Sorptive removal of malachite green dye by activated charcoal: Process optimization, kinetic, and thermodynamic evaluation

Abstract

Adsorbents are attracting growing interest due to their potential applications in various research areas like the sorption of toxic dyes from aqueous environments. This paper describes the sorptive removal of malachite green (MG) on activated charcoal (AC) from the aqueous solutions. Various sorption parameters such as adsorption capacity, the influence of pH, equilibration time, and initial dye concentration were systematically investigated. Experimental results that the maximum uptake of the dye onto the sorbent was 27 ​mg/g and the equilibrium was reached in about 45 ​min. The MG uptake by AC is strongly favored in an acidic environment. An abrupt decrease in adsorption was seen for pH values greater than 5. Different adsorption isotherms including Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) were tested to validate the sorption data. The kinetics reveals that the adsorption of MG on AC was a second-order kinetic process. The intraparticle diffusion rate, Kid, was 1.82 ​mmol ​g−1 min−1/2. Thermodynamic studies showed that the adsorption of MC on AC was exothermic and spontaneous. In short, powder activated charcoal can be used as a potential adsorbent for the removal of various effluents particularly dyes drained into the water systems.

Keywords

• Malachite green
• Activated charcoal
• Kinetics
• Thermodynamics
• Adsorption isotherms