Cr (Ⅵ)及 Ni (Ⅱ)在偏碱性土壤中的共运移及稳定化

Transport and immobilization of Cr(Ⅵ)anion and Ni (Ⅱ)cation in alkaline soil was studied through column experiments. Co-transport experiments showed that Cr(Ⅵ)and Ni(Ⅱ)responded differently to changes in flow rate and hydro-chemical conditions. For example, different flow rates and pH had little effect on the penetration amount of Cr(Ⅵ), while the penetration of Ni (Ⅱ)at the flow rate of 0.05 mL·min^-1 was obviously lower than that at the flow rate of 0.2 mL·min^-1, and its penetration decreased with increasing pH. Influent pH had a more significant effect on the penetration of Ni(Ⅱ)under the conditions of finer soil particle size and lower flow rate. The transport experiments and static surficial reaction experiment at the presence of humic acid, magnetite and zero valent iron showed that the three materials could simultaneously immobilize the two metals from the influent. However, the low reaction rate of humic acid and magnetite and the high reaction rate of zero-valent iron were found and Cr(Ⅵ)and Ni(Ⅱ)were almost completely removed from the solution by zero valent iron in 200 h. The properties of the soil medium, pore water pH, and contact time were key factors affecting the transport and retention of the two metals. In the penetration experiment of joint treatment, a large proportion of retained oxygen-containing Cr(Ⅵ)anions and the Ni (Ⅱ)cations in the humic acid + magnetite treatment were transformed into non-easy-mobile forms, while the treatment of humic acid+ zero valent iron had a high reaction efficiency and could simultaneously stabilize Cr(Ⅵ)and Ni (Ⅱ), transforming them mostly into non-easy-mobile forms. Despite the alkalinity of the soil, Cr (Ⅵ)was overwhelmingly transformed to Cr (Ⅲ)in the joint treatment of humic acid+ zero valent iron, with less than 6% Cr remaining as Cr (Ⅵ)in the deeper layers of the soil column.