Examinando por Materia "CELULOSA BACTERIANA"
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- Artículo de Publicación PeriódicaCarboxymethylated bacterial cellulose: an environmentally friendly adsorbent for lead removal from water(2018-12) Rossi, Ezequiel; Montoya Rojo, Úrsula; Cerrutti, Patricia; Foresti, María Laura; Errea, María Inés"Carboxymethylated bacterial cellulose (CMBC) was synthesized under controlled reaction condition to provide a material with a degree of substitution (DS) that guarantees that the characteristic water insolubility of cellulose is retained (DS = 0.17). The CMBC synthesized was fully characterized by conductometric titration, infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis and solubility assays. The suitability of the produced CMBC for lead removal from water was evaluated. Experimental isotherm data were fitted to different models of sorption isotherms: Langmuir, Freundlich, Dubinin-Radushkevich, and Frumkin, with Langmuir equation resulting in the best fit. Kinetic data were also adjusted to pseudo-first-order and pseudo-second-order models and results undoubtedly showed that the pseudosecond-order kinetic equation was the one that most appropriately described the lead adsorption of CMBC, indicating that lead is adsorbed on CMBC predominantly by chemical interaction. The breakthrough curve was fitted to different models: Bohart-Adams, Clark and Modified Dose-Response, being the Bohart-Adams equation the one that gave the best fit. Desorption studies were carried out in order to know the technical feasibility of the reuse of CMBC. Almost 96% of the retained lead was eluted in just 20 mL, and the CMBC lifetime was over 50 adsorption/desorption cycles. Overall, results obtained suggest that the CMBC herein synthesized may result in an alternative economic and environmentally friendly lead adsorbent for water treatment."
- Artículo de Publicación PeriódicaCompressive behavior of rigid polyurethane foams nanostructured with bacterial nanocellulose at low and intermediate strain rates(2019-05) Chiacchiarelli, Leonel Matías; Cerrutti, Patricia; Flores-Johnson, Emmanuel A."Nanocellulose reinforced foams are lightweight with improved mechanical properties; however, the strain-rate effect on their mechanical response is not yet fully understood. In this work, rigid polyurethane foams (PUFs) nanostructured with bacterial nanocellulose at 0.2 wt % (BNCF) and without it (PUF) are synthesized and subjected to compression tests at different strain rates. The BNC acts as a nucleation agent, reducing the cell size but maintaining a similar apparent density of 40.4 3.3 kg m −3 Both BNCF and PUF exhibit strain-rate effect on yield stress and densification strain. The BNCF exhibits localized progressive crushing and reduced friability, causing a remarkable recovery in the transverse direction. Numerical simulations show that functionally graded foams subjected to impact could be designed using different layers of PUF and BNCF to vary energy absorption and acceleration rate. The results presented herein warrant further research of the mechanical properties of nanostructured foams for impact applications."
- Artículo de Publicación PeriódicaDevelopment of poly(lactic acid) nanocomposites reinforced with hydrophobized bacterial cellulose(2020-01) Ávila Ramírez, Jhon Alejandro; Bovi, Jimena; Bernal, Celina; Foresti, María Laura; Errea, María Inés"Poly(lactic acid)/bacterial cellulose nanocomposites were prepared by solvent casting. Aiming to reduce the incompatibility between polar bacterial cellulose (BC) and the nonpolar poly(lactic acid) (PLA) matrix which induces filler aggregation and poor reinforcement dispersion, BC was acetylated by the use of a non-conventional route catalyzed by citric acid. The derivatized BC (AcBC) was incorporated into de PLA matrix at varying filler loadings, and optical, morphological, structural, thermal, tensile and barrier (water vapor) properties of PLA/AcBC in comparison with PLA/BC were evaluated. Noticeable changes in the nanocomposite properties were ascribed to the success of the route proposed to surface hydrophobize BC, which significantly improved its dispersibility within the PLA matrix and the matrix-filler interaction. By the way, the variation of filler loading allowed attaining remarkable increases in the nanocomposite films stiffness without significant reductions in tensile strength and water vapor permeability."
