Removal of basic dye from aqueous medium using a novel agricultural waste material: Pumpkin seed hull

In this work, pumpkin seed hull (PSH), an agricultural solid waste, is proposed as a novel material for the removal of methylene blue (MB) from aqueous solutions. The effects of the initial concentration, agitation time and solution pH were studied in batch experiments at 30 °C. The equilibrium process was described well by the multilayer adsorption isotherm. The adsorption kinetics can be predicted by the pseudo-first-order and the modified pseudo-first-order models. The mechanism of adsorption was also studied. It was found that for a short time period the rate of adsorption is controlled by film diffusion. However, at longer adsorption times, pore-diffusion controls the rate of adsorption. Pore diffusion takes place in two distinct regimes, corresponding to diffusion in macro- and mesopores. The results demonstrate that the PSH is very effective in the removal of MB from aqueous solutions.