Removal of Methylene Blue in Aqueous Solution by Economic Adsorbent Derived from Apricot Stone Activated Carbon

Abstract

Quantitative adsorption kinetic and equilibrium parameters for methylene blue (MB) used in the textile industry from aqueous solutions were reported in this study using pHPZC and UV-visible absorption spectroscopy. The effects of adsorbent dosage (1–10 g/l), agitation speed (100–1200 rpm), particule size (63 µm to 2 mm), initial dye concentration (4–15 mg/l), contact time, pH (2–14), and temperature (298–338 K) were determined to find the optimal conditions for adsorption. The FTIR spectroscopy is used to get information on interactions between the adsorbent and MB. The mechanism of adsorption of MB dyeing onto Apricot Stone Activated Carbon (ASAC) was investigated using the pseudo first-order, pseudo second-order kinetic, Elovich and intraparticles diffusion models. The adsorption isotherms of MB onto ASAC are determined and correlated with common isotherm equations. The smaller RMSE value obtained for the Langmuir model indicates the better curve-fitting and the monolayer adsorption capacity of MB is found to be 46.03 mg/g at 25 °C and 88.50 mg/g at 70 °C and pH 10. The evaluation of thermodynamics parameters such as the negative free energy ΔG° (+2.70025 to −1.76666 kJ/mol) and positive enthalpy change ΔH° (28.87613 kJ/mol) indicated a spontaneous and endothermic nature of the reaction with chemisorption process. This study in tiny batch gave rise to encouraging results, and we wish to achieve the adsorption tests in column mode under the real conditions applicable to the treatment of industrial effluents. The present investigation showed that ASAC is potentially a useful adsorbent for the heavy metals and dyes.