Table 2. Atomic Percentages of Each Sulfur Functionality Estimated from XPS Analysis.

	atomic percentage (%)
sample	mercaptan	thiophene	sulfoxide	sulfone	inorganic sulfur/sulfate
DP900	10.49	15.29	15.25	31.50	27.47
AC500	1.71	31.82	14.23	34.65	17.59
AC600	2.11	24.91	17.02	27.54	28.42
AC700	2.87	19.63	19.06	10.32	48.12
AC800	2.34	19.12	17.54	19.94	41.06
AC900	3.50	21.37	11.33	32.75	31.05