• Costello Andresen posted an update 4 hours, 15 minutes ago

    Cyclic volatile methylsiloxanes (cVMS) are widely used in consumer products and commonly detected in the environment. There are challenges in the analysis of cVMS because of their ubiquitous use which can introduce high background contamination. The current study introduces a sample preparation method based on headspace of solid-phase microextraction (SPME) for monitoring the cVMS in waters. Efforts were made to reduce the background contamination during sample preparation and instrument analysis. A laboratory prepared MIL-101 coating was prepared using polysulfone instead of polydimethylsiloxane as adhesive to avoid the contamination. The extraction performance of the MIL-101 fiber was optimized and evaluated. The optimized extraction time and temperature were 60 min and 40 °C, respectively. The method quantification limits of the MIL-101 fiber for octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecylcyclohexasiloxane (D6) in water were 0.15 ng mL-1, 0.14 ng mL-1, and 0.27 ng mL-1, respectively. The extraction efficiency of the proposed MIL-101 fiber was comparable to the commercial polydimethylsiloxane/divinylbenzene fiber. The developed method was applied to analyze the cVMS in wastewater treatment plant and the concentrations in the barscreen and in the aeration tank ranged from 0.73 to 3.3 ng mL-1 and 7.74-85.1 ng mL-1, respectively. The MIL-101 fiber was also applied to study the photodegradation of the cVMS in water under simulated sunlight. Approximately 25%, 20%, and 45% of D4, D5, and D6, respectively, were degraded after 10 h exposure. Arsenic- and trace metals-bearing gypsum (As-gypsum) is one of the major hazardous solid wastes produced from metallurgical industry that poses a serious threat to the environment. However, the method for effective extraction of As and trace metals from As-gypsum is still lacking. In this study, simultaneous extraction of As and trace metals from a hydrometallurgical As-gypsum via hydrothermal recrystallization in acid solution was investigated. The effects of the type (H2SO4 vs HCl) and concentration of acid, and temperature on extraction efficiency were assessed. mTOR inhibitor The results showed that 99% As, >92% Cu and >96% Zn could be extracted from the As-gypsum during hydrothermal treatment in 6 mol L-1 H2SO4 at 90 and 120 °C, but Pb and Cd could not be extracted efficiently. The results of hydrothermal treatment in HCl solutions demonstrated that higher HCl concentration and temperature significantly enhanced the extraction efficiency and 100% As, Cu2+, Zn2+, Pb2+ and >90% Cd were removed from the As-gypsum after treatment in 6 mol L-1 HCl, at 120 °C, for 12 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy results revealed that dissolution-recrystallization of gypsum is the key process for the removal of the incorporated As and trace metals. Thermodynamic modelling indicated that the released HAsO42-/Me2+ transformed into H3AsO4/MeCln(2-n) (1 ≤ n ≤ 4) species in HCl solution, hence inhibiting their reincorporation into the recrystallization products via isomorphic substitution for SO42-/Ca2+. This work provides a simple and effective method for detoxification and reclamation of As-gypsum. On 3rd to May 24, 2018, volatile organic compound (VOC) samples were collected four times a day by using stainless steel canisters at an urban site in Zhengzhou, China. The concentrations, compositions, sources, ozone (O3) formation potential (OFP), and health risk assessment of VOCs were discussed based on the measurements of 103 VOC species. Results show that the average mixing ratio of VOCs was 29.11 ± 15.33 ppbv, and the dominant components comprised oxygenated VOCs (OVOCs) and alkanes, followed by halocarbons, alkenes, aromatics, and a sulfide. Various groups of VOCs had typical diurnal variation characteristics. Alkenes, alkanes, and aromatics contributed most to the OFP. Five sources identified by the positive matrix factorization model revealed solvent utilization as the largest contributor, followed by industrial production, long-lived and secondary species, vehicular emission, and biogenic emission. Solvent utilization and vehicular emission were important sources to OFP. During O3 episode days, the mixing ratios of alkanes, alkenes, halocarbons, OVOCs, aromatics, and TVOCs decreased to varying degrees; the source contribution of solvent utilization decreased significantly while industrial production showed the opposite trend. VOC species and sources posed no non-carcinogenic risk while five species and all sources except for biogenic emission had carcinogenic risks to exposed population. Industrial emission was the largest contributor to both non-carcinogenic and carcinogenic risks. These results will help to provide some references for O3 pollution research and prevention and control of pollution sources. Metal/Air batteries are being developed and soon could become competitive with other battery technologies already in the market, such as Li-ion battery. The main problem to be addressed is the cyclability, although some progress has been recently achieved. A Life Cycle Assessment (LCA) of the manufacturing process of a Zn/Air battery is presented in this article, including raw extraction and process of materials and battery assembly at laboratory scale (cradle to gate approach). The results indicate that Zn/Air battery can be fabricated with low environmental impacts in most categories and only four deserve attention (still being low impacts), such as Human Toxicity (cancer and non-cancer), Freshwater Ecotoxicity and Resource Depletion (the later one depending mainly on Zn use, which is not a critical material, but has a strong impact on this category). Cathode fabrication arises as the subassembly with higher impacts, followed by membrane, then anode and finally electrolyte. An economic cost calculation indicates that if cyclability of Zn/Air batteries is achieved, they can become competitive with other technologies already in the market. In this study, an anoxic-oxic membrane bioreactor (A/O-MBR), was used to treat effluent tannery wastewater pretreated by physicochemical processes. The A/O-MBR performed well during the experimental period and was able to produce a high-quality effluent containing 90 ± 10 mg-CODcr/L and 0.5 ± 0.1 mg-NH4+-N/L. However, it was observed that at rates of approximately 1.02 kPa/day and 1.2 μm/day, both transmembrane pressure (TMP) and thickness of cake layer increased during wastewater treatment. The eventual thickness of the cake layer was between 47.8 and 51.5 μm. Furthermore, an Inductively Coupled Plasma-Optical Emission Spectrometer, used to analyze inorganic components of the cake layer, revealed that four inorganic elements, Cr, Ca, Mg and Al were predominant (weight percentage rate 4131072). Due to low solubility (Cr(OH)3 Ksp 6.3 × 10-31; Al(OH)3 Ksp 6.3 × 10-19), the elements of Cr and Al mainly existed in the forms of Cr(OH)3 and Al(OH)3, respectively. Other minerals in the cake layer included Al2O3, CaCO3, and MgCO3.