Adsorption kinetic and isotherms of Reactive Red 120 on Moringa oleifera seed as an eco-friendly process

Effects of parts of adsorbent, solution pH level, adsorbent dose, particle size, initial dye concentration, temperature, and contact time on the batch adsorption of Reactive Red (RR) 120 on Moringa oleifera seed (MOS) was studied. The surface structure of MOS was characterized using a scanning electron microscope and Fourier transform infrared (FTIR) spectroscopy. Significant changes were observed in the surface structures of MOS before and after the RR 120 adsorption. Changes in the peaks and appearance of new bands (between 1200 and 1500 cm(-1)) revealed on the interactions between RR 120 molecules and functional groups of MOS (e.g., amino, carbonyl and amide groups) play significant roles in this process. The pH at the point of zero charge (pH(pzc)) of MOS was found to be 4.5. Experimental kinetic data were well described by Logistic and pseudo second order kinetic models. The very fast process reached the equilibrium stage within 30 min. The Freundlich, Langmuir, and Dubinin-Radushkevish isotherms were applied to equilibrium data. Freundlich isotherm having low values of error function and high correlation coefficient, was the best model to describe the adsorption of RR 120 on MOS. The maximum adsorption capacity of RR 120 on MOS was found as 413.32 mg g(-1) at pH 1.0 and 323 K. These results indicate that the MOS had enormous potential for the removal of RR 120 as an eco-friendly process. (C) 2019 Elsevier B.V. All rights reserved.