Role of waste-based geopolymer spheres addition for pH control and efficiency enhancement of anaerobic digestion process.

In anaerobic digestion processes, pH has a vital role due to the direct impacts on the microbial community. An eco-friendly approach has been applied to control pH in anaerobic bioreactors, using waste-containing fly ash geopolymer spheres (GS) instead of powdered chemical compounds, to promote continuous alkalis leaching. The influence of GS porosity and concentration on the behavior of anaerobic sequential batch reactor treating cheese whey was evaluated. Results showed that the use of GS with the highest concentration and porosity promoted an increase in methane yield up to 30%, compared to the assay with powdered chemical compounds addition. In addition, GS boosted butyric acid production to the detriment of propionic acid, which favored methane production by a factor up to 1.2. This innovative approach indicates that GS addition can regulate pH in anaerobic digesters treating challenging wastewaters and, simultaneously, improve not only its efficiency but also the sustainability of the entire process.

Highly efficient lead extraction from aqueous solutions using inorganic polymer foams derived from biomass fly ash and metakaolin.

This work reports a simple and safe, but powerful, route to depollute lead-containing aqueous solutions. Inorganic polymer foams (cm-size) were used as bulk-type adsorbents. The influence of the specimens' porosity and activator molarity on the foams' physical properties and on their lead extraction ability was studied. Then, the best performing samples were deeply evaluated as lead adsorbents by studying the impact of pH, lead concentration, contact time, ionic strength and solution volume. Lead sorption kinetics is strongly affected by the pollutant concentration, pH and the solution ionic strength. Under the most favourable conditions the foams showed an impressive removal capacity (105.9 mg/g at pH 5, 23 °C, C0 = 800 ppm, deionised water), surpassing all other reported values on the use of bulk-type inorganic polymers. The foams' lead uptake is 2.3 times higher than the previous best performing bulk-type specimens (mm-size spheres), and sorption is 12.5-15 times faster. The foams can be easily regenerated using mild acidic conditions, and then reused as adsorbent, suggesting that the main adsorption mechanism is ion exchange.

Effective acid mine drainage remediation in fixed bed column using porous red mud/fly ash-containing geopolymer spheres.

Acid mine drainage (AMD) poses a significant threat to water quality worldwide, being amongst the most problematic environmental concerns of the millennium. This work reports for the first time the remediation of real AMD, from a Portuguese abandoned mine, in fixed bed column using porous red mud/fly ash-based geopolymeric spheres. Porous waste-based spheres (2.6 ± 0.2 mm) were obtained by a suspension-solidification method through the addition of optimum foaming agent dosage. The sorbent capacity in removing cations from AMD was evaluated by targeting selected hazardous elements: Zn, Cu, Co, Pb and Ni, based on their occurrence in the effluent and potential hazard. The spheres exhibited a dual mechanism of action, simultaneously neutralizing the acidic sample while removing cations through adsorption achieving removal efficiencies between 51 % and 80 %. Other elements present in high levels, such as iron were efficiently removed (>96 %). The role of precipitation, due to the pH neutralization, and adsorption was determined. The sorbent regeneration and reusability were evaluated for up to five cycles. Moreover, the effectiveness of waste-based geopolymers treating distinct AMD waters due to seasonal variations was also evaluated, further demonstrating the effectiveness of the proposed strategy to address environmental concerns stemming from mining activities.

Ultra-light-weight microwave X-band EMI shielding or RAM material made from sustainable pyrolysed cork templates.

