Sustainable activated carbons prepared from a sucrose-derived hydrochar: remarkable adsorbents for pharmaceutical compounds

Abstract

We present a two-step methodology for the preparation of highly activated carbons with tailored morphologies and micropore size distributions (MPSD) through the hydrothermal carbonization (HTC) of renewable biomass (i.e. sucrose) and further activation. Depending on the activation agent, activated carbons with spherical (K₂CO₃ or steam activation) or sponge-like morphologies (KOH activation) were obtained. The control of the activation variables allows tailoring the MPSD of the materials with K₂CO₃ activation at 700–800 °C originating porous materials with molecular sieve properties, and KOH activation giving porous carbon materials with wider MPSD. The highly developed porous structures of the activated carbons give them remarkable adsorption capacities for the removal of pharmaceutical compounds of distinct therapeutical classes (i.e. ibuprofen, paracetamol, clofibric acid, caffeine and iopamidol). Although the superactivated carbon obtained by the KOH activation at 800 °C has very high adsorption capacities for all the pharmaceutical compounds assayed, the material obtained by the K₂CO₃ activation at 800 °C has a similar adsorption capacity for all pharmaceuticals but iopamidol, the most voluminous compound. The distinct performance of the porous carbon materials for the removal of the pharmaceutical compounds is mainly related to their MPSD. The high performance of some of the synthetized carbons combined with the possibility of controlling the size of the particles in the HTC step allows not only their possible use as filter media but also coupling to other advanced water treatment technologies (e.g. membrane systems). Moreover, the abovementioned properties associated with the acidic surface chemistry of the developed activated carbons open new possibilities for the synthesis of functional carbon-based materials.