Reactive transport of arsenic(III) and arsenic(V) on natural hematite: experimental and modeling

Natural hematite was used for the removal of arsenic(III) and arsenic(V) from aqueous solution. The experimental breakthrough curves were obtained in fixed-bed columns. The transport of arsenic in a simplified fixed-bed configuration was quantified by using the CXTFIT code, which was used to estimate the transport and sorption parameters of the convective-dispersive equation (CDE) and the two-site deterministic nonequilibrium (TSM/CDE) model by fitting the models to the experimental breakthrough curves (BTC). The prediction of the breakthrough curves performed by the two-site nonequilibrium sorption model resulted in a good fit, indicating that this model can properly describe the transport and sorption processes of arsenic on natural hematite. Additionally the parameters obtained indicate that nonequilibrium sorption governs the As(III) and As(V) uptake onto hematite in a fixed-bed column. No significant differences in the transport and sorption parameters of As(III) and As(V) on natural hematite were obtained; the retardation factor values were in the same order of magnitude for both species.