Eco-friendly micro-mesoporous carbon from sucrose and sodium metasilicate template for ciprofloxacin adsorption: Effect of molecules self-association over diffusion mechanisms

Abstract

A green synthesis route of ordered mesoporous carbon by nanocasting of sucrose/sodium metasilicate with template removal only by hot water (70 °C) is proposed. The metasilicate-sucrose mesoporous carbon (MSMC) was characterized by structural, textural, surface chemistry properties and their effect on ciprofloxacin (CIP) adsorption. Phenomenological modeling was applied, including two surface-reaction models: adsorption on adsorbent sites (AAS) and on heterogeneous surface (AHS), and two mass transfer models: external film (EFD) and intraparticle homogeneous (IHD) diffusion. A controlled porous structure containing mesopores (3.8 nm) with micropores (1.8 and 0.87 nm) allowed the “pore filling effect” mechanism and strongly favorable kinetics. A highly oxygenated carbon material (C: 81.84 % O: 15.04 % Si: 1.72 % Na: 1.29 %) with efficient template removal was obtained. Unusual behavior of the rate-limiting step (AAS or IHD) as a function of CIP concentrations was observed, with mechanism changes due to self-aggregation of CIP molecules (dimers, trimers and tetramers).