Polydopamine-integrated cellulose/graphene oxide monoliths: A versatile platform for efficient continuous-flow iodine capture and photothermal-enhanced reduction of Cr(VI)

The global challenge of wastewater contamination, especially from persistent pollutants like radioactive isotopes and heavy metals, demands innovative purification solutions. Radioactive iodine isotopes (¹³¹I and ¹²⁹I), stemming from nuclear activities, pose serious health risks due to their mobility, bioaccumulation, and ionizing radiation, particularly impacting thyroid health. Similarly, hexavalent chromium, Cr(VI), is highly toxic and persistent in water, linked to cancer and other severe health issues. Developing effective technologies for iodine capture and Cr(VI) reduction is therefore critical for public health and environmental protection. This study presents two distinct cellulose-based composite materials tailored for environmental remediation: cellulose/graphene oxide/polydopamine (cellulose/GO/PDA) monoliths for iodine capture and cellulose/graphene oxide/polydopamine/palladium nano-crystals (cellulose/GO/PDA/Pd) monoliths for the reduction of Cr(VI). PDA substantially enhances the adsorptive, catalytic and photothermal properties of monoliths. The monoliths demonstrated exceptional performance in both batch and continuous-flow reactor studies. Complete iodine removal was achieved within 15 s, while Cr(VI) was entirely reduced within 9 min under dark conditions and 5 min under photothermal conditions. Continuous-flow experiments showed sustained iodine adsorption of 92 % and Cr(VI) reduction of 81 % over 240 min. This research highlights the potential of PDA-enhanced cellulose-based composites as highly efficient and sustainable platforms for practical water remediation and environmental protection.