Polydopamine-integrated cellulose/graphene oxide monoliths for continuous-flow iodine capture and photothermal-enhanced Cr(VI) reduction

Wastewater contamination by persistent pollutants such as radioactive isotopes and heavy metals remains a significant global challenge. Radioactive iodine isotopes (¹³¹I and ¹²⁹I), released from nuclear activities, pose serious health risks due to their mobility, bioaccumulation, and ionizing radiation, particularly to the thyroid gland. Likewise, hexavalent chromium (Cr(VI)) is a highly toxic ad persistent water contaminant associate with cancer and other severe health effects. Therefore, efficient technologies for iodine capture and Cr(VI) reduction are urgently needed. In this study, two cellulose-based composite monoliths were developed for environmental remediation: cellulose/graphene oxide/polydopamine (cellulose/GO/PDA) monoliths for iodine capture and cellulose/GO/PDA/Pd nanocrystal monoliths for Cr(VI) reduction. PDA significantly improved the adsorption, catalytic, and phothermal properties of the monoliths. Complete iodine removal was achieved within 15 s, while Cr(VI) was fully reduced within 9 min in the dark and within 5 min under photothermal conditions. Continuous-flow operation maintained 92% iodine adsorption and 81% Cr(VI) reduction over 240 min. These results demonstrate the potential of PDA-enhanced cellulose-based monoliths as efficient and sustainable materials for practical water remediation and environmental protection.