Metal-Organic Frameworks for Dual Photo-Oxidation and Capture of Arsenic from Water.

Despite rapid technological progress, heavy metal water pollution, particularly arsenic contamination, remains a significant global challenge. The stabilization of trivalent arsenic as neutral arsenite (AsIII) species hinders its removal by conventional adsorption methods. While adsorption of anionic arsenate (AsV) species is in principle more feasible, there are only a few adsorbents capable of adsorbing both forms of arsenic. In this work we study the potential of two well-known families of Metal-Organic Frameworks (MOFs), UiO-66 and MIL-125, to simultaneously adsorb and photo-oxidize arsenic species from water. Our results demonstrate that the formation of AsV ions upon light irradiation promotes the subsequent adsorption of additional AsIII species. Thus, we propose the combined utilization of photocatalysis and adsorption technologies for water remediation purposes.

Degradation of sulfamethoxazole by chlorination in water distribution systems: Kinetics, toxicity, and antibiotic resistance genes.

Sulfamethoxazole (SMX) is one of veterinary drugs and food additives, which has been frequently detected in surface waters in recent years and will cause damage to organisms. Therefore, SMX was selected as a target to be investigated, including the degradation kinetics, evolution of toxicity, and antibiotic resistance genes (ARGs) of SMX during chlorination in batch reactors and water distribution systems (WDS), to determine the optimal factors for removing SMX. In the range of investigated pH (6.3-9.0), the SMX degradation had the fastest rate at close to neutral pH. The chlorination of SMX was affected by the initial total free chlorine concentration, and the degradation of SMX was consistent with second-order kinetics. The rate constants in batch reactors are (2.23 ± 0.07) × 102 M-1  s-1 and (5.04 ± 0.30) × 10 M-1  s-1 for HClO and ClO-1 , respectively. Moreover, the rate constants in WDS are (1.76 ± 0.07) × 102 M-1  s-1 and (4.06 ± 0.62) × 10 M-1  s-1 , respectively. The degradation rate of SMX was also affected by pipe material, and the rate followed the following order: stainless-steel pipe (SS) > ductile iron pipe (DI) > polyethylene pipe (PE). The degradation rate of SMX in the DI increased with increasing flow rate, but the increase was limited. In addition, SMX could increase the toxicity of water initially, yet the toxicity reduced to the level of tap water after 2-h chlorination. And the relative abundance of ARGs (sul1 and sul2) of tap water samples was significantly increased under different chlorination conditions. PRACTITIONER POINTS: The degradation rate of SMX in batch reactor and WDS is different, and they could be described by first- or second-order kinetics. The degradation of SMX had the fastest rate at neutral pH. The degradation rate of SMX was also affected by pipe material and flow velocity. SMX increased the toxicity of water initially, yet the toxicity reduced after a 2-h chlorination. SMX increased the relative abundance of antibiotic resistance genes sul1 and sul2.

A State-of-the-Art of Metal-Organic Frameworks for Chromium Photoreduction vs. Photocatalytic Water Remediation.

Hexavalent chromium (Cr(VI)) is a highly mobile cancerogenic and teratogenic heavy metal ion. Among the varied technologies applied today to address chromium water pollution, photocatalysis offers a rapid reduction of Cr(VI) to the less toxic Cr(III). In contrast to classic photocatalysts, Metal-Organic frameworks (MOFs) are porous semiconductors that can couple the Cr(VI) to Cr(III) photoreduction to the chromium species immobilization. In this minireview, we wish to discuss and analyze the state-of-the-art of MOFs for Cr(VI) detoxification and contextualizing it to the most recent advances and strategies of MOFs for photocatalysis purposes. The minireview has been structured in three sections: (i) a detailed discussion of the specific experimental techniques employed to characterize MOF photocatalysts, (ii) a description and identification of the key characteristics of MOFs for Cr(VI) photoreduction, and (iii) an outlook and perspective section in order to identify future trends.

Copper-Modified Polymeric Membranes for Water Treatment: A Comprehensive Review.

