Membrane 10 Membrane 11 Membrane 12 Membrane 13 Initial Flux (

Table 22 - Characteristics of membranes used in experiment 2 Membranes in Series.

Table 23 - Characteristics of membranes used in experiment 3 Membranes in Series.

Membrane 2 Membrane 3 Membrane 4 Membrane 5 Initial Flux ( ^𝑳

Membrane 6 Membrane 10 Membrane 11 Membrane 12 Membrane 13 Initial Flux ( ^𝑳

Conclusions

The aim of this work was to evaluate the performance and the potential of regeneration of membrane performance during ultrafiltration of nangolignin suspensions in diafiltration mode. For this study only one type of straw was used (wheat straw), and as the literature explains, the results are dependent on the type of feedstock, as well as the pretreatment used (ethanol Organosolv). The precipitation method also influences the type of particles that are obtained, specific shapes and particle sizes. For the precipitation, water was used as an anti-solvent at an exact volume ratio.

This study allowed the successful analysis of the variation of the flux over time, which allowed the understanding of how the membranes are affected by the suspension used. To implement successfully a membrane filtration setup, it was important to select optimal operation conditions (1.2 L/min and 4 bar) at room temperature and use an ideal solvent to clean the setup (50wt% acetone and 15wt% ethanol).

Regarding the viability of this procedure, it was imperative that the particle size remained constant. The particle size for both experiments showed that the nanoparticles of lignin were approximately constant over time, which confirms that there is no agglomeration of the particles through the process. However, the time between the sample collection and the measurements should be shorter in order to minimize the possibility of errors. An additional goal was to remove the ethanol and the impurities from the nanoparticle’s suspension, which was analyzed using HPLC. The results showed a removal of ethanol of approximately 97% and acetic acid of approximately 87%. For the HMF and Furfural there were no valid values. Some errors in the measurements of the initial suspension occurred, therefore the values used for the suspension correspond to another experiment made in the laboratory.

To evaluate the performance of the ultrafiltration it was necessary to appraise the percentage of the solute that was retained by the membranes. The removal efficiency of dissolved components was calculated based on the Dry Matter content (measured in the permeate, the feed/retentate is depleted in these dissolved components). Both experiments showed a high value of efficiency, close to the desired value (90-95%). However, the experiment where 3 membranes were used in series showed higher efficiency (93.6%) than when using 2 membranes (85.2%), which means that the more membranes used, the less the components are retained by the membranes.

Fouling is one of the main aspects when it comes to ultrafiltration, and a consequence of it, is the decline of the membrane flux. On the other hand, the influence of the concentration of the suspension of nanoparticles was also studied in order to understand if this was also a factor in the decrease of the flux. The results showed that the flux decreases due to the increase of the concentration of the suspension, which means that the flux decline occurs mainly because of the accumulation of the particles deposited on the membrane surface and the increase of the suspension of nanoparticles concentration. Concerning the fouling, one of the membranes (membrane 1) was chosen to be regenerated, in order to elaborate a “long-term” stability and a performance comparation with new membranes. The results showed that the regeneration after the diafiltration step is less effective when compared to the values of regeneration after concentration mode. The regeneration not only removes Nanolignin particles from the membrane surface, but also the dissolved components that could block the membrane. These dissolved components are higher in UF and lower in DF steps.

For further work, membrane 1 should keep being used in other filtrations in order to understand if the membrane reached its stabilization and conditioning characteristics, since after the Flux and Concentration Experiment this membrane does not show a significant variance in its behavior. In addition to that, due to the divergent capacities of the membranes, it is essential to repeat the flushing quite a few times with different membrane materials, to reach statistically relevant values.

Being that fouling is one of the biggest problems when it comes to ultrafiltration, it’s important to focus on its improvement. It is essential to find the best cleaning method to clear the cross-flow system, ensuring that there are no particles left in the system. The membrane regeneration method should also be optimized. Several experiments should be realized using different operating conditions in order to determine the most promising results to regenerate a membrane. Another aspect that should be worked in the future, is to check if a different technique to store the membrane will affect its capacity. Since the membrane is regenerated using a solution of ethanol, it should be tested if this being stored in a solution of water instead of being stored in ethanol affects the membrane.

