Removal of toxic methyl orange by a cost-free and eco-friendly adsorbent: Mechanism, phytotoxicity, thermodynamics, and kinetics

Abstract

This article describes the adsorptive removal of acute toxic methyl orange (MO) dye using natural jackfruit leaves powder (JLP) adsorbent without any chemical modification. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope equipped with X-ray energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and point of zero charge (pHZPC) Analyses. Under the optimized condition, the highest removal efficiency of MO dye was found to be 78.10%. The adsorption kinetic models ensued pseudo-second order kinetics (R2 > 0.99) and mixed diffusion process (bulk and intra-particle diffusion). The Langmuir model was well fitted (R2 > 0.99) compared to other isotherms and indicated exothermic monolayer adsorption. The study of thermodynamic parameters revealed that the adsorption was spontaneous, physisorption, and exothermic in nature. Phytotoxicity trials on pea (Pisum sativum) seeds showed 0%, 76%, 82%, and 100% germination in experimental MO dye, treated dye, dye-loaded JLP adsorbent, and freshwater respectively, confirmed the nontoxic nature of treated dye as well as dye-loaded JLP adsorbent. Overall, simple preparation, abundant, cost-free, efficient, and environmentally benign nature make JLP a promising adsorbent for the remediation of harmful MO and other dyes contained wastewater.