Preparation Of Monovalent Selective Anion Exchange Membrane And Its System Optimization

The monovalent selective anion exchange membrane can separate monovalent and multivalent anions in solution because of its unique structure,so it has great application potential in practical industrial production.At present,the univalent selective anion exchange membrane studied in China has some defects such as unstable performance,easy pollution and high cost,so it has not been commercialized.To solve this problem,the common homogeneous anion exchange membrane was modified by electrodeposition,and the feasibility of this modified material and method was comprehensively evaluated by static electrodialysis and dynamic electrodialysis tests.The main research results are as follows:Using polyanion electrolyte,polyanion electrolyte and cross-linking agent as modified materials,the anion exchange membrane was modified by three-layer alternating electrodeposition and cross-linking.The influence of various modification conditions on the monovalent selectivity of the modified membrane was investigated by orthogonal test,and the best modification conditions were selected.The experimental results show that the factors affecting the modification effect of anion exchange membrane are in the order of PEI concentration>current density>electrodeposition time>DAS concentration,and the best modification conditions are PEI concentration5g/L,electrodeposition time 90min,current density 10m A/cm²and DAS concentration5g/L.Static electrodialysis test was carried out in the system of 0.5mol/L sodium chloride and sodium sulfate solution with concentration ratio of 1:1 for 2 hours.The experimental results show that the unit price selectivity coefficients of unmodified original membrane,commercial membrane and modified membrane under optimal reaction conditions are 0.85,3.00 and 14.03,respectively.After two hours of static electrodialysis,the surface of the original membrane was seriously polluted,while the surface of the modified membrane was slightly polluted.To sum up,the modified anion exchange membrane not only greatly improves its monovalent anion selectivity,but also enhances its anti-pollution ability.The electrodialysis device was assembled with modified membrane and cation exchange membrane under the optimal reaction conditions to efficiently separate monovalent and divalent anions in simulated high salt wastewater.The effects of flow rate,voltage,Cl^-/SO₄^2-concentration ratio and p H on Cl^-/SO₄^2-selective migration ratio and energy consumption were systematically investigated.The experimental results show that the optimal operation conditions of dynamic electrodialysis are as follows:the concentration ratio of Cl^-/SO₄^2-is 1:1,p H is 7,the flow rates of both the weak chamber and the concentrated chamber are 20L/h,and the voltage is 5V.Under these conditions,after electrodialysis for two hours,the selective migration ratio of Cl^-/SO₄^2-was 6.6,and the energy consumption was 0.67k Wh/kg,and the separation effect was the best.