One-step hydrothermal preparation of amino-functionalized carbon spheres at low temperature and their enhanced adsorption performance towards Cr(VI) for water purification

A facile one-step hydrothermal approach to prepare carbon spheres with amino groups on their surface is reported in this work. The obtained products are composed of carbon spheres with uniform size ∼2–3 μm. It was found that the addition of ammonia in the precursor solution would lead to modification of amino groups on the surface of carbon spheres. The existence of amino groups was verified by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Importantly, the carbon spheres with amino groups showed an excellent enhanced adsorption performance for the removal of heavy metal anions. Their removal capacity of Cr(VI) is ∼9 times higher than that of carbon spheres without amino groups. The enhanced adsorption performance was assumed to be induced by positively charged and increased reducing surface by modification of amino groups. This work not only supplies a novel low-cost approach to prepare amino-functionalized carbon spheres for water purification but also gives deep insight into understanding the adsorption behavior of carbon spheres.