Synchronous Stabilization Of Sb/As And Soil Function Regulation In Soils From Non-ferrous Smelting Sites

With the transformation and upgrading of the non-ferrous metal industry,a large number of antimony smelting sites have been left behind,and the situation of heavy metal pollution risk prevention and control is grim.In this study,according to the heavy metal pollution characteristics of an abandoned antimony smelting site in Hunan province,H₂O₂ modified iron-based biochar was prepared,and its adsorption performance and mechanism to antimony and arsenic in soil leaching solution were analyzed.Based on the field trial,the effects of H₂O₂modified iron-based biochar on Sb/As stabilization were investigated,and the combined effects of antimony oxide bacteria and H₂O₂ modified iron-based biochar on both heavy metal stabilization and soil structure regulation were explored.The findings constructed a combined restoration model of antimony oxidizing bacteria and H₂O₂ modified iron-based biochar based on Sb/As stabilization and soil structure regulation,which may provide theoretical basis and practical reference for soil functional restoration and ecological reconstruction in Sb smelting sites.The main research results were listed as follows:（1）H₂O₂ modified iron-based biochar（Fe@30%H₂O₂-BC）was prepared and its adsorption performance to antimony and arsenic in soil leaching solution were analyzed.When the dosage of Fe@30%H₂O₂-BC was 6 g/L,the effluent concentrations of Sb/As were both below the environmental quality standards for III surface water（GB 3838-2002）.It was observed that the adsorption of Sb/As in the leachate were well represented by both the Langmuir isotherm model and the pseudo-second-order kinetic model.The coexisting ions and p H may affect the adsorption efficiency of iron-modified biochar.Chemical adsorption was the main adsorption process and easily affected by the related functional groups including hydroxyl,carboxyl and iron.（2）1%（w/w）of H₂O₂ modified iron-based biochar could realize long-term Sb/As stabilization in soils.The 180-day field restoration trial results showed that the leaching concentration of soil Sb/As were both below the environmental quality standards for III surface water（GB3838-2002）steadily.During the restoration period,the proportion of residual Sb/As increased significantly.The bioavailability of Sb/As decreased by 65.0-95.6%and 91.1-96.0%,respectively.Furthermore,H₂O₂ modified iron-based biochar increased soil organic matter content and improved soil porosity and water-holding properties.Changes in soil physicochemical properties and mineral composition after H₂O₂ modified iron-based biochar addition may affect the Sb/As stabilization.（3）The combined addition of antimony oxidizing bacteria and H₂O₂modified iron-based biochar could stabilize antimony and arsenic,and improve soil structure and function effectively.The inoculation of antimony oxidizing bacteria had little effects on the stabilization of antimony and arsenic.Compare with the addition of iron-modified biochar,the combined addition could further improve the stabilization rate of antimony and arsenic.The field trail results showed that after180-day restoration,the stabilization rate of Sb/As was up to 97%,and the bioavailability of Sb/As was reduced by 98.2%and 96.0%,respectively.Furthermore,the content of 0.25-1 mm water-stable aggregates increased to 1.87%,whilst the mean weight diameter of soil aggregates increased 8.7%.Soil water holding capacity and porosity were also significantly improved following the combined addition.