| Pure terephthalic acid (PTA) is a type of important chemical product and chemical fiber raw material. As a major production country of chemical fibers, China accounts for 30% of global production of terephthalic acid (TA), which is the raw material for producing PTA. The wastewater generated in the production PTA process has become one of the main water pollution sources. Currently, most of the wastewater from PTA production process is treated with biological process and then discharged directly. There is almost not any report which concerns recovering TA solid particles, metal catalysts and water from the PTA production wastewater. This paper introduces a combination process of two-stage membrane separation and ion exchange which is used to recover resources from PTA wastewater. Stainless steel ultrofiltration membrane was applied to recover TA particle solids, ion exchange system was used to recover metal catalysts and reverse osmosis system was to purify and recover water.Stainless steel ultrofiltration membrane with wide channel and TiO2 coating was applied for recoving organic particles from PTA wastewater in bench scale test and pilot test. Almost all suspended particles in PTA wastewater were removed through ultrofiltration. In the meantime, parameters such as membrane material type, membrane pore size, operation pressure, wastewater temperature, wastewater concentration, as well as the way of membrane operating and cleaning were studied for their effect on cross-flow filtration efficiency. Through the experiments, suitable process operating parameters were obtained and an engineering application proposal was presented.For recovering the Co and Mn ions from PTA wastewater, the performance of slelectively adsorbtion catalysts by ion exchange resin was evulated in the experimental process. Through static ion exchange test, resin C with a strong selective separation performance for the Co, Mn, Fe, and Ni was screened out, and selecting the best agents and regeneration method for resin regenerating. Through continuous ion exchange pilot study, the appropriate process parameters were determined, the running stability of continuous ion exchange process and reliability of resin regeneration method were verified. The main process for recovering Co and Mn through continuous ion exchange was get through, and the Co ion concentration in recovery concentrate solution can reach 10000mg/L or more.The wastewater through out ion exchange resin colume was treated further by reverse osmosis for purifying and recovering water. The technical parameters of membrane system and membrane cleaning method were confirmed after testing, and the recovered water using reverse osmosis can be reused for PTA production.Combined two phases'membrane separation and ion exchange process was applied for PTA wastewater reutilization in this paper. The appropriate process conditions were determined through the experiment, and then made an engineering design based on research results. At the same time its economical efficiency was evaluated. The results showed that the recovery efficiencies of TA solid particles, Co catalyst and water were over 99%,90% and 75%, respectively. In addition, this combined process was also economically feasible and suitable for engineering application. |
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