Biosorption And Separation Of Lead And Its Ultilization

Agricultural byproducts have been widely used in heavy metal adsorption studies for its readily available and low processing cost.However,agricultural byproducts such as sugarcane bagasse were poor in adsorption capacity of heavy metal ions.Biosorption process were influenced by various factors,especially the co-ions:Mg²⁺,Ca²⁺,Cd²⁺and so on.In order to improve the adsorption capacity,the pyromellitic dianhydride modified sugarcane bagasses?SCB?were successfully prepared in this work.The effects of initial concentration of co-ions on the adsorption of Pb²⁺under batch and dynamic condition was studied respectively.The optimum condition for Pb²⁺removal was concluded.In the multicomponentsimulatedlead-containingwastewaterexperiment,the co-adsorption-desorption-precipitation method was applied to realize the ultilization of Pb²⁺in the waste water.The results are as follows.?1?SEM results and infrared spectrum analysis showed that a number of carboxyl was introduced to the surface of modified bagasses.The surface-active functional groups of the bagasse were significantly increased after modified.The adsorption capacity of Pb²⁺,Mg²⁺,Ca²⁺,Cd²⁺on PMDA modified SCB was 158.24 mg g^-1,13.33 mg g^-1,26.35 mg g^-1,43.75mg g^-1 respectively in the batch condition.?2?In the binary system,modified SCB was took as biosorbent to investigate the relationship between the saturated adsorption capacity ratios of co-ions:Mg²⁺,Ca²⁺,Cd²⁺and Pb²⁺and their initial concentration ratio.In the Mg²⁺/Pb²⁺system,Pb²⁺could be absorbed selectively from the mixture solution at the mole ratio of C₀^Mg:C₀^{P b}<6.86,while Mg²⁺could be absorbed selectively at C₀^Mg:C₀^{P b}>2967.47.In the Ca²⁺/Pb²⁺system,Pb²⁺could be absorbed selectively at the mole ratio ofC₀^Ca:C₀^{P b}<2.42,while Ca²⁺could be absorbed selectively at C₀^Ca:C₀^{P b}>1506.19.In the Cd²⁺/Pb²⁺system,Pb²⁺could be absorbed selectively from the mixture solution at the mole ratio of C₀^Cd:C₀^{P b}<0.42,while Cd²⁺could be absorbed selectively at C₀^Cd:C₀^{P b}>184.47.?3?The adsorption capacity of Pb²⁺,Mg²⁺,Ca²⁺,Cd²⁺on PMDA modified SCB was168.91 mg g^-1,13.47 mg g^-1,29.86 mg g^-1,55.77mg g^-1 respectively in the dynamic condition.In the Mg²⁺/Pb²⁺system,Pb²⁺and Mg²⁺could be respectively absorbed selectively at C₀^Mg:C₀^{P b}<1.24 and C₀^Mg:C₀^{P b}>585.5.In the Ca²⁺/Pb²⁺system,Pb²⁺and Ca²⁺couldberespectivelyabsorbedselectivelyatC₀^Ca:C₀^Pb<1.95andC₀^Ca:C₀^{P b}>1635.34.In the Cd²⁺/Pb²⁺system,Pb²⁺and Cd²⁺could be respectively absorbed selectively at C₀^Cd:C₀^{P b}<4.09 and C₀^Cd:C₀^{P b}>1623.50.?4?In the multicomponent system,competitive adsorption occured between Pb²⁺and Zn²⁺,Cd²⁺,Ca²⁺,K⁺,Na⁺,and Pb²⁺has the most affinity on modified SCB that the adeorbed co-ions was substituted by Pb²⁺.So Pb²⁺could be adsorbed selectively from the mixture solution.The results in desorption-precipitation expeiments showed that when Na₃PO₄ was took as precipitant,Pb²⁺in the elution could be efficient recovery.The solid got was Pb₉?PO₄?₆ and it had high purity,which could be reutilization.