Effects of Oxygen Element and Oxygen-Containing Functional Groups on Surface Wettability of Coal Dust with Various Metamorphic Degrees Based on XPS Experiment

Table 4

Contents of superficial oxygen-containing functional groups of different coal samples.

Coal samples	Molar content of oxygen-containing functional groups /%
	COO	C=O	C–OH	C–O–C	Polar oxygen groups; (C–OH, COO)
Beizao lignite	7.41	3.09	5.83	5.27	13.24
Daliuta long flame coal	6.88	1.81	3.83	4.74	10.71
Yushuwan gas coal	4.25	2.86	3.88	2.53	8.13
Xinjulong fat coal	4.72	3.69	2.34	1.96	7.06
Wugou coking coal	3.75	2.59	3.29	2.11	7.04
Yangquan anthracite	2.72	2.57	2.02	3.86	4.74