Facile Impregnation of Graphene into Porous Wood Filters for the Dynamic Removal and Recovery of Dyes from Aqueous Solutions

Ever increasing industrialization leads to a rise in contaminated water resources due to the release of pollutants, such as organic dyes, into aquatic environments. Carbon nanosorbents, such as graphene, often exhibit faster uptake, higher capacity, and superior regeneration than activated carbon, which is the world's most widely used adsorbent for point-of-use water purification. However, continuous-flow adsorption treatments using graphene-based adsorbents are relatively scarce and are challenged by pressure drop and low flow through efficiency. Solid-liquid separation after treatment is another great concern when dealing with carbon nanosorbents. One way to address these issues consists of impregnating basswood, which is uniquely designed for fluid transportation, with graphene to promote fast and efficient adsorption, eliminate the need for dispersing and recovering the nanomaterials, and limit pressure drop as well as nanoparticle aggregation. The properties of the modified wood filters to adsorb and desorb methylene blue in a dynamic system were examined based on a central composite design. Results show that graphene was well-dispersed and immobilized on the wood vessel sidewalls by a vacuum impregnation process. The Yan model provided a good fit to the experimental breakthrough curves, and high uptake capacities up to 46 mg/g were obtained even at relatively low feed concentration. Spent filters were recovered by solvent exchange and reused for five sorption cycles with regeneration efficiency >80%. The present study has important implications for the safe and efficient utilization of nanosorbents in environmental remediation and separation applications.