Study On Simultaneous Stabilization Of Multi-Metal (Loid) In Contaminated Soil Using Iron-Based Composite Materials

The situation of soil heavy metal pollution,especially the intricate contamination by multiple metal（loid）s,is severe in China,and it is urgent to adopt scientifically effective remediation measures for control.Stabilization remediation has emerged as a promising method capable of preserving soil ecological functions.Nonetheless,the majority of the developed remediation materials suffer from limitations such as difficulty in achieving simultaneous stabilization of multiple metal（loid）s and high cost.Furthermore,the stabilization mechanism of remediation materials on heavy metal（loid）s remains elusive,and their ecological impact on soil demands scientific assessment.In this paper,arsenic-antimony contaminated soil,cadmium-lead-copper-zinc contaminated soil and cadmium-lead-copper-zinc-arsenic-antimony combined contaminated soil were taken as the research objects,and three kinds of multi-metal simultaneous and efficient stabilizing functional materials were specifically developed.The immobilization behaviors and mechanisms of the remediation materials on target heavy metal（loid）ions were analyzed.In addition,the stabilizing effects of remediation materials on soil heavy metal（loid）s and their potential ecological impacts on the soil environment were also evaluated from the perspectives of leaching toxicity,heavy metal（loid）speciation,soil properties,and soil microbial communities.The main conclusions are as follows:（1）The personalized functional materials for different types of contaminated soil were developed,and the immobilization behaviors of functional materials on target heavy metal（loid）ions and their remediation effects on contaminated soil were investigated.For arsenic-antimony（anionic type）contaminated soil,the silica–biogenic iron（hydr）oxides composites（BS-Fe）was developed.After applying BS-Fe for 35 days,the stabilization effect of As met the solidification/stabilization remediation standard（"Technical specifications of contaminated soil remediation solidification/stabilization（HJ 1282-2023）"）,and the toxic leaching concentration of Sb was reduced to less than 0.40 mg/L.For cadmium-lead-copper-zinc（cationic type）contaminated soil,the Fe/Mn（hydr）oxide and phosphate mineral composites（FMPs）was developed.The stabilization effects of Cd,Pb,Cu and Zn in the soil met the solidification/stabilization remediation standard after 60 days of FMPs remediation.For the soil contaminated by cadmium,lead,copper,zinc,arsenic and antimony in the overlapping area of the two mining areas,the Fe/Mn（hydr）oxide-humic acid composites（FMHs）was developed.In the multi-component system,FMHs showed high immobilization performance towards all heavy metal（loid）ions,especially Sb（III/V）and Pb（II）.In the soil system,after60 days of applying FMHs,the contents of available Cd,Pb,Cu,Zn,As and Sb in soil was significantly reduced,and the stabilization effect of FMHs on the soil contaminated with cadmium,lead,copper,zinc,arsenic and antimony met the remediation standard of solidification/stabilization in a wide range of pollution levels.（2）The immobilization mechanism of each functional material on target heavy metal（loid）ions was revealed.The immobilization mechanism of BS-Fe to As and Sb could be attributed to the formation of inner complexes between BS-Fe and As and Sb.In addition,redox and hydrogen bonding further promoted the adsorption of BS-Fe to As and Sb.The immobilization mechanism of FMPs on Cd,Pb,Cu and Zn was mainly attributed to the fact that heavy metals could be complexed with phosphate to form metal phosphate precipitation.Other mechanisms such as surface complexation,chemical precipitation and ion exchange were also beneficial to the adsorption of FMPs.The immobilization mechanism of FMHs on heavy metal（loid）s could be attributed to the fact that Cd,Pb,Cu,Zn,As and Sb could form complexes by sharing electrons with functional groups on FMHs surface（such as C=O,C-O,C-NH,M-OH,etc.）.Moreover,chemical precipitation,ion exchange and redox were also conducive to the immobilization of these heavy metal（loid）ions.（3）The potential ecological effects of functional materials on soil environment were clarified.After the remediation of arsenic-antimony contaminated soil by BS-Fe,there was a noticeable decrease in soil p H value,while the values of Eh and EC increased significantly.Additionally,the soil TN content increased,as well as the activities of S＿UE,S＿CL,and S＿CAT.Redundancy analysis results indicated that the soil microbial community structure was mainly influenced by factors such as p H,EC,AK,and the contents of available As and Sb.In addition,the bacterial community richness decreased,while the fungal community diversity increased,and the distribution of key microbial taxa in the soil ecological network was altered after the application of BS-Fe.After the remediation of cadmium-lead-copper-zinc contaminated soil by FMPs,the contents of p H,EC,TP,AP and NH₄＿N contents,as well as the activities of S＿ACP,S＿CL and S＿CAT significantly increased.Moreover,the alpha diversity of the bacterial community decreased significantly,while that of the fungal community increased significantly.Molecular ecological network analysis showed that the ecological network connection of the bacterial community became tighter,while the complexity of the fungal community ecological network decreased after FMPs remediation.After the remediation of cadmium-lead-copper-zinc-arsenic-antimony contaminated soil by FMHs,the soil Eh,EC,TN,NH₄＿N and NO₃＿N contents significantly increased,as well as S＿ACP,S＿SC,S＿CL and S＿CAT activities.In addition,the application of FMHs significantly reduced the diversity of soil bacterial communities and the complexity of the soil microbial ecological network,while increasing the positive correlation in the ecological network.Figures 111,Tables 45,and References 376...