title: Effects of Oxygen Element and Oxygen-Containing Functional Groups on Surface Wettability of Coal Dust with Various Metamorphic Degrees Based on XPS Experiment.
abstract: To investigate the difference of surface oxygen element and oxygen-containing functional groups among coal dusts with different metamorphic degrees and their influence on surface wettability, a series of X-ray photoelectron spectroscopy experiments on 6 coal samples are carried out. The result demonstrates that the O/C ratio of coal surface shows an overall increasing trend compared with the result of its elements analysis. As the metamorphic degree increases, the O/C ratio on the surface gradually declines and the hydrophilic groups tend to fall off from coal surface. It could be found that different coals show different surface distributions of carboxyl and hydroxyl which are considered as the greatest promoter to the wettability of coal surface. With the change of metamorphic degree, the distribution of ether group is irregular while the carbonyl distribution keeps stable. In general, as the metamorphic degree goes higher, the content of oxygen-containing polar group tends to reduce. According to the measurement results, the contact angle is negatively related to the content of oxygen element, surface oxygen, and polar groups. In addition, compared with surface oxygen content, the content of oxygen-containing polar group serves as a more reasonable indicator of coal dust wettability.
authors.affiliation: State Key Laboratory of Mining Disaster Prevention and Control Co-Founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, China ; College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Mining Disaster Prevention and Control Co-Founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, China ; College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
authors.forename: Cuicui
authors.initials: C
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Mining Disaster Prevention and Control Co-Founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, China ; College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
authors.forename: Weimin
authors.initials: W
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Mining Disaster Prevention and Control Co-Founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, China ; College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Mining Disaster Prevention and Control Co-Founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, China ; College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Nie