Wanying Xie,Wei Song,Ji Li,Xiaolei Zhang,Wenyi Dong,Feiyun Sun
Modifying PVDF membrane by blending hydrophilic nano TiO 2 has been highly concerning, but its practical application is not well investigated. In this study, PVDF-TiO 2 membrane was employed in two modes to treat micro-polluted raw water for the first time, direct membrane filtration and pre-oxidation assists membrane filtration. At two filtration modes, the PVDF-TiO 2 membrane had comparable rejection capability to the unmodified PVDF membrane, as the removal of permanganate index (COD Mn ) was 0.26–0.72 mg/L, UV 254 was 0.0070–0.0618 cm −1 , turbidity was 1.60–4.49 NTU, and the total number of colonies was 360–23,780 CFU/mL. As for raw water treatment , using Fe 2+ /sodium dithionite (DTN)/O 2 system as the pre-oxidation process to assist the filtration of the PVDF-TiO 2 membrane was feasible. After optimization, the applicable conditions of the Fe 2+ /DTN/O 2 process were DTN dosage at 100 mg/L and a C Fe / C DTN of 1:4. As a result, the effluent qualities of the PVDF-TiO 2 membrane significantly improved. It was investigated that atrazine (ATZ), COD Mn , UV 254, and turbidity reduced, which was realized by the synergic effects of the pre-oxidation by free radicals and flocculation by iron. Pre-oxidation of the Fe 2+ /DTN/O 2 process could also enhance the permeability of the PVDF-TiO 2 membrane from 53.6 to 58.0 L/(m 2 ·h), nearly two times the PVDF membrane. Besides, the practical fouling of the PVDF-TiO 2 membrane was stably alleviated by the reduced R t , R re, and R ir , mainly due to constraining the internal pore fouling effectively.
Oil and organic pollutants removal becomes an efficient solution to dispose of industrial oily and textile dye wastewater. This study proposes a lotus leaf-like bionic nanofibrous membrane with underwater superoleophobic for highly efficient oil-water separation. Papillary structure of the bionic membrane is formed by electrospraying of PVDF and TiO 2 solutions on the surface of beaded-structure PVDF/TiO 2 membrane. Dopamine is then decorated on the resultant PVDF/TiO 2 membrane by in situ polymerization to be with hydrophilic-underwater oleophobic property for highly efficient oil-water separation. This bionic membrane has > 99 % oil-water separation efficiency, and high flux of 1389 ± 67 L m −2 h −1 . Its contact angle of underwater petroleum ether and dichlomethane reaches 155° and 152°, respectively. Moreover, it has excellent water transport capacity, photocatalytic property, as well as high separation efficiency and flux even after 5-cycle filtration. This bionic nanofibrous membrane will become a promising candidate in clean production, industrial oil/water separation, water purification and efficient liquid transmission.
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