Study On The Removal Of Divalent Mercury Ions From Water By Functionalized Diatomite Materials

The rapid development of modern industrialization has led to the production of various pollutants,especially heavy metal pollution,which has a serious impact on the environment and public health.Mercury,as a special heavy metal,is extremely dangerous due to its persistence,high bioaccumulation and difficulty in degradation,and divalent mercury in water is easily converted into methyl mercury,which is more deadly,under the action of some bacteria or microorganisms.How to control mercury pollution in the environment has become one of the major issues faced by human society.In this paper,natural diatomite was used as the base material,and the functional diatomite composite adsorbent was prepared by modifying it with different materials,which was used to remove divalent mercury ion(Hg²⁺)from aqueous solution.The paper studies the material preparation,influencing factors,optimal adsorption conditions,adsorption capacity,kinetics,isotherm,thermodynamics,selective adsorption,and reproducibility.the microscopic and macroscopic morphological structure of the material was revealed through a series of modern characterization methods SEM,TEM,FT-IR,VSM,BET,XPS and Zeta potential,etc and the advantages,adsorption capacity and regeneration effect of the material were analyzed.Finally,the in-depth mechanism analysis is carried out through the characterization results,and the research results are as follows:（1）Adsorption of Hg²⁺in aqueous solution by DMT/CoFe₂O₄-ATPDiatomite coated with magnetic nanoparticles CoFe₂O₄ was prepared by hydrothermal synthesis,and then the aminosilane coupling agent APTES was grafted on the surface of magnetic diatomite.Finally,poly（3-aminothiophenol）magnetic silicon was prepared by in situ method.The diatomite-based composite material DMT/CoFe₂O₄-ATP was used to study the adsorption of divalent mercury in water.The results show that the adsorption of divalent mercury in water by DMT/CoFe₂O₄-ATP can reach 269.81 when the initial concentration of mercury stock solution is C₀=37 mg/L,pH=7.8,T=39℃and the dosage of adsorbent is0.07 g/L.The adsorption is mainly through ion exchange and coordination chelation to achieve the removal of Hg²⁺.The fitting analysis shows that the adsorption process of Hg²⁺by DMT/CoFe₂O₄-ATP conforms to the pseudo-second-order kinetic model and the Langmuir isotherm model,which belongs to the monolayer chemisorption.The thermodynamic data analysis shows that the adsorption process is a spontaneous endothermic reaction.The functional magnetic diatomite based composite prepared in this paper has a good removal effect on divalent mercury in water,and in the presence of other heavy metal ions,it has excellent selective adsorption of mercury ion,the removal rate can reach 98.9%.The results of regeneration experiments show that after five desorption-adsorption cycles,the adsorption capacity of the material can still reach 230.97 mg/g.（2）Adsorption of Hg²⁺in taqueous solution by MCM-41-cPpyThMesoporous material Mc M-41 was prepared by hydrothermal method with natural diatomite as raw material and CTAB as template.The composite adsorbent of Mc M-41-cppyth was formed by loading N and S heteratomic polymer onto the surface of mesoporous molecular sieve Mc M-41 by chemical oxidation polymerization.The adsorption results showed that the adsorption of divalent mercury by MCM-41-cPpyTh could reach 537.15mg/g at the initial concentration of C₀=45.1 mg/L,pH=8.1,T=37.9℃and the dosage of adsorbent was 0.064 g/L.The fitting analysis showed that the adsorption of divalent mercury in water by MCM-41-cPpyTh conformed to the pseudo-second-order kinetics and Langmuir isotherm model,which belonged to the monolayer adsorption.Thermodynamic data analysis indicated that the adsorption of divalent mercury by the adsorbent was a spontaneous endothermic reaction.The adsorption capacity of MCM-41-cPpyTh remained above 87%after five desorption-adsorption cycles.Characterization analysis showed that the large specific surface area and high porosity of mesoporous molecular sieves greatly facilitated the entry of mercury ions into ligand sites,and the adsorbent mainly achieved the purpose of removing divalent mercury from water through ion exchange and electrostatic attraction.The use of natural diatomite material as the base material greatly reduces the synthesis cost of the material,broadens the application field of diatomite,and achieves the purpose of efficiently utilizing natural mineral resources.