Fast fabricating superhydrophilic PVDF membrane via proanthocyanidins crosslinking at room temperature

Mussels in nature can adhere to the surface of hydrophobic substances by secreting adhesive substances, which has attracted wide attention by coating method for membrane modification. However, complicated processing procedures remain major problems. Here, we proposed a simple, mild and fast surface coating method. Proanthocyanidins (PC) react with 3-aminopropyl triethoxysilane (KH550) under the accelerated action of the oxidant ammonium persulfate (APS) at room temperature to form a polyphenol network. The hydrophilic network coating was constructed on PVDF membrane by surface co-deposition method for 1 h, which could effectively separate different emulsions. The water permeability of modified membrane was 18,271 L∙m−2∙h−1∙bar−1. The permeability for separating isooctane-in-water emulsion arrived at 14,223 L∙m−2∙h−1∙bar−1 and the oil rejection rate was 99.6 %. After ten cycles, the separation flux was 10,836 L∙m−2∙h−1∙bar−1 with the rejection rate of 98.8 %. Modified membranes were soaked in acid and alkali salt solutions of different pH values for 30 days, and maintained good underwater oleophobic performance (>156°). The developed membrane showed excellent separation performance, oleophobic property and acid-base stability. The proposed membrane modification strategy was prospective for efficient separation of oily wastewater.