Cork is a renewable and sustainable material, highly porous and lightweight. We valorised waste cork and recycled wine stoppers to make pyrolysed/carbonised solid cork, for use as economic and sustainable microwave (MW) absorbers at the microwave X-band (8-12 GHz), without binder or additives. Although cork is already a very lightweight material (0.16 g cm-3), the pyrolysed cork is five-times less dense at 0.031 g cm-3, was amorphous graphitic carbon, and had an excellent shielding effectiveness (SET) of -18 to -38 dB, depending on thickness, with attenuation of the electromagnetic energy through internal reflection within the cellular cork structure. Furthermore, this ultra-light-weight material has an extremely high MW specific shielding effectiveness or efficiency (SSE), between -640 to -1235 dB g-1 cm3 over the entire X-band range, depending on thickness (3.0-8.6 mm), one of the highest reported for any pure carbon material, this upper value being more than twice that of any previously reported graphite-based foams.

Evaluation of the Nature and Concentration of the Surfactant on the Properties of Red Mud/Metakaolin Porous Geopolymers Foamed with Aluminium.

The chemical foaming technique is possibly the most common method of producing porous geopolymers. Despite this, to date, the role of the content and type of surfactant on the pore size distribution of porous geopolymers is not fully perceived, as constant surfactant dosages are usually employed. In addition, the comparison of literature studies is challenging since a distinct mixture of designs is employed. This investigation intends to provide additional insights on the topic, focusing on synthesizing red mud/metakaolin geopolymer foams and envisioning their use in thermal insulating applications. Various mixtures were prepared using three commercially available surfactants, namely Hostapur OSB, sodium dodecyl sulfate (SDS), and Triton X114. The content of the surfactant (0.025, 0.05, and 0.075 wt.%) and the amount of the foaming agent (aluminum powder, Al; 0.05, 0.075, and 0.10 wt.%) was modified, keeping the binder composition constant and the physical properties of the produced geopolymers were characterized. Results show that the combination between sodium dodecyl sulfate (0.025 wt.%) and aluminum (0.10 wt.%) leads to the strongest reduction in the foam density, the lowest value here reported being -400 kg/m3. On the other hand, samples produced with Hostapur OSB have much higher open porosity (up to 47.7%) and water absorption (up to 80.4%) values, showing that this surfactant leads to a pore network with higher connectivity. In addition, the microstructure of the foams, particularly pore morphology (size and shape) and connectivity between the produced pores are highly dependent on the type of surfactant, sodium dodecyl sulfate generating coarser pore size distribution with round, but mostly closed pores, while a narrower pore size distribution coupled with smaller size pores is seen with the Hostapur. These results suggest the feasibility of tuning the foams' properties (porosity and mechanical performance) according to the application by the proper combination of the type of surfactant and their concentration, enabling their use as thermal and acoustic insulators or as filters/membranes in wastewater treatment systems.

Effects of the COVID-19 pandemic on nurses' psychological well being in an emergency room.

OBJECTIVES: to assess the level of anxiety of nurses in an emergency room in view of the new Coronavirus and describe the relationship between the degrees of anxiety and their sociodemographic variables. METHODS: quantitative descriptive-correlational study with a sample of 60 nurses. A questionnaire was used as a data collection instrument based on the Hamilton Anxiety Assessment Scale. RESULTS: the nurses' average anxiety is mild. A statistically significant relationship was found between anxiety and the variables "sex" and "children", with women having higher levels of anxiety than men, and nurses who do not have children showing mild, moderate, or severe anxiety. CONCLUSIONS: COVID-19 triggers anxiety in nurses, sometimes at pathological levels. Being female and not having children increase the anxiety experienced. Sex can be considered the determining factor for the level of anxiety experienced.

Unravelling the Affinity of Alkali-Activated Fly Ash Cubic Foams towards Heavy Metals Sorption.

