Comparative removal of nickel ions from aqueous solution using adsorbents derived from agricultural biomasses: a kinetic modeling

The waste generation in the agricultural sector in North-Colombia represents a serious environmental problem owing to the attraction of vector-borne diseases, an increase in organic matter concentration, and an unsustainable life cycle of derived products. This leads to an increasing need for the identification of potential uses to these wastes, increasing its value-added. The aim of this work is to evaluate the adsorption capacity of five different biomasses from Theobroma cacao, Citrus lemon, Manihot esculenta, Dioscorea rotundata, and Elaeis guineensis crops to be used as promising biosorbents in the removal of nickel ions. This work provides insights into the current body of knowledge regarding the adsorption performance of different types of biomasses through the comparison of adsorption properties of five agricultural wastes under fixed operating parameters. The adsorption process was analyzed by defining optimum conditions of particle size and initial pH. The resulting adsorption data overtime was used to construct kinetic curves and study the phenomenon taking place during Ni(II) uptake. Results revealed higher removal yields for lemon peels (LP) biomass up to 96% compared with the other biosorbents. The optimum conditions for adsorption were observed at pH = 6 and particle size = 1 mm. The experimental data of cassava peels (CP), oil palm bagasse, and yam peels (YP) agreed with chemical adsorption nature of Elovich model, accounting for the sum of square errors at 0.14 and 0.46. The LP and cocoa (cocoa pod husk) biomasses were not properly fitted by these kinetic models. The resulting comparative study of adsorption kinetics allowed to prioritize those agricultural residues with the highest adsorption rates.