Kinetic modeling of pH-dependent antimony (V) sorption and transport in iron oxide-coated sand. (November 2015)

• Record Type: Journal Article
• Authors: Cai, Yongbing; Li, Lulu; Zhang, Hua
• Is Part Of: Chemosphere. Volume 138(2015)
• Page Start: 758
• Page End: 764
• Publication Date: 2015-11
• Subjects: Antimony -- Iron oxide-coated sand -- Adsorption–desorption -- Transport; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2015.07.067
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract : Highlights: Decreased Sb(V) sorption capacity and kinetic rate under alkaline condition. Inner-sphere surface complexation of Sb(V) on iron oxide coated sand. Increased mobility of Sb(V) caused by deprotonation on oxide surface. Nonlinear MRM model well describes time-dependent retention and transport. Abstract: Understanding the mechanisms and kinetics controlling the retention and transport of antimony (Sb) is prerequisite for evaluating the risk of groundwater contamination by the toxic element. In this study, kinetic batch and saturated miscible displacement experiments were performed to investigate effects of protonation–deprotonation reactions on sorption–desorption and transport of Sb(V) in iron oxide-coated sand (IOCS). Results clearly demonstrated that Sb(V) sorption was highly nonlinear and time dependent, where both sorption capacity and kinetic rates decreased with increasing solution pH. Breakthrough curves (BTCs) obtained at different solution pH exhibited that mobility of Sb(V) were higher under neutral to alkaline condition than under acidic condition. Because of the nonlinear and non-equilibrium nature of Sb(V) retention and transport, multi-reaction models (MRM) with equilibrium and kinetic sorption expressions were utilized successfully to simulate the experiment data. Equilibrium distribution coefficient ( Ke ) and reversible kinetic retention parameters ( k 1 and k 2 ) of both kinetic sorption and transport experiment showed marked decrease as pH increased from 4.0 to 7.5. Surface complexation is suggested as the dominant mechanism for the observed pH-dependent phenomena, which need to be incorporated into the kinetic models to accurately simulate the reactive transport of Sb(V) in vadose zone and aquifers.