In this work, alkali-activated fly ash-derived foams were produced at room temperature by direct foaming using aluminum powder. The 1 cm3 foams (cubes) were then evaluated as adsorbents to extract heavy metals from aqueous solutions. The foams' selectivity towards lead, cadmium, zinc, and copper ions was evaluated in single, binary, and multicomponent ionic solutions. In the single ion assays, the foams showed much higher affinity towards lead, compared to the other heavy metals; at 10 ppm, the removal efficiency reached 91.9% for lead, 83.2% for cadmium, 74.6% for copper, and 64.6% for zinc. The greater selectivity for lead was also seen in the binary tests. The results showed that the presence of zinc is detrimental to cadmium and copper sorption, while for lead it mainly affects the sorption rate, but not the ultimate removal efficiency. In the multicomponent assays, the removal efficiency for all the heavy metals was lower than the values seen in the single ion tests. However, the superior affinity for lead was preserved. This study decreases the existing knowledge gap regarding the potential of alkali-activated materials to act as heavy metals adsorbents under different scenarios.

Unzipping of functionalized multiwall carbon nanotubes induced by STM.

Carbon nanotubes (CNTs), functionalized by a cycloaddition reaction, were studied by ultrahigh vacuum scanning tunneling microscopy (STM). The STM images provided evidence for partial or total unzipping of the outer CNT layer. The formation of graphene ribbons was triggered by the STM tip, under specific operating conditions. A model for the unzipping is proposed, based on the perturbation of the pi-conjugation along the CNT surface induced by the cycloaddition reaction.

Waste-Based One-Part Alkali Activated Materials.

Ordinary Portland Cement is the most widely used binder in the construction sector; however, a very high carbon footprint is associated with its production process. Consequently, more sustainable alternative construction materials are being investigated, namely, one-part alkali activated materials (AAMs). In this work, waste-based one-part AAMs binders were developed using only a blast furnace slag, as the solid precursor, and sodium metasilicate, as the solid activator. For the first time, mortars in which the commercial sand was replaced by two exhausted sands from biomass boilers (CA and CT) were developed. Firstly, the characterization of the slag and sands (aggregates) was performed. After, the AAMs fresh and hardened state properties were evaluated, being the characterization complemented by FTIR and microstructural analysis. The binder and the mortars prepared with commercial sand presented high compressive strength values after 28 days of curing-56 MPa and 79 MPa, respectively. The mortars developed with exhausted sands exhibit outstanding compressive strength values, 86 and 70 MPa for CT and CA, respectively, and the other material's properties were not affected. Consequently, this work proved that high compressive strength waste-based one-part AAMs mortars can be produced and that it is feasible to use another waste as aggregate in the mortar's formulations: the exhausted sands from biomass boilers.

Red mud-based inorganic polymer spheres: Innovative and environmentally friendly anaerobic digestion enhancers.

Red mud-based inorganic polymer spheres were used as alternative pH regulators and process enhancers in sequencing batch anaerobic reactors treating cheese whey. This byproduct tends to quickly acidify under anaerobic conditions, and the common route to control pH and ensure suitable conditions for methane production involves the use of commercial alkaline raw materials. The spheres were synthesized using significant amounts of hazardous and toxic waste, red mud (50 wt% of solid components), whose recycling is challenging. The inorganic polymeric spheres, when compared to virgin alkaline raw materials, improved organic matter removal by 44%, prevented VFA accumulation (acidification degree less than 20%), maintained pH values in a range (6.5-7.2) to ensure maximum methanogenic activity by archaea microorganisms, and boosted the methane volume by ~90%. These promising results demonstrate the feasibility and performance advantages of using these innovative spheres instead of virgin raw materials, which is an important tool towards sustainable development.

A Review of Solar Thermochemical CO2 Splitting Using Ceria-Based Ceramics With Designed Morphologies and Microstructures.

