Table 2.

Preparation of Lignin Nanoparticles by Using Acid Solution as Anti-solvent.

Lignin Source	Solvent	Acid Solution	Diameter (nm)	Zeta Potential (mV)	Morphology	Advantage	Disadvantage	References
low- sulfonated lignin	ethylene glycol	HCl	84 ± 5	−33 ± 1	porous core nanoparticle	pH-stable, higher antimicrobial activity	irregular morphology	[34]
			50–250	---	spherical structure	increased thermal stability and crystallinity	no research on stability in medium	[59]
pristine lignin	ethylene glycol	HCl	48.85 ± 16.38	---	quasi- spherical	uniform size distribution	no research on stability in acidic medium	[57]
low- sulfonated lignin	ethylene glycol	HCl	40–200	−30	aggregate structure	biodegradable biocompatible	stable only at pH (1–9).	[60]
	NaOH solution (pH = 11.44)	HNO3 (0.25 M)	85.9	---			stable only at pH < 5
kraft lignin	ethylene glycol	HNO3 (0.025 M)	45–250	−20 to −30	quasi- spherical	stable within a broad pH range	irregular morphology	[55]
organosolv wheat straw	H2O/ ethanol mixture	H2SO4	100–463	−30 to −40	irregular	high yield, valorization of wheat straw	uncontrollable size, complex process	[61]