RESUMEN
Specific kinds of enzymes have been used as an eco-friendly pre-treatment for mechanical extraction of cellulose nanofibrils (CNFs) from vegetal pulps. Another well-established pre-treatment is the 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-mediated oxidation, which has gained considerable attention. Pre-treatments assist in fiber swelling, facilitating mechanical fibrillation, and reducing energy consumption; however, some of these methods are extremely expensive. This work aimed to evaluate the influence of enzymatic pre-treatment with endoglucanase on the energy consumption during mechanical fibrillation of cellulose pulps. Bleached pulps from Eucalyptus sp. and Pinus sp. were pre-treated with endoglucanase enzyme compared to TEMPO-meditated oxidation. Average diameters of CNFs pre-treated with enzymes were close to that found for TEMPO-oxidized nanofibrils (TOCNFs). Results showed that enzymatic pre-treatment did not significantly modify the pulp chemical and morphological characteristics with efficient stabilization of the CNFs suspension at higher supernatant turbidity. Energy consumption of pulps treated with endoglucanase enzymes was lower than that shown by pulps treated with TEMPO, reaching up to 58% of energy savings. The enzyme studied in the pulp treatment showed high efficiency in reducing energy consumption during mechanical fibrillation and production of films with high mechanical quality, being an eco-friendly option for pulp treatment.
Asunto(s)
Celulasa , Celulosa , Oxidación-Reducción , Compuestos de Sodio , Ácido HipoclorosoRESUMEN
A green approach to produce a cellulose-derived biocatalyst containing hydroxamic acids targeted for the neutralization of toxic organophosphates is shown. The cellulose source, rice husk, is among the largest agricultural waste worldwide and can be strategically functionalized, broadening its sustainable application. Herein, rice husk was oxidized in different degrees, leading to carboxylic acid-based colloidal and solid samples. These were functionalized with hydroxamic acids via amide bonds and fully characterized. The hydroxamic acid derived biocatalysts were evaluated in the cleavage of toxic organophosphates, including the pesticide Paraoxon. Catalytic increments reached up to 107-fold compared to non-catalyzed reactions. Most impressively, the materials showed P atom-selectivity and recyclability features. This guarantees only one reaction pathway that leads to less toxic products, hereby, detoxifies. Overall, highly sustainable catalysts are presented, that benefits from waste source, its green functionalization and is successfully employed for the promotion of chemical security of threatening organophosphates. To the best of our knowledge, this is the first report of a hydroxamate-derived rice husk (selectively modified at the C6 of cellulose) and its application in organophosphates reaction.
Asunto(s)
Oryza , Plaguicidas , Agricultura , Catálisis , CelulosaRESUMEN
Biodegradable aerogels may help to develop eco-friendly technological pathways to increase the efficiency of chemical processes. In the present work, we describe the preparation of a novel bacterial cellulose aerogel oxidized by TEMPO, nanofibrillated in a blender, and silanized with methyltrimethoxysilane, resulting in four different types of aerogel. The aerogels produced from the double-functionalized cellulose suspension (BCOXNS) were compared to other non-oxidized (BCN and BCNS) and non-silanized (BCOXN) aerogels All aerogels were very light (density 10-14 kg.m-3) and very porous (porosity >99 %). The aerogels of BCOXNS showed better mechanical properties (tension of 13.0 kPa, modulus of elasticity of 39.4 kPa) and hydrophobicity, and could absorb organic solvents of different polarities. The BCOXNS could be recycled at least 7 times after absorbing organic solvents while retaining an absorption capacity of 83 %. This material can be used as a standard for the further development of aerogels based on bacterial biopolymers.
Asunto(s)
Bacterias/química , Biopolímeros/química , Celulosa/química , Óxidos N-Cíclicos/química , Geles/química , Solventes/química , Antioxidantes/química , Porosidad , ReciclajeRESUMEN
In present research, Hevea brasiliensis (Rubber Wood) converted into cellulose by pre-treatment with NaOH (5%) and NaClO2 (5%). In addition, the cellulose was converted to nanocellulose (NC) using ionic liquid, acid hydrolysis and TEMPO oxidation accompanied by ultra-sonication. The prepared nanocellulose characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier transformation infrared spectroscopy (FT-IR). Thermal properties have been studied using thermogravimetric and differential thermal Analysis (TGA/DTA). FT-IR results clearly suggested that the synthetic approaches employed did not alter the principle chemical structure of rubber wood cellulose. SEM and AFM monographs reveal that synthetic approaches affect the morphology/surface topology of prepared nanocellulose. Among the three kinds of NC, NC by TEMPO approach had the largest aspect ratio and superior thermal stability.