The Research On Chalcogenide Sorbents For The Mercury Ions Removal From Acid Wastewater

Mercury is a global pollutant with the features of high toxicity,easy mobility and bioaccumulation,which has negative effects on human health and ecosystem.Mercury ions(Hg²⁺)in aqueous environment are considered as one of the most toxic and dangerous pollutants.The acid wastewater from gas purification system of the non-ferrous metal smelting contains high concentration of mercury.Among numerous methods for mercury ion removal from wastewater,adsorption method has unique advantages.For acid wastewater,the problem to be solved is to develop one sorbent with high-efficiency mercury removal and certain acid resistance.In this paper,based on the fact that mercury is a Lewis acid and sulfur has a strong affinity for mercury,two kinds of chalcogenide adsorbents have been successfully synthesized.ZnS/Al₂O₃ for mercury removal will release Zn²⁺when the pH value is lower than 3.0,which will cause secondary pollution.Other similar metal sulfide adsorbents based on ion exchange mechanism are also unstable under acidic conditions.Therefore,this study selected the transition metal sulfide（SnS₂）with stable layer structure.The synthesized SnS₂/α-Al₂O₃ was stable in acid solution and can effectively remove mercury ions.The adsorption effect was not influenced by other metal ions(Cd²⁺,Cr³⁺,Zn²⁺,Cu2+,Pb²⁺,Ni²⁺,Co²⁺,etc.),and the maximum adsorption capacity is 950 mg/g.After the treatment,regeneration and recycle can be realized for SnS₂/α-Al₂O₃.The adsorption process was monolayer chemical adsorption.SnS₂ combined with mercury ions then formed Hg-Sn-S compound.However,the removal rate of SnS₂/α-Al₂O₃ was low.For this point,[SnS₄]^4-/MgAl-LDHs with[SnS₄]^4-ion cluster for Hg²⁺removal was synthesized.The experimental results shown that[SnS₄]^4-/MgAl-LDHs material can quickly get 90%Hg²⁺removal efficiency within 5 min(pH².0,Hg²⁺:223.8 mg/L).The adsorption process was faster at a lower initial concentration of Hg²⁺.The maximum mercury adsorption capacity for this material was 360.6 mg/g.Matal ions that coexisted with mercury respectively,such as Zn²⁺,Na⁺,Cd²⁺,Cr³⁺,Pb²⁺,Co²⁺and Ni²⁺had no significant effect on the removal of Hg²⁺.Mercury ions exist as Hg₂（SnS₄）compound on the surface of[SnS₄]^4-/MgAl-LDHs adsorbent through monolayer chemical adsorption.Based on the research conclusions of this paper,chalcogenide adsorbents containing transition metal can be applied in acid solution as mercury adsorbent,however,it is necessary to find a modification method to greatly improve its adsorption properties for industrial application.