Preparation Of Coal Gangue-based Porous Materials And Their Adsorption Of Heavy Metal Ions

With the development of heavy industry,the content of heavy metal ions in China's water bodies is getting higher and higher.Mercury?Hg?,chromium?Gr?,cadmium?Cd?,lead?Pb?,copper?Cu?and other heavy metal ions seriously affect human health through the food chain.How to remove heavy metal ions from water has always been one of the frontier issues in the field of environmental engineering.The conventional method is to sprinkle zeolite powder or modified fly ash,coal gangue and other powder materials into sewage,and heavy metal ions in the water are adsorbed and deposited in sludge through the powder to realize purification of water body.However,the adsorption efficiency of this method is low,and the generated sludge is converted into hazardous waste due to a large amount of heavy metal ions,resulting in secondary pollution.In order to solve the above problems,modified coal gangue was used to foam porous materials with high porosity and high specific surface area.Adsorption filtration was used to reduce heavy metal ions in water.Combined with desorption technology,the recycling of porous materials was realized.Based on the investigation of the research and utilization status of coal gangue at home and abroad,the preparation method of porous materials is studied.On the basis of the study of fly ash,blast furnace slag modified materials and zeolite materials as adsorbents,a method of preparing porous materials with high porosity and strong ability to adsorb heavy metal ions is proposed.In this paper,coal gangue powder was used as the main raw material,foaming agent and pore-forming agent were added,and porous materials with high porosity and high specific surface area were prepared through foaming,modification and curing processes.The adsorption properties of heavy metal ions were studied by ICP,and the adsorption thermodynamics and adsorption kinetics models were explored.XRD,SEM and TG-DSC were used to study the adsorption mechanism of Pb^2+.The results show that:?1?The water-solid ratio,the amount of foaming agent and pore-forming agent,and the calcination temperature have important effects on the water absorption,apparent density,and porosity of porous materials.The water absorption rate of porous materials increases first and then decreases with the increase of water-solid ratio,increases first and then decreases with the increase of pore-forming agent,increases gradually with the increase of aluminate cement content,and increases gradually with the increase of foaming agent;The apparent density of porous materials gradually decreases with the increase of pore-forming agent content and decreases with the increase of foaming agent content.?2?The best preparation process of porous material:78%coal gangue,11%aluminate cement,10%pore-forming agent and 2.2‰aluminum powder are mixed with a certain amount of sodium hydroxide evenly,with a water-solid ratio of 0.68.After calcination at850?for 2h and curing at 60?for 6h,the porous material of coal gangue has the best performance,with water absorption rate of 131.5%,apparent density of 0.30 and adsorption rate of 99.91%for Pb²⁺.?3?Through XRD,SEM and TG-DSC characterization of raw materials and porous materials,it is concluded that coal gangue itself has developed pore structure and is suitable for heavy metal adsorbent.The porous material prepared by the experiment has irregular pore structure,large specific surface area,high activity and good adsorption performance for Pb²⁺.?4?The best conditions for the gangue-based porous material to adsorb Pb²⁺are as follows:at room temperature,100 mL of Pb²⁺solution with an initial concentration of 100mg/L,0.8 g of adsorbent is added,and the adsorption time is 10min.The adsorption rate of the gangue-based porous material to Pb²⁺reaches 99.92%,and the adsorption amount is 12.48mg/L.?5?Adsorption thermodynamics research shows that Freundlich isothermal adsorption model can better describe the adsorption process of Pb²⁺on coal gangue porous materials,indicating that under certain conditions,the surface of porous materials is rough and unsmooth,and the adsorption process is not simple monolayer adsorption and adsorption is easy.Studies on adsorption kinetics show that the adsorption of Pb²⁺by porous materials mainly conforms to pseudo-second-order kinetics.