Comparative Analysis Of Iron And Manganese Ion Removal Materials And Processes In Acid Coal Mine Wastewater

A large number of highly harmful acidic coal mine wastewater will be produced in the process of mining,washing and slagging.In this paper,an optimized and efficient treatment process is proposed for the high concentration of iron and manganese ions in the acidic coal mine wastewater.After treatment by this process,The total iron and manganese concentrations in the effluent all meet the Emission Standards of Coal Industry Pollutants and Guizhou Provincial Environmental Pollutant Emission Standards.In this paper,natural volcanic stone and attapulgite were used for adsorption experiment,and various modification methods were used to produce a variety of modified materials for the adsorption of manganese ions in wastewater.By exploring the adsorption process and mechanism,materials that can absorb manganese ions efficiently are screened out,which provides a new idea for the treatment of iron and manganese in acid coal mine wastewater.The main conclusions of this paper are as follows:（1）Explore the most suitable neutralizing and settling materials.The red mud,Ca（OH）₂and calcium carbide slag of the same mass were put into the simulated acid mine wastewater.It was found that after the reaction of 1.4g Ca（OH）₂ with acid mine wastewater for 60 min,the removal rates of total iron and manganese were 99.61%and 97.45%,respectively,while after the reaction of 1.4g calcium carbide slag with acid mine wastewater for 60 min,The removal rates of total iron and manganese were 99.91%and 98.06%,respectively.The removal effect of calcium carbide slag on iron and manganese was significantly better than that of Ca（OH）₂.After being treated with calcium carbide slag,the concentration of total manganese decreases rapidly,falling below 2 mg·L^-1 in 20 min and remaining stable.However,the concentration of total manganese after being treated with Ca（OH）₂ will fluctuate,and the effect is obviously worse than that of calcium carbide slag in the treatment of acid mine wastewater.Therefore,it is finally decided to use calcium carbide slag as the optimal neutralizing material in the first stage.（2）To explore the adsorption of manganese by natural volcanic stone and modified volcanic stone.When p H=5 and dosage was 1g,the adsorption capacity of natural volcanic stone reached the maximum of 1.047 mg·g^-1.The adsorption process of manganese on natural volcanic rocks accords with the quasi-second-order kinetic model and Freundlich model,indicating that the adsorption process belongs to chemical adsorption and heterogeneous multilayer adsorption.By comparing the adsorption effect of four modification methods of natural volcanic stone at different p H values,it is found that the adsorption effect of sodium hydroxide modified volcanic stone（W1）on manganese is better than other materials,so W1 material is selected for follow-up experiments.The adsorption capacity of W1 reached the maximum1.584 mg·g^-1 when p H=8 and dosage was 1g.The adsorption process of W1 for manganese is consistent with the quasi-second-order kinetic model and Freundlich model,indicating that the adsorption process belongs to chemisorption and is an uneven multilayer adsorption.Therefore,W1 is selected as the filter material for the next stage of filtration.（3）Explore the optimal filter material.Natural manganese sand,natural zeolite and W1were selected as filter materials to filter the supernatant after calcium carbide slag treatment.The removal effect of W1 modified by sodium hydroxide on iron and manganese was better than that of natural zeolite and natural manganese sand,and the p H of effluent could be reduced rapidly in a period of time.Therefore,W1 is selected as the optimal filter material for acid mine wastewater.The combined treatment of calcium carbide slag neutralization and W1 adsorption can reduce the effluent concentration of total iron and total manganese in acid coal mine wastewater to 0.15 mg·L^-1 and 0.25 mg·L^-1,respectively,and the effluent p H is7.64,which fully conforms to the Discharge Standard of pollutants in Coal Industry and the Discharge Standard of Environmental Pollutants in Guizhou Province.（4）To explore the adsorption of manganese by attapulgite and modified attapulgite.When the p H of attapulgite was 4 and the dosage was 0.1g,the adsorption capacity of manganese reached the maximum 12.87 mg·g^-1.The adsorption process of attapulgite for manganese is consistent with the quasi-second-order kinetic model and Langmuir model,indicating that the adsorption process belongs to chemical adsorption and is a homogeneous monolayer adsorption.By comparing the adsorption effect of three modification methods of attapulgite at different p H values,it is found that the adsorption effect of heat-modified attapulgite（W5）on manganese is better than that of other materials,so W5 is selected for follow-up experiments.When the p H of W5 was 7 and the dosage was 0.1g,the adsorption capacity of W5 reached the maximum of 60 mg·g^-1.The adsorption process of W5 for manganese is consistent with the quasi-second-order kinetic model and Freundlich model,indicating that the adsorption process belongs to chemisorption and heterogeneous multilayer adsorption.According to the fitting results of Langmuir model isotherm model,the maximum adsorption capacity of W5 for manganese at 25℃is 461.190 mg·g^-1.