Enhanced adsorption of Acid Red 88 by an excellent adsorbent prepared from alunite

BACKGROUND: Calcination significantly increased the adsorption performance of alunite for Acid Red 88. RESULTS: The adsorption properties of calcined alunite for Acid Red 88 were investigated. pH, adsorbent dosage, contact time and ionic strength were found to influence the adsorption. Temperature did not significantly affect the process. Kinetic data obey a pseudo-second-order model, while intraparticle diffusion is not the only rate-limiting step. The Langmuir isotherm well described the equilibrium data. The monolayer adsorption capacity of calcined alunite was found to be 832.81 mg g-1. It was successfully used for the removal of dye in continuous mode at a flow rate of 4.0 mL min-1. Co-anions affected the adsorption capacity of calcined alunite but the presence of other organic compounds in the same medium did not significantly change the adsorption performance. Reusability studies showed that the calcined alunite can be reused four times. Electrostatic interaction, ion-exchange and complexation were found to be effective mechanisms for the adsorption of Acid Red 88 by calcined alunite. CONCLUSION: This study demonstrated that calcined alunite has excellent adsorption performance and might be a very good adsorbent for Acid Red 88 as an abundant, economical and practical material. (c) 2012 Society of Chemical Industry