References

Agbor, V. B., Cicek, N., Sparling, R., Berlin, A., & Levin, D. B. (2011). Biomass pretreatment:

Fundamentals toward application. Biotechnology Advances, 29(6), 675–685.

https://doi.org/10.1016/j.biotechadv.2011.05.005

Agricultural, N., Service, S., Foster, C., Hilliard, P., & Pendarvis, S. (2016). NATIONAL AGRICULTURAL STATISTICS SERVICE AGRICULTURAL Agricultural Statistics 2016. (866).

Alonso, D. M., Wettstein, S. G., & Dumesic, J. A. (2012). Bimetallic catalysts for upgrading of biomass to fuels and chemicals. Chemical Society Reviews, 41(24), 8075–8098.

https://doi.org/10.1039/c2cs35188a

Aresta, Michele., Dumeignil, Angela. (2012). Biorefinery: From biomass to chemicals and fuels:

University of Bari: Gruyter, 2012.

Baker, Richard W. Membrane Technology and Applications: 2^nd Edition. John Wiley & Sons, Ltd (2004) Beisl, S., Biermair, F., Friedl, A., Mundigler, N., & Miltner, A. (2017). Sequential extrusion and organosolv pretreatment for wheat straw valorization. Chemical Engineering Transactions, 61, 853–858.

https://doi.org/10.3303/CET1761140

Beisl, S, Loidolt, P., Miltner, A., & Friedl, A. (2018). Direct precipitation of organosolv liquors leading to submicron lignin particles. Chemical Engineering Transactions, 70, 331–336.

https://doi.org/10.3303/CET1870056

Beisl, Stefan, Friedl, A., & Miltner, A. (2017). Lignin from micro- To nanosize: Applications. International Journal of Molecular Sciences, 18(11). https://doi.org/10.3390/ijms18112367

Beisl, Stefan, Loidolt, P., Miltner, A., Harasek, M., & Friedl, A. (2018). Production of micro- and nanoscale lignin from wheat straw using different precipitation setups. Molecules, 23(3).

https://doi.org/10.3390/molecules23030633

Beisl, Stefan, Miltner, A., & Friedl, A. (2017). Lignin from micro- to nanosize: Production methods. In International Journal of Molecular Sciences (Vol. 18). https://doi.org/10.3390/ijms18061244 Bhattacharjee, C., & Bhattacharya, P. K. (1992). Prediction of limiting flux in ultrafiltration of kraft black

liquor. Journal of Membrane Science, 72(2), 137–147. https://doi.org/10.1016/0376-7388(92)80194-O

Bhongsuwan, D., & Bhongsuwan, T. (2008). Preparation of Cellulose Acetate Membranes for Ultra- Nano- Filtrations. Pdf. 317, 311–317.

Buranov, A. U., & Mazza, G. (2008). Lignin in straw of herbaceous crops. Industrial Crops and Products, 28(3), 237–259. https://doi.org/10.1016/j.indcrop.2008.03.008

Calvo-Flores, F. G., Dobado, J. A., Isac-García, J., & Martín-MartíNez, F. J. (2015). Lignin and Lignans as Renewable Raw Materials. https://doi.org/10.1002/9781118682784

da Silva, A. R. G., Errico, M., & Rong, B. G. (2018). Evaluation of organosolv pretreatment for bioethanol production from lignocellulosic biomass: solvent recycle and process integration. Biomass Conversion and Biorefinery, 8(2), 397–411. https://doi.org/10.1007/s13399-017-0292-4

Drioli, Enrico., Giorno, Lidietta. (2010). Comprehensive membrane science and engineering: Institute of Membrane Techonology, Italy: Elsevier (2010).

Ferry, J. D. (1936). Ultrafilter membranes and ultrafiltration. Chemical Reviews, 18(3), 373–455.

https://doi.org/10.1021/cr60061a001

FitzPatrick, M., Champagne, P., Cunningham, M. F., & Whitney, R. A. (2010). A biorefinery processing perspective: Treatment of lignocellulosic materials for the production of value-added products.

