Synthesis of Oil/Water Separation Membranes via Grafting Acrylic Acid onto Poly (vinylidene fluoride) Modified by Tetraethyl Ammonium Hydroxide

Poly (vinylidene fluoride)-graft-poly (acrylic acid) (PVDF-g-PAA) membranes were prepared via phase bulk modification in tetraethyl ammonium hydroxide (TEAH) liquid, grafting acrylic acid (AA) onto PVDF by benzoyl peroxide (BPO) as a initiator. After that, the copolymer was casted into a flat membrane via immersion phase inversion. The chemical composition, morphology and the separation performance of the PVDF-g-PAA membrane were charaterized. Moreover, the effect of variable grafting conditions on grafting degree was investigated as well as the optimal surface contact angle for the grafting ration was obtained. It was proved that the PVDF was taken off HF to produce carbon double bonds and acrylic acid was grafted onto the modified PVDF backbones, forming a homogeneous pore distribution in interior and exterior of the membrane. The water contact angle of PVDF-g-PAA membranes decreased with increasing the grafting degree. The optimized hydrophilicity of the modified PVDF membrane was modified with 45% (mass fraction) of AA at 85 degrees C for 4 h, when this condition the grafting degree of membrane was 20. 1%; the porosity and mean pore size was 65. 3% and 78. 0 nm, respectively; the contact angle decreased from 57. 5 degrees to 14. 3 degrees within 60 s. Water flux increased to 571. 33 L/(m(2) . h), rejection ratio and flux recovery ratio up to 94. 3% and 88. 7%, respectively. The flux decline ratio was only 9. 8%. The separation performance of the PVDF-g-PAA membrane was significant improvement compared to that of the pure PVDF membrane.