Study On The Treatment Of Phenol Wastewater By Vacuum Membrane Distillation

The source of wastewater containing phenol and its hazard to the environment were introduced. Conventional treatment methods of phenol wastewater included physicochemical method, chemical method as well as biochemical method. And a review of the domestic development of treatment technology for wastewater containing phenol in recent years was also presented in this paper.Membrane distillation was a new type of technology integrated with physical process and chemical process, and many scholars paid attention to it. Removal phenol experiments from wastewater were investigated by direct-contact membrane distillation technique in the literatures, but the fluxes were small.Vacuum membrane distillation (VMD) is a newly developed technology, possessing merits of both pervaporation and membrane distillation, which had a large fluxes and an excellent separation efficiency. Microporous poly (vinylidene fluoride) and poly (terra fluoro ethylene) are ideal membrane distillation materials, which were hydrophobia and well processed.In this paper, the feasibility and superiority of treatment of phenol aqueous solution by VMD were studied. Some factors, such as temperature, pH values of the feed, the genre of porous membrane as well as concentration of phenol in the feed, were observed. Experiments of solute transport through porous and hydrophobic membranes have been carried out. Two kinds of commercial membranes PVDF and PTFE have been used. Results are as following: temperature of the feed had great influence on the membrane fluxes in VMD process, relationship between the feed temperature and fluxes were approximate to Arrhenius equation. The gauge pore sizes of PVDF and PTFE membranes were 0.22um and 0.20|am respectively. While the optimal feed temperature of PVDF and PTFE membranes were 50'Cand 60癈 respectively, the best ion rejection ratios and phenol removal ratios could be obtained. Because PTFE membrane was more hydrophobic than PVDF membrane, PTFE membrane employed in the treatment of phenol aqueous solution had a better efficiency and a higher ion rejection ratio.pH values of the feed had little impact on fluxes and ion rejection ratio, when pH^ 11, selectivity of the VMD process varied a little as the feed temperature increased; while when pH> 11, it varied enormously. Improvement of pH values of the feed favored the increase of selectivity. The greatest selectivity could be obtained when pH values of the feed reached 12.3. Therefore, it was seemly for the feed pH values about 12.It was technically feasible for the treatment of phenol aqueous solution by VMD, in the optimal process condition, much greater fluxes could be obtained than direct contact membrane distillation process, and higher the ion rejection ratio and selectivity, hence it was of great potential value for development and application.