Evaluate the performance of Populus nigra sawdust in the removal of methylene blue from aqueous solutions: isotherms, kinetics and thermodynamics studies

Abstract-Environmental pollution, in general, and water pollution, in particular, are of concern to the scientific community worldwide. Color removal from wastewater has been a matter of concern, both in the aesthetic sense and health point of view. Color removal from textile effluents on a continuous industrial scale has been given much attention in the last few years, not only because of its potential toxicity, but also mainly due to its visibility problem. Methylene Blue (MB) is cationic dye, used in several industries such as paper and pulp, leather, cotton, pulp, cosmetics, wool etc., for coloring their final products. The effluents of these industries containing huge amount of dyes, discharged into waters bodies, cause severe damage to the environment. Acute exposure to methylene blue will cause increased heart rate, vomiting, shock, cyanosis, jaundice and tissue necrosis in humans. Several methods have been used for the removal of dyes from the aquatic environment, including physical, chemical, and biological processes. These methods inevitably add to the cost of the overall process and some present the complication associated with the possible toxicity of degradation products. Among the methods, removal of dyes by adsorption is regarded as one of the competitive methods because of high efficiency, economic feasibility and simplicity of design/operation. Biosorption based on binding capacities of different low-cost adsorbents includes natural, agricultural, and industrial by-product wastes. They are attractive because of their abundant availability at low or no cost, their good performance in removing dyes from aqueous solutions as well as minimum volume of sludge to be disposed. Sawdust, among the low cost adsorbents, is one of the most promising adsorbent for removing dyes, and some other unwanted materials from waste water. Not only is sawdust abundant, but also it is actually an efficient adsorbent that is effective to many types of pollutants, such as, dyes, oil, salts, heavy metals, etc. If it was possible to use sawdust as adsorbent of contaminants from industrial waste water, it would solve simultaneously two problems, both waste disposal and purifying waste water of contaminants to desired limits. In the present study have been investigated the efficacy of Populus nigra sawdust as a wood waste (without chemical changes) in the removal of methylene blue from wastewater. Isotherms (using langmuir and freundlich isotherm models) and absorption kinetics (using pseudo first-order, pseudo-second order, elovich and intraparticle diffusion models) has been studied and was observed that the process treatment followed from langmuir isotherm model (R2 = 0.996) and its kinetic is consistent with pseudo-second order reaction (R2 = 0.999) and the mechanism was controlled by surface adsorption and intraparticle diffusion. The thermodynamic parameters such as change in enthalpy (ΔH°), entropy (ΔS°) and Gibb’s free energy (ΔG°) of adsorption systems were also determined and evaluated. This adsorbent had high absorption capacity equal 26.85 mg/g to the absorption of cationic dye methylene blue. The results showed that Populus nigra sawdust, natural sorbent is good to absorb methylene blue color of the water water which has removal percentage equal 84.68% in the optimal conditions.