Increase in Temperature and pH Enhance Methylene Blue removal by Activated Carbonaceous Coconut Shell

In-depth understanding the thermodynamics of dye adsorption is critical to the development of efficient adsorbent for water purification. Batch adsorption studies of methylene blue (MB) on activated carbonaceous coconut shell (ACCS) were carried out at 2 ≤ pH ≤ 5 between 10 – 40 oC. The dependence of the percentage MB removed on the adsorbent dosage as well as the dependence of adsorption capacity on equilibrium concentration of MB were determined. The data were subjected to linearized equations of three adsorption isotherm models. The percentage adsorbed dye increased with temperature and pH. van’t Hoff plot of Freundlich isotherm constant gave the following values of ∆Ho and ∆So: +7.031 kJ mol-1 and 29.36 J mol-1 respectively at pH 2.45; +3.181 kJ mol-1 and 17.81 J mol-1 respectively at pH 3.81 and +3.431 kJ mol-1 and 19.4 J mol-1 respectively at pH 4.71. The result reinforces the proposition that the dependence of proportion of adsorbate on adsorbent dosage at different temperatures as well as linear van’t Hoff plots are important for providing unambiguous insight on fitting isotherm for the system. A combination of increased temperature and pH of the water are essential for efficient remediation of water from MB contamination.