Lead (Pb²⁺) and cadmium (Cd²⁺) are widespread water contaminants with long environmental persistence and significant health risks. Children are particularly vulnerable when exposed to lead poisoning, while individuals living near industrial sources are also at higher risk for cadmium exposure. To address these issues, carboxylated cellulose nanofibers (CNF) were prepared from wood chips using a pressure-assisted nitro-oxidation process (PANOP) for the adsorptive removal of Pb²⁺ and Cd²⁺ from water. The PANOP-CNF sorbents demonstrated remarkable removal efficiency, capable of eliminating nearly 99% of both contaminants across various concentrations of the contaminants. The adsorption data were analysed by Langmuir and Freundlich isotherm models, where the former showed the maximum adsorption capacities of 1019 mg/g and 840 mg/g for Pb²⁺ and Cd²⁺respectively. A competitive adsorption study for Pb²⁺ and Cd²⁺removal was carried out in the presence of other cations including sodium(I), calcium(II), and iron(III). Additionally, the real wastewater was also tested. Characterizations of PANOP-CNF adsorbents by TEM, SEM, FTIR, XPS, BET, TGA, and Zeta-potential yielded new information on the structure-property (adsorption) relationship, where the presence of excess COO^- group was found to be primarily responsible for the effective removal of water contaminants. The results indicate that PANOP-CNF is an effective sorptive biomaterial for the removal of Pb²⁺ and Cd²⁺in drinking water and hydroponic applications.

christian Dimkpa

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