Adsorption of dyestuff on red perlite: isotherm, kinetics, and thermodynamics

Abstract

Environmental contamination by synthetic dyes has been a serious problem due to their adverse eco­toxicological effects. Recently, there is a growing interest in using low­cost adsorbents to adsorb dye. In this study, the adsorption experiments were carried out in the batch process to remove a commercial synthetic dye with Lopburi red perlite. The factors affecting the adsorption process, such as pH of dye solution, contact time (5-540 min), initial dye concentration (10-100 mg/L), and temperature (20-40°C) were investigated. The results showed that dye removal reached equilibrium at about 180 min at all temperatures. The Langmuir and Freundlich isotherm models were used to fit the equilibrium data. The better fitting isotherm model was found to be the Langmuir isotherm at all temperatures. The maximum monolayer adsorption capacity values were 13.70, 14.71, and 16.63 mg/g at 20, 30, and 40°C, respectively. The kinetic adsorption data could be better described by the pseudo­second­order model. Moreover, the thermodynamic study showed that the adsorption was a spontaneous and endothermic process. The results of this study indicated that the red perlite was a good adsorbent for removing dye.