Application Of Plant-microorganism Combined Remediation In Cadmium Polluted Wastewater And Soil Remediation

In this study the plant-microorganism combined action was adopted to repair cadmium pollution,and the selected cadmium-tolerant strains were respectively combined with iris and nightshade to form a joint remediation system for treating cadmium-contaminated wastewater and remediation of cadmium-contaminated soil,and the effect of the system was studied.The cadmium-tolerant strain was isolated from soil and identified as Streptomyces by sequencing.The morphological characteristics of cadmium-tolerant strains were observed by light/electron microscopy with or without Cd²⁺.The combined repair method of iris-strain cadmium-resistant strain was adopted to treat cadmium-polluted wastewater.Through the study on Cd²⁺removal rate of irises and irises plus cadmium-resistant strain,alkali treatment of irises and alkali treatment of irises plus cadmium-resistant strain,it can be seen that irises can well treat cadmium-polluted wastewater,and the highest removal rate is 73.6%when the cadmium concentration is50mg/L.After adding Cadmium-resistant strains,the removal effect of iris on Cd²⁺was significantly enhanced,with a removal rate of 91%.When the concentration of Cd²⁺was100mg/L after alkali treatment,the removal rate was 84.3%.After adding cadmium-resistant strains to the treated iris,it increased by 5.39%.Thus,cadmium-resistant strains can promote the treatment effect of Cd²⁺on iris,and the removal rate is the highest when planting iris and adding cadmium-resistant strains.According to the study of adsorption kinetics,the diffusion equation is not the only limiting condition in the adsorption process.The correlation coefficient R² value of the quasi-second-order dynamic equation is all greater than 0.99,and the simulated data of equilibrium adsorption amount are similar to the experimental values,indicating that the quasi-second-order dynamic equation can better explain the adsorption force of iris to Cd²⁺.According to the analysis of infrared spectroscopy,iris is rich in organic functional groups,such as hydroxyl,carboxyl,phenolic,carbonyl,aldehyde and other functional groups,which can well treat cadmium-polluted wastewater.The treated iris significantly increased the relative content of cellulose,enhanced the absorption peak of bending vibration of the group,and promoted the adsorption effect of Cd²⁺on iris.When cadm-tolerant strains were added,the stretch of protein C-H bond and N-H bond in cell wall and the stretching vibration of O-H bond in bound water in carbohydrates were increased,thus better promoting the adsorption of Cd²⁺by irises.The soil polluted by cadmium was improved by using the combined remediation method with microorganism.The dry weight,plant height,enrichment coefficient and transfer coefficient of solanum were analyzed and compared with the content of cadmium in the plant,indicating that solanum had the best tolerance and absorption capacity when the concentration was 20mg/kg.When different concentrations of Cd²⁺were added to the soil,higher concentrations of Cd²⁺inhibited the plant height,dry weight,adsorption and transfer rates.When cadmium-tolerant strains were added,the effect of cadmium on plant growth was weakened,and the absorption rate of Cd²⁺was significantly increased,with the enrichment coefficient up to 1.98,showing the superenrichment ability of Cd²⁺.