Ice- and MOF-templated porous carbonaceous monoliths for adsorptive removal of dyes in water with easy recycling

Various nanoporous particles, nanofibers have been employed for adsorptive removal of dyes from wastewater. However, these nanomaterials are difficult in separation from solution, generally by centrifugation or filtration. These processes are tedious and will limit the upscale applications. Herein, a hierarchically porous carbon monolith has been fabricated on grounds of ice and metal organic framework (MOF) templating method. The prepared carbonaceous monolith exhibited abundant ice-templated macropores, MOF-templated micropores and mesopores, and a high BET (Brunauer-Emmett-Teller) special surface area (530 m2 g−1). The monolith achieved an MB (methylene blue) adsorption capacity of 95.82 mg g−1 (10 mg adsorbent/5 mL aqueous dye solution) and a theoretic maximum value of 179.86 mg g−1 by the Langmuir model. Compared with MB, the adsorption capacity for MO (methyl orange) was lower. Several adsorption kinetics and isotherms models were used for analysis of adsorptive data, and the results demonstrated the adsorption of MB and MO on the porous carbon monolith is a spontaneous endothermic physisorption process, which was mainly controlled by electrostatic reaction. Importantly, the monolith could be easily picked up using tweezers and used for recycling tests. After four cycles, the 94% of the initial adsorption capacity for MB can be retained.