Study On Solidification Process Of Arsenic And Lead Containing Metallurgical Slag Using Different Mineral Materials

In recent years,China’s non-ferrous metal smelting industry is booming,and the production and development of metallurgical industry has made great contributions to social and economic development,while it is the massive development of these resources that has caused serious environmental pollution,directly threatening the safety and survival of human beings and causing widespread concern in society.Non-ferrous metal metallurgy produces slag with high content of heavy metals,and the long-term storage of these slags,in addition to polluting large areas of land,the toxic substances they contain may also seep into the groundwater and soil.This causes serious environmental pollution,which in turn endangers the entire ecosystem.Therefore,it is imperative to treat solid slags generated from metallurgical and other industrial activities.In this study,the slags generated from a metallurgical site in Hunan are used as the object of research,and are treated harmlessly by using cement as the main curing material and different fillers and additives as passivating and blocking materials,and the curing and stabilizing effect of various materials is used to achieve safe landfills and subsequent resource utilization of the slags.In this paper,cement solidification is firstly chosen for the environmentally sound treatment of the slag,followed by an investigation of the theoretical basis for curing the slag with cement,addition of different mineral fillers(fly ash,bentonite,zeolite,attapulgite),yellow sand,glass fiber and stabilizer,and based on this,a suitable experimental approach is adopted to investigate the process and conditions required for curing the slag.In this study,based on the leachability and compressive strength of the cured body,the optimum batching system was determined through a series of experiments,i.e.,the mass ratio of each material was cement: slag: mineral admixture: yellow sand: glass fiber = 4:1:0.6:0.9:0.05,the water-cement ratio was 0.5,and the amount of stabilizer ferric chloride was 1% of the total system mass.The effect of the experimental process on the stability of the curing body was explored through experiments,and the results showed that the best curing effect was achieved when the materials were mixed and ground for 30 min after taking the proportional weighing,the mixing time and oscillation time were 20 min and 5 min,respectively,and the experimental maintenance measures were the curing body was first maintained in the maintenance box for 14 days after demoulding,and then taken out and maintained under natural conditions for 14 days.The curing body made under the best ingredients system and process conditions,the compressive strength of 12 Mpa,to meet the requirements of industrial applications(more than 7 Mpa).And four of the highest content of heavy metal ions Pb,Cd,As,Zn also according to HJ 557-2010 "solid waste leaching toxicity leaching method-horizontal oscillation method" test,the results are much lower than GB5085.3-2007 "hazardous waste identification standards-leaching toxicity identification",indicating that the method effectively control the possibility of pollution by fugitive metallurgical waste,the formation of The solidified body can also be used for other purposes such as construction and road substrates,realizing the resource utilization of waste,with good socio-economic and environmental benefits.At the same time,due to the close correlation between the leaching performance,mechanical and physical properties,durability,and micro pore structure of the solidified body,this study also used X-ray computed tomography technology to investigate the effects of different mineral fillers,glass fiber content,yellow sand content,water cement ratio,stabilizer types,grinding methods,oscillation time,and other factors on the pore structure of the cement solidified body.From the quantitative analysis table of pore structure and the pore distribution diagram,it can be seen that the porosity of the cured body has a close relationship with its compressive strength and leaching rate,i.e.,the compressive strength and leaching rate of the cured body under certain conditions are optimal,and its porosity is also the smallest in its range,and the size of the porosity is directly proportional to the leaching rate.Finally,this study investigated the curing hindrance mechanism by analyzing the microstructure,hydration products and curing mechanism of the cured body with the help of SEM electron microscopy.