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| Author(s): |
Joice Jaqueline Kaschuk
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT) |
| Defense date: | 2019-04-12 |
| Examining board members: |
Elisabete Frollini;
Vagner Roberto Botaro;
Ivana Cesarino;
Antonio José Gonçalves da Cruz;
André Luiz Meleiro Porto
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| Advisor: | Elisabete Frollini |
| Abstract | |
The present study had as its primary goal the valorization of lignocellulosic sisal fibers (LSF) through the production of fermentable sugars via enzymatic hydrolysis. LSF was mercerized (20% aqueous NaOH solution) and the influence of the ratio fiber mass/volume NaOH, temperature (T) and time (t), during the treatment, were statistically evaluated. LSF with greater delignification was obtained in: <t (1.5h) and <ratio (10g.L-1); greater extraction of hemicelluloses in: > T (80oC) and <ratio (10g.L-1); higher cellulose content in: T (40oC), > ratio (30g.L-1), and > t (4.5h). Non-mercerized sisal fibers (NMS) were hydrolyzed (1g FLS, 0.5mL enzyme, 50mL citrate buffer, 48h) in the absence and presence of the surfactants rhamnolipid (NMS-R, 60mg L-1 80 mg L-1, 108 mg L-1) and sodium lignosulfonate (NMS-LS, 5.0 g L-1, and 7.5 g L-1). Subsequently, from the results obtained, the mercerization condition 10 gL-1, 40 ° C, 1.5h was selected for pretreatment, and mercerized sisal fibers (MS) were submitted to enzymatic hydrolysis (same conditions of NMS) in the absence or presence of surfactants (rhamnolipid, 80 mg L-1, and lignosulfonate, 5.0 g L-1). Comparing NMS and NMS-R no differences were observed for length and thickness throughout the reaction, whereas for NMS-LS5.0 hydrolysis was favored from the ends and for NMS-LS7.5 from the surface. Unreacted MS fibers showed variations that are more significant in crystallinity, and in length/thickness compared to NMS. Conversion of NMS to glucose led to a yield of 44 ± 5, and the best results in the presence of surfactants were for NMS-R80 (51 ± 3) and NMS-LS5.0 (62.60 ± 0.04). Mercerization significantly increased glucose yield (MS: 94 ± 3), yields using R (MS-R80: 97 ± 6) and LS (SM-LS5: 96 ± 2) were statistically the same as for MS. The results showed that the lignocellulosic fibers present high potential as an alternative source of ethanol. In addition, a cellulosic biomass derivative, a cellulose acetate (CA) with a degree of substitution around 1, was used to obtain membranes composed of submicron fibers and nanofibers, for applications in dye-sensitized solar cells (DSSC). Membranes were also obtained after AC deacetylation (ACD), and both were used as electrolytic membranes in DSSC and compared with reference DSSC (without membranes). AC and ACD membranes have increased the average efficiency of the device by up to 14%. Their presence increased the charge transfer in the counter electrode (evaluated by the ohmic resistance and charge transfer and by the corresponding Helmholtz capacitance). Simultaneously, the photoelectrode did not interfere with the performance measured by the short-circuit current density, open-circuit voltage, fill factor and conversion efficiency. Finally, the stability tests showed that the DSSC AC and ACD showed stability for at least 500 h. For long-term use and/or to serve as a support for other purposes, ACD performs better than AC. The results lead to the prospect that cellulose acetates can be used in the rapid and continuous assembly of DSSC by adding a biobased material to these devices. (AU) | |
| FAPESP's process: | 15/05240-5 - Lignocellulosic fibers: Source of Materials and Fermentable Sugars |
| Grantee: | Joice Jaqueline Kaschuk |
| Support Opportunities: | Scholarships in Brazil - Doctorate |