Preparation Of Phosphate Solubilizing Bacteria-Tricalcium Phosphate Capsules And Its Stable Remediation Of Lead Contaminated Sediments

Lead contaminated sediments are getting worse,many scholars have studied various lead polluted sediment remediation technologies.Among them,improving the stability of lead in sediments is the key to lead pollution recovery in sediments.Phosphate solubilizing bacteria can transform insoluble phosphate into soluble phosphate and can react with lead to form stable phosphate lead compounds.Phosphate solubilizing bacteria serve as an important role in the remediation of lead pollution.The purpose of this study was to prepare a phosphate solubilizing bacteria-tricalcium phosphate capsule.By changing the concentration of sodium alginate and Ca Cl₂ to explore the optimal ratio of capsule preparation,and adjusting the content of Ca₃?PO₄?₂ inside the capsule to optimize the capsule,and then to optimize the initial lead concentration,temperature,p H.And use it for lead-contaminated sediment remediation,explore the mechanism of lead passivation of capsules.In this study,Leclercia adecarboxylata and tricalcium phosphate were encapsulated with sodium alginate gel according to the interfacial polymerization method to prepare a new type of phosphate solubilizing bacteria-tricalcium phosphate capsule.The optimal ratio of the capsules was investigated by changing the concentrations of sodium alginate and Ca Cl₂.The results showed that when the concentration of sodium alginate was 0.3%and the concentration of Ca Cl₂ was 10%,phosphate solubilizing bacteria-tricalcium phosphate capsule with uniform shape could be obtained.The passivation rate of 98%can be achieved when 0.07 m M tricalcium phosphate is encapsulated.The experimental results show that the passivation rate of phosphate solubilizing bacteria-tricalcium phosphate capsules is higher under the condition of less than 1.5 m M Pb²⁺.The temperature had little effect on the removal efficiency of Pb²⁺and the capsules could be used for lead passivation in acidic environments?p H=3-6?.The capsules before and after the reaction with lead were subjected to scanning electron microscopy?SEM?,energy spectrum analysis?EDS?,X-ray diffraction?XRD?,and Fourier infrared spectroscopy?FTIR?.The confocal laser scanning microscope?CLSM?was used to analyze the activity of phosphate solubilizing bacteria.The experimental results showed that phosphate solubilizing bacteria and tricalcium phosphate were successfully coated inside the capsule,and the free hydroxyl,carbonyl,nitroso,and ether bond in aromatic and C-O in carbohydrates were the main functional groups in equilibrating with culture medium containing Pb²⁺.The lead was immobilized via the formation of Pb₅?PO₄?₃Cl and Pb₃?PO₄?₂,and the bacteria inside the capsule had strong activity.The results of simulated remediation experiments of lead-contaminated sediments showed that phosphate solubilizing bacteria-tricalcium phosphate capsule had a good stabilization effect on lead in the sediments.After 90 days,the passivation efficiency of acid soluble fraction of lead in 200 mg/kg lead-contaminated sediments and 800 mg/kg lead-contaminated sediments were 78%and 53%,respectively.The experimental results show that the soluble phosphorus content in the upper water during the remediation of low and high concentrations of lead-contaminated sediments is below 0.15mg/L,and the p H of the sediment varies between 7-8.In addition,the phosphate solubilizing bacteria-tricalcium phosphate capsules can augment the multiformity of the microbial community composition.L15 can be the dominant strain in the microbial community of sediments.In summary,the phosphate solubilizing bacteria-tricalcium phosphate capsule prepared in this research have a good remediation effect on lead-contaminated sediments.The experimental results provide theoretical support for lead-contaminated bioremediation technology.