Removal Of Manganese And Ammonia From Electrolytic Manganese Slag And Preparation Of Aerated Concrete With Red Mu

Electrolytic manganese slag is the industrial waste discharged in the process of electrolytic manganese production.It has the characteristics of high calcium and high silicon,and has great application potential in building materials.However,high concentration of manganese and ammonia nitrogen stays in the products,affecting the manganese residue content and material properties,and the ammonia nitrogen is discharged unorganized,polluting the environment,leading to hidden dangers in the safe use of the products.Therefore,manganese and ammonia should be removed before the resource utilization of manganese residue.The traditional washing method is simple in operation and low in cost,but it needs to be solved urgently because of its large water consumption and low removal rate of manganese and ammonia nitrogen.Aerated concrete is light in weight,good thermal insulation performance,gray and white,easy to popularize,and is an important way to absorb solid waste.Acidic deamination manganese slag and alkaline red mud were mixed in appropriate proportions to replace part of silicon sources to produce aerated concrete,which could neutralize the acidity and alkalinity of slurry and adjust the viscosity,providing better conditions for the gas generation of aluminum powder,and red mud could stimulate the activity of manganese slag and improve the performance of the product.It can broaden the way of resource utilization of manganese slag,promote the capacity expansion of nickel-cobalt-manganese ternary battery materials and the green and low-carbon development of electrolytic manganese industry.In this paper,on the basis of the traditional water washing method,the leaching agent was added to remove manganese and ammonia nitrogen in electrolytic manganese slag by one-step method.The relationship between the process parameters and the residual concentration of manganese and ammonia nitrogen in manganese slag was studied to determine the best leaching process.The leaching kinetics and characterization analysis were used to establish the leaching model and explore the leaching mechanism.Secondly,deammoniated manganese slag and red mud were used to replace part of silicon sources to prepare aerated concrete.The influence of raw material ratio and technological parameters of deammoniated manganese slag and red mud on the performance of aerated concrete was studied.The hydration mechanism of the co-preparation of aerated concrete by manganese slag and red mud was discussed through characterization analysis,and the sample leaching toxicity was tested.The main conclusions are as follows:(1)Using water as leaching agent and citric acid as leaching agent can greatly promote the leaching of manganese and ammonia nitrogen from manganese residue.When the dosage of citric acid is 25%,the ratio of liquid to solid is 5:1,the leaching time is 30 min,and the leaching temperature is 25℃,the leaching effect is better,and the removal rates of manganese and ammonia nitrogen are 93.6%and 97.9%,respectively.(2)When citric acid is used as leaching agent to leach manganese and ammonia nitrogen from electrolytic manganese slag,citric acid can not only REDOX reaction with high-valence manganese,but also reduce high-valence manganese to divalent manganese ion which is easily soluble in water.It can also destroy the structure of calcium sulfate dihydrate,convert calcium sulfate dihydrate into calcium sulfate hemihydrate,release ammonium manganese salt wrapped in calcium sulfate lattice,and promote the leaching of ammonia and manganese in electrolytic manganese slag.The leaching kinetics of manganese and ammonia nitrogen from electrolytic manganese slag accord with the shrinkage kernel model,which is controlled by chemical reaction and solid film mixing.(3)In cement dosage of 15%,quicklime dosage of 20%,sand dosage of 32%,manganese slag 20%,red mud dosage of 10%,gypsum dosage of 3%,aluminum powder content of 0.2%,water-to-material ratio of 0.8,the compressive strength of the product is 5.7 MPa,and the dry density is 745 kg/m~3,which meets the requirements of’Autoclaved AAC Block’(GB/T 11968-2020)A 5.0 strength level and B 07 dry density level;The leaching toxicity of heavy metal ions is within the specified range.(4)As the content of deaminated manganese slag decreases,the content of red mud increases,and the alkaline substances in the hardened body of aerated concrete gradually increase.When the mass ratio of deaminated manganese slag to red mud is1:0.5,the hydration products have more calcium sulfate content and good crystal shape,and there is a lot of tobermorite with good crystallinity.columnar calcium sulfate interspersed in the tobermorite,hydration products between the formation of a dense network,the structure is more stable.