This review explores the advances in the synthesis of ceria materials with specific morphologies or porous macro- and microstructures for the solar-driven production of carbon monoxide (CO) from carbon dioxide (CO2). As the demand for renewable energy and fuels continues to grow, there is a great deal of interest in solar thermochemical fuel production (STFP), with the use of concentrated solar light to power the splitting of carbon dioxide. This can be achieved in a two-step cycle, involving the reduction of CeO2 at high temperatures, followed by oxidation at lower temperatures with CO2, splitting it to produce CO, driven by concentrated solar radiation obtained with concentrating solar technologies (CST) to provide the high reaction temperatures of typically up to 1,500°C. Since cerium oxide was first explored as a solar-driven redox material in 2006, and to specifically split CO2 in 2010, there has been an increasing interest in this material. The solar-to-fuel conversion efficiency is influenced by the material composition itself, but also by the material morphology that mostly determines the available surface area for solid/gas reactions (the material oxidation mechanism is mainly governed by surface reaction). The diffusion length and specific surface area affect, respectively, the reduction and oxidation steps. They both depend on the reactive material morphology that also substantially affects the reaction kinetics and heat and mass transport in the material. Accordingly, the main relevant options for materials shaping are summarized. We explore the effects of microstructure and porosity, and the exploitation of designed structures such as fibers, 3-DOM (three-dimensionally ordered macroporous) materials, reticulated and replicated foams, and the new area of biomimetic/biomorphous porous ceria redox materials produced from natural and sustainable templates such as wood or cork, also known as ecoceramics.

O impacto do isolamento devido à COVID-19 em estudantes de enfermagem / The impact of isolation due to COVID-19 on nursing students / El impacto del aislamiento por COVID-19 en estudiantes de enfermería

Resumo Enquadramento: A pandemia de COVID-19 exigiu a implementação de medidas de isolamento nos casos de alto risco de doença. Objetivo: Avaliar o impacto do isolamento sobre a ansiedade, a satisfação com o apoio percebido, a aprendizagem e o aproveitamento escolar, de estudantes de enfermagem da região norte de Portugal. Metodologia: Estudo exploratório e quantitativo, realizado com 56 estudantes em isolamento devido à COVID-19. Foi aplicado um questionário de autopreenchimento para avaliação da evolução da ansiedade, da satisfação com o apoio percebido, ao nível pedagógico, emocional e do Serviço Nacional de Saúde e do impacto do isolamento na aprendizagem e aproveitamento escolar. Resultados: Foram reportados níveis de ansiedade com significado clínico. Foi referido maior satisfação com o apoio da instituição de ensino e menor com o Serviço Nacional de Saúde. A ausência às atividades letivas teve impacto negativo na aprendizagem e no aproveitamento escolar. Conclusão: O isolamento dos estudantes teve impacto na ansiedade e na aprendizagem. A saúde mental dos estudantes deve ser promovida pelas instituições de ensino superior.

Abstract Background: The COVID-19 pandemic demanded isolation measures in cases of high disease risk. Objective: To assess the impact of isolation on the anxiety, satisfaction with perceived support, learning and academic achievement of nursing students in the northern region of Portugal. Methodology: This exploratory and quantitative study was conducted with 56 students in isolation due to COVID-19. A self-completion questionnaire was applied to assess the evolution of the anxiety, the satisfaction with the perceived support at the pedagogical and emotional levels and from the Serviço Nacional de Saúde (SNS - National Health Service), and the impact of isolation on learning and academic achievement. Results: This study observed clinically significant levels of anxiety. The participants expressed greater satisfaction with the support received from the educational institution and less satisfaction with the SNS. The absence from school activities negatively impacted their learning and academic achievement. Conclusion: Student isolation impacted anxiety and learning. Higher education institutions must promote students' mental health.

