Study Of Mineral-type Materials Enhance Microbialmicrobial Mineralization Fix Pb,Cd,Zn Contaminated Soil

Microbial-induced carbonate precipitation is a technology that solidifies heavy metals by using mineralized microorganisms to produce urease to decompose urea and produce calcite with calcium ions.However,because different heavy metals show different differences,it is difficult for single microbial mineralization technology to deal with complex heavy metal pollution cooperatively.Therefore,several mineral-type solidified materials were selected in this study to enhance the effect of microbial mineralization,so as to achieve the purpose of improving the fixation of composite heavy metal pollution.In this study,the clay minerals were used as the research object,and the selected montmorillonite was used as the reinforcement agent for mineralization remediation to carry out the experimental study on the fixation of complex heavy metals in farmland soil.The results are as follows:（1）Screening of mineral-type solidified materials and testing of their enhanced microbial properties.The additives screening experiments show that the addition of montmorillonite to the three minerals can improve the microbial activity and the amount of mineralization precipitation,and the adsorption rate of heavy metals in Pb²⁺,Cd²⁺,Zn²⁺single,pairwise combination and three kinds of coexistence solutions is more than 97%,so the selection of montmorillonite as the mineralization repair reinforcement additives.The addition of montmorillonite can make the bacteria reach the logarithmic growth stage earlier,and increase the yield of mineralized products in the process of mineralized repair by 13.35%.（2）Optimization of technological conditions of mineral-type curing material montmorillonite enhanced microbial mineralization remediation technology.In the optimization experiment of soil composite heavy metal fixation by montmorillonite enhanced microbial mineralization remediation technology,when the montmorillonite content was 2%,the microbial activity and heavy metal fixation rate was the highest,and the urease,catalase and invertase activities increased by 27.58%,34.42%and 69.18%,respectively.The fixation rates of Pb,Cd and Zn were 25.88%,30.48%and50.00%,respectively.When the concentration of Ca²⁺was 0.25mol/L,the activity of urease,catalase and sucrase increased by 20.19%,29.37%and 78.97%,respectively,and the fixation rates of Pb,Cd and Zn reached 26.56%,34.76%and 51.16%,respectively.When montmorillonite was added with bacterial agent,the microbial activity and heavy metal fixation rate showed no advantages compared with the traditional addition method.Compared with the traditional addition method,the urease,catalase and sucrase activities decreased by 3.92%,7.50%and 33.78%,respectively.The fixation rates of Pb,Cd and Zn decreased by 13.22%,8.42%and 26.16%,respectively.（3）Field demonstration application of mineral-type solidified materials to enhance microbial mineralization remediation technology.The optimization results of montmorillonite enhanced microbial mineralization remediation technology were applied to the field remediation experiment.The results showed that the addition of montmorillonite successfully fixed the soil complex heavy metal pollution,and increased the yield and reduced the heavy metal content in the plant tissues after the remediation compared with the control group.In summary,montmorillonite and microbial mineralization remediation technology were used in this study to successfully achieve the fixation of soil composite heavy metals and their application in the field.Calcium carbonate produced by mineralized microorganisms was used to coordinate with montmorillonite to fix and adsorb heavy metals in calcite,which reduced the content of effective heavy metals and reduced the migration of heavy metals.At the same time,it can also improve soil nutrients and increase organic matter,and achieve the purpose of increasing production while reducing heavy metal content in plants.