMCS grafting. Successful membrane modification using MTCS was confirmed by the presence of silicon using FT-IR and EDX analysis. Modifying membranes greatly increased the water contact angle, from 74.7° to 125.3° after activation by 2 shots of oxygen plasma under 10 kV/0.3 mbar followed by grafting with MTCS for 4 h. The duration of the exposure of the membranes to ozone determined the membrane properties. The modified membrane also had a higher and more stable ozone flux than the original membrane. Using the modified membrane, DB 71 decolorization by ozonation with membrane contactor was almost complete after 90 min. COD and TOC removals were 63% and 20%, respectively. This study demonstrates that membrane modification via PICP grafted with MTCS has the potential to improve hydrophobicity and membrane contactor applications.