Research On The Recovery And Treatment Of DMAC Waste Liquid Produced From PES Hollow Fiber Membrane

DMAC is an important industrial solvent, amounts of wastewater containing DMAC will generate in the process of Polyethersulfone hollow fiber membrane's production, which will cause huge influence to water environment and endanger people's health if discharged into water. Therefore, the study on the recycling and treatment of DMAC wastewater in the production of Polyethersulfone hollow fiber membrane has very important role for environmental protection and reducing the production cost of enterprises.The advantages and disadvantages of various DMAC separation technologies were compared in this paper. The simulated wastewater was prepared according to the characteristics of wastewater generated by one plant. The feasibility of recycling and treating wastewater containing DMAC was analyzed and the optimum extractant was obtained through screening. The optimum extraction conditions were determined through single factor experiment of single-stage extraction. The optimum extraction crafts and operating conditions were obtained through multi-stage extraction experiment. Finally, the recovery of DMAC by batch distillation method and the treatment of low concentration DMAC wastewater by advanced oxidation were discussed.The stimulated waste liquid system of DMAC content of 10%,20%and 30% were prepared to carry out following experimental study according to the characteristic of DMAC production waste liquid. By comparing the extraction efficiency of several low boiling extraction agents commonly used in industry to DMAC and the physical properties of extractants, it was demonstrated that the recovery of DMAC in waste liquid by extraction method was totally feasible and the best extractant was chloroform. The single-factor experiment which influenced extraction efficiency showed that with the increase of extractant proportion, the extraction efficiency increased significantly, while the extractant proportion exceeded 2:1, the increasing speed of extraction efficiency became slow. The presence of LiCl in waste liquid was beneficial to the recovery of DMAC. When the concentration of LiCl in waste liquid increased from 0% to 10%, the extraction efficiency of DMAC increased from about 74% to about 80%. The increase of pH value was beneficial to the recovery of DMAC, but influenced little. When the pH value of waste liquid increased from 4 to 10, the extraction efficiency of DMAC increased from about 74% to about 75%.The increase of temperature was not beneficial to the recovery of DMAC, but influenced little. When the temperature of waste liquid increased from 20℃to 40℃, the extraction efficiency of DMAC decreased from about 74% to about 73%.The influence of many kinds of multi-stage extraction methods to the extraction efficiency were studied in this paper. The results showed that the five counter-current extraction was the best extraction method. The optimum extraction conditions were as follows: the extractant proportion was 2:1 and the temperature and pH value did not need to adjust. The theoretical calculation was carried out to the extraction effect of multi-stage. The difference between theoretical value and experimental value was not very large through the comparison with experimental value. This demonstrated the feasibility of simply deducing extraction stages, the concentration of raffinate phase and extraction efficiency of multi-stage extraction through theoretical calculation.The change of tower bottom's concentration of DMAC waste liquid along with time in the separation of DMAC using batch distillation tower and the influence of reflux ratio to distillation effect were studied. The results showed that it was feasible to recover DMAC by distillation method, but with a high energy consumption. More pure DMAC could be separated firstly by controlling the operating reflux ratio between 2 and 3, then gradually increasing it in the case of low energy.The experimental results showed that the multi-stage count-current extraction was suitable to recover 10%~30% DMAC waste liquid, the batch distillation method was suitable to recover DMAC waste liquid, in which the content of DMAC exceeded 30% and the Fenton agent oxidation method was suitable to treat DMAC waste liquid, in which the concentration of DMAC was less than 0.5%.