Bioresource Technology, 101(23), 8915–8922. https://doi.org/10.1016/j.biortech.2010.06.125 Gaspar, R. C. (2018). Simultaneous separation of impurities and exchange of surrounding media in

Nanolignin suspensions.

Gavrilescu, M. (2014). Biorefinery Systems. Bioenergy Research: Advances and Applications, 18(1), 219–241. https://doi.org/10.1016/b978-0-444-59561-4.00014-0

Gilca, I. A., Popa, V. I., & Crestini, C. (2015). Obtaining lignin nanoparticles by sonication. Ultrasonics Sonochemistry, 23, 369–375. https://doi.org/10.1016/j.ultsonch.2014.08.021

Hu, J., Zhang, Q., & Lee, D. J. (2018). Kraft lignin biorefinery: A perspective. Bioresource Technology, 247(August 2017), 1181–1183. https://doi.org/10.1016/j.biortech.2017.08.169

Jääskeläinen, A. S., Liitiä, T., Mikkelson, A., & Tamminen, T. (2017). Aqueous organic solvent fractionation as means to improve lignin homogeneity and purity. Industrial Crops and Products, 103, 51–58. https://doi.org/10.1016/j.indcrop.2017.03.039

Jaya Shankar Tumuluru, Christopher T Wright, Richard D Boardman, Neal A Yancey, & Shahab Sokhansanj. (2013). A review on biomass classification and composition, co-firing issues and pretreatment methods. (May 2014). https://doi.org/10.13031/2013.37191

Kovács, Z., Discacciati, M., & Samhaber, W. (2008). Numerical simulation and optimization of multi-step batch membrane processes. Journal of Membrane Science, 324(1–2), 50–58.

https://doi.org/10.1016/j.memsci.2008.06.060

Li, X., & Chapple, C. (2010). Understanding Lignification: Challenges Beyond Monolignol Biosynthesis.

Plant Physiology, 154(2), 449–452. https://doi.org/10.1104/pp.110.162842

Liu, F., Hashim, N. A., Liu, Y., Abed, M. R. M., & Li, K. (2011). Progress in the production and modification of PVDF membranes. Journal of Membrane Science, 375(1–2), 1–27.

https://doi.org/10.1016/j.memsci.2011.03.014

Matsutani, A., Harada, T., Ozaki, S., & Takaoka, T. (1993). Inhibitory effects of combination of CDDP and cepharanthin on the cultured cells from rat ascites hepatoma. In Journal of Japan Society for Cancer Therapy (Vol. 28).

McKendry, P. (2002). Energy production from biomass (Part 1): Overview of biomass. Bioresource Technology, 83(1), 37–46. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/12058829

Miltner, M., Beisl, S., Miltner, A., Adamcyk, J., Gaspar, R., Capelo, S., … Friedl, A. (2019). Application of Membrane Separation for Cleaning and Concentration of Nanolignin Suspensions in a Biorefinery Environment. XX.

Nitsos, C., Rova, U., & Christakopoulos, P. (2018). Organosolv fractionation of softwood biomass for biofuel and biorefinery applications. Energies, 11(1). https://doi.org/10.3390/en11010050

OSMO Membrane Systems GmbH. 2019. Technology Overview “Ultrafiltration” Retrieved (https://www.osmomembrane.de/index.php?option=com_content&view=article&id=81&Itemid=156&lan g=en)

Parmar, K. (2017). Biomass- An Overview on Composition Characteristics and Properties. IRA-International Journal of Applied Sciences (ISSN 2455-4499), 7(1), 42.

https://doi.org/10.21013/jas.v7.n1.p4

Prasad, S., Singh, A., & Joshi, H. C. (2007). Ethanol as an alternative fuel from agricultural, industrial and urban residues. Resources, Conservation and Recycling, 50(1), 1–39.

https://doi.org/10.1016/j.resconrec.2006.05.007

Ghosh, Raja. (2003). Protein Bioseparation Using Ultrafiltration. https://doi.org/10.1142/p257

