The Research On Optimum Selection Of Cadmium Tolerant Fungi In The Background Of High Antimony Content And Its Biosorption Characteristics Of Cadmium And Antimony

Soil pollution by heavy metals is one of the important environmental problems,which not only caused a lot of waste of land resources,but also seriously restricted the construction of "a beautiful China".Soil pollution by heavy metals is a common problem in mining areas.As the "antimony capital of the world",the remediation of heavy metals contaminated soils in Xikuangshan(Lengshuijiang,Hunan Province)has been widely concerned.Our investigation indicated that the soil pollution in Xikuangshan is a compound pollution with many heavy metal elements.The content of Sb,As,Cr and Cd in the soil exceeded the Chinese standard for risk control of soil pollution.Microbial remediation of heavy metals pollution is environmental friendliness and low cost,which shows a broad application prospect in the field of compound heavy metals pollution remediation.In this study,cadmium and antimony tolerant fungi were screened from the slags collected from the Xikuangshan.The physical and chemical characteristics of these fungi,as well as the single and binary biosorption characteristics of Sb(?)and Cd(?)were also studied.The main results are as follows:1.Three fungi isolated from the antimony slag,namely,XK8,XK10 and XK11,had high tolerance to cadmium and antimony.XK8 was identified as Curvularia coatesiae,XK10 and XK11 were identified as Penicillium spp.by ITS sequencing analysis.In the tolerance experiments,XK11 had the strongest tolerance to cadmium,followed by XK8 and XK10.The growth characteristics showed that the growth rate of XK10 was the fastest,and that of XK8 was the slowest in the liquid culture environment of 28? and pH 6.The plant growth promoting characteristics showed that three fungi had the ability of phosphate-solubilizing capability,among which XK11 had the strongest ability,reaching 257.8 ±8.9 mg L-1.In addition,XK8 could also produce IAA and siderophore.2.The single biosorption experiments on Cd(?)or Sb(?)were presented with three cadmium and antimony tolerant fungi as adsorbents.In the Cd(?)biosorption experiments,XK8 had the strongest biosorption capacity,and its maximum removal rate reached 60.9%under the initial concentration of Cd(?)was 0.1 mM,the initial pH was 4,and the biosorption time was 7 days.In the Sb(?)biosorption experiments,XK11 had the strongest biosorption capacity,and its maximum removal rate was 39.6%under the initial Sb(?)concentration was 1 mM,the initial pH was 6,and the biosorption time was 7 days.Langmuir and Freundlich isotherm models showed that the maximum biosorption capacity of three fungi onto Cd(?)was XK8>XK11>XK10,and the maximum biosorption capacity of XK8 was 22.8 mg g-1.The maximum biosorption capacity of three fungi onto Sb(?)was XK11>XK10>XK8,and the maximum biosorption capacity of XK11 was 11.7 mg g-1.3.The binary biosorption experiments on Cd(?)and Sb(?)were presented with the optimum fungus XK8 as adsorbent.Because XK8 had the strongest biosorption capacity for Cd(?).Response surface experiments showed that the main effects of initial Sb(?)concentration,biosorption time and initial pH on Cd(?)removal rate were positive,while the main effect of initial Cd(?)concentration was negative.The influence of initial pH on Cd(?)biosorption was the largest,followed by biosorption time,and the effects of both were stronger than that of co-existing ions.SAS analysis demonstrated that the theoretical optimum removal rate of Cd(?)was 100%under the initial concentration of Cd(?)was 6 mg L-1,the initial concentration of Sb(?)was 100 mg L-1,the biosorption time was 7 days,and the initial pH was 6.The interaction between Sb(?)and Cd(?)ions experiments showed that the maximum removal quantity of Cd(?)increased up to 0.95 mg g-1,which is higher than that of the control group.Besides,compared the single system with the binary system,the maximum biosorption capacity of XK8 was increased from 22.8 mg-1 to 23.6 mg-1.These results showed that Sb(?)could promote the Cd(?)biosorption of XK8 under the background of high antimony content.In summary,a fungus with tolerance to Sb and Cd was screened,and the fungus had strong biosorption capacity for Cd(?)under the background of high Sb(?)content.This study provides an important resource for the development on the molecular mechanism of heavy metals Sb and Cd using fungi as the adsorbents,and also provides potential microbial materials for the bioremediation of heavy metals Sb and Cd pollution in Xikuangshan.