Study On Migration And Solidification Of Heavy Metals From Tailings And Its Building Materials

The China’s existing tailings treatment methods are tailings re-election,tailings production of building materials,tailings for the production of fertilizer,filling mine mined-out area,etc.,which use tailings solid waste preparation of building materials,not only can significantly reduce the natural non-metallic mineral resources mining,but also conducive to energy conservation and ecological protection.In this paper,some tailings samples from Chengde area were collected for the production of building materials,and the leaching toxicity of heavy metals in products was tested,including steam-cured brick,concrete and aerated concrete.The scope of this sampling involves 12 counties in Chengde City,a total of 14 tailings,a total of 22 sampling points,according to the distribution of different points and the depth of a total of 85 samples.Because of the large amount of sample,the work has a certain time limit,so the use of X-ray fluorescence spectrometer on the tailings samples of chemical composition analysis,and according to chemical test results by SPSS software analysis,the final determination of seven samples for subsequent experiments.Chemical composition shows that the contents of SiO₂,CaO and Al in tailings are high,which are in accordance with the requirement of raw material composition and content in the preparation of building products.By particle size test,it was found that the fineness of the tailings of the average modulus of less than 1.5,in line with the production of building materials,particle size requirements.The total content of heavy metals in the tailings samples was detected by microwave digestion.The highest manganese content was Mn,E1 and G3 were more than 2000 mg/kg,which belonged to the ultrahigh concentration.Followed by T samples for the copper so the copper element is also higher,more than 1000 mg/kg.In order to study the bioavailability of the product and tailings,the European Community Reference Material Bureau（BCR）method was selected for heavy metal toxicity leaching experiments.The results showed that the leaching ratio of tailings samples in the acid exchange state was larger,and the leaching ratio was higher in the organic state and Fe-Mn oxidation state,and the leaching ratio was smaller in the residual state.The results of leaching of building materials produced by tailings show that the leaching ratio of heavy metals in the residual state increases,and the proportion of leaching in the acid exchange state decreases,indicating that the heavy metals of the tailings are better cured in the product internal.Through the XRD and SEM test,the products made of tailings,steam-cured brick and aerated concrete generated hydrated C-S-H gel and terbutaline,calcite and other minerals,These hydrated silicate materials are effective in curing heavy metals inside the crystal.Due to the different raw materials of the tailings and the conditions of the autoclaved curing,the crystal structure inside the products is different,and the curing effect of the heavy metals is different.The research results of this paper provide a theoretical basis for the tailings production of Chengde area,which can not only reduce the raw material cost of the building materials manufacturing industry in the area,but also solve the problem of tailings pollution in the area.