Experimental Investigation of Coal Dust Wettability Based on Surface Contact Angle

Table 2

Determination results of contact angles on test pieces of coal powder before and after being screened.

Name of surfactants	Contact angle/°
	Concentration/%	Sieving meshes					Coal particle milled for 30 s	Change rates of the contact angle; for different meshes/%
		70	100	160	200	320		70	100	160	200	320
Sodium dodecyl sulfate (SDS)/anionic	0.005	43.58	52.87	52.27	54.63	60.40	43.68	−0.1	9.19	8.59	10.95	16.72
	0.05	21.35	25.80	25.08	33.76	45.46	28.04	−6.69	−2.24	−2.96	5.72	17.42
	0.5	0	0	7.14	7.23	10.77	0	0	0	7.14	7.23	10.77
Cetyltrimethyl ammonium bromide (CTAB)/cationic	0.005	33.36	52.16	55.47	64.94	61.63	58.97	−25.61	−6.81	−3.5	5.97	2.66
	0.05	17.71	19.94	24.44	28.95	37.09	15.74	1.97	4.2	8.7	13.21	21.35
	0.5	9.03	16.08	20.16	21.79	21.96	12.28	−3.25	3.8	7.88	9.51	9.68
Cocoanut fatty acid diethanolamide (CFAD)/nonionic	0.005	27.94	21.17	41.54	45.16	50.11	47.40	−19.46	−26.23	−5.86	−2.24	2.71
	0.05	25.85	33.97	27.84	44.68	41.08	41.22	−15.37	−7.25	−13.38	3.46	−0.14
	0.5	17.82	26.69	27.77	32.76	33.07	22.89	−5.07	3.8	4.88	9.87	10.18
Dodecyl dimethyl betaine (DDB)/amphoteric	0.005	27.72	41.89	60.68	64.09	66.36	49.65	−21.93	−7.76	11.03	14.44	16.71
	0.05	26.10	29.50	46.78	51.66	59.14	48.74	−22.64	−19.24	−1.96	2.92	10.4
	0.5	7.82	13.73	20.08	15.69	19.40	16.47	−8.65	−2.74	3.61	−0.78	2.93