A simple process for lignin nanoparticle preparation

TLDR: In this paper, a straightforward method to produce lignin nanoparticles from waste lignins obtained from kraft pulping is introduced, which is a natural biopolymer obtained mainly as a byproduct from pulp and paper-making industries, and is primarily burned to produce energy.

About: This article is published in Green Chemistry.The article was published on 2016-02-29 and is currently open access. It has received 424 citations till now. The article focuses on the topics: Lignin & Kraft process.

Figures

Figure 5. Effect of pH on a) average hydrodynamic diameter and b) zeta potential of lignin nanoparticles. The lines are only visual guides.

Figure 6. Effect of PDADMAC coating on a) average hydrodynamic diameter and b) zeta potential of lignin nanoparticles. The line is only a visual guide.

Figure 4. Effect of salt concentration on a) average hydrodynamic diameter and b) zeta potential of lignin nanoparticles.

Figure 3. Stability of lignin nanoparticles: a) average hydrodynamic diameter and b) zeta potential of lignin nanoparticles in pure water as a function of time.

Table 1. Amounts of different hydroxyl group species in lignin samples according to 31P-NMR data. a The sulfur was assumed to be as thiol group. b Data provided by Sigma-Aldrich.

Figure 1. TEM images of lignin nanoparticles prepared from SW lignin dissolved in THF (top) and Sigma-Aldrich lignin dissolved in ethylene glycol (bottom).

Frequently asked questions

Q1. What is the effect of lignin on nanoparticles?

When lignin nanoparticles are dispersed in water, the phenolic hydroxyl groups and possible carboxyl groups provide the particles a surface charge that promotes the formation of electrical double layers, which can stabilize the nanoparticle dispersion via electrical double layer repulsion. 

Q2. What have the authors contributed in "Simple process for lignin nanoparticle preparation" ?

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Q3. What future works have the authors mentioned in the paper "Simple process for lignin nanoparticle preparation" ?

In the future, these nanoparticles could be applied in coatings, glues, nanocomposite structures, etc. Further investigations towards various properties such as surface interactions and biological compatibility should be carried out. 

Q4. What is the role of water in lignin nanoparticles?

Water acts as a nonsolvent reducing lignin’s degrees of freedom causing the segregation of hydrophobic regions to compartments within the forming nanoparticles. 

Q5. What is the effect of lignin concentration on the nanoparticles?

At very high lignin concentration (20 mg/ml) the nucleation-growth mechanism during the dialysis seems to occur so fast that nanoparticles with very different sizes are formed (high polydispersity). 

Q6. How does the dispersion of lignin nanoparticles work?

Effect of time, salt concentration and pH on particle stabilityFor some applications, such as coatings and drug delivery, it is crucial that the nanoparticles retain their nanosize and stay well dispersed to reach desired performance. 

Q7. How did the lignin nanoparticles be obtained?

Spherical lignin nanoparticles were obtained by dissolving soft wood kraft lignin in tetrahydrofuran (THF) and subsequently introducing water into the system through dialysis. 

Q8. What is the zeta potential of the lignin nanoparticles?

The extension of surface charge modification of the lignin nanoparticles was monitored by zeta potential measurements at different PDADMAC:LNP ratios. 

Q9. How long did the dispersion remain stable?

The nanoparticle dispersion was stable for at least one week time within the given pH range, with no significant change of average particle diameter after 7 days. 

Q10. How much THF remained in the nanoparticles after dialysis?

Negligible amount of residual THF (below 1 ppm) remained in the nanoparticle dispersions after dialysis, as revealed by gas chromatography-mass spectrometry. 

Q11. What is the recent research on lignin nanoparticles?

Successful utilization of lignin nanoparticles to reinforce phenolic foams or to stabilize Pickering emulsions has been reported in the literature. 

Q12. What is the method used for lignin dispersions?

The method uses a limited amount of organic solvents and produces the particles as an environmentally friendly aqueous dispersion. 

Q13. How did the lignin nanoparticles be produced?

It was further demonstrated that the surface charge of the particles could be reversed and stable cationic lignin nanoparticles were produced by adsorption of poly(diallyldimethylammonium chloride) (PDADMAC). 

Q14. What was the effect of the combination of SW lignin and THF on the nano?

Since spherical lignin nanoparticles were obtained from the combination of SW lignin and THF as solvent, the rest of the experiments were performed with this setup. 

Q15. What is the average PDI of lignin nanoparticles?

The average polydispersity indexes (PDI) range from 0.15 to 0.56 in a scale from 0 to 1 (the higher the PDI, the more polydisperse the particles are). 

Q16. What are the potential applications of lignin nanoparticles?

These water dispersed lignin nanoparticles (LNP) could have potential in applications such as bio based adhesives, stabilizers, crops additives, etc. 

Q17. How stable was the lignin nanoparticle dispersion in water?

The lignin nanoparticle dispersion was very stable in pure water and no specific aggregation occurred within 60 days (Figure 3a). 

Q18. What is the zeta potential of lignin nanoparticles?

Figure 6 shows how the zeta potential of lignin nanoparticles changes from negative to positive values when the relative PDADMAC concentration increases in the coating solution.