Thermodynamic and kinetic investigation of citric acid adsorption by rice bran

The aim of this study was to investigate the possibility of using rice bran as a natural adsorbent for the removal of citric acid from water and the effect of temperature, time, initial concentration of adsorbate and adsorbent concentration on the adsorption process. Fitting experimental data was performed using several adsorption models. Also, the thermodynamics and kinetics of adsorption have been studied. The equilibrium was reached after 60 minutes. The results showed that removal of citric acid decreased as temperature and initial concentration of citric acid increased in contrast, it increased as adsorbent concentration and time increased. In addition, the optimum adsorbent weight was obtained to be 4g. Freundlich isotherm was found to be a better fit than other isotherms. The thermodynamic study showed that the adsorption process was exothermic and spontaneous in nature. The adsorption of citric acid on the rice bran followed reversible second-order rate kinetics. This study showed that rice bran efficiently removed the citric acid from aqueous solutions.