| With the development of society and the acceleration of urbanization,the total amount of resources shows a decreasing trend.As a residual industrial waste,tailings contain a wide variety of heavy metals.In the process of transportation and disposal,the exposure of heavy metals will have an adverse impact on human health and ecological environment.As a new building material,heavy metals can be effectively solidified in glass-ceramics.Meanwhile,the oxides contained in tailings,such as quartz and calcium oxide,are the basic raw materials for the preparation of glassceramics.Therefore,the resource utilization of solid waste has a broad development prospect.However,in the process of high-temperature reconstruction,the heavy metals in tailings will interact with each other.Therefore,the migration and transformation trend and the solidification mechanism of single heavy metal in the process of high-temperature reconstruction of glassceramics are still unclear.Meanwhile,the relevant research is still limited.Thus,it is important to study the migration and transformation mechanism of single heavy metals and realize the accurate regulation and positioning.Based on this,under the guidance of SiO2-CaO-MgO silicate ternary phase diagram,the mix proportion with diopside（Ca Mg Si2O6）as the main crystalline phase was designed in this paper.Besides,different contents of single heavy metal were added step by step according to the mix proportion.The effect of heavy metals on the properties of glass-ceramics was clarified by crystallization kinetics calculation and Raman spectrum test.Secondly,the migration,transformation and enrichment characteristics of heavy metals and the influence on crystal size were analyzed by X-ray diffraction and scanning electron microscope.Then,the valence transition trend of heavy metals was clarified by X-ray photoelectron spectroscopy（XPS）,and the migration and transformation trend and solidification mechanism of single heavy metal were deeply discussed.Subsequently,the chemical forms of heavy metals were obtained by BCR continuous extraction.By simulating the acidic（p H=2.88）and neutral（p H=7）conditions,the leaching characteristics of heavy metals were analyzed by horizontal oscillation method,and the differences of the leaching characteristics of the four kinds of heavy metals were determined.Finally,glassceramics were successfully prepared with lead-zinc tailings as raw materials,and the resource utilization of solid waste was successfully realized.Based on the above test methods,this thesis found that:（1）With the increase content of Cu,Zn and Fe,the crystallization peak moved to the left,and the nucleation and crystallization temperature of glass-ceramics showed a downward trend as a whole,and the influence on the heat treatment system was Cu > Fe > Zn.The nucleation and crystallization of glass-ceramic was inhibited by Pb.Meanwhile,the inhibition effect was more obvious with the increase of heavy metal content.The damage degree of heavy metal elements to the network structure of glass-ceramics is Fe > Zn > Cu > Pb.（2）With the increase content of Cu,Zn and Fe,the bulk density and shrinkage can be increased by 15% and 32.6%,respectively.Pb has little effect on the bulk density and shrinkage of glass-ceramics.In addition,the effect of heavy metals on the water absorption of glass-ceramic changed little,which was lower than 0.6% compared with the reference group.（3）Cu was mainly solidified in the crystalline phase in the form of copper iron ore（Cu Al O2）in glass-ceramic.Zn replaced Mg with similar chemical valence and ion radius and was solidified in the form of continuous displacement solid solution.Fe replaced Al in pyroxene phase and solidifies in the form of discontinuous replacement solid solution.Due to the high volatilization rate,Pb was evenly distributed in the amorphous,that is,glass phase of glass-ceramics in the form of ions.In addition,before and after high-temperature calcination,only Cu had the transition of chemical valence from +2 valence to +1 valence,and the chemical valence of other elements had not changed,Zn and Pb were +2 valence and Fe was +3 valence.（4）The chemical forms of Cu,Zn,Pb and Fe in glass-ceramics were mainly in the state of residue.Although some Fe existed in the form of iron manganese oxidation,it gradually changed to a stable state with the increase content of Fe.In addition,with the increase of crystallinity,the proportion of heavy metals in stable state was also increasing.（5）Cu,Zn and Fe were conducive to the improvement of crystallinity and grain size of glassceramic,and generally had a positive correlation trend with the content.Among them,Zn played the most significant role.When the content of Zn was up to 2.0wt.%,the crystallinity was 97.97%,which was increased by 10.94% compared with the reference group.And the maximum particle size can reach 30μm,the maximum particle size increased by 87.5% compared with the reference group.Different from the above effects,with the continuous increase of Pb content,the crystallinity and grain size of glass-ceramics decreased significantly,and the maximum decreased by 39.1%and 66.7% respectively.（6）The leaching concentration of heavy metals were far lower than the threshold,and glassceramics had a significant effect on the solidification of heavy metals.In addition,the concentration of heavy metals under acidic leaching conditions were much more than that under neutral leaching solutions.The curing effect of glass-ceramics on heavy metals was Pb > Fe > Zn >Cu.Although the leaching concentration of heavy metals in lead-zinc tailings far exceeded the threshold,the leaching concentration of tailings-based glass-ceramics met the requirements due to the dual action of amorphous phase（glass phase）and crystalline phase of glass-ceramics.（7）The crystallization activation energy of lead-zinc tailings-based glass-ceramics was139.2KJ/mol.The glass-ceramics were in the form of volume crystallization in the crystallization process,and the heat release was uniform.At the same time,before and after high-temperature calcination,only Cu and Fe undergo chemical valence transition,Cu changed from +2 valence to+1 valence,Fe reduced from +3 to +2 valence,and the valence states of Zn and Pb did not change,both of which are +2 valence.The crystallinity of RF was 66.53%.For LZ1 and LZ2 samples,due to the large amount of Cu and Zn,the crystallinity was 70.23% and 77.63% respectively.Compared with RF,the crystallinity was increased by 5.56% and 16.68% respectively.It can be seen that the effect of Zn on promoting crystallization was much greater than that of Cu.For LZ3 sample,the crystallinity was only 53.89%,which was 23.465% lower than that of RF. |
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