Understanding the Reduction of Transition-Metal Phosphates to Transition-Metal Phosphides by Combining Temperature-Programmed Reduction and Infrared Spectroscopy.

Temperature-programmed reduction of transition-metal phosphate precursors is the most commonly used method for the preparation of transition-metal phosphides (a new class of versatile metal catalysts), but the reduction processes are still not clear. Here we describe the construction of a temperature-programmed reduction-infrared spectroscopy apparatus (TPR-IR) to analyze the gas flows during the reduction of nickel, molybdenum, and tungsten phosphates. PH3 and Pn+ species already appeared in the gas flows at low temperature (ca. 200 °C), and PH3 was involved in the formation of phosphides. The emission of PH3 and Pn+ during the reduction of the molybdenum and tungsten phosphates was smaller than that of the nickel phosphate. Ni2 P drastically accelerated the formation of the PH3 and Pn+ . These results explain why excess phosphorus is needed for the preparation of Ni2 P, and also demonstrate that the TPR-IR technique is an efficient method to understand the complex processes of catalyst preparation.

Carbonaceous adsorbents in wastewater treatment: From mechanism to emerging application.

Adsorption is of great significance in the water pollution control. Carbonaceous adsorbents, such as carbon quantum dots, carbon nanotubes, graphene, and activated carbon, have long been deployed in sustainable wastewater treatment due to their excellent physical structure and strong interaction with various pollutants; these features allow them to spark greater interest in environmental remediation. Although numerous eye-catch researches on carbon materials in wastewater treatment, there is a lack of comprehensive comparison and summary of the vivid structure-activity-application relationships of different types of carbonaceous adsorbents at the molecular and atomic level. Herein, this review aims to scrutinize and contrast the adsorption mechanisms of carbonaceous adsorbents with different dimensions, analyzing the qualitative differences in adsorption capacity from microscopic perspectives, structural diversity caused by preparation methods, and environmental external factors affecting adsorption occurrence. Then, a quantitatively in-depth critical appraisal of traditional and emerging contaminants in wastewater treatment using carbonaceous adsorbents, and innovative strategies for enhancing their adsorption capacity are discussed. Finally, in the context of growing imposed circularity and zero waste wishes, this review offers some promising insights for carbonaceous adsorbents in achieving sustainable wastewater treatment.

Effect of surface species on the alcohol-acid adsorption from FTS wastewater on graphene: A structure-capacity study.

Fischer-Tropsch synthesis (FTS) wastewater retaining low-carbon alcohols and acids are organic pollutants as a limiting factor for FTS industrialization. In this work, the structure-capacity relationships between alcohol-acid adsorption and surface species on graphene were reported, shedding light into their intricate interactions. The graphene oxide (GO) and reduced graphene oxide (rGO) were synthesized via improved Hummers method with flake graphite (G). The physicochemical properties of samples were characterized via SEM, XRD, XPS, FT-IR, and Raman. The alcohol-acid adsorption behaviors and adsorption quantities on G, GO, and rGO were measured via theoretical and experimental method. It was revealed that the presence of COOH, C=O and CO species on graphene occupy the adsorption sites and increase the interactions of water with graphene, which are unfavorable for alcohol-acid adsorption. The equilibrium adsorption quantities of alcohols and acids grow in pace with carbon number. The monolayer adsorption occurs on graphene was verified via model fitting. rGO has the highest FTS modeling wastewater adsorption quantity (110 mg/g) due to the reduction of oxygen species. These novel findings provide a foundation for the alcohol-acid wastewater treatment, as well as the design and development of high-performance carbon-based adsorbent materials.