无机盐改性膨润土钝化锌铅镉复合污染土壤

PASSIVATION OF ZINC,LEAD AND CADMIUM CONTAMINATED SOIL BY INORGANIC SALT MODIFIED BENTONITE

高浓度重金属复合污染土壤的同步钝化一直是土壤钝化研究中的难点,因此,探究了多种无机盐改性膨润土对高浓度重金属复合污染土壤的同步钝化效果,结果表明:NaCl、KCl、Na_(2)CO_(3)、K_(2)CO_(3)、NaNO_(3)、KNO_(3)、Na_(3)PO_(4)、KH_(2)PO_(4)、KMnO_(4)、K_(3)PO_(4)、NaH_(2)PO_(4)、NaHCO_(3)等无机盐药剂在相同条件下制备的改性膨润土对多种重金属高浓度复合污染土壤的同步钝化效果存在明显差异,择优选择Na_(2)CO_(3)、K_(3)PO_(4)和NaH_(2)PO_(4)3种改性药剂进行改性,在最佳改性条件下,NaH_(2)PO_(4)改性膨润土同步钝化效果整体最佳,有效态Zn、Pb、Cd的削减率最高分别达到26.28%、28.84%和31.42%。NaH_(2)PO_(4)改性过程能够将膨润土颗粒中的Ca元素交换并生成新的CaHPO_(4)·2H_(2)O独立晶体,同时使膨润土颗粒具有更好的插层、层状结构和裂缝结构以及更广泛的Na^(+)分布,膨润土改性过程中的阳离子交换作用可能会进一步促进改性膨润土对于重金属的钝化效果。

The synchronous passivation of soil contaminated with high concentration of heavy metals is a difficulty in soil passivation research.In this paper,the synchronous passivation effect of various inorganic salts modified bentonite on soil contaminated with high concentration of heavy metals was studied.The results showed the modified bentonite prepared by NaCl,KCl,Na_(2)CO_(3),K_(2)CO_(3),NaNO_(3),KNO_(3),Na_(3) PO_(4),KH_(2) PO_(4),KMnO_(4),K_(3) PO_(4),NaH_(2) PO_(4) and NaHCO_(3) under the same condition had obvious differences in the synchronous passivation effect of multiple heavy metal high concentration composite polluted soil.Na_(2)CO_(3),K_(3) PO_(4) and NaH_(2) PO_(4) were selected,by their performance to optimize the modification conditions.Under the optimal modification conditions,the synchronous passivation effect of NaH_(2) PO_(4) modified bentonite was the best overall.The reduction rates of available Zn,Pb and Cd reached 26.28%,28.84%and 31.42%.In the modification process of NaH_(2) PO_(4),calcium in bentonite particles could be exchanged and new independent crystals of CaHPO_(4)·2H_(2)O could be formed.Meanwhile,bentonite particles have better intercalation,layered structure,fracture structure and wider distribution of Na^(+).Cation exchange interaction during bentonite modification may further promote the passivation effect of modified bentonite on heavy metals.