Primeras etapas de corrosión de metales en agua de mar artificial: I. cobre

El cobre y sus aleaciones son utilizados en estructuras expuestas al agua del mar, donde están sometidos al ataque corrosivo, principalmente debido al alto contenido de iones de cloruro. El objetivo de este trabajo fue estudiar las primeras etapas de corrosión de cobre en agua de mar artificial (conocida como agua del acuario) con la finalidad de descartar la bio-corrosión debida a la incrustación de bio-organismos presentes en el mar (bio-fouling), enfocándose al desarrollo del proceso de corrosión en su ausencia. Muestras planas de Cu electrolítico fueron sumergidas por 1, 2, 3 y 4 meses en el agua del mar. A estos periodos de tiempo fue registrado su potencial de corrosión Ecorr y la pérdida de masa (Vcorr); así mismo, se analizó la morfología (mediante SEM) del ataque corrosivo y la composición (mediante XRD) de los productos de corrosión. Al inicio la fase mayoritaria cristalina fue la cuprita (Cu2O), conocida como patina, una capa protectora del metal, la cual posteriormente se transformó en paratacamita, Cu2(OH)3Cl. La velocidad de corrosión mostró un crecimiento no lineal, alcanzando un valor de 141 g m-2 (0.015 mm) en el cuarto mes siendo 0.21 g m-2 la liberación (runoff) de iones de cobre. Con el tiempo Ecorr tuvo una tendencia hacia valores más negativos, relacionado con las transformaciones en la fase cuprita. Las imágenes de SEM revelaron que con el avance del proceso de corrosión la superficie de cobre mostró una degradación más profunda y no uniforme

Use of agroindustrial waste to obtain cellulose from oil palm bagasse (Elaeis guinnensis)

Obtain cellulose from oil palm agro-industrial waste that meets standard physicochemical characteristics to produce value-added products. Bagasse fibers from the palm agroindustry were used to obtain cellulose, by means of the acid – alkaline hydrolysis methodology. The samples obtained in each stage and the cellulose obtained were characterized by Fourier Transform Infrared Spectroscopy (FTIR) technique and thermogravimetric analysis (TGA). The final characterized product presented a band corresponding to 1370 cm1 characteristic of cellulose. The peak at 1731 cm-1 is related to C=O bonds of unconjugated ketones present in hemicellulose. Major thermal event for treated fiber near to 355 °C, and a high residual mass indicate a good chemical treatment for hemicellulose and lignin elimination. During the process, a fiber yield of 39.3% cellulose was obtained from oil palm bagasse. Obtaining cellulose from a highly polluting residue such as palm bagasse and with high production figures in our state, this makes it a potential for use to generate biopolymers in combination with natural polysaccharides providing sustainable benefits and economic impact promoting sustainable development by replacing conventional fossil plastics. In addition to obtaining value-added products for the same agribusiness and in sectors such as the food industry.Objective: To obtain cellulose from oil palm agroindustrial waste that meets standard physicochemical characteristics to produce value-added products.   Design/methodology/approach: Bagasse fibers from the palm agroindustry were used to obtain cellulose, by means of the acid – alkaline hydrolysis methodology. The samples obtained in each stage and the cellulose obtained were characterized by the Fourier Transform Infrared Spectroscopy (FTIR) technique and thermogravimetric analysis (TGA). Results: The final characterized product presented a band corresponding to 1370 cm1 which is a characteristic value of cellulose. The peak at 1731 cm-1 is related to C=O bonds of unconjugated ketones present in hemicellulose. A major thermal event for treated fiber near 355 °C and the high residual mass indicate a good chemical treatment for hemicellulose and lignin elimination. Study limitations/implications: A fiber yield of 39.3% cellulose was obtained during the process from oil palm bagasse. Findings/conclusions: Obtaining cellulose from a highly polluting residue such as palm bagasse and with high production figures in our state, makes it a potential for use to generate biopolymers in combination with natural polysaccharides, providing sustainable benefits and economic impact and promoting sustainable development by replacing conventional fossil plastics, in addition to obtaining value-added products for the same agribusiness and in sectors such as the food industry

Procurement and characterization of cellulose nanocrystals from cassava bagasse (Manihot esculenta Crantz)