Rautenbach, R. & Albert, R. (1989). Membrane Process. John Wiley & Sons Ltd. New York. Retrieved from https://www.academia.edu/31551491/Modul_F_Reverse_Osmosis

Rheingaustr, M. G., & Tel, W. (2018). SPIRA-CEL. 49(0). Retrieved (https://www.lenntech.com/Data-sheets/Microdyn-Spira-Cel-L.pdf)

Satyanarayana, S. V., Bhattacharya, P. K., & De, S. (2000). Flux decline during ultrafiltration of kraft black liquor using different flow modules: A comparative study. Separation and Purification Technology, 20(2–3), 155–167. https://doi.org/10.1016/S1383-5866(00)00086-1

Strathmann, H. (2001). Membrane separation processes: Current relevance and future opportunities.

AIChE Journal, 47(5), 1077–1087. https://doi.org/10.1002/aic.690470514

Toledano, A., García, A., Mondragon, I., & Labidi, J. (2010). Lignin separation and fractionation by ultrafiltration. Separation and Purification Technology, 71(1), 38–43.

https://doi.org/10.1016/j.seppur.2009.10.024

Toledano, A., Serrano, L., Garcia, A., Mondragon, I., & Labidi, J. (2010). Comparative study of lignin fractionation by ultrafiltration and selective precipitation. Chemical Engineering Journal, 157(1), 93–99. https://doi.org/10.1016/j.cej.2009.10.056

Tröger, N., Richter, D., & Stahl, R. (2013). Effect of feedstock composition on product yields and energy recovery rates of fast pyrolysis products from different straw types. Journal of Analytical and Applied Pyrolysis, 100, 158–165. https://doi.org/10.1016/j.jaap.2012.12.012

Wallberg, O., Jönsson, A. S., & Wimmerstedt, R. (2003). Fractionation and concentration of kraft black liquor lignin with ultrafiltration. Desalination, 154(2), 187–199. https://doi.org/10.1016/S0011-9164(03)80019-X

Wavhal, D. S., & Fisher, E. R. (2002). Hydrophilic modification of polyethersulfone membranes by low temperature plasma-induced graft polymerization. Journal of Membrane Science, 209(1), 255–

269. https://doi.org/10.1016/S0376-7388(02)00352-6

Weinwurm, F., Drljo, A., Waldmüller, W., Fiala, B., Niedermayer, J., & Friedl, A. (2016). Lignin concentration and fractionation from ethanol organosolv liquors by ultra- and nanofiltration. Journal of Cleaner Production, 136, 62–71. https://doi.org/10.1016/j.jclepro.2016.04.048

Wu, D. (2015). Thin Film Composite Membranes Derived from Interfacial Polymerization for Nanofiltration and Pervaporation.

Yu, W., Xu, L., Graham, N., & Qu, J. (2014). Pre-treatment for ultrafiltration: Effect of pre-chlorination on membrane fouling. Scientific Reports, 4. https://doi.org/10.1038/srep06513

Appendix

The temperature of the product inside the reactor and the pressure was measured for all the experiments. Figure 51 describes the temperature and pressure versus time of one of the extractions done in this work.

Figure 51 - Product temperature (°C) and pressure (bar) for one extract production experiment.

Figure 52 - Membranes used in the experiment 2 Membranes in Series: (a) Membrane 1; (b) Membrane 2; (c) Membrane 3; (d) Membrane 4; (e) Membrane 5.

(a) (b) (c) (d) (e)

Figure 53 – (a) Membrane 1 (regenerated) at the end, after being used in all the experiments; (b) Membrane 6 (without regeneration) at the end, after being used in experiments Flux and

Concentration and 3 Membranes in Series

Figure 54 - Membranes used in the experiment Flux and Concentration:

(a) Membrane 3; (b) Membrane 4; (c) Membrane 5.

(a) (b) (c) (a) (b)

Figure 55 - Membranes used in the experiment 3 Membranes in Series: (a) Membrane 6; (b) Membrane 7; (c) Membrane 8; (d) Membrane 9.

(a) (b) (c) (d)