Table 2 A summary of common chemical and enzymatic treatment methods for producing (L)CNMs

Concentrated mineral acid hydrolysis

Sulfuric acid

 − 

Bleached wood pulp

CNCs

[HSO₃]

[21, 112]

Hydrochloric acid

 − 

Bleached softwood pulp

CNCs

None

[149]

Phosphoric acid

 − 

Whatman paper

CNCs

[PO₄]

[150]

Sulfuric acid

 − 

Bleached wood pulp

CNCs + CNFs

[HSO₃]

[126, 142]

Sulfuric acid

 − 

Poplar wood

LCNCs

[HSO₃]

[120]

Concentrated dicarboxylic acid hydrolysis

Oxalic acid or Maleic acid

 + 

Bleached wood pulp

CNCs + CNFs

[COOH]

[143, 148]

Oxalic acid

 + 

Whatman paper

CNCs + CNFs

[COOH]

[151]

Maleic acid

 + 

Unbleached hardwood pulp

LCNCs + LCNFs

[COOH]

[123, 124]

Acid hydrotrope

p-TsOH (aromatic sulfonic acid)

0

Undelignified birch fibers

Wheat straw

LCNFs

LCNFs

None

None

[72]

[44]

Maleic acid

 + 

Poplar, birch wood

Switchgrass

LCNFs

LCNFs

[COOH]

[COOH]

[45, 121]

[152]

Dilute acid

Oxalic acid

0

Bleached wood pulp

CNFs

None

[117]

Oxidation

Ammonia persulfate

 − 

Variety cellulosic materials

CNCs

[COOH]

[130]

Ammonia persulfate

 − 

Bleached birch pulp

CNFs

[COOH]

[153]

Periodate + chlorite

 − 

Bleached wood pulp

CNFs

[COOH]

[129]

TEMPO + NaBr + NaClO

0

Bleached wood pulp

CNFs

[COOH]

[140]

TEMPO + NaBr + NaClO

 − 

Softwood mechanical pulp

LCNFs

[COOH]

[154]

Solvent

DES

Choline chloride + urea

0

Bleached birch pulp

CNFs

None

[132]

GVL

GVL

0

Unbleached GVL pulp

LCNFs

None

[128]

Organosolv

Ethanol + SO₂

0

Wood

LCNCs, LCNFs

None

[127]

Ionic Liquid

[BMIMCI]

0

Cellulose powder

CNFs

None

[155]

[BMIM][HSO4]

0

Bleached wood pulp; microcrystalline cellulose

CNCs

None

[156]

[EMIM][OAc]

0

Wood

LCNCs

None

[157]

Enzymes

Endoglucanase

 ~ 

Bleached wood pulp

CNFs

None

[118, 119, 134]

Xylanase

 ~ 

Bleached wood pulp

CNFs

None

[135, 136]

Complex enzymes

 ~ 

Bleached wood pulp

CNFs

None

[137]