In the last decades, the incorporation of copper in polymeric membranes for water treatment has received greater attention, as an innovative potential solution against biofouling formation on membranes, as well as, by its ability to improve other relevant membrane properties. Copper has attractive characteristics: excellent antimicrobial activity, high natural abundance, low cost and the existence of multiple cost-effective synthesis routes for obtaining copper-based materials with tunable characteristics, which favor their incorporation into polymeric membranes. This study presents a comprehensive analysis of the progress made in the area regarding modified membranes for water treatment when incorporating copper. The notable use of copper materials (metallic and oxide nanoparticles, salts, composites, metal-polymer complexes, coordination polymers) for modifying microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), forward osmosis (FO) and reverse osmosis (RO) membranes have been identified. Antibacterial and anti-fouling effect, hydrophilicity increase, improvements of the water flux, the rejection of compounds capacity and structural membrane parameters and the reduction of concentration polarization phenomena are some outstanding properties that improved. Moreover, the study acknowledges different membrane modification approaches to incorporate copper, such as, the incorporation during the membrane synthesis process (immobilization in polymer and phase inversion) or its surface modification using physical (coating, layer by layer assembly and electrospinning) and chemical (grafting, one-pot chelating, co-deposition and mussel-inspired PDA) surface modification techniques. Thus, the advantages and limitations of these modifications and their methods with insights towards a possible industrial applicability are presented. Furthermore, when copper was incorporated into membrane matrices, the study identified relevant detrimental consequences with potential to be solved, such as formation of defects, pore block, and nanoparticles agglomeration during their fabrication. Among others, the low modification stability, the uncontrolled copper ion releasing or leaching of incorporated copper material are also identified concerns. Thus, this article offers modification strategies that allow an effective copper incorporation on these polymeric membranes and solve these hinders. The article finishes with some claims about scaling up the implementation process, including long-term performance under real conditions, feasibility of production at large scale, and assessment of environmental impact.

Influence of Multidimensional Graphene Oxide (GO) Sheets on Anti-Biofouling and Desalination Performance of Thin-Film Composite Membranes: Effects of GO Lateral Sizes and Oxidation Degree.

The influence of the lateral size and the content of graphene oxide (GO) flakes in specific oxygenate functional groups on the anti-biofouling properties and performance of thin-film composite membrane (TFC) was studied. Three different multidimensional GO samples were prepared with small (500-1200 nm), medium (1200-2300 nm), and large (2300-3600 nm) size distribution, and with different degrees of oxidation (GO3 > GO2 > GO1), varying the concentration of the hydrogen peroxide amount during GO synthesis. GO1 sheets' length have a heterogeneous size distribution containing all size groups, whilst GO2 is contained in a medium-size group, and GO3 is totally contained within a small-size group. Moreover, GO oxygenate groups were controlled. GO2 and GO3 have hydroxyl and epoxy groups at the basal plane of their sheets. Meanwhile, GO1 presented only hydroxyl groups. GO sheets were incorporated into the polyamide (PA) layer of the TFC membrane during the interfacial polymerization reaction. The incorporation of GO1 produced a modified membrane with excellent bactericidal properties and anti-adhesion capacity, as well as superior desalination performance with high water flow (133% as compared with the unmodified membrane). For GO2 and GO3, despite the significant anti-biofouling effect, a detrimental impact on desalination performance was observed. The high content of large sheets in GO2 and small sheet stacking in GO3 produced an unfavorable impact on the water flow. Therefore, the synergistic effect due to the presence of large- and small-sized GO sheets and high content of OH-functional groups (GO1) made it possible to balance the performance of the membrane.

Understanding the Phenomenon of Copper Ions Release from Copper-Modified TFC Membranes: A Mathematical and Experimental Methodology Using Shrinking Core Model.

