Kashi Banerjee

Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH)

Relatively limited information is available regarding the impacts of temperature on the adsorption kinetics and equilibrium capacities of granular ferric hydroxide (GFH) for arsenic (V) and arsenic (III) in an aqueous solution. In general, very little information is available on the kinetics and thermodynamic aspects of adsorption of arsenic compounds onto other iron oxide-based adsorbents as well. In order to gain an understanding of the adsorption process kinetics, a detailed study was conducted in a controlled batch system. The effects of temperature and pH on the adsorption rates of arsenic (V) and arsenic (III) were investigated. Reaction rate constants were calculated at pH levels of 6.5 and 7.5. Rate data are best described by a pseudo first-order kinetic model at each temperature and pH condition studied. At lower pH values, arsenic (V) exhibits greater removal rates than arsenic (III). An increase in temperature increases the overall adsorption reaction rate constant values for both arsenic (V) and arsenic (III). An examination of thermodynamic parameters shows that the adsorption of arsenic (V) as well as arsenic (III) by GFH is an endothermic process and is spontaneous at the specific temperatures investigated.

Adsorption kinetics of o-xylene by flyash

Relatively limited information is available regarding the kinetics of sorption of organic compounds from solution onto flyash. For this reason, a detailed study of the kinetics of sorption of o-xylene on flyash was conducted in a controlled batch system. The effects of solute concentration, particle size of the adsorbent, and temperature on the adsorption rate were investigated. The results of this research demonstrate that the adsorption reaction can be approximated to first-order reversible kinetics. A significant correlation was observed between the rate of adsorption and the inverse of the square of the particle diameter. An examination of thermodynamic parameters shows that the adsorption of o-xylene by flyash is an exothermic process and is spontaneous at the temperature investigated. Activation energies for the sorption process ranged between 3.1 and 4.3 kcal/mol. The rate at which o-xylene is adsorbed onto flyash was found to be controlled by the diffusion process.