Optimizing cellulose nanofiber composite for Co²⁺ ions recovery from lithium-ion battery wastes and removal from wastewater: A green environmental solution

In this study, we have introduced an advanced composite material that combines the remarkable properties of cellulose nanofibers (CNFs) with a tailored surface to enable the concentration, spectrophotometric detection, removal of Co²⁺ ions from wastewater samples and recovery of Co²⁺ ions from lithium-ion battery waste. CNFs, known for their eco-friendly nature and exceptional surface characteristics, serve as an ideal substrate for immobilizing the (3,3′-((1E,1′E)-((4-nitro-1,2-phenylene) bis(azaneylylidene)) bis(methaneylylidene)) bis(2-hydroxybenzoic acid) (NAMH) chromophoric ligand. The resulting CNFs-NAMH composite displays extraordinary sensitivity to Co²⁺ ions in aqueous solutions, achieving an impressive limit of detection (LOD) as 0.87 ppb. This exceptional sensitivity allows for straightforward visual detection with the naked eye. A noteworthy feature of the CNFs-NAMH composite is its rapid and distinct color change in approximately a minute upon exposure to varying concentrations of Co²⁺ ions. Moreover, this composite demonstrates high efficiency in removing Co²⁺ in polluted wastewater samples and recovering Co²⁺ ions from lithium-ion batteries, with a high efficiency of up to 79.5 % for Co²⁺ ions recovery from lithium-ion batteries and removal efficiency of 97.35 % for Co²⁺ from wastewater samples. This capability addresses critical environmental concerns associated with wastewater treatment and lithium-ion battery waste and provides a practical and sustainable approach for reclaiming valuable Cobalt ions.