Resumen Marco contextual: La pandemia de COVID-19 requirió la aplicación de medidas de aislamiento en casos de alto riesgo de enfermedad. Objetivo: Evaluar el impacto del aislamiento en la ansiedad, la satisfacción con el apoyo recibido, el aprendizaje y el rendimiento académico entre los estudiantes de enfermería de la región norte de Portugal. Metodología: Estudio exploratorio y cuantitativo, realizado con 56 estudiantes en aislamiento por COVID-19. Se utilizó un cuestionario de autocumplimentación para evaluar la evolución de la ansiedad, la satisfacción con el apoyo recibido a nivel educativo, emocional y del Sistema Nacional de Salud, y el impacto del aislamiento en el aprendizaje y el rendimiento académico. Resultados: Se notificaron niveles de ansiedad con significancia clínica. Se registró una mayor satisfacción con el apoyo de la institución educativa y una menor satisfacción con el Servicio Nacional de Salud. El absentismo escolar tuvo un impacto negativo en el aprendizaje y el rendimiento académico. Conclusión: El aislamiento de los estudiantes repercutió en la ansiedad y el aprendizaje. Los centros de enseñanza superior deben promover la salud mental de los estudiantes.

Innovative application for bauxite residue: Red mud-based inorganic polymer spheres as pH regulators.

In this study, and for the first time, red mud (RM)-based geopolymer spheres were synthesised, with varying porosity and RM content, and then their use as pH regulators was evaluated. The aluminosilicate sources of these inorganic polymers were 100% waste-based, consisting of a mixture of RM and fly ash wastes. Geopolymer spheres containing up to 60 wt.% RM were successfully produced, while higher RM contents distorted the specimens' spherical shape. Results showed that alkalis leaching from the spheres over time can be controlled by their porosity, while the RM content induces only minor changes to leaching. The RM-based spheres leached up to 0.0237 mol/dm3g of OH- ions from their structure, this being among the highest values ever reported for geopolymers. This allowed a continuous and prolonged pH buffer capacity with narrow pH decay over the 28 days (2.4 pH units), suggesting the use of the RM-based spheres as pH buffering materials in wastewater treatment and anaerobic digestion systems.

Effects of the COVID-19 pandemic on nurses' psychological well being in an emergency room / Efeitos da pandemia de COVID-19 no bem-estar psicológico dos enfermeiros de um serviço de urgência / Efectos de la pandemia de COVID-19 en el bienestar psicológico de los enfermeros de un servicio de urgencia

ABSTRACT Objectives: to assess the level of anxiety of nurses in an emergency room in view of the new Coronavirus and describe the relationship between the degrees of anxiety and their sociodemographic variables. Methods: quantitative descriptive-correlational study with a sample of 60 nurses. A questionnaire was used as a data collection instrument based on the Hamilton Anxiety Assessment Scale. Results: the nurses' average anxiety is mild. A statistically significant relationship was found between anxiety and the variables "sex" and "children", with women having higher levels of anxiety than men, and nurses who do not have children showing mild, moderate, or severe anxiety. Conclusions: COVID-19 triggers anxiety in nurses, sometimes at pathological levels. Being female and not having children increase the anxiety experienced. Sex can be considered the determining factor for the level of anxiety experienced.

RESUMO Objetivos: avaliar o nível de ansiedade dos enfermeiros de um serviço de urgência em face do novo coronavírus e descrever a relação entre os níveis de ansiedade e as variáveis sociodemográficas. Métodos: estudo quantitativo descritivo-correlacional com uma amostra de 60 enfermeiros. Recorreu-se à aplicação de um questionário como instrumento de coleta de dados baseando-se na Escala de Avaliação de Ansiedade de Hamilton. Resultados: o escore médio de ansiedade dos enfermeiros é leve. Verificou-se que existe uma relação estatisticamente significante entre a ansiedade e a variável "sexo" e "filhos", com as mulheres apresentando níveis de ansiedade superiores aos homens e os enfermeiros sem filhos apresentando níveis de ansiedade leve, moderada ou severa. Conclusões: a COVID-19 desencadeia ansiedade nos enfermeiros, por vezes a níveis patológicos; e ser do sexo feminino e não ter filhos a aumenta. É possível afirmar que o sexo foi o fator determinante para o nível de ansiedade experimentado.

