A potential biosorbent from Moringa oleifera pod husk for crystal violet adsorption: Kinetics, isotherms, thermodynamic and desorption studies

Abstract

Moringa oleifera pod husk (MOPH), an agricultural waste, is presented as a biosorbent for the adsorption of crystal violet (CV) in water. MOPH was characterized using Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) analysis. The effects of adsorption parameters on adsorption capacity were optimized. Adsorption of CV by MOPH was rapid in the first 10 min, and equilibrium was approached within 60 min at all initial CV concentrations. The adsorption kinetics study revealed a good correlation between the pseudo-second order model and the experimental results. The maximum monolayer capacity obtained by Langmuir model was 156.25 mg/g at 25 °C. The negative values of thermodynamic parameters indicated a spontaneous and exothermic sorption process. The desorption of CV from MOPH was highest in aqueous acetic acid solution, and the re-adsorption study confirmed the reusability of the MOPH biosorbent. Taking into account its abundance, low cost, non-toxicity and its effectiveness and reusability based on the present results, MOPH can be regarded as a promising biosorbent for the CV removal.