[Adsorption behavior and speciation transformation of Ag+ in phaeozem and red soil].

The batch equilibration experiments were carried out to study the adsorption characteristics of Ag+ and the effect of pH on the adsorption process in two typical Chinese soils, which the phaeozem from Northeast China and the red soil from Hunan province. The species transformation of Ag+ was investigated in the experiments using the sequential extraction method. The results showed that an adsorption quantity of Ag+ for both soils increased with increasing solutions initial pH. Adsorption quantity of Ag+ in the two soils also increased with increasing of initial Ag+ concentration in the range from 0 to 100 mg x L(-1), specifically, going up quickly in the concentration range of 0-20 mg x L(-1), but increased gently when Ag+ concentration exceeded 20 mg x L(-1). The Ag+ adsorption data of both soils were adequately described by Langmuir isotherm occurred in Ag+ sorption processes, their maximum adsorption quantities were 250 mg x kg(-1) the phaeozem soil and 88.5 mg x kg(-1) in the red soil, indicating a much higher adsorption capacity in northeast phaeozem soil than that of Hunan red soil. The two soils had similar adsorption kinetic characteristics, with respect to quickly reaching equilibrium within 30 minutes, but the adsorption rate of phaeozem soil was significantly greater than that of the red soil. The species analysis of Ag showed that exchangeable Ag and residual Ag increased in red soil, and metal-organic complex-bound Ag, exchangeable Ag, carbonate-bound Ag and residual Ag increased in phaeozem, respectively.