Preparation And Adsorption Behavior Study Of A Novel Three Dimensional Porous Adsorbent For Lead Ion

Objective: Direct discharge of wastewater containing excessive lead ions(Pb)produced in the process of oral diagnosis and treatment will seriously threaten human health.Therefore,it is particularly important and significant to actively explore new methods and technologies for efficient separation and recovery of Pb.Materials and methods:(1)Using sodium citrate as raw material,the frame carbon was prepared by one-step calcination method,and then activated by chemical method(3D AFC)for adsorption of Pbin aqueous solution.(2)Calcium alginate/graphene oxide(3D CA/GO)composite was constructed by3 D printing technology using sodium alginate(SA)and graphene oxide(GO)as raw materials.The structural morphology and chemical composition were characterized by SEM,Raman,FIIR,XPS and XRD.The effects of different conditions,such as solid-liquid ratio,ionic strength,pH value,initial concentration and contact time,on the adsorption behavior of Pbon 3D CA/GO surface were analyzed by batch adsorption experiments,and the adsorption mechanism of Pbon 3D Ca/Go surface was clarified by FTIR,XPS characterization and theoretical reasoning.Results:(1)3D AFC presents a "network-like" structure with a large number of oxygen-containing functional groups(mainly-OH and-COOH)on the surface.The adsorption behavior of Pbon 3D AFC was consistent with the quasi-second-order kinetic model.The maximum adsorption capacity of Pbon 3D AFC was 270.88mg/g(pH = 5.5,T = 298 k)by Freundlich isotherm model.(2)3D CA/GO has hierarchical macroporous structure,high specific surface area and excellent mechanical properties.The results of batch adsorption experiments showed that the maximum adsorption capacity of Pbin aqueous solution was507.6 mg/g(pH = 3.0),which was 2-5 times that of similar adsorbents reported in the literature.The adsorption mechanism is the synergistic action of electrostatic interaction,ion exchange and chelation.In the presence of competitive cations,the selective adsorption rate of Pbby 3D CA/GO is as high as 99.8%.After 8 cycles of adsorption-deadsorption,the adsorption capacity of Pbby 3D CA/GO did not decrease significantly.In addition,3D CA/GO showed good structural stability and Pbadsorption capacity stability after being immersed in oral medical wastewater for 1 week.Conclusions:(1)Combined with the simple preparation method and high adsorption capacity for Pb,3D AFC is considered to have a certain prospect for the adsorption of Pbin oral medical wastewater.(2)Combined with good structural stability,strong Pbadsorption capacity and outstanding Pbselective adsorption capacity,3D CA/GO has great application prospects for the separation and recovery of Pbfrom oral medical wastewater.