DTAB templated mesoporous silica nanoparticles for selective recovery of battery metal ions in complex water matrices

With the rapid rise of lithium-ion batteries (LIBs), sustainable strategies for recovering valuable metals from waste streams have become increasingly important, particularly as their release into aquatic environments may pose risks to human health. This study investigates a batch adsorption approach for recovering critical metals, specifically Ni²⁺, Co²⁺, Mn²⁺, and Li⁺, from battery effluents using amine-functionalized mesoporous silica nanoparticles (APTES-DT-SiO₂ NPs). The NPs were synthesized through a bi-phase growth method using dodecyltrimethylammonium bromide (DTAB), which offers a lower acute aquatic toxicity alternative to a conventional cetyltrimethylammonium bromide (CTAB) templating agent. The structure and surface properties of the synthesized nanoparticles were characterized using a combination of microscopy, spectroscopy, surface area analysis, and thermal stability techniques. Batch adsorption experiments demonstrated high uptake for Ni²⁺ (37.2 mg/g), Co²⁺ (38.9 mg/g), and Mn²⁺ (54.3 mg/g) under near-neutral pH, while Li⁺ showed moderate uptake (18 mg/g) compared to other metals under the studied conditions. The adsorption behavior followed pseudo-second order kinetics and the Freundlich isotherm model, indicating heterogeneous surface adsorption and diffusion-influenced uptake. The nanoparticles achieved 90 %-100 % removal for Ni²⁺/Co²⁺/Mn²⁺ in tap, river, and groundwater matrices at pH 7, demonstrating robust performance across the tested water matrices, while Li⁺ removal remained moderate. Reusability experiments showed that the adsorbent retained high divalent-metal removal over multiple adsorption-desorption cycles, demonstrating short-term regenerability under batch conditions. Overall, this study highlights the potential of APTES-DT-SiO₂ nanoparticles as a promising proof-of-concept platform for the selective recovery of divalent battery metals from aqueous systems under environmentally relevant conditions.