Green and facile synthesis of hierarchically porous carbon monoliths via surface self-assembly on sugarcane bagasse scaffold: Influence of mesoporosity on efficiency of dye adsorption

Hierarchically macro- and mesoporous carbon materials (HPCs) were prepared from environmentally friendly phloroglucinol/glyoxylic acid precursors with soft-template F127 using sugarcane bagasse as scaffold via self-assembly surface coating. The sugarcane bagasse scaffold provided macroporosity. Effects of carbon precursor/template ratio as well as slight modification using air treatment on the physicochemical properties of the carbon monoliths were systematically studied and samples were fully characterized. The resulting monoliths prepared using our method exhibited a stable monolithic feature with a hierarchically porous structure and BET surface areas as high as similar to 500-645 m(2)/g, total pore volume 0.2-0.4 cm(2)/g, mesoporosity contribution as large as 50-60% volume, and mesopore sizes of similar to 5 nm. Carbon materials prepared without F127 showed BET surface area and total pore volumes comparable to those of the HPCs but they exhibit much lower degree of mesoporosity (<20% volume). Regardless of the similar chemical properties of all samples, the difference in pore texture largely influenced the adsorption performance of dyes. The selected HPC sample showed the best performance in adsorption of methylene blue dye (MB) with the maximum capacity of similar to 100 mg/g, outperforming or being comparable to the monolithic adsorbents reported in literature. Moreover, the monolith shape could be well retained even after complete adsorption. The MB adsorption capacity of the adsorbents is perfectly linearly correlated with the mesoporosity, stressing the importance of mesopores in dye adsorption. The combination of environmentally friendly carbon precursors and sugarcane bagasse as starting materials can efficiently lead to novel monolith carbon adsorbents avoiding the use of toxic chemicals.