Type of metal and metal-oxide NPs added to modify Thin-Film Composites Reverse Osmosis Membranes (TFC-RO) can alter their anti-biofouling properties by changing the dissolution process. The development of a mathematical model can facilitate the selection of these NPs. This work consists of a mathematical and experimental methodology to understand copper-based NPs dissolution of three copper species incorporated into TFC-RO membranes: Cu-NPs, CuO-NPs and Cu-Oligomer complexes formed in situ during the polymerization process. Biocidal capacity of copper species into the membrane was evaluated using colony forming unit method (CFU) over E. coli. In addition, copper ion release kinetics for both NPs and modified membranes were determined. A model based on the shrinking core model (SCM) was validated and applied to determine the limiting rate step in the dissolution process and simulate the ion release kinetics. Fitted curves reached a good adjustment with the experimental data, demonstrating the SCM can be applied to predict ion release process for copper-based NPs in suspension and the modified membranes. All membranes reached similar inhibition rate >50%, however, differences in the dissolution level of copper-based NPs in membrane were noted, suggesting a dual-type effect that defined the copper toxicity into the membrane, associated to the dissolution capacity and ROS production.

Chromium Speciation in Zirconium-Based Metal-Organic Frameworks for Environmental Remediation.

Acute CrVI water pollution due to anthropogenic activities is an increasing worldwide concern. The high toxicity and mobility of CrVI makes it necessary to develop dual adsorbent/ion-reductive materials that are able to capture CrVI and transform it efficiently into the less hazardous CrIII . An accurate description of chromium speciation at the adsorbent/ion-reductive matrix is key to assessing whether CrVI is completely reduced to CrIII , or if its incomplete transformation has led to the stabilization of highly reactive, transient CrV species within the material. With this goal in mind, a dual ultraviolet-visible and electron paramagnetic spectroscopy approach has been applied to determine the chromium speciation within zirconium-based metal-organic frameworks (MOFs). Our findings point out that the generation of defects at Zr-MOFs boosts CrVI adsorption, whilst the presence of reductive groups on the organic linkers play a key role in stabilizing it as isolated and/or clustered CrIII ions.

Prevalencia de lesiones bucales en tejido blando encontradas en la Clínica de Estomatología de la Facultad de Odontología de la Universidad de los Andes: periodo 2015-2018 / Prevalence of oral lesions in soft tissue found in the Clinic of Stomatology of the Faculty of Dentistry of the University of los Andes: 2015-2018 period

Introducción: La epidemiología sobre alteraciones en tejidos blandos bucales es limitada cuando se compara con caries, enfermedades periodontales y maloclusiones, por lo que su estudio representa un paso adelante en la odontología más allá de los dientes. Objetivo: Describir la prevalencia de las lesiones bucales en tejido blando encontradas en la Clínica de Estomatología de la Facultad de Odontología de la ULA, del 2015 al 2018, con la finalidad de proporcionar una fuente de datos actualizada, que oriente a una mejor prevención y oportuno diagnóstico. Material y métodos: Se realizó una investigación descriptiva, documental, retrospectiva y multivariable. Resultados: De 1,000 fichas clínicas estudiadas, las patologías más frecuentes fueron: lengua saburral (50.6%), queilitis (33.4%), traumatismo de la mucosa de los carrillos (27.6%), várices linguales (18.3%), anquiloglosia (13.7%) y agrandamiento de rugas palatinas (11.7%). La zona con mayor alteración fue la lengua (92.1%), mientras que el paladar fue la menos afectada (29%). De los hábitos predisponentes a la formación de lesiones, el mordisqueo de mucosa fue el más común (16.5%). En cuanto a los factores locales asociados, una higiene oral regular/ deficiente resultó el principal (53.8%). Conclusión: La educación del paciente sigue siendo considerada la clave para disminuir la aparición de patologías y su evolución a entidades más graves (AU)

Introduction: Epidemiological studies on soft tissue alterations in the mouth are limited when compared with caries, periodontal diseases and malocclusions, so their study represents a step forward in dentistry beyond the teeth. Objective: To describe the prevalence of soft tissue oral lesions found in the Stomatology Clinic of the ULA School of Dentistry, from 2015 to 2018, in order to provide an up-to-date data source, to guide better prevention and timely diagnosis. Material and methods: A descriptive and documentary, retrospective and multivariable research was carried out. The statistical package IBM SPSS Statistics v 23 was applied for the analysis. Results: 1,000 clinical records studied, the most frequent pathologies were: saburral tongue (50.6%), cheilitis (33.4%), traumatism of the cheek mucosa (27.6%), lingual varices (18.3%), ankyloglossia (13.7%) and enlargement of palatal rugas (11.7%). The tongue was the most affected (92.1%), while the palate was the least affected (29%). Of the predisposing habits to the formation of lesions, mucosal nipping was the most common (16.5%). Regarding the associated local factors, a regular / deficient oral hygiene was the main one (53.8%). Conclusion: Patient education is still considered the key to diminish not only the appearance of pathologies but their evolution to more serious entities (AU)

Easy, Quick, and Reproducible Sonochemical Synthesis of CuO Nanoparticles.

