Waste to resource approach: CoFe2O4-modified spent tea waste for magnetic solid-phase extraction of toxic metal ions from water samples

In this research, within the framework of a waste-to-resource conversion approach, biochar obtained from spent tea waste (STWB), a widely available and cost-free biomass source, was modified with magnetic CoFe2O4 nanoparticles to develop an environmentally friendly adsorbent (CoFe2O4/STWB). The applicability of this material for efficient separation and preconcentration of Cd(ii), Pb(ii), and Ni(ii) ions from mining wastewater, stream water, and wastewater samples collected from an organized industrial zone was systematically investigated using the solid phase extraction (SPE) method. Optimization of the experimental variables was conducted to enhance the extraction performance of the target analyte ions. The fact that the adsorption and desorption equilibrium times occur in less than 1 min demonstrates the rapid and highly efficient extraction performance of the developed adsorbent. Langmuir isotherm model analysis revealed that CoFe2O4/STWB exhibits adsorption capacities of 69.4 mg g−1 for Cd(ii), 185.2 mg g−1 for Pb(ii), and 45.2 mg g−1 for Ni(ii). In contrast, the corresponding adsorption capacities obtained for unmodified STWB were considerably lower, with values of 42.9, 75.8, and 16.8 mg g−1 for Cd(ii), Pb(ii), and Ni(ii), respectively. These results clearly demonstrate that modification with CoFe2O4 significantly enhances the adsorption performance of STWB. Consequently, CoFe2O4-modified spent tea waste can be regarded as an effective, economical, and sustainable adsorbent for trace heavy metal analysis in environmental water samples, owing to its rapid extraction kinetics, high adsorption capacity, and low detection limits. This journal is