Nutraceutical industrial chillies stalk waste as a new adsorbent for the removal of acid violet 49 from water and textile industrial effluent: Adsorption isotherms and kinetic models

First-ever study on the adsorption of Acid Violet 49 (AV49) dye, onto nutraceutical industrial chillies stalk waste (NICSW) is reported. A two-level fractional factorial experiment design and analysis of variance (ANOVA) were adopted to study how initial concentration of the dye, adsorbent dos­age, duration of adsorption process, speed of agitation, pH of the reaction mixture and temperature affect the adsorption process. The adsorption capacity of NICSW at equilibrium was analyzed using Langmuir, Freundlich, Jovanovic, Temkin, Dubinin–Radushkevich and Harkins–Jura isotherms. The pseudo-first-order and pseudo-second-order models were considered for kinetic studies. Maximum adsorption capacity of 45.40 mg/g was obtained by Langmuir isotherm as against the experimental value of 29.00 mg/g, with correlation coefficient of 0.979 at near neutral pH. NICSW was characterized by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller, scanning electron microscope and energy dispersive X-ray spectroscopy. Elemental (C, H, N, S) analyses of the adsorbent were con­ducted. Along with thermodynamic parameter evaluation such as Gibb’s free energy, enthalpy and entropy and results of the surface characterization showed that the dye adsorption onto the biosorbent has taken place such as a physical process. These results proved that NICSW is a fast and effective adsorbent to remove AV49 from water and textile industrial effluent.