Research Of Microwave Assisted Photocatalytic Membrane Distillation On Treating Organic Wastewater With High Salinity

In this paper, organic wastewater with salinity was treated by microwave assistedphotocatalytic membrane distillation （MPMD）, taking the advantage of membranedistillation （MD）, as the situation of treating high concentration industrial wastewaterwith high salinity was not very well. The strengthening and mechanism of microwaveand photocatalysis on membrane distillation were investigated. On the basis of theformer researches, MPMD was applied for the treatment of reactive black solutionand industrial salty wastewater （the effluent of SBR after treating coal gasificationwastewater and practical printing and dyeing wastewater）. The main conclusions areas follows:1. Influence of microwave to polarization and mass transfer on MD process wasinvestigated. The effect of operating condition to enhancement of MD by microwavewas also discussed. The results show that the temperature polarization on membranesurface is weakened by microwave, and the gas mass transfer coefficient in themembrane pores is also enhanced, which make the permeate flux about31.4%higherthan that without microwave. The higher of the feed temperature the larger of thepermeate flux. During MD process treating NaCl solution, the decrease of permeateflux is slow, as microwave could make polarization more weakened. Membranefouling is relieved by microwave during saturated NaCl solution MD process.2. Influence and mechanism of microwave and photocatalysis on membranefouling was investigated during MD process of organic wastewater with salinity. Theresults show that bivalent catio （Ca2+） will form complex with humic acid, andmicrowave will weaken this process, at the same time, organic matter will bephotodegraded by photocatalysis. The stability of hollow fibre membrane will beaffected by photocatalysis. 3. Experimental study on reactive black solution treating by MPMD wasinvestigated in the paper. The results show that when the concentration of TiO₂is0.6g/L and the pH value is3, the photodegradation of reactive black is at optimumefficiency. CO₃^2- and SO₄^2- will decrease the efficiency, but the influence of NO₃isnegligible. The photocatalyst, reactive black and degradation product can beintercepted in the feed by MD, and the permeate is pure.4. Experimental study on the effluent of SBR after treating coal gasificationwastewater and practical printing and dyeing wastewater by MPMD was discussed.The preliminary conclusions are:（1） During MPMD process of the effluent of SBRafter treating coal gasification wastewater,96%of COD is removed, afteracidification of the feed,98%of ammonian is removed. With microwave drying thewetted membrane and photocatalysis decomposing the deposit on membrane surface,the MD process runs stably.（2） During MPMD process of practical printing anddyeing wastewater,86.3%of COD in the feed is photodegraded. Contaminants areintercepted in the feed by MD, and the permeate is pure enough for reuse.