The removal of methyl violet 2B dye using palm kernel activated carbon: thermodynamic and kinetics model

Abstract

Methyl violet is one of the most important pollutants responsible for destabilizing aquatic ecosystems, and it is poisonous to most of the animals. Inhalation of methyl violet in humans may cause irritation in the respiratory tract, while eating it may irritate the digestive tract. In this study, the carbon of palm kernel was used as a biological absorbent to remove the methyl violet pollutants from textile industry sewages. Further, the influential variables were studied on sorption, such as the amount of adsorbent (0.04–0.15 g), pH (4–10), contact time (1–120 min), temperature (25–40 °C) and different dye concentrations (10–120 mg L−1). The optimum values of adsorbent, pH, contact time, temperature and dye concentration were 0.1 g, 7, 30 min, 25 °C and 50 mg L−1, respectively. Under optimum conditions, the percentages of dye removal were 98.85 and 91.08 in relation to modified and unmodified adsorbent, respectively. The adsorption data were in good agreement with Langmuir–Freundlich isotherm. Based on the results, data were mostly consistent with pseudo-second-order kinetics; different thermodynamic parameters such as free energy absorption (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) were further investigated. These studies (ΔG° = − 7651.9141 kJ mol−1 for unmodified adsorbent and ΔG° = − 13,799.6138 kJ mol−1 for modified adsorbent, ΔS° = 0.135 for unmodified adsorbent and ΔS° = 26.195 for modified adsorbent, ΔH° = 32.702 kJ mol−1 K−1 for unmodified adsorbent and ΔH° = 0.069 kJ mol−1 K−1 for modified adsorbent) showed that adsorption is a spontaneous and endothermic process. The maximum adsorption capacities of methyl violet were 107.3 and 83.91 mg g−1 in relation to the modified and unmodified adsorbent, respectively.