Malachite green sequestration from aqueous system by untreated <i>Dacryodes edulis</i> seed

Abstract

This paper presents an assessment of the kinetics and thermodynamics of malachite green (MG) abstraction from an aqueous system onto untreated pear seed (Dacryodes edulis) biomass as an adsorbent at pH 12. The experiments were conducted in batches at 25 °C, with a biomass dose of 0.5 g, and at different durations (5 to 240 minutes) using a 50 mg/L malachite green dye solution. The kinetics data were examined using four models: pseudo-first-order, pseudo-second-order, intraparticle, and Elovich models. The fallouts indicated that the pseudo-second-order model represented the process’ kinetics well, with R² values of 0.9998, rate constant, 0.346 g/mg/min, and a 90% adsorption efficiency. Thermodynamics study revealed a negative free energy change, ΔGº, indicating a feasible and spontaneous process that is endothermic, having a positive ΔHº. Comparing the findings with the findings of others reveals that malachite green adsorption onto various adsorbents is usually endothermic and follows the Pseudo-second-order mechanism most times. Overall, untreated pear seed biomass has the potential as an alternative to traditional adsorbents for extracting malachite green from an aqueous medium.