Figure 1.
General XPS spectra of (a) WMS, (b) SNCH2SO4,3, (c) SNCH2SO4,7, and (d) SNCHCl,7.
Table 1.
Elemental surface composition (atomic %) and oxygen to carbon ratio of starch, HCl- and H2SO4-hydrolyzed SNC.
Figure 2.
The high-resolution C 1 s deconvoluted XPS spectra of (a) WMS, (b) SNCH2SO4,3, (c) SNCH2SO4,7, (d) SNCHCl,7.
Table 2.
Surface functional group composition as obtained from the deconvolution of the C 1
Figure 3.
The high-resolution S 2p deconvoluted XPS spectra of (e) WMS, (f) SNCH2SO4,3, (g) SNCH2SO4,7, and (h) SNCHCl,7.
Figure 4.
FT-IR spectra of (a) WMS, (b) SNCH2SO4,3, (c) SNCH2SO4,7, and (d) SNCHCl,7.
Figure 5.
Formation of sulfate esters and adsorption of formic and levulinic acids on the surface of SNC (a: Formation of sulfate ester, b: adsorption of formic and levulinic acids).
Figure 6.
Zeta potential of SNCH2SO4,7 (gray color) and SNCHCl,7 (white color) suspensions at pH 6.5 and 10.6 placed for 2 h and 48 h, respectively.
Data are represented as the mean ± standard deviation (n = 3).
Figure 7.
TEM pictures and sedimentation properties of HCl (a and b) and H2SO4 (c and d) hydrolyzed SNC suspensions after 2 h and 48 h.