Research On Oxygen-containing Functional Groups On Coal Surface

Five types of different rank coals (Yunnan, Tiefa, Datong, Pingshuo, Changcim) and coals oxidized by H2O2 and HNO3 were researched by FTIR and Zeta potential; Adsorption energy of H+, OH", H2O, CH3OH on coal surface were calculated by semi-expirical quantum chemistry calculation ZINDO of Cerius2, the model compounds that were constructed from naphthalene, anthracene, double anthracene linked with methyl, hydroxyl, carbonyl and carboxyl were simulated the original and oxidized coal surface of different rank. The conclusions were:Hydroxyl group on coal surface were the most important group to surface properties and Zeta potential; oxidation can increase hydroxyl, carboxyl and carbonyl groups on coal surface; the sites that can be oxidized on different rank coals have different chemical activation.Coal surface charged negatively in H2O system, and ions in Stern layer charged positively. IEP (isoelectric point) of original coal increased regularly as coal rank rose. Most of the coals charged more negatively after oxidationAdsorption ability increased as coal rank rose. Adsorption of H+, OH- was belong to chemical adsorption. The bonds linked with carbon atoms can be looked as single bond. Net charge of atom carbon on coal surface was calculated to conclude that net charge on coal surface was distributed unevenly which can affect adsorption behavior on coal surface. The results of quantum chemistry calculation can support most of experimental facts.