Facile synthesis of soft-templated carbon monoliths with hierarchical porosity for fast adsorption from liquid media

An easy synthesis of carbon monoliths with hierarchical porosities is presented here combining phenolic sol-gel and soft-templating methods (use of amphiphilic surfactant Pluronic F127 as mesopores template). By varying the synthesis conditions, purely microporous or micro-mesoporous or micro-meso-macroporous carbon materials were obtained. While micropores and mesopores arise during the carbonisation, macropores formation occurs during the gelling step through a controlled macroscopic phase separation process. The same pyrolytic temperature was used to ensure comparable surface chemistry (proved by FTIR and TGA-MS measurements for the templated samples), textural properties were investigated by a group of techniques: TEM, CO2 and N-2 sorption, Hg porosimetry and SAXS. The benefit of the different porosities was evidenced on blocs of 1-2.5 mm diameter by studying adsorption kinetic of phenol and methylene blue aqueous solutions. Due to comparable surface chemistry of the templated samples, only their difference of porosity was considered as a decisive factor for the kinetics of adsorption. The relative role of each porosity was evidenced and quantified. It was found that mesopores are crucial for a fast transport of adsorptive into the adsorption sites (micropores/smaller mesopores) while the additional presence of macropores further accelerates the rate of sorption for both adsorptives.