Biosorption of malachite green dye onto araucaria cookii bark: Optimization using response surface methodology

Abstract

Araucaria cookii bark has been studied as low cost, easily available natural biosorbent for removal of malachite green from aqueous solution. The influence of operating parameters such as contact time, pH, temperature, adsorbent dosage and initial dye concentration on the sorption of malachite green were analyzed using response surface methodology. The proposed quadratic model of central composite design fitted so well to the experimental data that it could be used to navigate the design space according to the results of the analysis of variance. The optimum sorption conditions were determined. Characterization of the biosorbent was performed using scanning electron microscopy and Fourier transform infrared spectroscopy. Equilibrium isotherms were analyzed by the Langmuir, Freundlich and Tempkin isotherm models. Dye biosorption equilibrium data fitted well to the Freundlich isotherm rather than the others. The kinetic studies for malachite green biosorption showed rapid sorption dynamics by a pseudo second order kinetic model. Thermodynamic studies showed that malachite green biosorption onto Araucaria cookii bark was mainly a spontaneous and exothermic process.