Study On Removal Of Arsenic And Antimony Contamination In Soil Washing Solution Using Sulfidated Nano Zero-valent Iron Supported By Graphene Oxide

The rapid development of metallurgical and mining industries has led to increasingly serious soil pollution with heavy metals.Among them,arsenic and antimony are mainly associated with mineral metal pollution is particularly prominent.Soil washing technique is widely used because of its short remediation time and thorough remediation,but the waste liquid of arsenic and antimony generated after soil washing can cause potential environmental pollution.However,arsenic and antimony in the washing solution are not only highly toxic,but also can form stable complex with the reagent,which is difficult to be directly treated by the traditional precipitation method.Therefore,it is necessary to remove heavy metals（arsenic and antimony）from the waste liquid of washing.Based on this,this paper developed a new nano-iron-based material,graphene oxide loaded sulfated nano-zero-valent iron（S-n ZVI@GO）,by sulfidation and loading modification of nano-zero-valent iron（n ZVI）with As（III）and Sb（III）as the target pollutants,and investigated the removal characteristics of As（III）and Sb（III）by S-n ZVI@GO under different environmental conditions（dosage,p H,initial concentration,temperature,presence or absence of oxygen,etc.）,revealed the reaction mechanism of S-n ZVI@GO for the removal of As（III）and Sb（III）,constructed immobilized materials based on S-n ZVI@GO,and realized the effect of S-n ZVI@GO on the removal of target pollutants As（III）and Sb（III）in soil washing solution.The following main conclusions were drawn in this study:（1）Graphene oxide supported sulfated nano zero-valent iron（S-n ZVI@GO）was successfully prepared by two-step synthesis and self-assembly method,and analyzed its related characterization（SEM-EDS,XRD,electrochemistry,etc.）.The results show that S-n ZVI can be uniform Ly dispersed on GO,and Fe is the major element（50.9%）of S-n ZVI@GO.Compared with n ZVI and S-n ZVI,the electron transfer rate of S-n ZVI@GO is faster and the reactivity is higher.（2）The best removal of Sb（III）by S-n ZVI@GO was achieved when the ratios of S/Fe and GO/S-n ZVI were 0.286 and 0.08,respectively,and the removal process of Sb（III）was in accordance with the pseudo-second-order kinetic model.The removal efficiency of S-n ZVI@GO was higher under aerobic conditions（96.7%）than under anoxic conditions（57.8%）,because the molecular oxygen in solution produce reactive oxygen species（·O₂^-,H₂O₂）through a single electron pathway and further oxidized Sb（III）to Sb（V）and separated it by synergistic adsorption and co-precipitation.The high efficiency of antimony removal（>90%）was still maintained by S-n ZVI@GO at p H=3～9,indicating that the material can adapt to most p H environments.In addition,the removal of Sb（III）by S-n ZVI@GO was a spontaneous heat absorption process with a maximum adsorption capacity of 311.75 mg/g.（3）The removal process of As（III）by S-n ZVI@GO was conform to the pseudo-first-order kinetic model.Molecular oxygen in solution had a significant effect on the removal of As（III）by S-n ZVI@GO,and the removal rate was significantly higher under aerobic conditions（91.2%）than under anoxic conditions（44.79%）.The active species involved in the arsenic removal process are·O₂^-and H₂O₂,and efficient arsenic removal was achieved through the synergistic effects of oxidation,adsorption and co-precipitation.The removal of arsenic by S-n ZVI@GO was maintained above 95%at different p H（3-9）conditions.Besides,S-n ZVI@GO have a large removal capacity of arsenic with a maximum adsorption capacity of444.68 mg/g,and the removal process of As（III）was a spontaneous heat absorption process.（4）Compared with ceramic pellets and foam ceramics,quartz plates as immobilization carriers for S-n ZVI@GO can efficiently remove As（III）and Sb（III）from the washing solution（As:90.02%and Sb:79.12%）with reaction rates of As:k=0.01211 min^-1 and Sb:k=0.012783 min^-1,respectively.The immobilized materials with quartz plates as carriers maintained more than 50%of the removal of arsenic and antimony from the washing solution after three reuses.It can be seen that quartz plates can be used as immobilization carriers for S-n ZVI@GO for the removal of As（III）and Sb（III）from soil washing solution.