Experimental Study On Remediation Of Chromium Residue Site Cr(Ⅵ) Contaminated Water And Soil Environment Using Furfural Residue

Chromium pollution of soil and water environment had received significant attention.The pollution of soil and water environment caused by chromium residue is particularly acute.Chromium contamination soil and water environment is mostly caused by chromium slag leaching filtrate,which has significant difference in pH,chromium existing form and soil permeability with other chromium pollution sources pollution.It is necessary to research the appropriate repair technology according to its pollution characteristics.Furfural residue is a solid waste produced by the production of furfural from corn cob,which is produced about millions of tons annually in China.Furfural residue is acidic,and the surface pore channels are plentiful.It is rich in cellulose,lignin and various functional groups such as hydroxyl,carbonyl and amino group.It is a kind of adsorbent and reductant with good performance.It can reduce environmental pollution and get economic and social benefits by using solid waste-furfural residues to repair Cr(Ⅵ)polluted soil and water environment on chromium residue sites.Through some experiments,this paper carried out the chromium slag field research on typical soil pollution process and its characteristics,furfural residue repair chromium residue site Cr(Ⅵ)contaminated soil research,furfural residue as PRB filling medium repair Cr(Ⅵ)contaminated groundwater and mechanism study.The following conclusions are mainly obtained:(1)Chromium contamination soil and water environment of chromium residue site is mostly caused by chromium slag leaching filtrate,which is strongly alkaline,high concentrations of Cr(Ⅵ)and total chromium,Cr(Ⅲ)accounted for a small.The Cr(Ⅵ)could stranded in soil into the soil after reduction,adsorption,complexation and precipitation by the soil organic matter,iron and aluminum oxide and soil particles.Among them,the reduction effect accounted for 61% ~ 93%,and 65% ~ 85% of chromium will translate into stable residual and Fe-Mn oxides bound.The contaminated soil of chromium residue site is alkaline,harden serious and Low permeability.The heavily polluted soil is yellow,and the main existing form of chromium is Cr(Ⅵ).There are large differences in Cr(Ⅵ)existing forms,redox properties and precipitation dissolution characteristics with other chromium pollution sources,such as electroplating,leather making,electronics and other sites.(2)The key technical parameters of repairing chromium residue contaminated soil are as follows: Cr(Ⅵ)pollution concentration of 500mg/kg,the furfural residues particle size 40 meshes,dosage of 0.3g/g,liquid-solid ratio of 5:1 and reaction time of 72 h,the removal rate of Cr(Ⅵ)can reach more than 99.5%.Furfural residues particle size,adding amount,liquid-solid ratio and reaction time will affect the removal rate of Cr(Ⅵ)in chromium pollution soil.The agglomeration of furfurfural residues is easy to occur when the particle size is too small,but the effect can be eliminated by increasing the mechanical stirring intensity and extending the reaction time.Increase the furfural residues adding amount,can improve the removal rate of Cr(Ⅵ),shortening the time of reaction equilibrium.(3)The water removal rate of Cr(Ⅵ)can reach 99.86% under the condition of pH 6 ~ 7,Cr(Ⅵ)concentration of 10 mg/L,40 mesh furfural residue dosage of 25 g/L,the reaction time of 150 min.Cr(Ⅵ)concentration was decreased to 0.014 mg/L,conform to the standard for groundwater quality(GB/T14848-2017)Ⅲ class requirements.Using furfural residue and zeolite as PRB filling medium in situ repair Cr(Ⅵ)pollution of groundwater,water pH value is neutral.when the hydraulic retention time of 30 h and raw water Cr(Ⅵ)concentration of 7.46 mg/L,water removal rate of Cr(Ⅵ)can reach more than 97%.(4)The reduction amount of furfural residue to Cr(Ⅵ)in water accounted for about 80% of total removal,and the reduction process mainly concentrated at the beginning of the reaction.The absorption of total chromium by furfural residue is given priority to with monolayer adsorption,and the reaction process followed a second-order kinetic model.The control step of reaction rate is the chemical reaction based on electron transfer.Hydroxyl and amino groups on the surface involved in the reduction and adsorption reaction of Cr(Ⅵ).The surface pores and channels were filled by the adsorbed Cr(Ⅵ)and Cr(Ⅲ).