Research On Properties Of Lightweight Aggregate And Solidification Of Heavy Metals Produced By Contaminated Soil

With the development of our country’s industry,more and more chemical plants and mining smelter areas have been established,or the needs of urban development,the old chemical plant area has been dismantled and relocated,and heavy metal pollution is likely to exist around or around the plant area.The governance of heavy metal-contaminated soil has become an important problem for industrial and urban development and has attracted more and more attention of scholars.In this paper,heavy metals were added to the shale powder to simulate heavy metal soils.High-temperature sintering was used to solidify heavy metals.The effect of sintering system and sintering components on the properties of sintered products and the solidification of heavy metals was studied by changing the sintering time,sintering temperature,the content of Na₂O,MgO,CaO,Fe₂O₃ and carbon powder in the raw materials.the ceramic preparation performance and solidification mechanism of heavy metals were explored by TG,XRD,SEM,XPS,EDX,MIP and other meansThrough the analysis and comparison of the data,the following conclusions were obtained:（1）For the sintering temperature,the increase of sintering temperature on the volume of the sintered product showed the tendency of shrinking first and then expanding.apparent density was firstly increased and then decreased,and the water absorption rate was reduced first and then unchanged or slightly increased.The effect of sintering time was weaker.Except 1200°C,the increase of sintering temperature and the increase of sintering time were favorable to the solidification of heavy metal chromium.（2）The effect of the oxide sintering component on the properties of the ceramic particles is mainly to change the eutectic point,the liquid viscosity,and the liquid phase amount during the sintering process,thereby affecting the expansion and escape of the gas phase.The oxides used as variables in this paper could reduce the eutectic point in a certain extent.Therefore,when the content was appropriate,the number and volume of closed cells can be increased,the density of the sample surface can be increased,the volume can be expanded,the apparent density can be reduced,and the water absorption can be reduced.However,if mixtures were added too much,the gas escapes,the opposite effect would be showed up.（3）The effect of oxides on the solidification of heavy metals was mainly manifested in the coating of liquid phase,the opening and closing of pores,and the reaction with heavy metals such as chromium.The addition of Na₂O,CaO increased the solidification of heavy metals before they decreased,and the increase of Fe₂O₃and MgO increased the leaching of heavy metals.（4）The main crystals in the sintered sample were quartz,magnesium（aluminum-iron-chromium）spinel,and green chrome ore.When the sintering temperature was low,the crystal phase was dominated by quartz.With the increase of sintering temperature,magnesium（aluminum-iron-chromium）spinel was increased to solidify heavy metal chromium.（5）Within a certain range（Pk=3.2-5.0,K=0.12-0.20）,Pk value and K value both had a certain relationship with the leaching of heavy metal chromium.When the Pk value was larger or the K value was smaller,the solidification rate of heavy metal is higher.it can be used as a basis for the experimental design and inference of heavy metal chromium leaching.However,the fitted curve of the Pk value was obviously closer to 1 than the fitted curve of the K value,which proves that the Pk value was more reasonable.（6）The limit of heavy metal chromium content was 4%.After exceeding 4%,the leaching amount had a huge increase.When the chromium incorporation was excessive,more and more chromium would be present in the form of chromite from the sample.And excessive chromite formation would be detrimental to the solidification of heavy metals.Magnesium,Aluminum and other elements were conducive to the reaction and solidification of heavy metal chromium,and the heavy metal chromium tended to form a magnesium（aluminum iron chromium）spinel structure or enter the molten phase to form a solid solution.