Copper oxide nanoparticles (CuO NPs) were synthesized in air by reducing copper (II) sulfate pentahydrate salt (CuSO4·5H2O) in the presence of sodium borohydride. The reaction was stabilized with Hexadecyltrimethylammonium bromide (CTAB) in a basic medium and using ultrasound waves. Different molar ratios of CTAB:Cu2+ and NaBH4:Cu2+ were explored, to optimize the synthesis conditions, and to study the stability, size, and Zeta potential of the colloidal suspension. Optimum conditions to generate spherical, stable, and monodispersed nanoparticles with hydrodynamic diameters of 36 ± 1.3 nm were obtained, using 16 mM CTAB and 2 M NaBH4 (molar ratios Cu2+:CTAB:NaBH4 of 1:6:10). X-ray diffraction (XRD) was implemented, and a monoclinic CuO crystal system was formed. This demonstrated a monoclinic crystal system corresponding to CuO. The diffraction peaks were identified and confirmed according to their selected area electron diffraction (SAED) patterns.

Evaluación de la calidad del agua y su tendencia corrosiva en los morichales Guaricongo y Los Caribes, municipio Heres, Ciudad Bolívar, estado Bolívar, Venezuela / Evaluation of the quality of the water and its corrosive trend in the morichales Guaricongo and Los Caribes, Heres municipality, Ciudad Bolívar, Bolívar state, Venezuela

El presente trabajo consistió en evaluar los niveles de calidad del agua y su tendencia corrosiva en los morichales “Guaricongo” y “Los Caribes”, Municipio Heres, Ciudad Bolívar, estado Bolívar. Se tomaron muestras de agua en cada subcuenca de estudio y en la confluencia de las mismas. Se determinaron parámetros fisicoquímicos (temperatura, pH, oxígeno disuelto, sólidos totales y disueltos, demanda bioquímica de oxígeno, demanda química de oxígeno, dureza total, alcalinidad, calcio, magnesio, nitratos, sulfatos y cloruros), a partir de esta data se calcularon los índices de corrosión e incrustación de Langelier (IL), Potencial de Precipitación (PPCC), Ryznar (IR), Agresividad (IA), Larson (RL), Singley, Capacidad Buffer, Snoeyink. Los resultados indican que las aguas de estos morichales presentaron pH ligeramente ácido, levemente duras indicativos de aguas agresivas con tendencia corrosiva, lo cual fue corroborado a través de los índices de corrosión calculados, clasificando a estas aguas como insaturadas, con preferencia a disolver el CaCO3 indicativo de un carácter corrosivo.

The present work was to evaluate the levels of water quality and its corrosive trend in "morichales" "Guaricongo" and "Caribbean" Heres municipality, Ciudad Bolivar, Bolivar State. Water samples were taken in each subwatershed study and at the confluence of the same. Physicochemical parameters were determined (temperature, pH, dissolved oxygen, total and dissolved solids, biochemical oxygen demand, chemical oxygen demand, total hardness, alkalinity, calcium, magnesium, nitrates, sulfates and chlorides). From this data rates of corrosion and scaling of Langelier (IL), Precipitation Potential (PPCC),m Ryznar (IR), Aggression (IA), Larson (RL), Singley, Buffer Capacity, Snoeyink were calculated. The results indicate that the waters of these "morichales" were slightly acidic and slightly hard water, indicative of an aggressive corrosive tendency, which was corroborated by the corrosion rates calculated by classifying these waters as unsaturated, preferably to dissolve the CaCO3 indicative of a corrosive nature.

Efecto de raciones con harina de follaje de yuca sobre el comportamiento productivo en pollos de engorde. / Effect of Rations With Cassava Leaf Flour on the Productive Performance of Broilers.

