Study On The Characteristics Of Calcined Dolomite Sand And Its Effect On The Stabilization Of Mn²⁺ In Electrolytic Manganese Sla

In this paper,aiming at the influence of leaching and migration of Mn²⁺produced in the process of manganese slag stacking on the surrounding water environment,and the influence of dolomite sand calcined at different temperatures and the combined calcined composites of dolomite sand-attapulgite and dolomite sand-phosphorus tailings on the stability of Mn²⁺in electrolytic manganese slag was discussed.The shape change of the above materials and the mechanism of their influence on Mn²⁺in electrolytic manganese slag were studied comprehensively.Advanced techniques such as XRD,SEM-EDS,BET and TG-DSC were adopted.The stability mechanism of calcined dolomite sand,dolomite sand-attapulgite,dolomite sand-phosphorus tailings combined calcined composite material on Mn²⁺in electrolytic manganese slag was comprehensively analyzed.The main conclusions are as follows:（1）The adsorption effects of dolomite sand calcined at 900℃,attapulgite,and phosphorus tailings calcined at 700℃on Mn²⁺in the leachate of electrolytic manganese slag were studied through adsorption experiments.The experimental results showed that the adsorption effect of Mn²⁺in the leaching solution was best for dolomite sand calcined at 900℃,followed by attapulgite,and then phosphate tailings calcined at 700℃.The addition amount of three materials has significant difference on the removal rate.The concentration of Mn²⁺in the leaching solution reached2mg/L of the comprehensive sewage discharge standard.When the adsorption time is180 min and the adsorption temperature is 55℃,The additive amounts of dolomite sand of 900℃,attapulgite,and phosphorus tailings of 700℃were 30 g/L,120 g/L,and 120 g/L,respectively,and the maximum adsorption capacities were 26.13 mg·g-1,6.556 mg/g and 6.524 mg/g,respectively.Among them,calcined at 900℃dolomite sand has the best removal effect.（2）The change of properties of dolomite sand under different calcination temperatures and the stabilization effect on Mn²⁺in electrolytic manganese slag showed that:when the dolomite sand content is 10%and the calcination temperature increases from 600℃to 800℃,the stabilization efficiency of Mn²⁺is 29.14%to99.95%.When the calcination temperature is greater than or equal to 900℃,the concentration of Mn²⁺in the leaching solution is lower than the detection detection limit of the instrument（0.01mg/L）.When the calcination temperature is 800℃,the stability efficiency of dolomite sand on electrolytic manganese slag is increased by70.81%and 38.69%compared with 600℃and 700℃.Therefore,the optimal calcination temperature is 800℃when dolomite sand is used as electrolytic manganese slag stabilizer.and the performance analysis of dolomite sand calcined at600℃to 800℃:when the calcination temperature rises from 600℃to 800℃,the total alkalinity of dolomite sand increases by 25.2%,and XRD results show that alkaline（3）The stabilization effect of dolomite sand-attapulgite combined calcined composite on Mn²⁺in electrolytic manganese slag shows that:the stability efficiency of the dolomite sand-attapulgite composite is better than that of dolomite sand and attapulgite under the same dosage and calcining temperature.when the addition of composite material increases 25%,the stabilization effect of Mn²⁺in electrolytic manganese slag is increased by 0.21%and 34.22%compared with that of 700℃dolomite sand and attapulgite,respectively.The addition of composite material increases from 5%to 25%,and the stability efficiency increases from 33.45%to97.92%,which is higher than 95%.The following experiments show that the performance of the composite is better than that of dolomite sand and attapulgite alone:Compared with 700℃calcined dolomite sand and 700℃calcined attapulgite,the total alkalinity of the composite increases by 1.5%and 27.19%,respectively.XRD shows that alkaline oxides such as Ca O and Mg O can be decomposed after the composite calcined at 700℃for 2 h,providing a stronger alkaline environment for stability.SEM results show that the nanocrystalline rods of attapulgite in the combined calcining stabilizer have not been completely destroyed calcined at 700℃,the lamellar structure of dolomite sand is decomposed into small particles,and micropores are formed between the particles.After calcination,the specific surface area and pore volume of the composite decreased,but the pore size and total basicity increased significantly.In addition,the synergistic action of dolomite sand and attapulgite during combined calcination promoted the thermal decomposition of the composite and improved the stability efficiency of Mn²⁺in electrolytic manganese slag.（4）The stabilization effect of dolomite sand-phosphorus tailings combined calcined composite on electrolytic manganese slag shows that:the stability effect of dolomite sand-phosphorus tailings combined calcined composite on electrolytic manganese slag is better than that of dolomite sand and phosphorus tailings under the same addition amount and calcination temperature.The stabilization effect of Mn²⁺in electrolytic manganese slag at 15%is 5.93%and 25.14%higher than that at 700℃calcined dolomite sand and 700℃calcined phosphorus tailings,respectively.The stabilization efficiency increases from 60%to 97.02%with the addition amount increasing from 5%to 15%,and the stabilization efficiency is more than 95%.The following experiments show that the performance of composite material is better than that of dolomite sand and phosphorus tailings alone:compared with that of dolomite sand and phosphorus tailings calcined at 700℃,the total alkalinity of composite material increases by 4.00%and 2.56%,respectively.The XRD of the composite material shows that alkaline oxides such as Ca O and Mg O can be decomposed after calcined 2h calcination at 700℃,indicating that the composite provides a stronger alkaline environment for stability.SEM results show that the co-pyrolytic materials are decomposed into granules and a large number of pores are generated at 700℃.Moreover,the specific surface area,pore size and pore volume of the dolomite sand-phosphorus tailings combined calcined materials improving by 2.28,1.47 and4.14 times respectively after calcination,providing more attachment points for Mn²⁺.Therefore,with the increase of total alkalinity,surface area and porosity of the composite material,a large amount of phosphate produced by phosphorus tailings is easy to combine with manganese ions to form refractory substances,in addition,the synergistic action during the combined calcination of dolomite sand and phosphorus tailings promotes thermal decomposition and improves the stability efficiency of the material on Mn²⁺in electrolytic manganese slag.In conclusion,dolomite sand-phosphorus tailings have the best calcination effect on the stability of Mn²⁺in electrolytic manganese slag,which can be applied to the environmental treatment of electrolytic manganese slag yard.