Preparation Of Schwertmannite And Its Adsorption Properties And Mechanism For Sb(Ⅲ)

Schwertmannite has the characteristics of low crystallinity and large specific surface area,and it has a significant effect on the interface behavior of antimony in the environment.The previous studies on the adsorption mechanism of heavy metals by schwertmannite mainly focus on arsenic,chromium,copper,etc.There are few studies on antimony,and comparative studies on schwertmannite from different preparation sources have not been involved.In particular,most studies adopt the characterization method of"starting and ending in two states",and dynamic monitoring of the whole process is rarely seen.In this study,three kinds of schwertmannites（H-SCH,M-SCH and Y-SCH）were synthesized in the laboratory.With the study of adsorption properties of three schwertmannite on Sb（Ⅲ）as the main line,exploration experiments on adsorption kinetics,adsorption thermodynamics and influencing factors were carried out.Combined with the dynamic characterization monitoring of the whole process of kinetics,the mechanism of Sb（Ⅲ）adsorption of schwertmannites synthesized by different chemical methods was revealed.The main research results are as follows:1.By comparing the composition and structure of the three kinds of chemical synthesis of schwertmannites,it can be seen that H-SCH combines more Fe and has a more stable skeleton structure;M-SCH and Y-SCH have more SO₄^2-than H-SCH.Y-SCH has larger specific surface area and abundant surface active hydroxyl group.2.The adsorption kinetic process revealed that the adsorption of Sb（Ⅲ）by three chemical synthesis of schwertmannites was consistent with the pseudo-second-order kinetic,the in-particle diffusion model and Elovich kinetic model,which were mainly chemical adsorption.The thermodynamic process of adsorption revealed that the adsorption of Sb（Ⅲ）by three kinds of schwertmannites was a spontaneous endothermic process.The saturated adsorption capacities of H-SCH,M-SCH and Y-SCH for Sb（Ⅲ）were 79.81 mg/g,81.70 mg/g and 73.53 mg/g,respectively,at room temperature.3.The analysis results of environmental factors show that the adsorption effect of Sb（Ⅲ）is the best when p H=4;Common ions Ca²⁺,SO₄^2-and PO₄^3-have inhibitory effects on the adsorption of Sb（Ⅲ）;Fulvic acid（FA）has inhibitory effects on the adsorption of Sb（Ⅲ）by schwertmannites,which is mainly attributed to the fact that FA can compete with antimony for active sites on the surface of minerals,but the formation of SCH-FA-Sb complex enhanced the stability of the mineral at the same time.In the competitive adsorption system,coexistence As（Ⅲ）and Cr（Ⅵ）can inhibit the adsorption of Sb（Ⅲ）,and the inhibition effect of As（Ⅲ）is stronger than that of Cr（Ⅵ）.4.XRD and other mineral characterization analysis show that Y-SCH has good stability and no ore phase conversion occurs during the adsorption of Sb（Ⅲ）by schwertmannites.While H-SCH and M-SCH showed a characteristic peak of ferrihydrite in the middle and late stage of adsorption.Since ferrihydrite also has a certain adsorption capacity for Sb（Ⅲ）,it promoted the adsorption of these two schwertmannites on Sb（Ⅲ）to a certain extent.5.The three kinds of chemical synthesis of schwertmannites adsorb antimony mainly through the complexation of hydroxyl functional groups on the outer surface.In the adsorption process,Sb（Ⅲ）will be probably oxidized by Fe（III）to Sb（Ⅴ）,and the formed Sb（OH）₆^-further carries out ion exchange with SO₄^2-on the surface of schwertmannite,which further promotes the adsorption of antimony by schwertmannites.