ABSTRACT Objective: Obtaining and characterizing cellulose nanocrystals from cassava bagasse. Design/methodology/approach: Cellulose nanocrystals were obtained from cassava bagasse by acid hydrolysis (HCI), ultrasonication, centrifugation, dialysis, deep freezing and lyophilization. The cassava bagasse and the cellulose nanocrystals obtained were physiochemically characterized by Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy with Coupled Elemental Analysis (SEM-EDS). As an additional technique, Atomic Force Microscopy (AFM) was used. Results: The analyzes performed show that the cellulose obtained was type Iβ. This study reports a percentage of crystallinity of cassava bagasse cellulose of 37.1%, increasing the percentage to 48% of crystallinity in cellulose nanocrystals. The diameters of the cassava bagasse fibers were reported to be 2 μm and their elemental composition (SEM-EDS) mainly constituted by carbon (C), oxygen (O) and traces of (N). The morphology observed through AFM of the nanocrystals of cassava bagasse (Manihot esculenta) was rod-shaped, with a helical appearance without residual charge, with diameters between 8.7 and 9.3 nm. Limitations on study/implications: The acid hydrolysis process showed a low percentage of crystallinity, although higher than other works reported for cassava bagasse. Findings/conclusions: The results obtained show the possibility of obtaining cellulose nanocrystals from cassava bagasse ().    Objective: To procure and characterize cellulose nanocrystals from cassava bagasse. Design/methodology/approach: Cellulose nanocrystals were obtained from cassava bagasse by acid hydrolysis (HCI), ultrasonication, centrifugation, dialysis, deep freezing and lyophilization. The cassava bagasse and the cellulose nanocrystals obtained were physicochemically characterized by Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy with Coupled Elemental Analysis (SEM-EDS). As an additional technique, Atomic Force Microscopy (AFM) was used. Results: The analyses performed show that the cellulose obtained was type Iβ. This study reports a percentage of crystallinity of the cassava bagasse cellulose of 37.1%, increasing the percentage to 48% crystallinity in cellulose nanocrystals. The diameters of the cassava bagasse fibers were reported to be 2 μm and their elemental composition (SEM-EDS) mainly constituted by carbon (C), oxygen (O) and traces of nitrogen (N). The morphology observed through AFM of the nanocrystals of cassava bagasse (Manihot esculenta) was rod-shaped, with helicoidal appearance without residual charge, with diameters between 8.7 and 9.3 nm. Limitations on study/implications: The acid hydrolysis process showed a low percentage of crystallinity, although higher than other works reported for cassava bagasse. Findings/conclusions: The results obtained confirm the possibility of obtaining cellulose nanocrystals from cassava bagasse (Manihot esculenta)

Blanqueo de la fibra de celulosa de paja de caña de azúcar (Saccharum spp.) con peróxido de hidrógeno

Objective: Optimize the treatment of cellulose bleaching, replacing the use of sodium hypochlorite with hydrogen peroxide. Design/methodology/approach: A completely randomized design was used, the treatments were six processes of cellulose bleaching, which were carried out with 18 repetitions. To extract the cellulose, the artisanal method and 40 g of straw were used per treatment. The extraction and yield of cellulose and cellulose fiber, whiteness, crystallinity, granule size, purity of the cellulose and an economic analysis of the cost of the bleaching process were evaluated. Results: The average cellulose fiber extracted was 14 g, meaning that the yield of cellulose fiber was 35%. The average cellulose was 8 g, which represents a yield of 39.9% cellulose. The whiteness with sodium hypochlorite was 86.6 %, with a crystallinity of 65.9% and the cellulose granule size was 2.6 nm, and with hydrogen peroxide whiteness was 83%, the crystallinity was 68 % and the average granule size was 2.7 nm, according to the XRD method. This means similarity in both bleaching process. According to the FTIR analysis, the cellulose bleached in both processes is similar to the cellulose structure. Limitations on study/implications: Cellulose bleaching is more expensive with hydrogen peroxide process. Findings/conclusions: The cellulose extracted from the sugar cane straw, bleached with hydrogen peroxide presents acceptable characteristics to produce artisanal paperObjetivo: Optimizar el tratamiento de blanqueo de celulosa, sustituyendo el uso de hipoclorito de sodio por peróxido de hidrógeno. Diseño/metodología/aproximación: Se utilizó un diseño completamente al azar, donde los tratamientos fueron seis procesos de blanqueo de celulosa, que se realizaron con 18 repeticiones. Para extraer la celulosa se usó el método artesanal y 40 g de paja por tratamiento. Se evaluó la extracción y rendimiento de fibra de celulosa y celulosa, blancura, cristalinidad, tamaño de gránulo, pureza de la celulosa y un análisis económico del costo del proceso de blanqueo. Resultados: El promedio de fibra de celulosa extraída fue de 14 g, esto significa que el rendimiento de fibra de celulosa fue 35 %. El promedio de celulosa fue de 8 g que representa un rendimiento de 39.9 % de celulosa. La blancura con hipoclorito de sodio fue del 86.6%, la cristalinidad de 65.9 % y un tamaño de granulo de celulosa de 2.6 nm, y con peróxido de hidrógeno fue del 83 %, la cristalinidad del 68% y el tamaño de granulo promedio fue 2.7 nm, según el método de XRD, indicando resultados similares. De acuerdo al análisis de FTIR, la celulosa blanqueada en ambos procesos, es similar a la estructura de celulosa reportada en la literatura. Limitaciones del estudio/implicaciones: Se observó un costo más elevado en el blanqueo de la celulosa con el peróxido de hidrógeno. Hallazgos/conclusiones: La celulosa de la paja de caña de azúcar blanqueada con peróxido de hidrógeno presenta características adecuadas para elaborar papel artesanal

