Removal of gallium, germanium and zinc from multi-element solutions onto selenium and tellurium nanoparticles immobilized in alginate beads using fixed-bed adsorption columns

• Adsorptive removal of Ga, Ge and Zn is efficient with biogenic Se and Te NPs immobilized alginate matrix. • The thermogravimetric and swelling index of the beads further signifies the increased stability and integrity of the NPs immobilized alginate matrix. • Batch and continuous fixed bed column study follow the Langmuir and Thomas isotherm models, respectively for both individual and multi-metal solution. The scarcity and critical importance of gallium (Ga), germanium (Ge), and zinc (Zn) have intensified the need for sustainable recovery technologies from secondary sources. This study investigates the use of biogenic selenium (Se) and tellurium (Te) nanoparticles (NPs) immobilized in calcium alginate beads for metal recovery via adsorption. These immobilized systems were tested under batch and continuous fixed-bed column conditions. The immobilization enhanced mechanical strength and prevented NP loss, addressing key challenges in dynamic systems. Adsorption revealed distinct selectivity: Te NPs preferred Ga > Zn > Ge, while Se NPs showed Zn > Ga > Ge. In multi-metal solutions, Zn exhibited the highest adsorption, followed by Ga and Ge for both adsorbents. The adsorption mechanism followed pseudo second order kinetics and the experimental data fitted to the Langmuir isotherm, indicating monolayer adsorption with maximum adsorption capacities. Fixed-bed column tests further validated these findings, with the Thomas model fitting the breakthrough data. Thermal analyses showed improved stability of NP-loaded beads compared to controls and swelling tests confirmed reduced expansion under acidic conditions, enhancing operational durability. These findings demonstrate the potential of Se and Te NP-alginate beads for scalable, eco-friendly recovery of Ga, Ge, and Zn from industrial effluents and metallurgical residues, offering a sustainable recovery process to meet the future demand in advanced technologies.