Simultaneously Recovery of Thorium and Tungsten through Hybrid Electrolysis-Nanofiltration Processes.

The recovery and recycling of metals that generate toxic ions in the environment is of particular importance, especially when these are tungsten and, in particular, thorium. The radioactive element thorium has unexpectedly accessible domestic applications (filaments of light bulbs and electronic tubes, welding electrodes, and working alloys containing aluminum and magnesium), which lead to its appearance in electrical and electronic waste from municipal waste management platforms. The current paper proposes the simultaneous recovery of waste containing tungsten and thorium from welding electrodes. Simultaneous recovery is achieved by applying a hybrid membrane electrolysis technology coupled with nanofiltration. An electrolysis cell with sulphonated polyether-ether-ketone membranes (sPEEK) and a nanofiltration module with chitosan-polypropylene membranes (C-PHF-M) are used to carry out the hybrid process. The analysis of welding electrodes led to a composition of W (tungsten) 89.4%; Th 7.1%; O2 2.5%; and Al 1.1%. Thus, the parameters of the electrolysis process were chosen according to the speciation of the three metals suggested by the superimposed Pourbaix diagrams. At a constant potential of 20.0 V and an electrolysis current of 1.0 A, the pH is varied and the possible composition of the solution in the anodic workspace is analyzed. Favorable conditions for both electrolysis and nanofiltration were obtained at pH from 6 to 9, when the soluble tungstate ion, the aluminum hydroxide, and solid thorium dioxide were formed. Through the first nanofiltration, the tungstate ion is obtained in the permeate, and thorium dioxide and aluminum hydroxide in the concentrate. By adding a pH 13 solution over the two precipitates, the aluminum is solubilized as sodium aluminate, which will be found after the second nanofiltration in the permeate, with the thorium dioxide remaining integrally (within an error of ±0.1 ppm) on the C-PHF-M membrane.

Recent progresses in compound specific isotope analysis of halogenated persistent organic pollutants. Assessing the transformation of halogenated persistent organic pollutants at contaminated sites.

Compound specific isotope analysis was extensively used to characterise the environmental processes associated with the abiotic and biotic transformation of persistent halogenated organic pollutants including those of contaminants of emerging concern (CECs). In the last years, the compound specific isotope analysis was applied as tool to evaluate the environmental fate and was expanded to larger molecules like brominated flame retardants and polychlorinated biphenyls. Multi-element (C, H, Cl, Br) CSIA methods have been also employed both in laboratory and field experiments. Nevertheless, despite the instrumental advances of isotope ratio mass spectrometers systems, the instrumental detection limit for gas chromatography-combustion-isotope ratio mass spectrometer (GC-C-IRMS) systems is challenging, especially when it is utilized to δ13C analysis. Liquid chromatography-combustion isotope ratio mass spectrometry methods are challenging, taking into consideration the chromatographic resolution required when analysing complex mixtures. For chiral contaminants, enantioselective stable isotope analysis (ESIA) has turned up as alternative approach but, up to now, it has been used for a limited number of compounds. Taking into consideration the occurrence of new emerging halogenated organic contaminants, new GC and LC methods for non-target screening using high resolution mass spectrometry are needed to be developed prior to the compound specific isotope analysis (CSIA) methods.

Comparative Antioxidant and Antimicrobial Activities of Several Conifer Needles and Bark Extracts.

Nowadays, an increased concern regarding using natural products for their health benefits can be observed. The aim of this study was to assess and compare several phenolic compounds found in 15- to 60-year-old Douglas fir, silver fir, larch, pine, and spruce needle and bark extracts and to evaluate their antioxidant and antimicrobial activities. Spectrophotometric assays were used to determine the total polyphenol content and the antioxidant activity that was assessed by using the DPPH• radical scavenging assay (RSA), the ferric reducing antioxidant power assay (FRAP), and the ABTS•+ radical cation scavenging assay (ABTS). The phytochemical content was determined by using high-performance liquid chromatography, and the antimicrobial activity was determined by assessing the minimal inhibition concentration (MIC). The results of the study show a total polyphenol content of 62.45-109.80 mg GAE/g d.w. and an antioxidant activity of 91.18-99.32% for RSA, 29.16-35.74 µmol TE/g d.w. for FRAP, and 38.23-53.57 µmol TE/g d.w. for ABTS. The greatest quantity of phenolic compound for most of the extracts was for (+)-catechin, and it had values between 165.79 and 5343.27 µg/g d.w. for these samples. The antimicrobial inhibition for all the extracts was the strongest for Staphylococcus aureus (MIC 62.5-125 µg/mL). The extracts analyzed could be used for their bioactive potential after further investigations.