Conversion of Lignocellulosic Biomass to Nanocellulose: Structure and Chemical Process

Table 4

Summary of depolymerisation treatments for nanocellulose synthesis.

Chemical treatment
Chemical	Cellulose source	Concentration of chemical	Ratio of substrate : acid	Reaction time	Temperature (°C)	Pretreatment	Particle size (nm)*	Yield of NC
Sulfuric acid [43]	Branch barks of mulberry (Morus alba L.)	64% (w/w)	1 : 10	0.5 h	60	Pulping treatment	20–40	N/A
Sulfuric acid [44]	Sugarcane bagasse	60% (w/v)	1 : 20	5 h	50	Pulping treatment	35	N/A
Sulfuric acid [45]	Waste cotton fabrics	63.5% (w/w)	1 : 15	3 h	44	Pulping treatment	20–100	21.50%
TEMPO mediated oxidation [46]	Pure rice straw	0.016 g	1 : 10	N/A	N/A	Oxidation	1.73	20%
Sulfuric acid [47]	Raw cotton linter	60% (w/w)	1 : 20	1 h	45	Grinding	12	N/A
Mechanical treatment
Method	Cellulose source	Pressure/energy	Temperature (°C)		Pretreatment		Particle size (nm)*	Yield of NC
High pressure homogenizer [48]	Wood pulp	500 bar	55–60		Pulping		ND	N/A
Sonification [49]	Wood powder from poplar trees	400–1200 W	<10		Pulping		5–20	N/A
High pressure homogenizer [50]	Sugarcane bagasse	40–140 MPa	130		Bleaching and ionic liquid treatment		20–100	N/A
Sonification [51]	Eucalyptus kraft pulp	50% amplitude, ~80 W	N/A		Pulping treatment		30	N/A
High shear homogenizer [52]	Bleached softwood pulp	22 000 rpm	N/A		Pulping and bleaching		16–28	N/A
High pressure homogenizer [53]	Nonwoody plants (flax, hemp, jute, and sisal)	600 bar	60–70		TEMPO-mediated oxidation		20–50	N/A
Biological treatment
Enzyme/microorganism	Cellulose source		Time and temperature		Pretreatment		Particle size (nm)*	Yield of NC
Anaerobic microbial [54]	Cotton fibers		7 days and 35°C		Pulping treatment		43 ± 13 & 119 ± 9	12.30%
Hemicell/pectinase and endoglucanase [55]	Curaua and sugarcane bagasse fibers		3 days and 50°C		Pulping treatment		55 ± 21	N/A

*Measured by Transmission Electron Microscope (TEM).
N/A is not available; NC is nanocellulose.