Study On The Application Of Diffusion Dialysis In The Treatment Of Resin Desorption Solution Containing Fluorine

Fluorine contamination in water seriously threatens the health of human.The technology for lessen fluoride pollution in water is one of the hot spots in the field of water pollution control.Recent research showed that the advanced treatment technology based on nanocomposite resin has become the most effective method to solve this problem.However,the desorption solution produced in the regeneration process has the characteristics of high contaminants concentration,poor biodegradability,and waste resources for direct disposal.In this study,diffusion dialysis technology was used for separating and reusing the desorption solution.The factors such as membrane type,temperature,dialysis time,stirring speed and concentration of the dialysis solution were used to evaluate the separation and reuse performance of desorption solution.The parameters of the dynamic diffusion dialysis device were optimized,and the feasibility of resin adsorption-diffusion dialysis combined technology was demonstrated,which provided a theoretical and practical reference for similar desorption solution.The results showed that the diffusion dialysis technology was feasible for separation and reuse of alkaline desorption solution,however,the performance of high-salt desorption solution needed to be strengthened.Consequently,it suggest that the alkaline solution replaced the mixed solution of salt and alkali as the regenerant was proposed.Static diffusion dialysis experiments showed that:the ion exchange membranes with high content of water,small thickness and large interstitial space demonstrated excellent performance on separation and reuse of desorption solution.The polyethylene cation exchange membrane(LF)and the polyethersulfone cation exchange membrane(TWDDC)were chosen for treating the alkaline and high-salt desorption solution,respectively.The temperature affected the reuse efficiency through changing solution viscosity,ion mobility,and membrane boundary layer.High temperature enhanced the reuse efficiency of the desorption solution,however,it had no effect on the separation performance.Considering the cost of industrial application,the optimal operation temperature was 25?.The concentration difference between both sides of the membrane changed with dialysis time,and led to the change of the mass transfer driving force,thence affected the performance of the desorption solution.The dialysis time had a greater influence on the diffusion of OH-,however,it had no effect on F-and Cl-.The membrane boundary layer was affected by the stirring speed and the effect on different systems was different.The optimal stirring speed of the alkaline desorption solution was 300 r/min,and that of the high-salt desorption solution was 200 r/min.The different concentration of dialysate led to the change of mass transfer driving force directly.The results showed that the recovery performance promoted by the ion concentration of the dialysate increased,and the single component changed in the dialysate had no effect on the diffusion of other components.The alkali recovery efficiency reached 45%at the desorption solution flow rate of 0.6 L/h,and the ratio of desorption solution and receiving liquid was 1.Electrical assisted reinforcement experiments showed that a weak electric field could enhance the performance of the ion diffusion,but the performance of actual application had yet to be investigated.The adsorption-diffusion dialysis combined technology indicated that the treated solution had little effect on the resin adsorption as a regenerant.In addition,in order to demonstrate the engineering value of the combined technology,this paper carried out a laboratory study on the effluent containing fluorine from Haitai Semiconductor Co.,Ltd.,and designed a technical scheme.The design included the civil engineering,equipment and processes,estimated the total investment for construction,operating costs,and recycling benefits.The estimation results indicated that the total investment for the combined technology was 13.4095 million yuan,of which 4.6508 million yuan will be invested in diffusion dialysis.The annual operating cost reduced to 4.2486 million yuan by the diffusion dialysis technology,resulted in saving capital of 2.4911 million yuan.This result fully demonstrated that the combined process had high economic value.