Fenton Oxidation Of Leaching Wastewater Produced By Heavy Metal Contaminated Soil

In recent years,with the upgrading of our country’s industrial structure and the relocation of old industrial bases,a large number of industrial sites have been left behind.The problem of soil pollution in industrial sites is prominent,mostly heavy metals,organic matter and compound pollution,which seriously affects the reuse of land resources.In order to solve this kind of industrial site pollution problem as soon as possible,soil leaching technology is widely used in the remediation of heavy metal contaminated soil because of its short remediation period and remarkable remediation effect.However,the leaching process will produce a large amount of leaching wastewater,and the complexed heavy metals in the leaching wastewater are highly stable and difficult to be directly treated by the traditional precipitation method to reach the standard.Therefore,it is particularly important to develop a method suitable for treating such heavy metal leaching wastewater.This paper examines the leaching removal effect of iminodisuccinic acid（IDS）on Pb in the actual industrial contaminated soil through the oscillation leaching experiment,and optimizes the leaching conditions,including the concentration of the eluent,the initial pH of the system,the liquid-to-solid ratio,Factors such as the initial temperature of the system and the rinsing time.Using the strong oxidizing property of Fenton’s method to carry out oxidative degradation research on waste liquid containing IDS-metal complex,and explore the best degradation conditions.Furthermore,in order to save the dosage of H₂O₂ and Fe²⁺,a new type of cathode material was prepared by loading graphene oxide on graphite felt（GO@GF）,and generating H₂O₂ in situ.The electro-Fenton method was compared and studied.For the degradation effect of washing waste liquid,the optimal electrolysis conditions were explored,including factors such as system pH,applied voltage,and electrolysis time.The main experimental results are as follows:（1）The best elution conditions were determined by batch oscillation elution method,which the elution concentration is 4.4 mmol/L,the liquid-to-solid ratio is 10:1,the elution time is 2h,and the initial pH of is 3.0,the initial temperature of the system is 25℃,and the highest removal rate of medium and heavy metals under this condition is 14.58%.The BCR continuous extraction method was further used to analyze the form of heavy metal Pb in this industrial contaminated soil,and it was found that the main occurrence form of Pb in this industrial contaminated soil was oxidizable state>residue state>acid soluble state>reducible state,and it was in the leaching state.Under the action of the agent,the residual Pb can be transformed into other forms.（2）Fenton method was used to degrade the leaching wastewater.The optimal degradation conditions are:H₂O₂ dosage of 0.75 mol/L,Fe SO₄·The dosage of 7H₂O is 0.05 mol/L,the initial pH of the system is 3.0,the initial temperature of the system is 25℃,and the reaction time is 60 min.Under this optimal degradation condition,the TOC removal rate of the leaching wastewater can reach 56.02%.The Pb content of the effluent is less than 0.1 mg/L,which meets the Class A emission limit in the"Integrated Wastewater Discharge Standard Shanghai Municipal Standard（DB 31/199-2018）".（3）The effect of electro-Fenton method on the treatment of leaching wastewater was further compared and studied.First,prepare a high-activity graphite felt cathode material,optimize the optimal loading conditions of graphene oxide,and explore the optimal electro-generated H₂O₂ conditions,that is,the applied voltage is 2.5V,the initial pH of the system is3.0,and the power-on time is 3h.The oxygen flux is 100 m L/min.Under these conditions,the output of H₂O₂ can reach 120 mg/L,and the removal rate of TOC in the leaching wastewater can reach 56.29%,which is higher than the effect of Fenton oxidation under the same conditions.