Deactivation of Heavy Metal in Soil Using Hydrothermally Modified Attapulgite for Remediation of Farmland Soil Around Mining Area
With the introduction of exogenous Si2+,Ca2+and Mg2+to low-grade mixed-dimensional attapulgite(ATP),the authors prepared the high-grade ATP(PSMC)at laboratory scale using hydro-thermal modification method,which was further characterized using scanning electron microscopy,X-ray diffraction,and Fourier infrared spectroscopy.The deactiva-tion effect of ATP and PSMC on heavy metals in a mining area-neighboring farmland soils was evaluated through the passiv-ation tests,and the result indicated that the hydrothermal modification could cause ATP and its associated minerals turning into the amorphous that was of defective crystal structure or low-crystalline crystallinity.Besides,the addition of PSMC significantly reduced DTPA extractable Cd,Pb,Cu and Zn in soil,and as addition of PSMC was 5％(w/w)the reduction tend-ed minimized;and the addition of PSMC led to the transformation of acid-soluble Cd,Pb,Cu and Zn to the residual fraction that was much more stable.In particular,the deactivation efficiencies of Cd,Pb,Cu and Zn could be up to 91.15％,84.70％,90.51％and 90.09％,respectively when 5％PSMC was addied.Consequently,the potential environmental risk index of heavy metals decreased with the increase of PSMC application amount:according to the risk grade of the relevent soil management and control standard,the indexes of Pb,Cu,and Zn were all below 1％while Cd was well below 3％.Therefore,hydrothermal modification greatly enhances the heavy-metal deactivation capacity of ATP,thus providing an alternative approach for the high-value utilization of low-grade ATP.
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