Optimization and kinetic study of nitrate removal from aqueous solution using tea waste

Abstract

BACKGROUND

Nitrate contamination in groundwater poses significant risks to public health and the environment worldwide. This study explores the optimized use of tea waste, a byproduct of tea extraction and consumption, as an adsorbent for the removal of nitrate from aqueous solutions.

RESULTS

Scanning electron microscopy and Brunauer–Emmett–Teller (BET) analysis revealed that tea waste has irregular cluster cavities and visible pore formations, indicating numerous active sites for nitrate adsorption. The specific surface area, total pore volume, and pore diameter were found to be 2.4914 m² g⁻¹, 0.0036 cm³ g⁻¹, and 9.8077 nm, respectively. A total of 20 adsorption experiments were conducted based on conditions recommended by a statistical tool using Design-Expert 13.0 software. The data showed a strong fit to a quadratic model, with a significant P-value of 0.0109 and a high determination coefficient (R² = 0.9327). Using response surface methodology, the study achieved a maximum nitrate removal efficiency of 84.49% under optimal conditions, which included an initial nitrate concentration of 50 mg L⁻¹, an adsorbent weight of 0.706 g, and a contact time of 15 min. Further analysis of adsorption isotherms and kinetics revealed that the Freundlich isotherm (R² = 0.9556) and the pseudo-second-order kinetic model (R² = 0.9454) best described the experimental data.

CONCLUSION

These findings indicate that tea waste is an effective and sustainable adsorbent for mitigating nitrate contamination in aqueous solutions, offering a promising approach to address water quality challenges globally. © 2024 Society of Chemical Industry (SCI).