Diazo dye sorption by Ni-modified pumpkin husk

The aim of this study was to investigate the potential of raw and modified pumpkin husk (PH) by loading of Ni2+ ions for removing Acid Black (AB 1). Surface structures of adsorbents were characterized by using Fourier Transform Infrared. Amine, amide, and carboxyl groups of PH played significant roles in the sorption process. Modification by Ni2+ ions led to increase in the sorption capacity of AB 1. AB 1 sorption on these adsorbents increased with decreasing particle size, adsorbent dose, solution pH, and temperature but increased with increasing contact time and initial dye concentration. Rapid sorption occurred in the first 5min and equilibrium was reached within 50min. Kinetic sorption data was well described by logistic model. Equilibrium data was best represented by Freundlich isotherm. Monolayer adsorption (maximum capacities of the PH as 227.62mgg(-1) and Ni-modified PH to adsorb AB 1 as 228.49mgg(-1)) was obtained when the experimental data were fitted to the Langmuir isotherm model. Activation energy and thermodynamic studies have shown that this process was physical, exothermic, and spontaneous. This study indicated that redundant PH had a great potential for the removal of AB 1 as an alternative eco-friendly process.