Preparation of an environmentally friendly lead adsorbent. A contribution to the rational design of heavy metal adsorbents

This work described the preparation and characterization of water insoluble chitosan derivatives as lead adsorbents. In highly regioselective reactions, N-substituted crosslinked chitosan derivatives were obtained by crosslinking native chitosan with mucic and adipic acid (a polyhydroxylated and a non-functionalized diacid of the same length chains). The crosslinking degree of the chitosan modified with adipic acid was significantly higher than that crosslinked with mucic acid (0.446 and 0.316, respectively), while the degree of substitution was almost the same (approximately 80 %). Lead adsorption isotherms were constructed at different temperatures and adjusted to well-known models, obtaining the best fit to the experimental data with Langmuir model. The lead adsorption capacity of new materials was greater than many of the adsorbents described in literature (76.3 and 69.7 mg g−1 for chitosan modified with mucic and adipic acid, respectively). Moreover, thermodynamic parameters were calculated, and results showed that the lead adsorption on the derivatives was spontaneous, exothermic, and governed by chemical interaction. Besides, kinetic studies were performed and adjusted to well-known models. The pseudo-second order kinetic equation was the one that most appropriately described the lead adsorption on the new materials. Results were consistent with the strong electrostatic attraction established between the lead cations and the free carboxylate groups of the derivatives.Fil: Rossi, Ezequiel. Instituto Tecnológico de Buenos Aires. Departamento de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Avila Ramirez, Jhon Alejandro. Instituto Tecnológico de Buenos Aires. Departamento de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Errea, María Inés. Instituto Tecnológico de Buenos Aires. Departamento de Ingeniería Química; Argentin

Carboxymethylated bacterial cellulose: An environmentally friendly adsorbent for lead removal from water

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 pseudo-second-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.Fil: Rossi, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Montoya Rojo, Ursula Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Cerrutti, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; ArgentinaFil: Foresti, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Errea, María Inés. Instituto Tecnológico de Buenos Aires; Argentin

Detection of chlorantraniliprole residues in tomato using field-deployable MIP photonic sensors

A photonic sensor based on inversed opal molecular imprinted polymer (MIP) film to detect the presence of chlorantraniliprole (CHL) residue in tomatoes was developed. Acrylic acid was polymerized in the presence of CHL inside the structure of a colloidal crystal, followed by etching of the colloids and CHL elution. Colloidal crystals and MIP films were characterized by scanning electron microscopy and FT-IR, confirming the inner structure and chemical structure of the material. MIP films supported on polymethylmethacrylate (PMMA) slides were incubated in aqueous solutions of the pesticide and in blended tomato samples. The MIP sensor displayed shifts of the peak wavelength of the reflection spectra in the visible range when incubated in CHL concentrations between 0.5 and 10 μg L−1, while almost no peak displacement was observed for non-imprinted (NIP) films. Whole tomatoes were blended into a liquid and spiked with CHL; the sensor was able to detect CHL residues down to 0.5 μg kg−1, significantly below the tolerance level established by the US Environmental Protection Agency of 1.4 mg kg−1. Stable values were reached after about 30-min incubation in test samples. Control samples (unspiked processed tomatoes) produced peak shifts both in MIP and NIP films; however, this matrix effect did not affect the detection of CHL in the spiked samples. These promising results support the application of photonic MIP sensors as an economical and field-deployable screening tool for the detection of CHL in crops.Fil: Rossi, Ezequiel. Instituto Tecnológico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Salahshoor, Zahra. University of Missouri; Estados UnidosFil: Ho, Khanh Van. University of Missouri; Estados UnidosFil: Lin, Chung Ho. University of Missouri; Estados UnidosFil: Errea, María Inés. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Fidalgo, Maria M.. University of Missouri; Estados Unido

Trielectrode plasma reactor for water treatment

Water pollution due to emerging organic pollutants, such as agrochemicals, has become a topic of growing interest worldwide. The increase of pollutants in aquatic systems stimulated the development of new strategies for water remediation. Plasma technology is an advanced oxidation process which has proved to be an efficient method for organic matter degradation. In this work, a novel design of a trielectrode plasma reactor based on a dielectric barrier discharge extended to a third electrode operated in ambient air is presented. The water to be treated flows through a gutter with low impedance and far from the electrodes connected to the voltage sources. The reactor operates in ambient air, and it does not rely on the use of expensive inert gases. The design of the reactor is easily scalable. The performance of the reactor, in terms of the removal efficiency and the energy yield, was tested in an aqueous solution of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), one of the most widely used around the world. The reactor presents a good efficiency in the removal of the herbicide 2,4-D and values of energy yield of about 240 mg/kW h.Fil: Giuliani, Leandro Estanislao. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: De Angelis, L.. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Díaz Bukvic, Gema. Instituto Tecnológico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zanini, Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Errea, María Inés. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Grondona, Diana Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentin

