RESUMEN
The contamination of water by dyes in high concentrations is a worldwide concern, and it has prompted the development of efficient, economical, and environmentally friendly materials and technologies for water purification. The hydration and adsorption capacity for methylene blue (MB) in biocomposites (BCs) based on cellulose nanofiber (CNF) (0 to 2 wt%) were studied. BCs were synthesized through a simple and straightforward route and characterized by spectroscopy, microscopic techniques and thermogravimetric analysis, among others. Hydration studies showed that BCs prepared with 2 wt% of CNF can absorb large volumes of water, approximately 2274 % in the case of poly 2-acrylamide-2-methyl-1-propanesulfonic acid (PAMPS)-CNF and 2408 % in poly sodium 4-styrene sulfonate (PSSNa)-CNF. These BCs showed outstanding adsorption capacity for highly concentrated MB solutions (4536 mg g-1 PAMPS-CNF and 11,930 mg g-1 PSSNa-CNF). It was confirmed that the adsorption mechanism is through electrostatic interactions. Finally, BCs showed high MB adsorption efficiency after several sorption-desorption cycles and on a simulated textile effluent. Furthermore, the theoretical results showed a preferential interaction between MB and the semiflexible polymer chains at the lowest energy setting. The development and study of a new adsorbent material with high MB removal performance that is easy to prepare, economical and reusable for potential use in water purification treatments was successfully achieved.
Asunto(s)
Nanofibras , Contaminantes Químicos del Agua , Celulosa/química , Colorantes , Azul de Metileno/química , Nanofibras/química , Moléculas de Patrón Molecular Asociado a Patógenos , Contaminantes Químicos del Agua/química , Adsorción , Metilcelulosa , Agua/química , CinéticaRESUMEN
Cellulose nanofibers (CNF) are renewable and biodegradable nanomaterials with attractive barrier, mechanical and surface properties. In this work, three different recombinant enzymes: an endoglucanase, a xylanase and a lytic polysaccharide monooxygenase, were combined to enhance cellulose fibrillation and to produce CNF from sugarcane bagasse (SCB). Prior to the enzymatic catalysis, SCB was chemically pretreated by sodium chlorite and KOH, while defibrillation was accomplished via sonication. We obtained much longer (µm scale length) and more thermostable (resisting up to 260 °C) CNFs as compared to the CNFs prepared by TEMPO-mediated oxidation. Our results showed that a cooperative action of the set of hydrolytic and oxidative enzymes can be used as a "green" treatment prior to the sonication step to produce nanofibrillated cellulose with advanced properties.
Asunto(s)
Celulasa/química , Celulosa/química , Endo-1,4-beta Xilanasas/química , Oxigenasas de Función Mixta/química , Nanofibras/química , Biocatálisis , Biodegradación Ambiental , Cloruros/química , Óxidos N-Cíclicos/química , Tecnología Química Verde , Humanos , Hidrólisis , Hidróxidos/química , Nanofibras/ultraestructura , Oxidación-Reducción , Polisacáridos/química , Compuestos de Potasio/química , Saccharum/química , SonicaciónRESUMEN
Cellulose nanofibers (CNF) can present a high viscosity and thixotropic behavior when dispersed in water. In this work, CNF isolated from sugarcane bagasse and modified by N-oxyl-2,2,6,6-tetramethylpiperidine (TEMPO) oxidation was added to a solution of carboxymethyl cellulose (CMC). This process produced an unexpected viscosity due to a synergistic effect that was observed macroscopically through rheology analysis. The phenomenon known as depletion flocculation was observed, which was caused by the reduction of the excluded volume. The interactions of the system were studied by ultraviolet-visible spectroscopy (UV-Vis), optical microscopy, and cryogenic transmission electron microscopy (cryo-TEM), which demonstrated the presence of the particle/polymer repulsion and subsequent formation of domains composed of aligned micro and nanocellulose particles clusters and nanofibers distributed throughout the sample, forming a percolated 3D structure responsible for a strong gelling and colloidal stability.