Research On The Influence Of Electrolytic Manganese Residue Leachate On The Surrounding Geotechnical Environment And Environmental Risk Assessment Of A Slag Silo

Electrolytic manganese residue is generally stored in the open air.Under the action of natural factors such as rainwater scouring and surface runoff,electrolytic manganese residue leachate is formed,polluting the ecological environment around the slag yard.Firstly,a domestic electrolytic manganese residue warehouse was investigated on the spot,and the basic physical and chemical properties and leaching toxicity of electrolytic manganese residue in the slag yard were analyzed.According to the test results,the simulated electrolytic manganese residue leachate was configured.The effects of leachate from electrolytic manganese residue silo on soil physical and chemical properties,microstructure and mechanical properties were studied through indoor simulated soil pollution test.The effects of leachate from electrolytic manganese residue silo on the physicochemical properties and mechanical properties of carbonate rocks under different hydrodynamic forces and different dissolution ages were discussed through indoor carbonate rock dissolution experiments.Based on the fuzzy hierarchy comprehensive evaluation method,the environmental risk assessment model of electrolytic manganese residue storage is established.The main conclusions of this paper are as follows:(1)The chemical composition of electrolytic manganese residue is mainly S,Si,Ca,Al,Fe,Mn and Mg,including quartz,gypsum and other mineral phases,which are mainly from the raw ore of electrolytic manganese and the by-products of electrolytic manganese process.According to the leaching toxicity test results of electrolytic manganese residue,the main components of simulated electrolytic manganese residue leachate are determined as Mn²⁺,NH₄⁺-N,Mg²⁺,Ca²⁺,SO₄^2-.(2)With the increase of the concentration of electrolytic manganese residue leachate,the p H of the contaminated soil gradually decreases,the conductivity gradually increases,the cation exchange capacity and organic matter content first increase and then decrease,and reach the peak at 50%of the pollution concentration.With the extension of pollution time,the p H of the contaminated soil increased first and then decreased,the conductivity gradually decreased,and the cation exchange capacity and organic matter content gradually increased.The XRD results of the contaminated soil showed that the aluminosilicate minerals in the contaminated soil were dissolved in varying degrees.The microstructure analysis of the contaminated soil shows that the soil cement is corroded,the soil particle bonding force is weakened,and the large particles are transformed into smaller tubular and spherical particles.However,due to the accumulation of organic matter over time,the bonding force between the particles in the soil is increased,the soil structure is more compact,and the decomposed small particles are reunited and form flocs.Under the control of organic cementation,the compression of electrolyte on the electric double layer and the dissolution of H⁺,the shear strength of soil first increases and then tends to be flat.(3)The water rock interaction between electrolytic manganese residue leachate and carbonate rock results in the transformation of surface pores of rock samples to small pores,fracture cavity pores,large pores and through fractures.The reddish-brown sediment(manganite)is deposited in large area in the third month,and the yellow powder sediment(dissolved carbonate rock)is enriched in the fifth month.With the extension of the dissolution time,the quality,porosity and wave velocity of the carbonate rock showed a downward trend as a whole.However,due to the enrichment of manganese ore on the surface of the carbonate rock in the third month,the quality of the carbonate rock increased sharply in the third month.Under the control of H⁺etching,salt effect,common ion effect and ion pair effect,carbonate rocks enter the cycle of de dolomitization and dolomitization.Under the chemical action of electrolytic manganese residue leachate,the structural plane of carbonate rock increases,and the particle bonding force decreases,resulting in the decrease of uniaxial compressive strength of carbonate rock with the passage of time.Hydrodynamic scouring can accelerate the dissolution of electrolytic manganese residue leachate to carbonate rocks.(4)Based on the existing literature and data,combined with the characteristics of the electrolytic manganese residue reservoir,and based on the fuzzy hierarchical comprehensive evaluation method,three indicators such as environmental pollution,geological environment damage and ecological environment damage are taken as the criterion layer,and 10 indicators such as water environment pollution,atmospheric environment pollution,soil environment pollution,collapse,fissure,collapse,landslide,number of biological species,vegetation coverage and human health are taken as the indicator layer,The environmental risk assessment index system of electrolytic manganese residue silo is established,the value standards of various quantitative and qualitative indexes are established,and the four level assessment standard from low risk to major risk is set.The environmental risk assessment model is used to assess the environmental risk of the electrolytic manganese residue storage in the study area.The results show that the risk level of the electrolytic manganese residue storage in the study area is general risk.