Adsorption and Transport of Arsenic(V) in Experimental Subsurface Systems

Abstract

The adsorption and transport of As(V) in a heterogeneous, iron oxide-containing soil was investigated in batch and column laboratory experiments. The As(V) adsorbed rapidly to the soil over the first 48 h, but continued to adsorb slowly over the next several weeks, clearly indicating the potential for rate-limited transport. The equilibrium As(V) adsorption isotherm was markedly nonlinear, further indicating the potential for nonideal transport. A model developed for the adsorption of As(V) to hydrous ferric oxide (HFO) was able to predict the pH-dependent adsorption of As(V) to the soil in batch experiments within 0.116 to 0.726 root mean square error (RMSE). Arsenic(V) was significantly retarded in column transport experiments. The column transport experiments were modeled using the one-dimensional advection-dispersion equation, considering both linear and nonlinear adsorption equilibrium. Although the nonlinear local equilibrium model (NLLE, RMSE = 0.273) predicted the data better than the linear local equilibrium model (LLE, RMSE = 0.317), As(V) breakthrough occurred more rapidly than predicted by either model due to adsorption nonequilibrium. However, due to the presence of an irreversible or slowly desorbing fraction, the peak aqueous As(V) concentration (0.624 mg L(-1)) and the total amount of As(V) recovered (44%) was lower than predicted based on the two equilibrium models (NLLE and LLE). For the conditions used in this study [1 mg L(-1) As(V), pH 4.5 and 9,0-0.25 mM PO4, 0.53-1.6 cm min(-1) pore water velocity], the effect on As(V) mobility and recovery increased in the order pH < pore water velocity < PO4.

Groundwater arsenic removal using granular TiO2: integrated laboratory and field study

“…On the other hand, the As transport process in an iron oxidecontaining soil column could not be predicted using batch equilibrium adsorption parameters due to kinetic limitations (Williams et al 2003). This limitation was mainly due to the fact that adsorption equilibrium at local micro-interfacial areas in a column is hard to reach without sufficient contact time (Zhang and Selim 2006).…”

“…This difference should be attributed to the competition from coexisting anions in groundwater (Figs. 3 and 5) and the short contact time in filters to reach adsorption equilibrium (Williams et al 2003;Zhang and Selim 2006). To evaluate the social acceptability of the household filter, the cost of the filtered water was calculated to be CNY 0.03-0.06 (USD 0.0048-0.0096) per liter.…”

Modeling and simulation of iron/sand filters

“…The hydrodynamic dispersion coefficient, d z , includes turbulence effects caused by species and gravity. ρ b is the iron bulk density of the porous media, n the sorption intensity parameter and K f the sorption capacity parameter (WILLIAms et al, 2003). The main feature of this equation 2 is the time dependence of the flow velocity q and the porosity ϕ.…”

Potential Impacts of Tailings and Tailings Cover Fertilization on Arsenic Mobility in Surface and Ground Waters

“…6,7,8 More recent batch and column laboratory experiments investigating the adsorption and transport of As(V) in heterogeneous iron oxide containing soils have shown the effects on As(V) mobility and recovery increase in the order pH<pore water velocity<phosphate concentration. 9 Higher…”