KINETICS AND MECHANISMS OF SULFATE ADSORPTION DESORPTION ON GOETHITE USING PRESSURE-JUMP RELAXATION

Sulphate adsorption/desorption on goethite (FeOOH) in aqueous suspension was investigated thermodynamically and kinetically. Pressure-jump relaxation was used to determine the kinetics of SO4 adsorption/desportiion on goethite. A single relaxation was observed due to adsorption/desorption processes. Based on the equilibrium and kinetic studies, the authors hypothesized and tested 2 reaction mechanisms for SO4 retention. the first postulated mechanism assumed that SO4 was adsorbed on a positively charged surface site through electrostatic attraction. It was found that the adsorption of SO4 on goethite occurred simultaneously with the protonation of a neutral surface site, as assumed in the second hypothesized mechanism. Based on this mechanism, a linear relationship between the reciprocal relaxation time and various concentration terms was observed. -from Authors