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Membrane Water Treatment Volume 7, Number 5, September 2016 , pages 417-431 DOI: https://doi.org/10.12989/mwt.2016.7.5.417 |
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Preparation and characterization of PVDF/alkali-treated-PVDF blend membranes |
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Q.F. Liu, F.Z. Li, Y.Q. Guo, Y.L. Dong, J.Y. Liu, H.B. Shao and Z.M. Fu
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| Abstract | ||
| Poly(vinylidene fluoride) (PVDF) powder was treated with aqueous sodium hydroxide to obtain partially defluorinated fluoropolymers with expected properties such as improving hydrophilicity and fouling resistance. Raman spectrum and FT-IR results confirmed the existence of conjugated carbon double bonds after alkaline treatment. As the concentration increased, the degree of defluorination increased. The morphology and structure of membranes were examined. The permeation performance was investigated. The results showed that membrane's hydrophilicity increased with increase of the percentage of alkaline treated PVDF powder. Moreover, in terms of the water contact angle, it decreased from 92° to a minimum of 68°; while water up take increased from 128 to 138%. Fluxof pure water and the cleaning efficiency increased with the increase of alkaline treated PVDF powder. The fouling potential also decreased with the increase of the percentage of alkaline treated PVDF powder. The reason that makes blending PVDF show different characteristics because of partial defluorination, which led the formation of conjugated C = C bonds and the inclusion of oxygen functionalities. The polyene structure followed by hydroxide attack to yield hydroxyl and carbonyl groups. Therefore, the hydrophilicity of blending membrane was improved. The SEM and porosity measurements showed that no obvious variations of the pore dimensions and structures for blend membranes were observed. Mechanical tests suggest that the high content of the alkaline treated PVDF result in membranes with less tolerance of tensile stress and higher brittleness. TGA results exhibited that the blend of alkaline treated PVDF did not change membrane thermal stability. | ||
| Key Words | ||
| PVDF; alkaline treatment; blend; hydrophilicity | ||
| Address | ||
| (1) Q.F. Liu, F.Z. Li, Y.Q. Guo, Y.L. Dong, J.Y. Liu, Z.M. Fu: College of Environment and Resources, Inner Mongolia University, No. 235 West College Road, Hohhot, Inner Mongolia, Hohhot 010021, China; (2) H.B. Shao: Key Laboratory of Coastal Biology & Bioresources Utilization, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Yantai 264003, China; (3) H.B. Shao: Institute of Biotechnology, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China. | ||
