Removal Of Nitrobenzene From Groundwater By Iron-based Materials And Its Application In PRB

With the acceleration of industrialization and agriculture,a large number of industrial wastewater and agricultural sewage permeate into the groundwater environment.A large number of refractory organic pollutants pose a great threat to human health,which poses a new challenge to the remediation technology of groundwater.In this paper,the carbon-based material Cu Fe/Carbon containing zero valent metals was prepared by using Cu Fe-LDH as the precursor by carbothermal reduction method.Taking Zero-valent iron（ZVI）and Cu Fe/Carbon as the research objects and nitrobenzene as the target pollutant,the influence and mechanism of groundwater background factors（different anions,cations and small molecular organic acids）on the removal of nitrobenzene by environmental functional materials were discussed.It was also applied to PRB to provide a theoretical basis for practical groundwater treatment design.The main research contents are as follows:（1）The effects of five anions(Cl^-,SO₄^2-,HCO₃^-,NO₃^-and HPO₄^2-),four cations(Ca²⁺,Mg²⁺,Mn²⁺and Fe³⁺)and low-molecular-weight organic acids（OA oxalate,CA citrate,GA L-glutamic acid,AA L-alanine）on the removal of nitrobenzene by Cu Fe/Carbon and ZVI were investigated.The results show that Cu Fe/Carbon material can effectively remove nitrobenzene wastewater,and its degradation efficiency reaches 66.3%,which is 1.97 times（33.6%）that of ZVI material.Among them,when Cl^-,SO₄^2-and NO₃^-coexist in ZVI system,the degradation performance of nitrobenzene is improved to more than 55%;When HPO₄^2-coexisted in ZVI system,the removal rate of nitrobenzene decreased to 24.5%;When Fe³⁺coexists in the reaction system,the removal effect of nitrobenzene is significantly improved.It may be that the addition of Fe³⁺induces the formation of Fe（II）-ligand complex,which promotes the degradation of nitrobenzene.When the concentration of Fe³⁺in the solution reached 0.8 m M,the removal rates of nitrobenzene in cufe/carbon and ZVI increased to 90.2%and 79.9%respectively.In Cu Fe/Carbon and ZVI systems,when the concentration of small molecular organic acid is 0.002 M,the removal efficiency of nitrobenzene is increased to more than 77%.Through the characterization technology,it is clarified that the number of surface functional groups is changed under the chelation of small molecular acids,the proportion of-COOH:-OH groups on the surface is increased,the affinity of Cu Fe/Carbon and ZVI materials for nitrobenzene is improved,the surface charge distribution is changed,and the electromotive potential is increased.（2）Compared with ZVI material,based on the removal effect of Cu Fe/Carbon material on nitrobenzene and its tolerance to various influencing factors in water environment medium,Cu Fe/Carbon was selected as the research object and immobilized into sodium alginate based cufe/carbon gel beads for fixed bed column experiment to simulate the removal of nitrobenzene in groundwater.The effects of Cu Fe/Carbon gel beads on the removal efficiency of nitrobenzene under different media,flow rate,column bed height and other parameters were investigated.The results showed that when the flow rate was 0.078 m/d,the removal rate of nitrobenzene reached 45.1%;In the medium particle size influence experiment,the removal rate of nitrobenzene by Cu Fe/Carbon gel pellets in fine sand column（particle size 0.1-0.25 mm）was 46.1%,which was higher than that of coarse sand（particle size0.5-1.00 mm）（24.9%）and medium sand（particle size 0.25-0.5 mm）（34.7%）;The higher the column bed filler thickness（L=6 cm）,the adsorption sites will also increase,and the removal rate of nitrobenzene will increase significantly（66%）.