Residence Time Effects on Arsenate Adsorption/Desorption Mechanisms on Goethite

Abstract

In order to make sound decisions regarding arsenate contamination rish, 1979, 1983; Jacobs et al., 1970). Arsenate sorption in soil and water environments, it is necessary to have a thorough understanding of the mechanisms of arsenate sorption and desorption on soils and soil components vs. pH increases until maxiover extended periods. The major objectives of this study were to mum sorption is reached and then sorption decreases determine the effects of aging or residence time on the kinetics of with further pH increase (Goldberg and Glaubig, 1988; arsenate sorption and desorption on goethite, and to combine spectro-Xu et al., 1988). For example, arsenate sorption on scopic x-ray absorption fine structure (XAFS) and macroscopic studies montmorillonite and kaolinite increased at low pH, disin order to determine sorption and desorption mechanisms over time played a peak near pH 5, and decreased at higher pH at pH 4 and 6. Sorption studies, conducted from 4 min to ≈12 mo, values (Goldberg and Glaubig, 1988). showed that arsenate sorption on goethite increased with time. Sorp-Goethite (␣-FeOOH), the most common iron oxide tion was initially rapid, with over 93% arsenate being sorbed in a 24-h in soils, has double bands of FeO 3 (OH) 3 octahedra period at pH 6. Similar arsenate adsorption behavior was observed which share edges and corners to form 2 by 1 octahedra at pH 4. Analysis of the samples with extended x-ray absorption fine structure (EXAFS) revealed that there exist two distinct atomic shells tunnels (only large enough to accommodate the passage surrounding the adsorbed As. The closest atomic shell was identified of protons) partially bonded by H bonds (Cornell and as an O atom, the next shell out was identified as an Fe atom. The

Effects of Oxalate and Humic Acid on Arsenate Sorption by and Desorption from a Chinese Red Soil

“…After 840 h the total desorption ratio reached about 50% and 41% for the samples with the sorption equilibrium time of 24 h and 840 h, respectively. The results indicate that a significant amount of As(V) was still retained in the soil even after 840 h of desorption since the phosphate added was three times higher than the initial As(V) concentration for the sorption experiments, which is in agreement with the observations of O'Reilly et al (2001).…”

“…The two-stage sorption kinetics observed in this experiment was similar to the results for As(V) sorption on goethite reported by O'Reilly et al (2001). In the presence of oxalate or HA, As(V) sorption within 24 h was decreased by 34.6% and 36.2%, respectively, for the samples with the initial As(V) loading of 0.2 mM.…”

“…But the difference was not significant for HA. It has been confirmed that both oxalate/HA and As(V) sorption are time-dependent (Fox et al, 1990;O'Reilly et al, 2001). If competition for sorption sites was the only way that oxalate/HA affected As(V) sorption, such effects should also be affected by residence time and we would not get the conflicting data on the comparative effects of oxalate and HA sorption.…”

Adsorption and mobility of aromatic arsenicals in Japanese agricultural soils

“…1), would have been adsorbed mainly onto the surface hydroxyl groups at layer silicate edges, onto oxyhydroxides of Fe and Al, and onto non-crystalline aluminosilicates. It has been suggested that the adsorption mechanisms of arsenate are similar to those of phosphate (Fendorf et al 1997;O'Reilly et al 2001). Thus, these AAs would be chemisorbed by variablecharge minerals to make inner-sphere complexes by ligand exchange reactions as well as by phosphate sorption (Obihara and Russell 1972;Nanzyo and Watanabe 1981).…”

Inorganic arsenic sorption by drinking-water treatment residual-amended sandy soil: effect of soil solution chemistry

“…Furthermore, sorption of As(V) on soil minerals depends on the residence time, which has been attributed to different sites of reactivity, surface nucleation-precipitation or diffusion into micropores of the sorbent (Sparks 1999). Several kinetic studies have shown that the sorption rate of As(V) on Fe/Al oxide minerals and WTR was initially rapid, but was followed by a slower phase (Raven et al 1998;O'Reilly et al 2001;Makris et al 2006). Sarkar et al (2007) observed linear As(V) sorption by WTR (without soil) for different As(V) loads (ranging from 225 to 7,500 mg As kg -1 WTR) but proceeded slower thereafter, reaching 100 % after 48 h. There were numerous studies conducted on the effects of soil/solution chemistry on As(V) sorption by pure hydroxides, soils, and WTR (no soil) systems; to the best of our knowledge, no work has been conducted to investigate the effect of soil solution chemistry on As(V) sorption in WTR-amended soils.…”