Study On In-situ Remediation Technology Of As Contaminated Groundwater In Taojia River In The Xianghualing Area

A large number of waste rocks are produced by open-pit stripping and pit mining after the completion of the mining mission in the mining area.Many tailings are produced by beneficiation and slag are produced by smelting,which have not been effectively treated,and pollutants are easy to penetrate into the underground water system and spread rapidly.The pollution is serious in Xianghualing area,and the annual average concentration reaches 0.225 mg/L.As to water,it may directly endanger human health,leading to nausea,vomiting,diarrhea,abdominal pain and so on.However,the traditional treatment methods of wastewater containing have some shortcomings.It is urgent to find a suitable way to treat arsenic pollution in water.Based on the geological survey and hydrogeological study of as polluted water body of Taojia River in Xianghualing area,this thesis investigates the water pollution situation and main causes in this area,and explores the flow characteristics of water body in the area.Using nZVI slurry as the raw material and biomass activated carbon powder as dispersed carrier,the supported nano zero valent iron material BC-nZVI was synthesized by a mechanical loading method,which reduced the agglomeration effect of nZVI.The materials were analyzed by powder X-ray diffraction(XRD),scanning electron microscopy(SEM)and infrared spectroscopy(FT-IR).The effects of different materials,storage time,carrier load,initial concentration,material addition,initial p H and treatment time on pollutant removal efficiency were studied.According to the actual polluted water body,an in-situ remediation demonstration area of arsenic containing water system was established,which provides a reference for the in-situ remediation of underground-polluted water systems in the mining area.The main work and conclusions of this paper are as follows:(1)Exploration and research found that there are many limestones in the Xianghualing area and the underground rivers have been formed.Carbonate rocks are widely distributed and karst is strongly developed.Loose rock pore water is free water,and most spring well flows are less than 0.51 L/s.Bedrock fissure water flow is generally 0.135-0.224 L/s and carbonate karst water flow is generally 113.90-464.6 L/s.(2)nZVI was prepared by pulse electrodeposition and nanocomposite BC-nZVI with core-shell structure was obtained by mechanical stirring,which improved the dispersion and increased the specific surface area of nZVI.The adsorption capacity and removal efficiency of arsenic by BC-nZVI were affected by the change of p H.When p H < 6,the adsorption capacity of BC-nZVI increased with the increase in p H.When p H value is 6 ～ 9,BC-nZVI shows excellent adsorption performance.When p H > 9,the adsorption of arsenic decreases with the increase in p H.The removal efficiency reaches a peak at p H = 3,and the reduction or increase of p H will reduce the removal rate of arsenic.(3)To improve the use of NZVI,the effects of different initial concentrations,material addition and reaction times on the arsenic removal rate were investigated.The materials were analyzed by powder X-ray diffraction(XRD),scanning electron microscopy(SEM)and infrared spectroscopy(FT-IR).The results show that the adsorption and degradation of as by BC-nZVI conforms to the second-order rate equation and the removal process mainly includes redox reaction and adsorption coprecipitation.(4)The polluted area of Taojia River system was treated,and a reagent injection and recovery system was designed.The results show that the river can meet the drinking water standard and the nanocomposites were successfully recovered.Through the construction of in-situ groundwater remediation model base,it provides a certain theoretical and data basis for the popularization of nZVI.