Study On Preparation And Application Of Dynamic Membrane In Strontium-Containing Wastewater Treatment

90Sr in low-level radioactive wastewater had the characteristics of long half-life and strong biological toxicity.Chemical precipitation technology was simple,low cost.The hybrid of chemical precipitation technology and membrane technology was always used to remove strontium from radioactive wastewater.However,membrane fouling problem limited the further development of the hybrid process.In this study,a pre-coated composite dynamic membrane process was proposed to improve strontium removal effect solve the problem of membrane fouling.Dynamic membrane chemical reactor(DMCR)was a new type of wastewater treatment process which combined dynamic membrane filtration technology and chemical wastewater treatment technology.The process had the advantages of traditional membrane chemical reactor(MCR).Meanwhile,it was characteristic by low energy consumption and low cost.The pre-coated dynamic membrane technology was pre-coated with CaCO3 seed and Fe(OH)3 floccules on a new membrane assembly.it was expected that the pre-film seeding can induce nucleation,enhance strontium effect.Meanwhile,the floc can form a cake layer to prevent small particles from entering the membrane pore and delay membrane fouling.CaCO3 seed was obtained by repeatedly washing small CaCO3 particles.The final grain size of seed was larger and the sedimentation performance was better.The main crystal form was aragonite with high ability to capture strontium.In this study,the number of washing and granulation was 30 times.After granulation,the turbidity and hardness of effluent tended to be stable,and the grain size was relatively dense.The average particle size of seed was 35.56 micron.The particle size distribution was concentrated and had good sedimentation performance.In beaker test,the concentration of strontium in effluent was reduced to 0.0287 mg/L by pre-coating CaCO3 seed dynamic film.Correspondingly,the decontamination factor was 174.Fe(OH3)floccules were produced by double hydrolysis by adding ferric chloride solution to sodium carbonate solution.In the process of membrane filtration,strontium was removed by floc adsorption.The loose floc cake layer can alleviate membrane fouling to a certain extent.In beaker test,when the concentration of FeCl3 is 20 mg/L,the concentration of strontium in effluent can be reduced to 0.0261 mg/L,and the decontamination factor was 194.In the beaker test of Fe(OH)3/CaCO3 composite dynamic membrane,Fe(OH)3 flocs were pre-coated on the surface of 0.22 ?m microfiltration membrane,and then CaCO3 seed solution of 1 g/L was filtered.The seed continued to adhere to the surface of the pre-coated flocs and formed Fe(OH)3/CaCO3 composite dynamic membrane.Subsequently,the supersaturated solution formed by the reaction of strontium chloride and sodium carbonate was filtered in batches.when the 7500 mL solution was filtered to,the membrane flux decreased from 2800 L/(m2 h)to 60 L/(m2 h).Strontium concentration in effluent decreased to 0.0224 mg/L.Decontamination factor was 230.In the pilot-scale experiment,the specific flux of membrane decreased from 90.11 L/(h·m2·m)to 74 L/(h·m2·m).The strontium concentration in effluent decreased to 0.0883 mg/L,and the removal rate reached to 98%.