Organosolv pretreatment assisted by carbocation scavenger to mitigate surface barrier effect of lignin for improving biomass saccharification and utilization

Table 4 Surface lignin coverage and percentage of various bonds or functional groups on fiber surface determined by XPS analysis (EOS-20 mM ethanol organosolv pretreatment with 20 mM sulfuric acid, 2N 2-naphthol, NS 2-naphthol-7-sulfonate, MT mannitol, SA syringic acid)

	Lignin coverage (XPS)	C₁ (%)^a	C₂ (%)^a	C₃ (%)^a	C₁/C₂	O₁ (%)^b	O₂ (%)^b	O₃ (%)^b
	Lignin coverage (XPS)	284.7 eV	286.6 eV	288.4 eV	C₁/C₂	531.3 eV	532.4 eV	533.3 eV
EOS-20 mM	0.72	41.78	45.42	12.80	0.92	26.75	32.86	40.40
20 mM + 2 N	0.91	37.15	44.50	18.35	0.83	31.69	45.01	23.30
20 mM + NS	0.54	26.06	51.73	22.21	0.50	36.32	33.14	30.54
20 mM + MT	0.59	28.27	50.70	21.03	0.56	36.82	36.08	27.09
20 mM + SA	0.61	24.99	48.54	26.47	0.51	36.52	35.57	27.91

^aSubpeaks in C_1s correspond to C₁ (C–C, C−H or C=C), C₂ (C–S, C–OH or C–O–C) and C₃ (O–C–O or C=O), respectively
^bSubpeaks in O_1s correspond to O₁ (O–C=O and Ar–O–Ar), O₂ (C–O–, C=O, C–O–C and O–C=O), O₃ (Ph–O), respectively

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