Remediation of 137Cs-contaminated concrete rubble by supercritical CO2 extraction

Desorption of Cs from vermiculite by ultrasound assisted ion exchange

Nuclear power plant accidents typically lead to the contamination of large volumes of soils with radioactive cesium. This element is hard to desorb from soil, especially when it is bound to mica minerals, and aggressive and energy-consuming techniques are often required. In this study, we investigated the use of ultrasound with Mg²⁺ cation exchange for the removal of a¹³³Cs-contaminated vermiculite over a wide range of temperatures (20-200 °C). At room temperature, ultrasound was found to significantly accelerate Cs desorption but only reversibly adsorbed Cs species were removed. Under hydrothermal conditions and ultrasonic irradiation in contrast, the removal efficiency after 1 h was 50% at 100 °C and more than 95% at 200 °C, compared with only 50% without ultrasonication at 200 °C. Cs contamination can therefore be nearly totally removed, even from collapsed vermiculite sites where sorption is considered irreversible. Ultrasound waves and high temperatures both make trapped Cs more accessible by spreading the sheets and improving mass transfer. Acoustic noise spectra show that even at high pressure and temperature, cavitation bubbles form, oscillate and collapse, with the desired physical effects. These results demonstrate the potential of synergistic ultrasound and hydrothermal treatment for soil remediation.

Historical and current usage of per- and polyfluoroalkyl substances (PFAS): A literature review

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) have uniquely useful chemical and physical properties, leading to their extensive industrial, commercial, and consumer applications since at least the 1950s. Some industries have publicly reported at least some degree of information regarding their PFAS use, while other industries have reported little, if any, such information publicly.

METHODS

Publicly available sources were extensively researched for information. Literature searches were performed on key words via a variety of search mechanisms, including existing PFAS use and synthesis literature, patent databases, manufacturers' websites, public government databases, and library catalogs. Additional searches were conducted specifically for suspected or known uses.

RESULTS

PFAS have been used in a wide variety of applications, which are summarized into several industries and applications. The expanded literature search yielded additional references as well as greater details, such as concentrations and specific PFAS used, on several previously reported uses.

CONCLUSIONS

This knowledge will help inform which industries and occupations may lead to potential exposure to workers and to the environment.

Supercritical carbon dioxide extraction of plant phytochemicals for biological and environmental applications - A review

Recently, supercritical fluid CO₂ extraction (SFE) has emerged as a promising and pervasive technology over conventional extraction techniques for various applications, especially for bioactive compounds extraction and environmental pollutants removal. In this context, temperature and pressure regulate the solvent density and thereby effects the yield, selectivity, and biological/therapeutic properties of the extracted components. However, the nature of plant matrices primarily determines the extraction mechanism based on either density or vapor pressure. The present review aims to cover the recent research and developments of SFE technique in the extraction of bioactive plant phytochemicals with high antioxidant, antibacterial, antimalarial, and anti-inflammatory activities, influencing parameters, process conditions, the investigations for improving the yield and selectivity. In another portion of this review focuses on the ecotoxicology and toxic metal recovery applications. Nonpolar properties of Sc-CO₂ create strong solvent strength via distinct intermolecular interaction forces with micro-pollutants and toxic metal complexes. This results in efficient removal of these contaminants and makes SFE technology as a superior alternative for conventional solvent-based treatment methods. Moreover, a compelling assessment on the therapeutic, functional, and solvent properties of SFE is rarely focused, and hence this review would add significant value to the SFE based research studies. Furthermore, we mention the limitations and potential of future perspectives related to SFE applications.