- Artículo de Publicación PeriódicaIn-situ thermal aging of biobased and conventional rigid polyurethane foams nanostructured with bacterial nanocellulose(2021-11-02) Diaz, Tomás Joaquin; Cerrutti, Patricia; Chiacchiarelli, Leonel Matías"The incorporation of nanofillers and the use of biobased polyols might have a deleterious effect on the aging performance of rigid polyurethane foams (RPUFs) applied in the insulation and marine industries. To study this, RPUFs obtained from petroleum based (RPUF) and castor oil (RPUFRIC) polyols were nanostructured with bacterial nanocellulose (BNC) up to 0.3 wt%. Water immersion experiments revealed that the normalized water absorption (NWA) at the steady state was not affected by lower BNC contents (<0.2 wt%). Higher BNC contents caused a complex effect on post-cure and foaming, generating cell size expansion as well as shrinkage. In-situ DMA aging analysis revealed that the specific storage modulus (E'sp) under flexural conditions of the RPUFRIC and RPUF decreased by a maximum amount of 7.27% and 6.19%, respectively. The effect of BNC on the E'sp was negligible, expect for the case of the RPUF, where higher BNC concentrations (>0.2 wt%) caused a decrease of up to 13.69%. The previous results reinforce the hypothesis that the incorporation of BNC in both conventional and biobased polyurethane systems do not cause significant changes on the aging performance of the resulting foams, provided that low BNC concentrations are employed."
- Artículo de Publicación PeriódicaNanocomposites based on poly(lactic acid) and bacterial cellulose acetylated by an α-hydroxyacid catalyzed route(2019-01) Ávila Ramírez, Jhon Alejandro; Cerrutti, Patricia; Bernal, Celina; Errea, María Inés; Foresti, María Laura"Poly(lactic acid) (PLA) nanocomposite films reinforced with acetylated bacterial cellulose nanoribbons were prepared by solvent casting. Acetylation of bacterial cellulose (BC) was performed by an innovative and sustainable direct solventfree route catalyzed by citric acid. The effect of derivatization and its extent on the morphological, optical, thermal and mechani-cal properties of the nanocomposites was analyzed. Data collected from the above studies showed that acetylation of BC nanoribbons clearly improved the nanofibers dispersion in the PLA matrix with respect to unmodified BC, which in turn resulted in increased transparency and mechanical properties of the nanocomposites produced."
- Artículo de Publicación PeriódicaNanostructured rigid polyurethane foams with improved specific thermo-mechanical properties using bacterial nanocellulose as a hard Segment(2021-01) Chiacchiarelli, Leonel Matías; Benavides, Sara; Armanasco, Franco; Cerrutti, Patricia"Bacterial nanocellulose (BNC) was used to synthesize rigid polyurethane foams (RPUFs) based on its reaction with the isocyanate precursor (ISO route) and also by using the conventional procedure (POL route). The results indicated that at only 0.1 wt. % of BNC, drastic improvements of specific elastic compressive modulus (+244.2 %) and strength (+77.5 %) were found. The reaction of BNC with the precursor was corroborated through the measurement of isocyanate number and the BNC caused a significant nucleation effect, decreasing the cell size up to 39.7%. DSC analysis revealed that the BNC had a strong effect on post-cure enthalpy, decreasing its value when the ISO route was implemented. DMA analysis revealed that the RPUFs developed using the ISO route proved to have an improved damping factor, regardless of BNC concentration. These results emphasize the importance of using the ISO route to achieve foamed nanocomposites with improved specific mechanical properties."
- Artículo de Publicación PeriódicaPreparation of water insoluble carboxymethylated bacterial cellulose with maximum lead retention capacity(2021-06) Montoya Rojo, Úrsula; Rossi, Ezequiel; Cerrutti, Patricia; Errea, María Inés; Foresti, María Laura"Chemical modification of bacterial cellulose (BC) through carboxymethylation was carried out to prepare a low-cost highly stable lead adsorbent material (CMBC). Aiming to maximize its adsorption capacity, the effect of the carboxymethylation extent conferred to BC on the lead retention ability of the insoluble CMBC products obtained was studied. Results evidenced a strong linear correlation between the lead retention capacity of CMBC samples and their degree of substitution, highlight-ing a key role on the biobased adsorbents performance of the amount of negatively charged carboxylate groups available for an ion-exchange-governed lead adsorption process. Proper tuning of the carboxymethylation extent conferred to BC thus allowed maximizing its lead adsorption capacity, reaching values (i.e.127.2 mg g−1) that doubled those previously reported."