This study details the green synthesis of silver nanoparticles (AgNPs) utilizing Terminalia catappa leaf extract and their incorporation into biochar (BC) sourced from coconut coir waste, targeting the efficient elimination of hexavalent chromium [Cr(VI)] and nigrosine B dye from aqueous solutions. A quick change in color from light yellow to dark brown showed that Ag NPs were synthesized. UV–vis spectroscopy showed a characteristic surface plasmon resonance peak at 425 nm. Biochar (BC) was made by treating coconut coir with acid and then carbonizing it at high temperatures. This was followed by the successful impregnation of Ag NPs, which was confirmed by UV-vis, FT-IR, SEM, EDX, and XRD tests. FTIR showed the functional groups that keep nanoparticles stable, and XRD confirmed that Ag NPs are in crystalline form. The Ag/BC nanocomposite showed great adsorption ability, removing up to 98.18±1.46% of Cr (VI) at 10 ppm/10 mL in 240 minutes and 90.10±1.31% of nigrosine at 10 mg/L in 60 minutes. The increased effectiveness of removal is due to the combination of the redox activity of Ag NPs and the large surface area of biochar. The results show that Ag/BC nanocomposites made from green materials could be useful, long-lasting adsorbents for environmental cleanup process. Moreover, this study directly supports the United Nations Sustainable Development Goals through the use of waste-derived materials for environmental cleanup and eco-friendly processes. This approach contributes to SDG 6, and 12 which correspond to Clean Water and Sanitation, and Responsible Consumption and Production, respectively.
