碳酸钙改性滑石施加量对土壤重金属铬的形态影响研究

Effect of Calcium Carbonate Modified Talc on the Speciation of Soil Heavy Metal Chromium

通过将碳酸钙与滑石按照摩尔比2∶1混合后,在马弗炉中1150℃焙烧2 h后得到改性滑石,然后利用XRD、FTIR和BET对其进行系统表征,最后通过土壤培育实验探讨碳酸钙改性滑石不同施加量(添加量分别为0%、0.5%、1%、2%、3%和4%)对土壤铬形态动态影响效应。结果表明:碳酸钙改性滑石主要物相组成为Ca2Mg(Si2O7)和少量的Ca3Mg(SiO4)2,疏松多孔,平均孔径为18.809 nm,通过FTIR可以观测到明显的特征峰Si-O-Si,改性滑石有效硅含量高达19.09%。施加该材料在土壤中可以通过形成硅酸盐络合物来改变土壤铬的形态,有助于降低土壤中重金属铬的可交换态含量,最大降低幅度能够达到60%以上,并且对碳酸盐结合态有着明显的降低效果,但对铁锰氧化物结合态的影响不大,对于有机物结合态含量同样有着降低的效果。在第60天的时候,施加量为0.5%时,土壤中铬的残渣态含量增加了15%。过量的施加该材料会导致土壤的pH变成强碱性,因此适当的施加该材料有助于改变重金属铬在土壤中的存在形态,有助于降低铬的生物有效性,从而可以治理重金属污染。

In this study,the calcium carbonate and talc were mixed at a molar ratio of 2∶1,and then calcined at 1150℃for 2 h in a muffle furnace to obtain modified talc,which was then characterized by XRD,FTIR,and BET.The effects of different amounts of calcium carbonate modified talc(0%,0.5%,1%,2%,3%and 4%)on the speciation of soil chromium(Cr)were investigated in a lab incubation experiment.The results showed that the main phase composition of calcium carbonate modified talc was Ca2Mg(Si2O7)and a small amount of Ca3Mg(SiO4)2.The modified talcwas porous and had an average pore diameter of 18.809 nm,with a characteristic peak of Si-O-Si by FTIR.The effective silicon content of the modified talc was as high as 19.09%.The application of modified talc changed the speciation of soil Cr by forming a silicate complex and reduced the content of soil exchangeable Cr by more than 60%.It also significantly decreased thecontents of carbonate bound Cr and organic matter bound Cr and had little effects on the iron-manganese oxide bound Cr.The content of soilresidual Crwas increased by 15%after the 60th day of modified talc application at the amount of 0.5%.The soil became strongly alkaline after excessive application of modified talc.Sothe appropriate application of the material helps to change the presence of heavy metal soilCrand reduce the bioavailability of Cr,and thus control heavy metal pollution.