Remediation Of Pesticide-contaminated Groundwater By Molecularly Imprinted Permeable Reactive Barrier Technology

As the industrial and agricultural industries continue to expand in scope,a large number of pesticides are used to flow into the undergroud layer through the surface.Although the pescide content is not high,it is extremely difficult to handle.Comnining moleclarly imprinting technology with premeable reative barrier technology can efficiently and directionally treat groundwater conraminated by pesticides.First,polystyrene microspheres(Ps)are synthesized by dispersion polymerization in this paper,review reaction conditions and determine the optimal reaction conditions in the preparation of polystyrene: The St concenteation of the monomer is 24 %,the ratio of ethanol/water in the dispersion medium is 50:0,the reaction time is 12 h,the reaction temperature is 70 ?,the mass fration of the initiator AIBN is 2 %,and the mass fraction of the dispersant PVP is 15 %,the polystyrene seed spheres synthesized under the above conditions have a uniform particle size,good sphericity,and good dispersibility,it lays foundation for the future prepatation of pesticide molecularly imprinted microspheres.Subsequently,atrazine molecularly imprinted microspheres were prepared by single-step swelling and multi-step swelling,after comparing the results,it was determined to chose a multistep swelling method.And under the control of a single variable,determine the optimal reaction conditions: The rotation speed of the polymerization is 150 rpm,the molar ratio of the template molecule,the functional monomer and the crosslinking sgent is 1:4:12.Preparation of carbofuran molecularly imprinted microspheres by multi-step swelling method,it is confirmed that toluene was selected as the solvent in this experoment.The molar ratio of the cross-linking agent MAA to the temple molecule is 4:1.Synthetic molecularly imprinted microspheres are the best.The particle size of the synthesized molecularly imprinted microspheres are about 7 ?m,microspheres have uniform particle size and good microsphere dispersibility,they have a honeycomb morphology on the surface and have recognition sites that specifically bind to temple molecules.Then two kind of pesticide molecularly imprinted microspheres are studied for adsorption kinetics,adsorption performance and selective performance: The pesticide molecularly imprinted microspheres will reach adsorption saturation in about 100 minutes,both types of molecularly imprinted microspheres have two types of adsorption sites.Atrazine MIPMs showed good selective adsorption to atrazine under the conditions of coexistence of atrazine and carbofuran;carbofuran MIPMs showed good selective adsorption to carbofuran under the conditions of coexistence of carbofuran and methomyl and 3-hydroxy carbofuran,it is confirmed that the prepared molecularly imprinted microspheres had excellent performance.Finally,the treatment effect of the combination of PRB column and molecular imprinting technology is investigated.first,the purification effect and reusability of simulated wastewater are investigated,atrazine and carbofuran molecularly imprinted microspheres are used as packing media to assemble the imprinted PRB column.The date shows that the binding times of the two blotted PRB columns are shortened to 1/5 and 1/6 before loading,respectively,and the maximum adsorption capacity is greatly increased by 200 and 220 times.Moreover,the two types of PRB columns have obvious removal effects on their respective characteristic pollutants,with recovery rates as high as 89.1 % and 91.1 %.After 5 reuses,the recovery rates of the two PRB columns for the pesticides atrazine and carbofuran are respectively maintained above 80 % and 85 %.Then,the actual groundwater is sampled,and the actual application effect of pesticide imprinted PRB column is investigated through the enrichment experiment.The results show that complex components of the actual water body have little effect on the performance of the PRB column,and the performance is close to that of the simulated water body.And the recycling is good,after 5 cycles of ues,although the adsorption amount and recovery rate are slightly reduced,the recovery rate of the characteristic pesticides atrazine and carbofuran is stable at about 80 %.The imprinted PRB column showed good performance of reduction and regeneration and recycling,which laid the foundation for further research and industrial application in the future.