Kinetic modeling of As release from contaminated soils: Consideration of particle size and co-contamination of Cu

Prediction on the release kinetics of metalloids from soils is challenging due to the physio-chemical heterogeneity of soil and the varying binding abilities of metalloid contaminants on soil. In this study, the kinetics of As(V), together with Cu(II), release from two typical field contaminated soils were investigated by the stirred-flow experiments. We formulated the quantitative models to describe the release kinetics of As(V) from the contaminated soils with consideration of varying soil particle size and presence of Cu(II). The results showed that the release kinetics of As(V) and Cu(II) from different particle size fractions and at different reaction pH was well described by the model. The models also indicated that the bidentate binding sites on goethite were the major contributor for As(V) release, while soil organic matter (SOM) mainly controlled the Cu(II) release. Finer particle size fractions had more significant contributions to As(V) and Cu(II) release due to higher concentrations of reactive metal(loid)s and more reactive adsorbents. Moreover, the models also showed applicability for predicting metal(loid) release from the bulk soils by considering the contribution of each soil particle size fraction, and the kinetic behaviors of two individual contaminants, As(V) and Cu(II), can be modeled independently. Our results provided a modeling framework to predict the release kinetics of metal(loid)s from soils co-contaminated with different cation and anion pollutants with consideration on the effects of physical and chemical heterogeneity of soils. [Display omitted] •The release kinetics of As(V) and Cu(II) from soils were modeled independently.•The model considered the complexity of soil adsorbents and binding sites.•The model well described the effects of particle size fractions and reaction pH.•Metal release from bulk soils was predicted from different particle size fractions.