Arsenic removal from groundwater by ion exchange and adsorption processes: comparison of two different materials

Abstract

Among the different technologies for reducing arsenic concentration in drinking water, adsorption has demonstrated in many cases to be superior in terms of performance and costs. However, there are numerous types of commercial adsorbents potentially capable of treating arsenic-contaminated groundwater. The present paper compares arsenic uptake efficiency of two different commercial media, one (FerriXTM) using mainly the adsorption process, and the other (IRA 400) working as an ion-exchange resin. Firstly, batch studies with artificially contaminated solutions were run to determine the isotherm equations and the theoretical uptake capacity. The following values of the equilibrium coefficients were determined: for IRA 400, using a two-site model K = 1.749; for FerriXTM, using the Freundlich isotherm model n50 = 3.02 mg L/g and k50 = 12.07 mg L/g, and n100 = 2.32 mg L/g and k100 = 6.75 mg L/g, for 50 mg L/g and 100 mg/L initial arsenic concentrations, respectively. Then, a series of experiments were carried out on column plants using real contaminated feeding solutions to determine the breakthrough curves. Both media showed very high duration of the cycle run. However, performance of IRA 400 was negatively affected by the presence of interfering ions, such as sulfates, which accelerated the achievement of the breakthrough condition. Instead, FerriXTM removed arsenic for a much higher number of bed volumes than IRA 400, but it was ineffective against the other contaminants of the solution.