Adsorption and decolorization of hydrogenated coal tar on resin-based activated carbon spheres

Resin-based activated carbon spheres (ACSs) were firstly prepared by a combined suspension polymerization, carbonization and activation method. The ACSs were oxidized with nitric acid (NACSs) to modify the surface properties for enhancing the decolorization effect for hydrogenated coal tar. The morphology, pore structure, elemental composition and pyrolysis kinetics of the polymer sample were characterized by SEM, N2 adsorption, FTIR, XPS and TGA. Results show that the oxidation modification of ACSs has little influence on the surface morphology and pore structure while the numbers of surface oxygen functional groups are remarkably increased. P-benzoquinone (DBD) and N,N-di-sec-butyl-1,4-phenylenediamine (PBQ) were selected as model color compounds for decolorization tests with ACSs and NACSs. The effects of adsorption time, temperature and adsorbent dosage on the decolorization performance were investigated. Under the same adsorption conditions, the decolorization rates of DBD and PBQ are 94.5% and 96.6%, respectively for NACSs while those for ACSs are much lower, indicative of an outstanding adsorption performance of NACSs. The hydrogen bonds formed between surface functional groups and colored compounds may play a key role in the improvement of adsorption performance. Moreover, the decolorization rate of NACSs still reach more than 90% after NACSs are recycled for 6 times. The decolorization effect of NACSs for real hydrogenated coal tar is also significant and the color is basically faded after adsorption with NACSs, confirming the feasibility of NACSs in practical applications.