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The quantitative kinetic and equilibrium adsorption parameters for chlorure de méthylrosaniline (gentian violet, crystal violet) removed by commercial activated carbon were studied by UV–visible spectroscopy.Activated carbon with a high specific surface area 1250 m2/g was characterized by the Brunauer, Emmett et Teller (BET) method and the zero charge point pH (pzc). The adsorption properties of both activated carbon with gentian violet were conducted at variable stirring speed 100–700 trs/min, adsorbent dose 1–8 g/l, solution pH 1–14, initial gentian violet concentration 5–15 mg/l, contact time 0–50 min, and temperature 299–323 K using batch mode operation to find the optimal conditions for a maximum adsorption. The adsorption mechanism of gentian violet was studied using the pseudo-first-order, pseudo-second-order, and Elovich kinetic models. The adsorption kinetics was found to follow a pseudo-second-order kinetic model with a determination coefficient (R2) of 0.999. The Weber–Morris diffusion model was applied for the adsorption mechanism. The equilibrium adsorption data of gentian violet were analyzed by the Langmuir, Freundlich, Elovich, and Temkin models. The results indicate that the Langmuir model provides the best correlation (qmax = 22.727, 32.258 mg/g at 26 and 40°C, respectively). The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters, i.e. free energy (ΔG° = − 2.30 to −5.34 kJ/mol), enthalpy (ΔH° = 36.966 kJ/mol), entropy (ΔS° = 0.131 kJ/mol K), and activation energy (Ea) 40.208 kJ/mol of gentian violet adsorption. The negative ΔG° and positive ΔH° indicate that the overall adsorption is spontaneous and endothermic in nature.

This study investigates the potential use of activated carbon, prepared from pomegranate peels, as an adsorbent activated using H3PO4 and its ability to remove crystal violet from an aqueous solution. The adsorbent was characterized by the Brunauer–Emmett–Teller method (specific surface area: 51.0674 m2 g−1) and point of zero charge (pHPZC = 5.2). However, some examined factors were found to have significant impacts on the adsorption capacity of activated carbon derived from pomegranate peels such as the initial dye concentration (5–15 mg L−1), solution pH (2–14), adsorbent dose (1–8 g L−1), agitation speed (100–700 r/min), and temperature (298–338 K). The best adsorption capacity was found at pH 11 with an adsorbent dose of 1 g L−1, an agitation speed at 400 r/min, and a contact time of 45 min. The adsorption mechanism of crystal violet onto activated carbon derived from pomegranate peels was studied using the pseudo-first-order, pseudo-second-order, Elovich, and Webber–Morris diffusion models. The adsorption kinetics were found to rather follow a pseudo-second order kinetic model with a determination coefficient ( R2) of 0.999. The equilibrium adsorption data for crystal violet adsorbed onto activated carbon derived from pomegranate peels were analyzed by the Langmuir, Freundlich, Elovich, and Temkin models. The results indicate that the Langmuir model provides the best correlation with qmax capacities of 23.26 and 76.92 mg g−1 at 27°C and 32°C, respectively. The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters like the free energy, enthalpy, and entropy to predict the nature of adsorption process. The negative values Δ G0 (−5.221 to −1.571 kJ mol−1) and Δ H0 (−86.141 kJ mol−1) indicate that the overall adsorption is spontaneous and exothermic with a physisorption process. The adsorbent derived from pomegranate peels was found to be very effective and suitable for the removal of reactive dyes from aqueous solutions, due to its availability, low-cost preparation, and good adsorption capacity.

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Adsorption techniques are widely used to remove certain classes of pollutants from waters, especially those that are not easily biodegradable. The aim of this study was to evaluate the adsorption of Methylene Blue (MB) dye onto activated carbon from aqueous solutions was realized in a batch system. However, some examined factors such as contact time, pH solution, initial concentration of MB, adsorbent dosage and temperature were found to have significant impacts on the adsorption capacity of AC. The AC was characterized by BET surface area measurement, Point of Zero Charge (pHpzc), FTIR spectroscopy and X-ray diffraction analysis. Batch studies were conducted in order to determine the optimal parameters required to reach the adsorption equilibrium. The maximum adsorption capacity of the AC for MB at 298 K was determined to be 170.357 mg/g. The adsorption kinetic data were analyzed employing several kinetic models: pseudo-first order, pseudo-Second order, Elovich equation, and intraparticles diffusion model. It was established that the adsorption process obeyed the pseudo-second-order kinetic model with a determination coefficient (R2) equal to 0.999. The evaluation of thermodynamics parameters such as the Gibbs free energy ΔG° (−7.856 to −6.142 kJ/mol), positive enthalpy ΔH° (13.384 kJ/mol) and the change of entropy (63.46 J/mol K) indicated a spontaneous and endothermic nature of the reaction with a chemisorption process. Comparative tests by the heterogeneous photocatalysis of MB in the presence of a semiconductor will be the subject of the rest of this study.