Analysis Of Stability And Removal Effect Of Apatite Composites On Mn In Coal Gangue And Leachate

China is the world's largest producer and consumer of coal.Coal gangue is a kind of solid waste discharged during coal mining,washing and processing.The coal gangue piled in the open air will form leaching solution under the conditions of rainfall and weathering,and the heavy metals in the coal gangue will be transferred to the leaching solution,which will eventually cause pollution to the surrounding soil and water,and even to the drinking water source of residents.Based on the exploration of magnesium modified hydroxyapatite adsorption behaviors of Mn,one through the adsorption thermodynamics and adsorption kinetics equation fitting for modification of materials such as adsorption behaviors of Mn,secondly by material modification and characterization of before and after the adsorption of Mn?SEM,XRD,XPS?analysis,to study the adsorption mechanism of Mn material;Finally,the influence of magnesium modified hydroxyapatite on Mn migration in waste residue and its leaching solution was investigated and evaluated to provide theoretical basis for the application of apatite modified materials as environmental treatment materials.The main conclusions are as follows:?1?In this paper,hydroxyapatite was modified by introducing different proportions of Mg in the process of preparing hydroxyapatite by chemical precipitation.According to the results of static adsorption experiments,the material with a molar ratio of Mg:?Ca+Mg?of 3:1?75%Mg-HAp?was the best adsorbent for Mn²⁺,and the optimal adsorption conditions were as follows:adsorbent addition was 0.67 g·L^-1,solution p H=5.When the initial concentration is 100 mg·L^-1,the maximum adsorption capacity is 159.24 mg·g^-1.When the initial concentration is 150 mg·L^-1,the maximum adsorption capacity is 248.74 mg·g^-1.For other Mn²⁺adsorption materials,this material has better adsorption performance.According to the characterization,the specific surface area and pore volume of 75%Mg-HAp were the largest,82.34 m²·g^-1and 0.37 cm²·g^-1,respectively.Compared with unmodified HAp,the specific surface area and pore volume were increased by 32.09 m²·g^-1and 0.26 cm²·g^-1,showing relatively excellent adsorption performance.?2?According to the results of isothermal adsorption equation fitting,the adsorption behavior of Mn²⁺by 75%Mg-HAp is more consistent with Langmuir equation,indicating that it belongs to uniform adsorption of monolayer.And the increase of K_Lwith the increase of temperature is reflected laterally as endothermic reaction.According to the fitting results of adsorption kinetics equation,the adsorption process of Mn²⁺by 75%Mg-HAp is a physical and chemical adsorption involving multiple adsorption behaviors such as liquid film diffusion and particle internal diffusion.?3?According to the comparison of the characterization before and after adsorption of Mn²⁺by 75%Mg-HAp,the material synthesis method has successfully synthesized the target material HAp with high purity,and the successful introduction of Mg has changed the material composition and morphology.When the material adsorbed Mn²⁺,the surface of the material was transformed from Mg?HPO₄?·3H₂O,Mg?NH₄??PO₄?·6H₂O into NH₄Mn₂P₃O₁₀·5H₂O and Mn?HP₂O₇?.Redox reactions occurred in some parts,while complex chemical reactions occurred in other parts,which were neither solution-precipitation,complexation,nor pure ion exchange reactions.?4?75%Mg-HAp was mixed into gangue in different proportions?1%,2%,5%,7%?,and treated for 7-30 days before leaching.When the 75%Mg-HAp doping amount is more than 5%,after curing for 7 days,the Mn in gangue has been all fixed,the Mn in the leaching solution of gangue is 0,and the p H rises to 6.57.When the 75%Mg-HAp dosage is 1.33 g·L^-1,the Mn content in the coal gangue leaching solution is 0.07mg·L^-1and p H=7.95. 75%Mg-HAp was mixed into electrolytic manganese slag in different proportions?1%,2%,5%,7%,10%?,and treated for 7-30 days before leaching.When the75%Mg-HAp doping amount was 10%and the curing days were 7 days,the dissolution amount of Mn decreased to 125.33 mg·L^-1,which was 90.8%lower than that when no material was added.When the dosage of 75%Mg-HAp was 3 g·L^-1,the content of Mn in the leaching solution decreased to 793.2 mg·L^-1at the highest,a decrease of 45.0%,indicating that 75%Mg-HAp had a certain effect on the removal of Mn from waste liquid containing high concentration of Mn.