Determinação do grau de sulfonação do SPEEK por titulação

Aromatic thermoplastics polymers such as poly (ether-ether ketone) PEEK, have shown to be very promising for the production of proton exchange membranes, due to their characteristics. Studies demonstrate that chemically modified polymers can have improved original properties. The sulfonation functionalization process is one of the strategies for modifying polymeric materials, which promote greater hydrophilicity, better ionic conductivity, greater wettability and better performance as a proton exchange membrane. PEEK was treated with sulfuric acid, obtaining SPEEK. The polymer was titrated in order to study its degree of sulfonation (SD), evaluate its relationship with the ion exchange capacity (IEC) and its potential application as PEM. In order to investigate the sulfonation degree (DS) of SPEEK and evaluate its relationship with the polymer's ionic exchange capacity (IEC), 0.3 g SPEEK samples were immersed in a sodium chloride solution to carry out the proton exchange. The titrations of saline solutions were performed with sodium hydroxide and, through the volume obtained, its IEC = 0.5435 meq.g-1 and its SD = 0.6 were obtained. It was proved that the relationship between the polymer mass, degree of sulfonation and ion exchange capacity can be modified, due to the optimization of the available amount of polymer and that, having knowledge of the SD of the polymer, it is possible to estimate the amount of base to be consumed, which is related to the amount of protons coming from SPEEK and present in the saline solution.Los polímeros termoplásticos aromáticos como el poli (éter-éter cetona) PEEK han demostrado ser muy prometedores para la producción de membranas de intercambio de protones (PEM), debido a sus propiedades. Los estudios demuestran que los polímeros modificados químicamente pueden presentar características originales mejoradas. El proceso de funcionalización por sulfonación es una de las estrategias de modificación de los materiales poliméricos, que promueve una mayor hidrofilia, mejor conductividad iónica, mayor humectabilidad y mejor desempeño como PEM. Se trató PEEK con ácido sulfúrico, obteniendo SPEEK. El polímero fue titulado con el fin de estudiar su grado de sulfonación (SD), evaluar su relación con la capacidad de intercambio iónico (IEC) y su potencial aplicación como PEM. Se sumergieron muestras de 0,3 g de SPEEK en solución de cloruro de sodio para realizar el intercambio de protones. Las titulaciones de las soluciones salinas se realizaron con hidróxido de sodio y, a través del volumen obtenido, se obtuvo su IEC = 0,5435 meq.g-1 y su SD = 0,61. Se comprobó que la relación entre la masa del polímero, el grado de sulfonación y la capacidad de intercambio iónico puede modificarse, debido a la optimización de la cantidad disponible de polímero y que, conociendo la SD del polímero, es posible estimar la cantidad de base a consumir, que está relacionada con la cantidad de protones provenientes de SPEEK y presentes en la solución salina.Polímeros termoplásticos aromáticos como o poli (éter-éter cetona) PEEK têm se mostrado muito promissores para a produção de membranas trocadoras de prótons (PEM), devido as suas propriedades. Estudos demonstram que polímeros modificados quimicamente podem apresentar características originais melhoradas. O processo de funcionalização por sulfonação é uma das estratégias de modificação de materiais poliméricos, que promove maior hidrofilicidade, melhor condutividade iônica, maior molhabilidade e melhor desempenho como PEM. O PEEK foi tratado com ácido sulfúrico, obtendo-se o SPEEK. O polímero foi titulado a fim de estudar seu grau de sulfonação (SD), avaliar sua relação com a capacidade de troca iônica (IEC) e sua potencial aplicação como PEM. Amostras de 0,3 g SPEEK foram imersas em solução de cloreto de sódio para a realização da troca protônica. Foram realizadas as titulações das soluções salinas com hidróxido de sódio e, através do volume obtido, foram obtidos sua IEC = 0,5435 meq.g-1 e seu SD = 0,61. Comprovou-se que a relação entre a massa de polímero, grau de sulfonação e capacidade de troca iônica pode ser modificada, em razão da otimização da quantidade disponível de polímero e que, tendo o conhecimento do SD do polímero é possível estimar a quantidade de base a ser consumida, que está relacionada quantidade de prótons oriundos do SPEEK e presentes na solução salina

Utilização de coagulação/floculação/sedimentação e nanofiltração no tratamento de lixiviado de aterro sanitário estabilizado

