Convenient synthesis of porous carbon nanospheres with tunable pore structure and excellent adsorption capacity

A novel adsorbent, porous carbon nanosphere (PCNS), was conveniently prepared by the chemical activation of hydrothermally synthesized carbon nanosphere (CNS) with ZnCl2. The obtained PCNS materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 sorption technology and transmission electron microscope, and the results indicated that these materials possessed superior porosity with high surface area and large pore volume, in the meantime maintaining the nanospherical morphologies. Moreover, the porous structure of PCNS can be tuned from micropores to mesopores by adjusting the mass ratio of ZnCl2/CNS and the activation temperature. The porous structure endued PCNS excellent performance for the adsorption of bulky dyes from aqueous solution. Detailed adsorption behaviors of the optimized PCNS material, including adsorption isotherms and adsorption kinetics, were investigated. The experimental data of equilibrium adsorption capacity well matched Langmuir isotherms, and the maximum adsorption amounts of methylene blue, malachite green and rhodamine B were calculated as 3152, 1455 and 1409 mg g−1, respectively, which were much higher than those of activated carbon and mesoporous carbon. The kinetic data were fitted to the models of pseudo-first-order and pseudo-second-order, which followed more closely the pseudo-second-order chemisorptions model. In addition, PCNS exhibited a good reusable property after five consecutive cycles.