Solid-Contact Potentiometric Anion Sensing Based on Classic Silver/Silver Insoluble Salts Electrodes without Ion-Selective Membrane

Current solid potentiometric ion sensors mostly rely on polymeric-membrane-based, solid-contact, ion-selective electrodes (SC-ISEs). However, anion sensing has been a challenge with respect to cations due to the rareness of anion ionophores. Classic metal/metal insoluble salt electrodes (such as Ag/AgCl) without an ion-selective membrane (ISM) offer an alternative. In this work, we first compared the two types of SC-ISEs of Cl− with/without the ISM. It is found that the ISM-free Ag/AgCl electrode discloses a comparable selectivity regarding organic chloride ionophores. Additionally, the electrode exhibits better comprehensive performances (stability, reproducibility, and anti-interference ability) than the ISM-based SC-ISE. In addition to Cl−, other Ag/AgX electrodes also work toward single and multi-valent anions sensing. Finally, a flexible Cl− sensor was fabricated for on-body monitoring the concentration of sweat Cl− to illustrate a proof-of-concept application in wearable anion sensors. This work re-emphasizes the ISM-free SC-ISEs for solid anion sensing.

Formation of oxidized gases and secondary organic aerosol from a commercial oxidant-generating electronic air cleaner

Airborne virus transmission during the COVID-19 pandemic increased the demand for indoor air cleaners. While some commercial electronic air cleaners could be effective in reducing primary pollutants and inactivating bioaerosol, studies on the formation of secondary products from oxidation chemistry during their use are limited. Here, we measured oxygenated volatile organic compounds (OVOCs) and the chemical composition of particles generated from a hydroxyl radical generator in an office. During operation, enhancements in OVOCs, especially low-molecular-weight organic and inorganic acids, were detected. Rapid increases in particle number and volume concentrations were observed, corresponding to the formation of highly-oxidized secondary organic aerosol (SOA) (O:C ~1.3). The organic mass spectra showed an enhanced signal at m/z 44 (CO2+) and the aerosol evolved with a slope of ~ -1 in the Van Krevelen diagram. These results suggest that organic acids generated during VOC oxidation contributed to particle nucleation and SOA formation. Nitrate, sulfate, and chloride also increased during the oxidation without a corresponding increase in ammonium, suggesting organic nitrate, organic sulfate, and organic chloride formation. As secondary species are reported to have detrimental health effects, further studies are needed to evaluate potential OVOCs and SOA formation from electronic air cleaners in different indoor environments.

Integrating single-cobalt-site and electric field of boron nitride in dechlorination electrocatalysts by bioinspired design

The construction of enzyme-inspired artificial catalysts with enzyme-like active sites and microenvironment remains a great challenge. Herein, we report a single-atomic-site Co catalyst supported by carbon doped boron nitride (BCN) with locally polarized B–N bonds (Co SAs/BCN) to simulate the reductive dehalogenases. Density functional theory analysis suggests that the BCN supports, featured with ionic characteristics, provide additional electric field effect compared with graphitic carbon or N-doped carbon (CN), which could facilitate the adsorption of polarized organochlorides. Consistent with the theoretical results, the Co SAs/BCN catalyst delivers a high activity with nearly complete dechlorination (~98%) at a potential of −0.9 V versus Ag/AgCl for chloramphenicol (CAP), showing that the rate constant (k) contributed by unit mass of metal (k/ratio) is 4 and 19 times more active than those of the Co SAs/CN and state-of-the-art Pd/C catalyst, respectively. We show that Co single atoms coupled with BCN host exhibit high stability and selectivity in CAP dechlorination and suppress the competing hydrogen evolution reaction, endowing the Co SAs/BCN as a candidate for sustainable conversion of organic chloride.

Determination of Organic Chloride Content in the Specialty Oilfield Chemicals Used in the Crude Oil Extraction, Transportation and Refining by X-ray Fluorescence Spectrometry

The organic chloride content in crude oil being among the most crucial quality characteristics of the crude is strictly controlled. The presence of organic chlorides in crude oil greatly endangers the oil refineries since it causes a severe equipment corrosion. Specialty oilfield chemicals, which are widely used in the crude oil extraction, transportation, refining and storage, could be a source of the crude oil contamination with organic chlorides. As a consequence, the organic chloride content determination in the chemicals is required. It was demonstrated that the organic chloride content in the specialty oilfield chemicals can be determined by X-ray fluorescence spectrometry (XRF) using an appropriate specimen preparation procedure. Two specimen preparation procedures, i.e. the solvent extraction and the distillation of a specimen mixed with the crude oil or its model, were tested. It was established that an organic chloride content can be successfully determined in a broad range of the specialty oilfield chemicals by the XRF technique when applying these specimen preparation procedures. The investigation of four types of the specialty oilfield chemicals confirmed that the specimen preparation procedure, involving a solvent extraction of organic chlorides from the chemicals into isooctane, is more comprehensive than the distillation procedure since it is free from the limitations associated with the use of high temperatures.