The applicability of evaluable wastes for the adsorption of Reactive Black 5

In this study, it is proposed that pumpkin seed hulls and eggshells that are household wastes are low-cost materials to remove the Reactive Black 5 from water media. Through a number of experiments, the influences of the contact time, adsorption quantity, temperature, and pH of the solution were studied. Characterization of pumpkin seed hulls and eggshells was done by using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Adsorption of the experimental data well fitted with both the models called Langmuir and Freundlich isotherm. The maximum experimental capacities of adsorption related to pumpkin seed hulls and eggshells were 9.18 and 18.46 mg g -1 , respectively. The optimum conditions were determined as adsorbent amount = 0.5 g L -1 , pH = 6, and contact time = 15 min for the eggshells adsorption process and adsorbent dosage = 1 g L -1 , pH = 2, and contact time = 30 min for the pumpkin seed hulls adsorption system. In addition, pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics were used to study the adsorbing dynamics of Reactive Black 5 onto pumpkin seed hulls and eggshells. In this study, it was observed that the pseudo-second-order kinetic was appropriate. Calculation of the thermodynamic parameters, such as changes in the free energy, enthalpy, and entropy of adsorption, was performed. According to the thermodynamic parameters, these processes were less spontaneous, practicable, and exothermic. To remove the dye from aqueous solutions, the pumpkin seed hulls and eggshells can be used as an alternative cheap adsorbent. © 2018, Islamic Azad University (IAU)