Highly Porous Core–Shell Structured Graphene-Chitosan Beads

Abstract

Graphene oxide (GO) sheets have been assembled into various three-dimensional porous structures and composites, with potential applications in energy and environmental areas. Here, we show the combination of GO and chitosan (CTS) into inorganic-organic heterocomposites as ∼3 mm diameter core-shell beads with controlled microstructure. The spherical GO-CTS beads, made by a two-step freeze-casting method, consist of a GO core wrapped by a CTS shell with abrupt interface; both parts have high porosities (94-96%) and mesopores volume (0.246 cm(3)/g) yet with different pore morphologies. Incorporation of a GO core into the CTS beads significantly improved the methyl orange adsorption capacity (353 mg/g at 318 K) compared with pure CTS beads. Key factors such as the pH value, adsorbent dosage, concentration, time, and temperature have been studied in detail, whereas adsorption isotherm and kinetic studies reveal a Langmuir model following the pseudo-second order.