Kinetic and thermodynamic aspects of arsenic (III) adsorption onto iron oxide obtained from iron oxalate

Abstract

Drinking water has been identified as one of the major sources of arsenic exposure by the general population. A variety of treatment processes has been studied for arsenic removal from water. One of the most used methods is adsorption. The most efficient adsorbent materials are those with iron content considering the affinity of arsenic towards iron. Relatively limited information is available regarding the impact of temperature on the arsenic (As) (III) adsorption kinetic and equilibrium capacities on iron oxide. In this paper we studied the possibility of using iron oxide as an adsorbent for the removal of As (III) from aqueous solutions. The iron oxide was obtained through annealing of iron oxalate at 550°C. The effects of contact time, initial concentration of the solutions and temperature on the removal of As (III) were investigated in order to explain the adsorption mechanism. The kinetic of As (III) adsorption can be described well by the pseudo-second-order models. The equilibrium adsorption data were fitted using Freundlich and Langmuir isotherm equations and the corresponding parameters were calculated and discussed in detail. An increase in temperature increases the values of the overall adsorption reaction rate constant. An examination of thermodynamic parameters shows that the adsorption of As (III) by iron oxide is an endothermic process and is spontaneous at the specific temperature investigated. © 2010 WIT Press.