Differences in Sb(V) and As(V) adsorption onto a poorly crystalline phyllomanganate (δ-MnO₂): Adsorption kinetics, isotherms, and mechanisms

The environmental behavior of antimony (Sb) in soils is often considered to be similar to that of arsenic (As). Comparing the adsorption behavior of these two elements on soil minerals is important because both elements coexist in contamination areas. In this study, the differences in antimonate (Sb(V)) and arsenate (As(V)) adsorption reaction kinetics and isotherm characteristics on a poorly crystalline phyllomanganate (δ-MnO₂) were studied. The potential mechanisms were identified using zeta potential, Fourier transform infrared spectrometry (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherm results indicated that the maximum adsorption capacity for As(V) was 1.5 times higher than that for Sb(V). The adsorption kinetics of Sb(V) and As(V) were well fitted using pseudo-first-order model, and the adsorption rate of Sb(V) and As(V) significantly depended on δ-MnO₂ dosage and pH. At all tested pH values (3.0–9.0), the adsorption rate of As(V) was 4.0–7.7 times faster than that of Sb(V) at the same δ-MnO₂ dosage and pH conditions. FTIR and XPS analysis confirmed that M (metal)-O was bonded with Sb(V) and As(V). The adsorption capacity and rate of As(V) were significantly higher than those of Sb(V), suggesting that δ-MnO₂ had higher affinity toward As(V). The different adsorption behaviors of Sb(V) and As(V) onto δ-MnO₂ should be considered in soils. Copyright © 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.