Prussian blue analogs (PBAs) are promising cathode materials for many next‐generation metal‐ion batteries due to their exceptional electrochemical performance. Their oxygen‐free structure avoids a common battery thermal runaway pathway which requires O2 liberation. Herein, the thermal runaway mechanisms of PBAs are studied from the level of material and full cell in nonaqueous sodium‐ and potassium‐ion batteries (SIBs and KIBs). Their hidden safety issue and a novel runaway mechanism that requires no oxygen evolution are identified. The cyanide groups are released (≈51.4 wt%) as toxic cyanides above 200 °C, which also exothermically react with the electrolyte and cause the runaway. The cyanide gas generation mechanism is proposed as cathode hydrolytic disproportionation by Raman spectroscopy, X‐ray photoelectron spectroscopy, in situ environmental transmission electron microscopy, and operando synchrotron X‐ray diffraction studies. In addition, full‐cell level calorimetric studies reveal mitigated heat generation but lower initiation temperature of runaway from such SIBs and KIBs than conventional LiCoO2–graphite system. These results change how PBA materials are evaluated from a safety standpoint, suggesting that they cannot be regarded as safe cathodes. They also indicate the correlations between thermal safety and their crystal defects or trapped water content. The proposed thermal runaway mechanism provides insights to assist in the building of safer next‐generation batteries.

Abstract:The presence of heavy metals in water for human use or consumption represents a major risk to human health. It is therefore important to find materials to remove or minimise the concentration of these pollutants. The adsorption process for the removal of heavy metals is favoured by the use of low-cost materials that exhibit a porous structure and a high cation exchange capacity, such as zeolites and clays. On the other hand, chemical treatments, e.g., using acids and bases, can modify the properties of these materials, but more recently the application of surfactants has also shown to be successful for broadening their metal affinity and allowing the removal of diverse organic and inorganic pollutants from water. This paper reviews the application of modified zeolites and clays for the removal of heavy metals from water.

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To determine the role of organic matter in the attenuation of acid rock drainage (ARD), microcosm-based experiments were performed using ARD stimulated with plants and manures. Initial mineralogical, organic geochemical and microbial analyses indicated a predominance of goethite, a substantial amount of organic carbon originating from local sources, and a bacterial community comparable with those detected in a range of ARD sites worldwide. After 100 days of incubation, changes in the mineralogical, organic and microbiological composition of the ARD demonstrated that the plant additions stimulate microbes with the potential to degrade this organic matter but do not necessarily cause substantial Fe(III) reduction. Conversely, the greatest observed stimulation of Fe(III) reduction, associated with an increase in pH to near-neutral values, was observed using manure additions. These results demonstrate that the use of the optimal natural carbon source is important and can promote the metabolism of microorganisms potentially fuelling a range of geomicrobial processes, including iron and sulfate reduction.

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Se reporta en este estudio la caracterización de una zona contaminada por lixiviados, siguiendo una metodología que integra datos geofísicos y geohidrológicos para proponer un modelo hidrogeológico del fenómeno. La caracterización del sitio (la estructura del subsuelo, y las características del suelo) incluyó seis perfiles sísmicos de refracción, tres líneas electromagnéticas (FDEM), dos perfiles eléctricos (ERT), cinco sondeos eléctricos verticales (SEV), y una serie de pruebas geohidrológicas para delimitar la pluma contaminante. El área de estudio corresponde a la laguna de lixiviados del relleno sanitario de la ciudad de Oaxaca, sur de México. El modelo hidrogeológico que se presenta constituye un ejemplo del potencial de la integración de varios métodos aplicados con el mismo objetivo; reduciendo así la ambigüedad de la respuesta geofísica. Los resultados indican que los valores de baja resistividad (1.5 a 2.5 Ohm-m) se relacionan con un suelo contaminado subyaciendo a la laguna de lixiviados y al medio fracturado. También se detectó un desplazamiento de la pluma contaminante hacia el SW de la laguna. La calidad del agua es buena, pero la actividad humana en el área de estudio confiere un riesgo para el acuífero superficial de Zaachila.

Chromium is a non-biodegradable element predominantly found in two chemical forms, Cr(VI) and Cr(III). Several remediation strategies have been implemented to achieve its removal from aquatic environments with limited results. This review article focuses on the analysis of removal strategies including the use of: (1) raw materials (agro-wastes, activated carbons, extracts and solutions) and (2) treated materials (alkaline and acid treatments). The article also reviews and analyses results obtained with surfactant modified organic biomasses. Although this review aims to summarise chromium removal techniques by highlighting relevant results of several studies, surface modification is outlined as a promising method to improve removal efficiency in aqueous solutions. The information presented in this article can help in the development of more efficient methods considering the improvements that surfactants may offer.

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