The Immobilization Of Lead With Chemical And Biological Method

In this paper,the chemical immobilization of Lead by apatite and struvite were discussed;two heavy metal-tolerant strains,Pseudomonas putida and Pseudomonas fluorescens,were isolated from the heavy metal contaminated soils in Changxing country,and studied the biologic immobilization of Pb(Ⅱ).Then on the base of the research before-mentioned,the interaction of microorganism-clay-metal and the sorptive ability of Pb(Ⅱ)by phosphorite and immobilized microorganism were investigated,which could provide theory basis for the chemical and biological remediation of heavy metal contaminated water and soil.The main results were as follows:The sorption ability of Pb(Ⅱ)in the solution by apatite and struvite are very strong.The sorption of Pb(Ⅱ)by apatite is fast firstly,then slow followed,which fits to second kinetic equation,and the relative rate constant was 0.97.And the bound character could also be reflected by the Langmuir isotherm,which has the maximum sorption of 37.74mg/g.pH is an important factor which influences the sorption of Pb(Ⅱ)by apatite and struvite.Apatite has better sorption than struvite at very acidic condition,but when pH＞4,the instance is just opposite.Use of organic fertilizer during farming would affect the chemical immobilization of Pb(Ⅱ),and the influence of water soluble matter released by organic fertilizer to apatite is bigger than struvite.It was found that the optimun pH for Pb(Ⅱ)removal by living and nonliving cells was 5.0 and 4.0,respectively.The biosorption of nonliving cells is a fast and passive process which doesn't depend on metabolism,whereas,heavy metal could be actively taken up by living cells besides passive bound.the metal ion biosorption was increased as the initial metal concentration increased.The binding capacity of living cell is higher than that of nonliving cell.The adsorption data with respect to both living and nonliving cells provide an excellent fit to the Langrniur isotherm.Both apatite and heavy metal can influence the viability of resting cell of Pseudomonas putida,however,the toxicity to cells will decrease when bacterium and apatite combined cultured.The composite ration of microorganism and apatite could influence the adsorption capacities.Four different sorbents have different sorption abilities to Pb(Ⅱ),among which,immobilized microorganism by PVA and SA is the most effective,indicating that immobilized microorganism could be used to remove Pb(Ⅱ)in the wastewater.Apatite,struvite and organic manure could all effectively reduce the availability of Pb.Inoculated resistance microbes maybe decrease the water-soluble Pb but increase the available Pb,on the one hand,organic manure could be decompounded by microbe,on the other hand Pb can easly be extracted by acid.The water-soluble Pb was increased after planting Brassica rapa chinensis,and because of the pH in the Brassica rapa chinensis rhizosphere was increased,indicating the rhizosphere water-soluble Pb may be increased by soluble substance.Inoculated resistance microbes can improve the decomposability of organic manure,and then increase the water-soluble Pb.Taking the water-soluble Pb,available Pb and pH into account,it was suggested that T4,T5(Apatite and organic manure with inoculated microbes) had the best Pb-immobilized effect.