A tecnologia de aterros sanitários é o método mais amplamente utilizado para a disposição de resíduos sólidos urbanos. No aterro, o resíduo sólido sofre uma série de reações físico-químicas e biológicas, sendo o lixiviado um produto dessas reações. O tratamento do lixiviado depende de suas características. Apenas o processo biológico não atinge os níveis de descarte permitidos, devido à presença de matéria orgânica recalcitrante. Nesse contexto, o objetivo do presente estudo foi avaliar a remoção de matéria orgânica recalcitrante do lixiviado obtido no Aterro Metropolitano de Gramacho, localizado no município de Duque de Caxias (RJ). Para isto utilizou-se como tratamento o processo de coagulação/floculação/sedimentação (CF) seguido da filtração em membrana de nanofiltração (NF). No processo de CF, foram utilizados parâmetros otimizados de pH, concentração de coagulante (FeCl3), velocidade e tempo de misturas rápida e lenta e tempo de decantação. Foram obtidas as remoções médias de 43% de COT, 47% de DQO e diminuição de 64% da absorvância em 254 nm. Utilizando-se o lixiviado pré-tratado do jar test, testou-se a permeabilidade de duas membranas de NF: NP010 e NP030 (membranas importadas, marca Nadir). A membrana NP010 apresentou maior permeabilidade em água (13 L/h.m2.bar). Portanto, esta foi a membrana escolhida para os demais testes (filtrações em 3, 5, 6 e 7 bar). A membrana NP030 apresentou permeabilidade muito baixa (1 L/h.m2.bar), e portanto foi utilizada somente na pressão de 8 bar. Os resultados da etapa de NF foram analisados segundo o fluxo de permeado, remoção de COT e DQO e diminuição da absorvância a 254 nm. Com relação ao fluxo, a membrana NP010, a pressões mais elevadas (6 e 7 bar) permite fluxos elevados no início, estabilizando-se após um tempo em cerca de 20 L/hm², maiores que os valores estabilizados para as pressões de 3 e 5 bar (15 L/hm²). A membrana NP030 apresentou fluxo baixo durante toda a filtração a 8 bar (15 L/hm²), sem apresentar queda do mesmo durante o período de filtração. Com relação à eficiência do processo combinado (coagulação/floculação/sedimentação e nanofiltração), as remoções médias obtidas nos experimentos foram: 67% de COT, 81% de DQO e diminuição de 78% de absorvância a 254 nm. Os valores no efluente tratado foram de 223 mg/L de COT e 448 mg/L de DQO, mostrando elevada eficiência para a remoção de matéria orgânica recalcitrante

A Bayesian reanalysis of the Standard versus Accelerated Initiation of Renal-Replacement Therapy in Acute Kidney Injury (STARRT-AKI) trial

Background Timing of initiation of kidney-replacement therapy (KRT) in critically ill patients remains controversial. The Standard versus Accelerated Initiation of Renal-Replacement Therapy in Acute Kidney Injury (STARRT-AKI) trial compared two strategies of KRT initiation (accelerated versus standard) in critically ill patients with acute kidney injury and found neutral results for 90-day all-cause mortality. Probabilistic exploration of the trial endpoints may enable greater understanding of the trial findings. We aimed to perform a reanalysis using a Bayesian framework. Methods We performed a secondary analysis of all 2927 patients randomized in multi-national STARRT-AKI trial, performed at 168 centers in 15 countries. The primary endpoint, 90-day all-cause mortality, was evaluated using hierarchical Bayesian logistic regression. A spectrum of priors includes optimistic, neutral, and pessimistic priors, along with priors informed from earlier clinical trials. Secondary endpoints (KRT-free days and hospital-free days) were assessed using zero–one inflated beta regression. Results The posterior probability of benefit comparing an accelerated versus a standard KRT initiation strategy for the primary endpoint suggested no important difference, regardless of the prior used (absolute difference of 0.13% [95% credible interval [CrI] − 3.30%; 3.40%], − 0.39% [95% CrI − 3.46%; 3.00%], and 0.64% [95% CrI − 2.53%; 3.88%] for neutral, optimistic, and pessimistic priors, respectively). There was a very low probability that the effect size was equal or larger than a consensus-defined minimal clinically important difference. Patients allocated to the accelerated strategy had a lower number of KRT-free days (median absolute difference of − 3.55 days [95% CrI − 6.38; − 0.48]), with a probability that the accelerated strategy was associated with more KRT-free days of 0.008. Hospital-free days were similar between strategies, with the accelerated strategy having a median absolute difference of 0.48 more hospital-free days (95% CrI − 1.87; 2.72) compared with the standard strategy and the probability that the accelerated strategy had more hospital-free days was 0.66. Conclusions In a Bayesian reanalysis of the STARRT-AKI trial, we found very low probability that an accelerated strategy has clinically important benefits compared with the standard strategy. Patients receiving the accelerated strategy probably have fewer days alive and KRT-free. These findings do not support the adoption of an accelerated strategy of KRT initiation

Regional Practice Variation and Outcomes in the Standard Versus Accelerated Initiation of Renal Replacement Therapy in Acute Kidney Injury (STARRT-AKI) Trial: A Post Hoc Secondary Analysis.

ObjectivesAmong patients with severe acute kidney injury (AKI) admitted to the ICU in high-income countries, regional practice variations for fluid balance (FB) management, timing, and choice of renal replacement therapy (RRT) modality may be significant.DesignSecondary post hoc analysis of the STandard vs. Accelerated initiation of Renal Replacement Therapy in Acute Kidney Injury (STARRT-AKI) trial (ClinicalTrials.gov number NCT02568722).SettingOne hundred-fifty-three ICUs in 13 countries.PatientsAltogether 2693 critically ill patients with AKI, of whom 994 were North American, 1143 European, and 556 from Australia and New Zealand (ANZ).InterventionsNone.Measurements and main resultsTotal mean FB to a maximum of 14 days was +7199 mL in North America, +5641 mL in Europe, and +2211 mL in ANZ (p p p p p p p p = 0.007).ConclusionsAmong STARRT-AKI trial centers, significant regional practice variation exists regarding FB, timing of initiation of RRT, and initial use of continuous RRT. After adjustment, such practice variation was associated with lower ICU and hospital stay and 90-day mortality among ANZ patients compared with other regions

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care