Calcium-assisted hydrothermal carbonization of an alginate for the production of carbon microspheres with unique surface nanopores

摘要

Carbon microspheres with diameter ranging from 1 to 2 μm were obtained by calcium-assisted hydrothermal carbonization of alginate under acidic condition. These microspheres exhibited unique surface morphologies, dependent upon the concentration of calcium chloride present in the acidic alginate. Without using calcium chloride, the obtained product was smooth carbon spheres. In contrast, hydrothermal carbonization in the presence of calcium chloride yielded microspheres with unique surface morphologies. A random distribution of 130-250 nm pores was observed on the surface of microspheres obtained in the presence of 0.05 mol/L calcium chloride. But, a matte shaggy surface appeared when the concentration of calcium chloride was increased to 1 mol/L Meanwhile, the formation of these nanopores on the surface was also reaction time-dependent. The Ca-assisted formation mechanism was further discussed. These alginate-derived carbon spheres were functiona-lized with hydroxyl and carboxyl groups, thereby having potential applications in many fields such as biochemistry, drug delivery, and catalyst supports.