Removal of toxic metals in contaminated water by adsorption using filters with a combination of nanomaterial and biomass

The presence of toxic metals in water represents an environmental and public health challenge on a global scale, due to the persistence of these elements in ecosystems, their toxicity, and the risk of bioaccumulation in the food chain. Among the various remediation technologies, adsorption stands out for its cost-effectiveness. This study evaluated various filters composed of activated carbon (AC), δ-FeOOH (iron oxyhydroxide), K-jarosite, rice husk biomass, and banana peel biomass, alone and in combinations, for their ability to remove contaminants As⁵⁺, Cd²⁺, Cu²⁺, and Pb²⁺ from solutions. The filters were constructed in 50-mL Falcon® tubes, filled with specific adsorbent materials and tested using standard metal solutions at two concentration levels (30 and 300 µg L⁻¹). Filters combining AC with δ-FeOOH (F6) and banana peel biomass with δ-FeOOH (F11) showed high efficiency. F11 was the most effective, achieving 100% removal of As⁵⁺ and Pb²⁺, 99.95% of Cd²⁺, and 85.88% of Cu²⁺ in the lower concentration range and complete removal of several contaminants across both tested concentrations (30 µg L⁻¹ e 300 µg L⁻¹). At the same concentration (30 µg L⁻¹), F11 also removed 53.58% of Cd²⁺ and 69.17% of Cu²⁺. Filter F6 also demonstrated remarkable performance in the lower concentration range (30 µg L⁻¹) removing 100% of As⁵⁺, 95.31% of Cd²⁺, 95.12% of Cu²⁺, and 89.27% of Pb²⁺. The δ-FeOOH component was particularly effective for As⁵⁺ removal due to its surface properties, while banana peel biomass excelled in Pb²⁺ and Cu²⁺ removal due to its oxygen-rich functional groups. Field tests with water samples from the Doce River in Brazil further demonstrated the practical potential of the F11 filter in significantly reducing toxic metal concentrations, showcasing its promise as a low-cost, efficient solution for water purification.