Facile method of synthesizing multilayer graphene capsuled sulfur nanoparticles for water treatment

Multilayer graphene capsuled sulfur nanoparticles were successfully prepared by adsorption of the sulfur vapor on amorphous activated carbon (AC) at 700 degrees C. The samples were characterized by BET, SEM, TEM, XPS, FTIR, Raman and Zeta-potential testing measurements and adsorption tests. The results demonstrated that most of the elemental sulfur nanoparticles were in size of 22 nm and located in the mesopores of the graphitized AC. The sulfur nanoparticles were strongly interacting with neighboring carbons by forming -C-S- and -C-SOx- bonds. The adsorption capacities of the multilayer graphene capsuled sulfur nanoparticles were 785 mg g(-1) for methylene blue and 49 mg g(-1) for Cd2+ ions, which showed two times higher Cd2+ adsorption capacity but similar methene blue adsorption capacity compared with the pristine amorphous AC, although the BET surface area and pore volume of AC decreased significantly by sulfur modification. Cd2+ ions mainly chemically adsorbed on sulfur species which did not influence the adsorption capacity of small organics molecules, such as methene blue, in the micropores of AC. The method in this work provides a facile way to prepare a promising metal-free adsorbent for water treatment.