Application of tobacco hairy roots for the removal of malachite green from aqueous solutions: Experimental design, kinetic, equilibrium, and thermodynamic studies

ABSTRACT

Tobacco hairy roots (THR) were used to evaluate its potential for the biosorption and removal of malachite green (MG) from aqueous solutions. A 3² full factorial design was applied to study the effects of pH and THR concentration on the biosorption capacity. Under the optimal conditions (pH of 7.0 and THR concentration of 1 g L⁻¹), dye removal efficiency was around 92%. Experimental data obtained from kinetic studies demonstrated good concordance with the pseudo-second-order model. Equilibrium studies were developed and the data were evaluated by Langmuir, Freundlich, and Sips models, being the Sips model the most adequate (maximum biosorption capacity of 277.2 mg g⁻¹). Thermodynamically, the biosorption of MG on THR proved to be endothermic, spontaneous, and favorable. Desorption was feasible under acidic conditions and the biosorbent could be reused three times. THR was tested in simulated effluent and the removal percentage was 87%, demonstrating that this material is a promising biosorbent which can be used to treat colored wastewaters.

KEYWORDS:

• Biosorption
• dye removal
• hairy roots
• kinetics
• malachite green
• thermodynamics

Acknowledgments

The authors would like to thank National Council for Scientific and Technological Development (CNPq), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Agencia Nacional de Promoción Científica y Tecnológica (FONCYT) (Project PICT-2015-1338), and Universidad Nacional de Cuyo for the financial support.