Preparation Of A Novel Lanthanum-manganese Binary Oxide And Its Behavior And Mechanism For The Removal Of Antimony From Aqueous Solution

Antimony is highly toxic,similar to arsenic,and Sb???is 10 times more toxic than Sb???.In recent years,some Sb entered into the aquatic systems through natural processes and anthropogenic activities,which poses a serious threat to human health and ecosystems.The problem of antimony pollution is one of the global environmental problems to be solved urgently,which has been paid more and more attention by researchers.Among many antimony removal technologies,the adsorption method has attracted much attention due to its simple operation,high efficiency.The metal oxides stand out with a higher adsorption capacity than carbonaceous materials and minerals.Moreover,composite metal oxides have better adsorption properties than single metal oxides.With the increasingly antimony pollution in aquatic environments,it is essential to develop novel adsorbents with high adsorption capacity and ability of simultaneous removal of Sb???and Sb???.The purpose of this study is to synthesize a novel lanthanum-manganese binary oxide for removal of antimony in aqueous solution,which combines the advantages of the oxidizability of manganese oxide and the strong ability of lanthanum oxide.FTIR,EDS-Mapping,XPS and other techniques were employed to characterize the lanthanum-manganese composite oxide before and after adsorption of antimony.The adsorption behaviors of Sb???and Sb???by lanthanum-manganese binary oxides were investigated.Moreover,the possible removal mechanisms of Sb???and Sb???by lanthanum-manganese binary oxides were explored.The main results are as follows:?1?The lanthanum-manganese binary oxide is formed with nanoparticles?50-100nm?.Its specific surface area is 180.4 m²·g^-1 and isoelectric point is 6.0.The Mn of the binary oxide mainly exists in the form of Mn?IV?,and the surface of the material has abundant metal hydroxyl groups.?2?Pseudo-second-order kinetic model may better describe the adsorption kinetics process of both Sb???,and Sb???,suggsting that the adsorption is chemical adsorption.The isotherm data is fitted better with the Frendilich model,which indicates that adsorption reaction is multi-molecular layer adsorption.The maximum adsorption capacitiey for Sb???,[50%Sb???+50%Sb???],and Sb???is 282.95 mg·g^-1,220.57mg·g^-1,and 134.04 mg·g^-1,respectively.When the pH value of the solution is in the range of 3-6,the removal of Sb???gradually increases with the pH value increases.While,the removal of Sb???gradually decreases when the pH value continues to rise to 8;The removal of Sb???by the lanthanum-manganese binary oxide gradually increased with the pH value from 3 increase to 4,however,the removal of Sb???gradually decreased with further increase in the pH value.The ionic strength has little effect on Sb???and Sb???adsorption by lanthanum-manganese binary oxide,while the present anions PO₄^3-have competitive effect.?3?The removal of Sb???in aqueous solution is mainly achieved through the complexation reaction between antimonate and metal hydroxyl groups on the surface of the adsorbent.The Sb???removal mechanism oxide could be described as follows:Firstly,Sb???is adsorbed to the surface of the adsorbent.Then,Mn?IV?on the surface of the adsorbent oxidizes Sb???to Sb???.Meanwhlie,Mn?IV?is reduced to Mn?II?and released into the solution,and then re-adsorbed to the surface of the adsorbent.