Valorization of Agricultural Wastes as Low-Cost Adsorbents Towards Efficient Removal of Aqueous Cr(Vi): Parametric, Kinetic, Mechanism and Thermodynamic Study

Extent of heavy metal as hexavalent chromium ions Cr(VI) in natural aqueous environment increases alarmingly owing to improper discharge of waste water from industries. This not only deteriorates the water quality but also potentially threatens human health through the water cycle. Biosorption is preferred over other existing technologies for remediation of aqueous Cr(VI) as it is environmentally benevolent, inexpensive, and logistically easier. Biomaterials like agricultural wastes are found beneficial for Cr(VI) sequestration since these have advantages of no sludge generation, high metal selectivity, efficient regeneration and good recycling ability. In this study, a bio-adsorbent fabricated from agricultural waste: potato peels (PP) was tested for the adsorption of Cr(VI) from simulated wastewater. The physicochemical and textural characterization of the prepared adsorbent was accomplished by using available techniques: Infrared spectroscopy (IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). We have overviewed the influence of adsorption parameters like pH, time, temperature, initial Cr(VI) concentration, and bio-adsorbent dose for maximum removal. Adsorption kinetics was assessed by fitting the experimental data with the chosen kinetic models. The ability of potato peels to adsorb Cr(VI) ion was determined from the adsorption isotherms plots and the thermodynamic parameters were estimated. Furthermore, a comparison of the results obtained is carried out with commercial powdered activated carbon (CAP). The best removal efficiencies are obtained at pH of order 2 and 12 for CAP and PP respectively, an optimal mass of PP at 0,5 g and 1 g of CAP at 300 rpm. The most appropriate model is Langmuir model and the kinetics are the pseudo second order. The adsorption reaction is a chemisorption according to Elovich's model and the diffusion is extraparticle by Webber and Morris