Effect of combined sulfuric and hydrochloric acid hydrolysis on the morphology and properties of bacterial cellulose nanocrystals

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1 Effect of combined sulfuric and hydrochloric acid hydrolysis on the morphology and properties of bacterial cellulose nanocrystals PRESENTED BY Morsyleide de Freitas Rosa Researcher Embrapa Tropical Agroindustry

2 Embrapa - Brazilian Agricultural Research Corporation Embrapa Units Brazil

3 Biobased products from agricultural residues and industrial crops Nanocellulose Gelatin Nanofibers Bioadhesive Nanocomposites Lignin Cellulose Hemicellulose Hydrogels Sugars Seafood processing Pectin Biomaterials Fenols Aerogels Starch Gelatin Collagen Chitosan Biogas Bacterial cellulose Hydrogen Waste Compounds New products Ethanol Butanol

4 Nanocellulose cellulosic nanoparticles Top down approach Bottom up approach Mechanically Cellulose nanofibrils Chemically Cellulose nanocrystals Biochemically Bacterial cellulose Width 5 30 nm L/D > 50 (TAPPI, 2013) Width 3 10 nm L/D > 5 (TAPPI, 2013) Dufresne, 2012

5 Bacterial cellulose BC pellicle structure is composed of cellulose nanofibers that form an ultrafine network

6 Bacterial cellulose outstanding material high porosity high water retention capacity high mechanical strength low density biocompatibility non toxicity biodegradability Important applications! LIMITATIONS!

7 Synthetic medium (HS) BC from agroindustrial sources

8 DECONSTRUCTION CHEMICAL PROCESS MECHANICAL PROCESS CHEMICAL/MECHANICAL PROCESS

9 Cellulose nanocrystals - CNC Crystal domains Cellulose fiber Microfibril Adapted Lin et al, 2012 Acid hydrolysis H 2 SO 4 + HCl Amorphous chains High negative surface charge Highly stable colloidal suspension Low thermal stability Stable and thermally resistant CNC Low density surface charges Dispersion is limited High thermal stability

10 MATERIALS AND METHODS Influence of the H 2 SO 4 concentration and reaction time in the BCNC production Experiment H 2 SO 4 sol. (%, w/w) Time (min) Bacterial cellulose (1:100 w/v) 45⁰C / H 2 SO 4 sol. XRD TGA SEM/TEM Zeta potential

11 MATERIALS AND METHODS Effect of HCl addition on the BCNC production Experiment H 2 SO 4 sol. (%, w/w) HCl sol. (%, w/w) Time (min.) ,5 60 Bacterial cellulose (1:100 w/v) 45⁰C / HCl H 2 SO 4 XRD TGA SEM/TEM Zeta potential

12 Zeta potential Exp. H 2 SO 4 sol. (%, w/w) HCl sol. (%, w/w) Time (min.) Zeta potential (mv) ,6 ±1, ,3 ±1, ,6 ±0, , ,9 ±0,8 high negative surface charge density due to the sulphate groups present on the cellulose surface with sulfuric acid; higher [H 2 SO 4 ] and reaction times resulted in an increase in Zeta potential modulus, favouring the stability of the nanocrystals suspension; the combination of acids resulted in good zeta potential. (Lagerwall et al, 2014)

13 TGA HCl/H 2 SO 4 improves the thermal stability of CNC due to a lower surface amount of sulphate groups Exp. H 2 SO 4 sol. (%, w/w) HCl sol. (%, w/w) Time (min.) Zeta potential (mv) Tonset (ºC) ,6 ± 1,5 222, ,3 ±1,1 224, ,6 ±0,7 217, , ,9 ±0,8 263,3

14 XRD All BCNC presented CrI greater than native BC. CI = 79% The increase in crystallinity after the acid hydrolysis reaction is due to the reduction of the amorphous content. Exp. H 2 SO 4 sol. (%, w/w) HCl sol. (%, w/w) Time (min.) Zeta potential (mv) Tonset (ºC) ,6 ± 1,5 222, ,3 ±1,1 224, ,6 ±0,7 217, , ,9 ±0,8 263,3 83 CrI (%)

15 XRD The combination of acids results in lower CrI than the BCNC obtained only with H 2 SO 4. CI = 79% This should be related to the fact that the combination of acids results in mild hydrolysis conditions, generating BCNC with higher amorphous content. Exp. H 2 SO 4 sol. (%, w/w) HCl sol. (%, w/w) Time (min.) Zeta potential (mv) Tonset (ºC) ,6 ± 1,5 222, ,3 ±1,1 224, ,6 ±0,7 217, , ,9 ±0,8 263,3 83 CrI (%)

16 MICROSCOPY TEM micrographs of BCNC H 2 SO 4 and BCNC H 2 SO 4 /HCl showed welldispersed needle shaped structures, an expected pattern for acid hydrolysis nanocrystals. The greatest lengths of BCNC obtained with the combined use of acids may have resulted in crystals with higher amorphous content, which consequently leads to lower crystallinity index. BCNC H 2 SO 4 (CrI = 91%) BCNC H 2 SO 4 /HCl (CrI = 84%) ( ) 622 nm ( ) 34 nm ( / ) 18 ( ) 1322 nm ( ) 44 nm ( / ) 30

17 CONCLUSIONS This work evaluated the use and combination of of inorganic acids to obtain BCNC. The BCNC obtained by the combination of H 2 SO 4 and HCl showed better characteristics than BCNC obtained by only H 2 SO 4. Combined use of acids favoured the production of promising BCNC with high aspect ratio.

18 Deconstruction of bacterial cellulose Blender + CMC (a)blender (30 min) (b)blender (60 min) (c) Blender (30 min) + 0,2% CMC (30 min) (d) Blender (30 min) + 0,5% CMC (30 min)

19 Deconstruction of bacterial cellulose TEMPO + Blender

20 Thank you

21 Vasconcelos NF Thank you Feitosa JPA Andrade FK Alexandre LC Cassales AR Souza Filho MSM MORAIS JPS PRESENTED BY Morsyleide de Freitas Rosa Researcher - Biomass Technology Embrapa Tropical Agroindustry morsyleide.rosa@embrapa.br