| Pure terephthalic acid(PTA)is an important textile raw material.At present,China's PTA production capacity accounts for about 56%of global PTA production capacity.In the next two years,PTA capacity growth rate will reach more than 20%.The rapid development of the PTA market is followed by the treatment of PTA process wastewater.The production of PTA wastewater is large,and its solid content is about 0.5%with a high temperature.Its p H is 2 to 4,and it has a high organic content,thus it is difficult to treat.The silicon carbide film has excellent performances such as high temperature resistance,acid and alkali corrosion resistance,high chemical stability and resistance to organic solvents,and is suitable for treating PTA wastewater.With dead end filtration,the effluent recovery rate can reach 95%,which will greatly improve the treatment efficiency.In view of the fact that most of the silicon carbide films on the market are honeycomb ceramic membranes for cross-flow filtration,this study studied the preparation of single-channel full silicon carbide membranes for dead-end filtration,and applied the prepared full silicon carbide membranes to treat PTA wastewater.In this experiment,the silicon carbide film support body was prepared by extrusion molding method.The influence of plasticizer content and water content on the plasticity of the mud was studied.The formula of the mud material was determined:the plasticizer was added in an amount of 8 wt%of HPMC,3 wt%of glycerin,and 20 wt%of solvent deionized water.The extruded silicon carbide support body under the formulation had a high circularity and no defects on the surface.The ceramic body got dried and discharged,and then sintered at 2100??2250?.The influence of sintering temperature on the performance of the support was investigated.The results show that when the sintering temperature is 2200?,the prepared silicon carbide film support has the best performance,the porosity is 49.37%,the flexural strength is 15.66 MPa,the average pore diameter is 3.01?m,the pore size distribution is concentrated,and the pure water flux is up to 76.98 m~3/(m~2×h).The transition layer and separation layer of silicon carbide film were prepared by solid particle sintering method.The stabilized silicon carbide suspension slurry was prepared with different particle size silicon carbide particles and then coated on the inner wall of support body.After drying and sintering,silicon carbide membrane was prepared.The effects of the distribution and sintering temperature on the properties of the silicon carbide membrane were studied.The results show that the silicon carbide film transition layer is prepared by A1 and A2 silicon carbide powders.The optimum ratio of particle gradation is 7:3,the optimum sintering temperature is 1950?,and the average pore size of the transition layer is 1.86?m;the separation layer adopts the number A2 and A4 with the best ratio of mass ratio of 7:3.The optimum sintering temperature is 1900?,the average pore diameter is 0.83?m,the pore size distribution is narrow,and the pure water flux reaches 14.68 m~3/(m~2×h).The PTA wastewater was pretreated by self-made silicon carbide membrane dead-end filtration,and the process system of filtering the PTA wastewater from the dead end of silicon carbide membrane was determined.The membrane pore size was 0.8?m,the transmembrane pressure difference was 0.2 MPa,and the membrane flux was up to1845 L/(m~2×h),the retention rate of solid particles in wastewater is 99.4%;the system backflushing period is 40 min,the recoil pressure is 0.3 MPa,the recoil time is 2 s,and the membrane flux recovery rate is 97.6%. |
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