Polysaccharides as Economic and Sustainable Raw Materials for the Preparation of Adsorbents for Water Treatment

Adsorption processes, due to their technical simplicity and cost-effectiveness, have arisen as one of the most well-known, straightforward solutions to water pollution. In this context, polysaccharides, due to their abundance, biodegradability, and biocompatibility, are appealing raw materials for the design of adsorbents. Moreover, some of them, such as chitosan, can be obtained from organic waste products, and their use additionally contributes to solving another concerning problem: organic waste accumulation. Unfortunately, due to their low adsorption capacities and/or physicochemical properties, native polysaccharides are not suitable for this purpose. However, there are alternatives that can overcome these physical or chemical limitations, often taking advantage of the versatility of their polyhydroxylated structure. In this context, this review aims to present an overview of the advances from 2019 onwards in the design of new adsorbents for water treatment from cellulose, alginate, chitosan, and starch, addressing the two main strategies reported in the literature: the preparation of either polysaccharide-based composites or polysaccharide derivatives. It is important to point out that, herein, special emphasis is placed on the relationship between the chemical structure and the efficiency as adsorbents of the analyzed materials, in an attempt to contribute to the rational design of adsorbents obtained from polysaccharides

Synthesis of imidazo[2,1-b]thiazoles linked to an unprotected carbohydrate moiety

Two series of imidazo[2,1-b]thiazoles substituted on C-3 or C-5 with an unprotected carbohydrate moiety were synthesized. Different protective groups for position 3 of the carbohydrate moiety were tested (acetyl, tert-butyldimethylsilyl (TBDMS), and p-methoxybenzyl (PMB)) and the latter turn out to be the best strategy to obtain the desired products. Full deprotection of the carbohydrate was performed successfully in only one step.Fil: Barradas, Jose Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Errea, María Inés. Instituto Tecnológico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: D'accorso, Norma Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentin

Imidazothiazole and related heterocyclic systems. Synthesis, chemical and biological properties

Fused heterobicyclic systems have gained much importance in the field of medicinal chemistry because of their broad spectrum of physiological activities. Among the heterocyclic rings containing bridgehead nitrogen atom, imidazothiazoles derivatives are especially attractive because of their different biological activities. Since many imidazothiazoles derivatives are effective for treating several diseases, is interesting to analyze the behavior of some isosteric related heterocycles, such as pirrolothiazoles, imidazothiadiazoles and imidazotriazoles. In this context, this review summarizes the current knowledge about the syntheses and biological behavior of these families of heterocycles. Traditional synthetic methodologies as well as alternative synthetic procedures are described. Among these last methodologies, the use of multicomponent reaction, novel and efficient coupling reagents, and environmental friendly strategies, like microwave assistance and solvent-free condition in ionic liquids are also summarized. This review includes the biological assessments, docking research and studies of mechanism of action performed in order to obtain the compounds leading to the development of new drugs.Fil: Fascio, Mirta Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Errea, María Inés. Instituto Tecnológico de Buenos Aires. Departamento de Ingeniería Química; ArgentinaFil: D'accorso, Norma Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentin

Hidrofobización organocatalítica de nanofibras y nanocristales de celulosa para aplicaciones en materiales compuestos biodegradables

