Synthesis of lignin-based covalent organic frameworks bio-composites: Quantitative evaluation of adsorption-photoreduction of hexavalent chromium

A novel bio-covalent organic framework (COF: TpPa-SO3H/Lignin) based on TpPa-SO3H and lignin from lignocellulose was synthesized for chromium (Cr(VI)) remediation in this study. Results showed that TpPa-SO3H/Lignin had a highest adsorption capacity at the range of 5 ∼ 75 mg/L Cr(VI) under 10 mg/L dosage, in which 100 % Cr(VI) could be removal within 120 min. Likewise, the introduction of lignin improved the visible light response range, charge separation and photogenerated carriers, thereby improving the photocatalytic efficiency of Cr(VI) by TpPa-SO3H/Lignin. The highest photocatalytic efficiency of TpPa-SO3H/Lignin (98.56 %) was observed at the acidic conditions. ESR result shows that e- and ·O2– are generated and played an important role during the photocatalytic reaction, while the contribution of ·OH to Cr(VI) photoreduction is negligible. This study presents a sustainable and efficient approach to mitigating Cr(VI) pollution. It opens up avenues for further exploration of lignocellulose-derived materials in environmental applications and highlights the potential of COFs in addressing heavy metal contaminants.