An Insight to the Composition of Pre-Hispanic Mayan Funerary Pigments by 1H-NMR Analysis

The funerary rites of particular members of the pre-Hispanic Mayan society included the pigmentation of the corpse with a red color. In order to understand this ritual, it is first necessary to identify the constituents of the pigment mixture and then, based on its properties, analyze the possible form and moment of application. In the present approach, 1H-NMR analysis was carried to detect organic components in the funerary pigments of Xcambó, a small Maya settlement in the Yucatan Peninsula. The comparison of the spectra belonging to the pigment found in the bone remains of seven individuals, and those from natural materials, led to the identification of beeswax and an abietane resin as constituents of the pigment, thus conferring it agglutinant and aromatic properties, respectively. The 1H-NMR analysis also allowed to rule out the presence of copal, a resin found in the pigment cover from paramount chiefs from the Mayan society. Additionally, a protocol for the extraction of the organic fraction from the bone segment without visible signs of analysis was developed, thus broadening the techniques available to investigate these valuable samples

Obtención de celulosa a partir de residuos de piña (Ananas Comosus L. Merril): ISOLATION OF CELLULOSE FROM PINEAPPLE WASTE (Ananas Comosus L.)

Objective: This work explores obtaining high quality cellulose from pineapple residues. Design/methodology/approach: Pineapple crowns were used to obtain the cellulose using the 0.5% acid pre-hydrolysis treatment with sulfuric acid combined with the Sosa-Anthraquinone pulping method (SQ) and elemental chlorine-free bleaching (ECF). The cellulose obtained was characterized by the TAPPI techniques of Fourier Transformed Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy with coupled elemental analyzer (SEM-EDX). Results: It was demonstrated that cellulose-free cellulose was obtained from the chlorination and bleaching stages determined by SEM elemental analysis (EDX) with an alpha (?) cellulose content of 93%, which exhibits the typical crystalline structure of type I cellulose commonly found in the natural plant fibers, Limitations of the study/implications: In the process, a relatively low fiber yield of 29.3% was obtained. Findings/conclusions: Obtaining cellulose from pineapple residues (crowns) is proposed as an alternative of use due to its reinforcement capacity in composite materials, as well as in the production of biomaterials; showing that agricultural residues from pineapple are feasible to obtain cellulose.  Objetivo: Este trabajo explora la obtención de celulosa de alta calidad a partir de residuos de piña.   Diseño/metodología/aproximación: Se utilizaron coronas de piña para la obtención de la celulosa utilizando el tratamiento de pre-hidrólisis ácida al 0.5% con ácido sulfúrico combinado con el método de pulpeo Sosa-Antraquinona (SQ) y blanqueo libre de cloro elemental (ECF).  La celulosa obtenida fue caracterizada por las técnicas TAPPI de Espectroscopia Infrarroja por Transformada de Fourier (FTIR), Difracción de Rayos-X (XRD) y Microscopía Electrónica de Barrido con analizador elemental acoplado (SEM-EDX).   Resultados: Se demostró obtener celulosa libre de residuos de las etapas de cloración y blanqueo determinado mediante el análisis elemental SEM (EDX) con un contenido de alfa (?) celulosa de 93%, que exhibe la estructura cristalina típica de celulosa tipo I encontrada comúnmente en las fibras vegetales naturales.   Limitaciones/implicaciones: En el proceso se obtuvo un rendimiento de fibra del 29.3% relativamente bajo. Hallazgos/conclusiones: La obtención de celulosa a partir de los residuos de piña (coronas), se propone como una alternativa de uso debido a su capacidad de refuerzo en los materiales compuestos, así como en la elaboración de biomateriales; mostrando que los residuos agrícolas procedentes de la piña son factibles para la obtención de celulosa.   &nbsp