RESUMEN Objetivos: evaluar nivel de ansiedad de enfermeros de un servicio de urgencia frente al nuevo coronavirus y describir la relación entre niveles de ansiedad y variables sociodemográficas. Métodos: estudio cuantitativo descriptivo-correlacional con una muestra de 60 enfermeros. Recorrido a la aplicación de una encuesta como instrumento de recolecta de datos basándose en la Escala de Evaluación de Ansiedad de Hamilton. Resultados: el escore mediano de ansiedad de los enfermeros es leve. Verificado que hay una relación estadísticamente significante entre la ansiedad y la variable "sexo" e "hijos", con mujeres presentando niveles de ansiedad superiores a los hombres y los enfermeros sin hijos presentando niveles de ansiedad leve, moderada o severa. Conclusiones: la COVID-19 desencadena ansiedad en los enfermeros, por veces a niveles patológicos; y ser del sexo femenino y no tener hijos la aumenta. Es posible afirmar que el sexo fue el factor determinante para el nivel de ansiedad experimentado.

Waste glass from end-of-life fluorescent lamps as raw material in geopolymers.

Nowadays the stunning volume of generated wastes, the exhaustion of raw materials, and the disturbing greenhouse gases emission levels show that a paradigm shift is mandatory. In this context, the possibility of using wastes instead of virgin raw materials can mitigate the environmental problems related to wastes, while reducing the consumption of the Earth's natural resources. This innovative work reports the incorporation of unexplored waste glass coming from end-of-life fluorescent lamps into geopolymers. The influence of the waste glass incorporation level, NaOH molarity and curing conditions on the microstructure, physical and mechanical properties of the geopolymers was evaluated. Results demonstrate that curing conditions are the most influential factor on the geopolymer characteristics, while the NaOH molarity is less important. Geopolymers containing 37.5% (wt) waste glass were successfully produced, showing compressive strength of 14MPa (after 28days of curing), suggesting the possibility of their use in non-structural applications. Porous waste-based geopolymers for novel applications were also fabricated.

Novel porous fly-ash containing geopolymer monoliths for lead adsorption from wastewaters.

In this study novel porous biomass fly ash-containing geopolymer monoliths were produced using a simple and flexible procedure. Geopolymers exhibiting distinct total porosities (ranging from 41.0 to 78.4%) and low apparent density (between 1.21 and 0.44g/cm(3)) were fabricated. Afterwards, the possibility of using these innovative materials as lead adsorbents under distinct conditions was evaluated. Results demonstrate that the geopolymers' porosity and the pH of the ion solution strongly affect the lead adsorption capacity. Lead adsorption by the geopolymer monoliths ranged between 0.95 and 6.34mglead/ggeopolymer. More porous geopolymers presented better lead removal efficiency, while higher pH in the solution reduced their removal ability, since metal precipitation is enhanced. These novel geopolymeric monoliths can be used in packed beds that are easily collected when exhausted, which is a major advantage in comparison with the use of powdered adsorbents. Furthermore, their production encompasses the reuse of biomass fly-ash, mitigating the environmental impact associated with this waste disposal, while decreasing the adsorbents production costs.

Controlled functionalization of carbon nanotubes by a solvent-free multicomponent approach.

The present work reports the solvent-free, one-pot functionalization of multiwall carbon nanotubes (CNTs) based on the 1,3-dipolar cycloaddition of azomethine ylides using N-benzyloxycarbonyl glycine and formaldehyde. The surface morphology of the functionalized CNTs was investigated by scanning tunneling microscopy. The effect of temperature on the reaction was studied by thermogravimetry and X-ray photoelectron spectroscopy (XPS). XPS was a key technique for the detailed chemical analysis of the CNT surface. The formation of two major reaction products was observed, namely a cyclic benzyl carbamate and a pyrrolidine. The concentration of the two products varied with reaction temperature and time. At 180 °C, the main product was the cyclic benzyl carbamate, while at 250 °C the major product was the pyrrolidine. This simple, solvent-free chemical procedure yields CNTs with fine-tuned surface functionality.