Performance Ang Mechanism Of U(Ⅵ) And Cr(Ⅵ) In Wastewater By Aluminum Sludge Based Gel Spheres

The aluminum sludge based gel spheres adsorbent was prepared by using aluminum sludge,polyvinyl alcohol,sodium alginate as raw materials and titration-gel method,freeze-drying as synthetic technology.In this paper,AS-Ca-Gel and AS-Fe-Gel have been synthesized to adsorption solution of U（Ⅵ）and Cr（Ⅵ）.By measuring the physical properties of AS-Ca-Gel and AS-Fe-Gel,it is shown that the application of aluminum sludge as a substrate and freeze-drying technology not only improves the mechanical strength of the gel ball,but also keep the volume of the gel spheres unchanged.The swelling ratio of As-Ca-Gel and As-Fe-Gel increases with the increase of p H value under acidic conditions.The apparent morphology and structural composition of the two adsorbents were studied by SEM,FT-IR,XRD.According to the analysis results,AS-Ca-Gel and As-Fe-Gel have denser structures than AS,with an increase in functional groups and partial crystal phase disappearance.After a large number of static adsorption experiments,this paper discusses the influence of solution p H,adsorbent dosage,reaction time,initial ion concentration,and coexisting interference ions on adsorption.The experimental data were fitted by kinetic model and isothermal adsorption model.At the same time,the adsorption mechanism was studied and analyzed by SEM,FT-IR,XPS.（1）Adsorption of AS-Ca-Gel on U（Ⅵ）:At a temperature of 298K,AS-Ca-Gel dosage of 0.6 g/L,the best p H for AS-Ca-Gel to adsorb U（Ⅵ）is 4.The concentration ratio of U（Ⅵ）to Cu²⁺,Ca²⁺,Pb²⁺,SO₄^2-,Cl^-and NO₃^-is below 1:2,and the adsorption rate decreases to a certain extent.The kinetic model fitting experimental data shows that the adsorption process is controlled by chemical reaction,and Freundlich can better explain the adsorption of U（Ⅵ）by AS-Ca-Gel.FTIR and XPS analysis of the AS-Ca-Gel before and after adsorption showed that the main adsorption mechanism was the complexation reaction between functional groups and U（Ⅵ）,the bonding reaction between oxides and U（Ⅵ）.（2）Adsorption of AS-Fe-Gel on Cr（Ⅵ）:The maximum adsorption capacity of Cr（Ⅵ）on AS-GEL was 73.36 mg/g（temperature of 308K,p H=4,As-Fe-Gel dosage of 1.2 g/L,initial ion concentration of 200 mg/L,adsorption time of 120 min）through static adsorption test.The isothermal adsorption model and kinetic model fit the experimental data,the adsorption reaction exists a monolayer chemical and physical interaction.The order of coexisting anions is PO₄^3->NO₃^->Cl^-.FT-IR and XPS analysis showed that the adsorption mechanism of AS-Fe-Gel was electrostatic adsorption and reduction between the protonated group and Cr（Ⅵ）,and the reduced Cr（III）was complexed with the active group.In conclusion,AS-Ca-Gel and AS-Fe-Gel has good adsorption properties,easy solid-liquid separation,late after acid resolution can be recycled many times,which has the prospect of engineering application.