Study On The Solidification Behavior Of Cadmium During Clay Sintering

At present,the main pollutants of the soil environmental quality of agricultural land in my country are heavy metals,of which cadmium is the primary pollutant.Sintering solidification method can effectively deal with soil heavy metal pollution,but domestic research on the treatment and disposal of sintering technology is mainly sludge and incineration fly ash,and the research on the sintering of cadmium-containing soil is relatively lack.This article uses clay as the raw material,CdO is added to simulate soils contaminated by different degrees of Cd.The cadmium release behavior of cadmium-containing clays added with Fe₂O₃,CaO,Al2O3 during high-temperature sintering is studied,which provides a reference for high-temperature treatment of cadmium-containing soil.In the experiment,design sintered materials with different components,study the curing characteristics and leaching characteristics of cadmium in the sintered body,and use X-ray diffraction（XRD）,scanning electron microscope（SEM）and energy spectrometer（EDS）to analyze the cadmium in the high-temperature sintered body,discusses different composition and different cadmium content of cadmium in containing cadmium waste sintered body fixed,leaching,and the influence of the mineral phase and morphology of sintered body.The following conclusions are drawn:（1）By preparing sintered materials with different contents of CdO,Fe₂O₃,CaO and Al2O3/SiO2,the volume change,solid solution and leaching under different conditions were studied.The results show that proper addition of Fe₂O₃,CaO and Al2O3 has a good effect on restraining the expansion of the material containing cadmium and controlling the shape change of the billet.Increasing CaO content has a good effect on the solid solution rate,but an excessively high CaO content will produce more liquid phase,which will deform the billet body.At the same time,excessive CaO will also inhibit the leaching of Cd by increasing the pH of the aqueous solution,It is advisable to add 3%CaO.The sintered material with high Al/Si ratio is not easy to deform at high temperature and has a good curing effect on cadmium.（2）The morphology of heavy metals,mineral phase composition and microscopic morphology of sintered materials were characterized and analyzed to explore their relationship.The results show that Cd mainly exists in the form of residue after sintering at high temperature,and the leaching concentration is low.Cd in sintered materials is mostly in the form of Cd silicate aluminate,which has certain resistance to chemical erosion.Cd can be solidified in silicate structure to reduce its leaching toxicity.Appropriate addition of metal oxides can deepen the melting inside the material,generate a more compact structure,and seal Cd in the liquid phase.（3）The main reasons for the solidification of heavy metal Cd by sintered materials are as follows:1.Silicate minerals generated at a lower sintering temperature can effectively fix heavy metal Cd and limit its migration;2.After high temperature sintering,the liquid phase fills into the pores,and the sintered material forms a denser structure,which wraps up the heavy metal Cd and isolates the external contact,thus reducing its toxicity.