Modelling arsenic(III) adsorption from water by sulfate-modified iron oxide-coated sand (SMIOCS)

A medium developed by coating BaSO4 and Fe on quartz sand known as sulfate-modified iron oxide-coated sand (SMIOCS) was evaluated for the removal of arsenic(III) from simulated water with an ionic strength of 0.01M NaNO3 during batch studies. The medium was characterised for BET surface area, alkali-resistance, acid-resistance and the presence of iron and barium on the coated surface. Two simplified kinetic models, ie active available site (AAS) and chemical reaction rate models, were tested to investigate the adsorption mechanisms. The values of rate constants for both the models were found to decrease with increasing As(Ill) concentrations in the solute. The inverse relationship of rate constants of the reaction rate model with BET surface area showed that As(III) adsorption on SMIOCS was not due to physisorption but to chemisorption. A study of the effect of solute temperature showed that the adsorption of As(III) on SMIOCS media was due to chemisorption. The results of isothermal studies conducted at different pH values showed that adsorption data satisfied both the Langmuir and the Freundlich isotherm models. The adsorption of As(III) on the medium was pH dependent and maximum removal was observed in the pH range of 7-9. (C) 2002 Society of Chemical Industry

Arsenic(V) removal by sulfate modified iron oxide-coated sand (SMIOCS) in a fixed bed column

A novel granular media developed by the coating of iron, barium and sulfur on quartz sand surface has been demonstrated to be an effective sorbent for removal of arsenic(V) from a 0.01 M NaNO3-Spiked distilled water system in laboratory-scale tests. The results of fixed bed studies indicate that arsenic(V) removal is dependent on pH, the size of sorbent and influent arsenic concentrations. The particle size of media has shown significant differences in reactor breakthrough times in similar experimental conditions. The removal of As(V) may be explained using the surface complexation theory. The presence of alkalinity (250-260 mg/L as CaCO3) and hardness (200 mg/L as CaCO3) slightly increases reactor breakthrough time for similar experimental conditions without alkalinity and hardness. Desorption studies using 0.2 M NaOH as elutant resulted in nearly 92% recovery of arsenic(V). A theoretical model based on two parameters has shown good correlation with observed experimental data generated during depth variation studies

Coated sand filtration: an emerging technology for water treatment

The use of oxide coated sand filtration as an alternative to current costly methods for water treatment has been reviewed. The paper highlights the importance of iron, aluminium and manganese oxides, including sand coated with these oxides, for removal of heavy metals and other impurities from water. The literature review showed that oxide coated sand is able to remove heavy metals (both anions and cations) and other impurities (e.g. natural organic matter, microorganisms, sulphate, manganese, etc.) from surface water or groundwater. in this review an extensive list of the use of oxide (iron, aluminium and manganese) coated sand in water treatment by adsorption and filtration processes has been compiled to provide a summary of available information. The information available on the capacity of coated sand for pollutant uptake is very scarce, however some data on the capacity of coated sand for heavy metals uptake have been compiled and presented. The coated sand could be an alternative emerging technology for water treatment without any side effects or treatment process alterations

Fixed-bed modeling of arsenic(III) adsorption from water by sulfate modified iron oxide coated sand (SMIOCS)

A medium known as sulfate modified iron oxide coated sand (SMIOCS) was evaluated for the removal of As(III) from symthetic water with ionic strength of 0.01M NaNO3 employing fixed bed mode. The medium was characterised for BET surface area; alkali and acid resistance; and presence of iron, barium and sulfur on sand surface. The particle size of media shown significant impact on bed volume treated with similar experimental protocol. A theoretical model, Wolborska model, has shown good correlation with observed experimental data generated during depth variation studies at flow rate of 1.56 m(3)/m(2) /hr with influent As(III) concentration of 1.0 mg/L. Regeneration studies using 0.2 M NaOH as regenerant resulted in nearly 83% recovery of As(III) during up flow mode