Investigation of Taguchi method, equilibrium isotherms and kinetic study for dye removal by eggshell powder adsorbent

This study investigates the potential of eggshell powder as a waste adsorbent for the removal of methylene blue dye from an aqueous solution. Taguchi method was employed for experimental design, and the data were analyzed using the signal-to-noise (S/N) ratio for the removal of methylene blue dye from aqueous solutions. During the removal process, a batch technique was used to determine the effects of several controllable factors on the percent of removal. These factors were pH of the solution (3, 6, 9 and 12), initial dye concentration (100, 150, 200 and 250 ppm), and adsorbent dose (0.25, 0.5, 0.75 and 1 g). The results revealed that the optimum conditions for methylene blue removal of about 70% were obtained at an adsorbent dose of 1 g, pH 9 and 100 ppm dye concentration for a contact time of about 1 hour and at agitation speed of 250 rpm. The effect of contact time was studied on the percent of removal from aqueous solution by eggshell powder. It was found that the rates of adsorption were rapid initially within the first 20 minutes and reached maximum adsorption after 1 hour. Analyses of results were achieved to discuss the contribution of the individual factors on the objective functions. Various adsorption isotherm models were investigated such as Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Harkins-Henderson. Kinetic studies were conducted on the adsorption of dye on eggshell powder. These kinetic models were the zero-order, pseudo-first order, pseudo-second-order, intra-particle diffusion, and Elovich models.