La nanocelulosa bacteriana (BNC) por sus excelentes propiedades mecánicas, alta relación superficie/volumen, biodegradabilidad y pureza, resulta de interés para aplicaciones como refuerzo de matrices poliméricas. Sin embargo, la hidrofilicidad de las nanofibras de celulosa limita su uso como refuerzo de matrices hidrofóbicas, como, por ejemplo, el ácido poliláctico (PLA). Con el objetivo de mejorar la compatibilidad entre el refuerzo y la matriz y promover la adecuada dispersión de las nanofibras en el PLA, se estudió la esterificación de la superficie de las nanofibras de celulosa bacteriana implementando una ruta no convencional catalizada por α- hidroxiácidos (ácidos láctico, tartárico y cítrico) de origen natural. Como acilante se utilizó anhídrido acético y se operó sin cosolventes agregados. La obtención de la BNC se llevó a cabo en cultivo estático usando una cepa de Gluconacetobacter xylinus y desechos agroindustriales como fuente de carbono. Se estudió la influencia del tipo de catalizador, el tiempo de reacción, la carga de catalizador y la temperatura de reacción sobre el grado de sustitución (GS) de la BNC, obteniéndose BNC con GS comprendidos entre 0.27 y 0.90. La mayor actividad catalítica se registró usando ácido cítrico. Debido a que se observó una ligera pérdida de cristalinidad en las muestras con DS superior a 0.75, se modificaron las condiciones de reacción a efectos de limitar el GS al rango de 0.20 y 0.73. Se evaluó, también, la posibilidad de reutilizar el catalizador. Los resultados obtenidos estimularon la extensión de la ruta de acetilación a nanocristales de celulosa vegetal (CNC). Variando la carga de catalizador, se obtuvieron CNC con GS entre 0.18 y 0.34. Los materiales se caracterizaron por FTIR y RMN13C CP/MAS. Se confirmó, además, que la acetilación no afectó la morfología (SEM) ni la cristalinidad (DRX) aunque se evidenció una leve disminución de la estabilidad térmica (TGA) de los materiales acetilados.Due to its excellent mechanical properties, high surface/volume ratio, biodegradability and purity, bacterial nanocellulose (BNC) deserves great interest as reinforcement of polymeric matrices. However,the hydrophilicity of BNC limits its use as reinforcement of hydrophobic matrices, such as for example polylactic acid (PLA). Aiming to improve the compatibility between BNC and polymeric matrices such as PLA and thus promote a proper dispersion of cellulose nanofibers, in the current contribution surface esterification of BNC was studied by use of a non-conventional route catalyzed by naturally occurring α-hydroxy acids (acids lactic, tartaric and citric). Acetic anhydride was used as acylant and the reaction was performed without additional solvents. BNC was obtained in static culture using a strain of Gluconacetobacter xylinus and using agroindustrial byproducts as a carbon source. The influence of the type of catalyst, reaction time, catalyst load and the reaction temperature on the degree of substitution (DS) conferred to BNC were studied, leading to products with DS between 0.27 and 0.90.The highest catalytic activity was recorded using citric acid. Since there was a slight loss of crystallinity in the samples with DS greater than 0.75, reaction conditions were tuned in order to keep the DS in the 0.20-0.73 interval. The possibility of reusing the catalyst was also evaluated. The results obtained triggered the evaluation of the acetylation route on cellulose nanocrystals (CNC) isolated from vegetable sources. By varying the catalyst load, CNC with DS between 0.18 and 0.34were obtained.The materials were characterized by FTIR and 13CNMR CP/MAS to confirm derivatization. Data showed that the acetylation did not affect the morphology (SEM) nor the crystallinity (XRD) of CNC, although a slight decrease in the thermal stability (TGA) of the acetylated materials was evidenced.Fil: Avila Ramirez, Jhon Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Cerrutti, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; ArgentinaFil: Errea, María Inés. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Foresti, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentin

Selective determination of Cr (VI) by on-line solid phase extraction FI-SPE-FAAS using an ion exchanger resin as sorbent: An improvement treatment of the analytical signal

A flow injection (FI) technique based on an on-line solid phase extraction (SPE) coupled with flame atomic absorption spectroscopy (FAAS) to selectively quantify chromium (VI) in the presence of chromium (III) was developed. An anion exchanger was used as solid sorbent and the detection limit found was two order of magnitude lower than that expected quantifying by FAAS. Until now, quantitative determinations in FAAS were carried out by measuring the height of the peaks rather than their area. In our hands, the software was reconfigured and the area under the peaks could be measured. Considering area instead of height, the enhancement factor increases from 6.7 to 360 (approx. 54 times) giving a detection limit of 0.034 μg·L− 1, lower than that obtained using much more expensive instruments such as electrothermal atomic absorption spectrometry (ETAAS) or inductively coupled plasma-atomic emission spectrometry (IPC-AES), greatly enhancing the potential of this methodology for future use in speciation studies. The operation conditions were: pH 3, sample loading 50 mL·min− 1, elution flow rate 7.5 mL·min− 1. The anion exchanger lifetime was over 100 adsorption/desorption cycles. Anions commonly present in natural aqueous systems did not interfere in the chromium retention. The accuracy was validated using a certified reference material (Fluka Analytical, QC3453).Fil: Rossi, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; ArgentinaFil: Errea, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; ArgentinaFil: de Cortalezzi, María Marta Fidalgo. University of Missouri; Estados UnidosFil: Stripeikis, Jorge Daniel. Instituto Tecnológico de Buenos Aires; Argentin