Se realizó un ensayo con la finalidad de evaluar el efecto de raciones con harina de follaje de yuca (HFY) sobre el comportamiento productivo en pollos de engorde. Se utilizaron 640 pollos bebes de la línea Cobb distribuidas al azar en 32 corrales, con ocho repeticiones por tratamiento y 20 por corral. Se evaluaron los siguientes tratamientos por un periodo de 42 días: T1 = 0% de HFY, T2 = 2,5% de HFY; T3 = 5% de HFY y T4 = 7,5% HFY. Los parámetros productivos estudiados fueron: ganancia de peso (GP), consumo de alimento (CONA), conversión alimenticia (CA), mortalidad (M) e índice económico relativo (IER). El diseño estadístico empleado fue un totalmente al azar, analizando los datos con procedimiento de varianza por cuadrados mínimos. Las aves que consumieron las raciones correspondiente a T1 y T2 presentaron un comportamiento similar, para GP (2,099 Kg. y 2,090 Kg.) y CA (1,69 y 1,70), pero arrojaron diferencias significativas (P < 0,05) con respecto a T3 y T4 para la variable GP (2,033 Kg. y 2,048 Kg.) y CA (1,74 y 1,74), respectivamente. Sin embargo, CONA no arrojó diferencias significativas entre los tratamientos. Durante el ensayo la mortalidad fue nula. Para IER no se detectó efecto de los tratamientos. Los resultados sugieren que es posible incorporar HFY hasta niveles de 7,5% sin afectar en gran medida los parámetros productivos y permitiendo un ahorro en el costo total de la alimentación, siendo éstos similares al estándar de la producción de pollos de engorde en Venezuela.

A trial was conducted to study the effect of cassava leaf meal (CLM) in diets on the productive performance of broilers. A total of 640 Cobb broilers line were used, distributed at random in 32 poultry-yards with 8 repetitions per treatment and 20 per poultry-yard. The following treatments were evaluated during 42 days: T1 = 0%; T2= 2.5%; T3=5.0%, and T4=7.5% of CLM. The productive parameters studied were: weight gain (WG), food intake (FI), food conversion (FC), mortality (M), and relative economical index (REI). A totally random design was used. The variance. The data was analyzed using SAS with a variance procedure and least means squares method. Broilers that consumed T1 and T2 rations showed similar results for WG (2.099 and 2.090 kg) and FC (1.69 and 1.70), but these treatments were significant different (P<0.05) compared to T3 and T4 for WG (2.033 kg and 2.048 kg) and FC (1.74 and 1.74), respectively. There were no differences between treatments for CF and REI. During the experiment, mortality was null. The results suggest that is possible to use up to 7.5% of CLM in the diets of broilers without affecting productive parameters, allowing a saving in the total feeding cost. These parameters were similar to the broilers production average in Venezuela.

Calidad y corrosión en aguas de las plantas de tratamiento Angostura y Guri del Estado Bolívar, Venezuela / Quality and corrosion in Angostura and Guri water treatment plants at Bolivar state, Venezuela

La presente investigación tuvo como propósito: determinar índices de calidad, caracterizar físicoquímicamente y bacteriológicamente y determinar índices de tendencias corrosivas (Langelier, Ryznar, Puckorius, Saturación y Tasa Singley) en muestras de aguas crudas y tratadas de los ríos Orinoco y Caroní, en las plantas de potabilización Angostura y Guri y de la red de distribución para los sectores: Las Flores, Medina Angarita, Paseo Gaspari, y Negro Primero de Ciudad Bolívar. La investigación fue de corte transversal, descriptivo y analítico. Las diferentes muestras de aguas analizadas presentan pH < 5, otros parámetros fisicoquímicos se encuentran por debajo de los valores de acuerdo a la norma vigente, se detectan coliformes totales en las muestras de aguas y los índices y tasa de corrosión reflejan una alta tendencia corrosiva. Se concluye que los índices de calidad de las aguas crudas son inadecuados. Se recomienda la caracterización fisicoquímica y bacteriológica para estanques de almacenamiento, redes de distribución para sectores residenciales, comerciales e industriales