In-situ Fenton oxidation experiment of compound benzene pollutants in high salt and strong acid groundwater

In the process of in-situ oxidation, the physical and chemical characteristics of actual ground water and water-bearing media are the important factors affecting the oxidation effect, but there are few specific studies on this effect at present. The actual high-salt and strong-acid compound benzene contaminated groundwater in a certain site is used as the research object, and 2-nitro-4-methoxyaniline (2-N) and 3-nitro-4-methoxyaniline (3-N) in groundwater are characteristic pollutants. The in-situ oxidation characteristics of Fenton’s reagent are explored, and the liquid environmental factors (initial H₂O₂ concentration, initial Fe²⁺ concentration, initial pH value, initial acetic acid (HAc) concentration, initial \rmSO_4^2- concentration) and aquifer media on the removal of 2-N and 3-N by Fenton method are examined. The results show that (1) the Fenton method has a significant effect on removal of 2-N and 3-N, and when the initial liquid phase conditions are c(H₂O₂)=7 mmol/L, c(Fe²⁺)=4 mmol/L, pH=4, c(HAc)=0 mg/L and c(\rmSO_4^2- )=0 mmol/L, the removal effect is the best. (2) Each factor affects the oxidation of 2-N and 3-N by the Fenton method. The effect of the addition of H₂O₂ and Fe²⁺ increases the removal rate of 2-N and 3-N. Increase in the concentration of HAc decreases the removal rate of 2-N and 3-N. (3) The groundwater medium has a strong effect on 2-N and 3-N, and the adsorption of 3-N is stronger than that of 2-N. In this experiment, the two largest adsorption states accounte for 29 % and 42 %, respectively. The existence of the adsorption state will inhibit the Fenton method to 2-N. (4) The mineral analysis results show that the medium contains a small amount of pyrite. In a sulfuric acid environment, the medium corrodes and dissolves to release Fe²⁺. Therefore, the Fenton reaction can be completed without additional Fe²⁺ to remove 2-N and 3-N.