•A life-cycle comparison of three clean energy technologies is conducted.•The evaluation covers not only the GHG emissions but also other impact categories.•An example is provided to showcase the ...proposed evaluation method.
Energy sector is one of biggest contributors to the Greenhouse Gas (GHG) emissions. As a result, it has attracted considerable attention to reduce the GHG emissions of electricity production. Hydro-electric, nuclear and wind power are the top three clean energy in China. In this study, the environmental impacts of these three technologies are analyzed, assessed and compared via a life-cycle assessment approach. The entire life cycle, including the manufacturing, construction, operation and decommissioning stages is examined. Apart from global warming potential (GWP100) caused by GHG emissions, the environmental impacts assessed in this study also included acidification potential (AP), eutrophication potential (EP), photochemical ozone creation potential (POCP) and human toxicity potential (HTP). The results show that wind power technology has the most significant environmental impacts amongst these three clean energies, followed by nuclear power and hydropower. For example, in terms of global warming potential, wind power produces 28.6 ± 3.2 g CO2-eq/kWh of GWP100 throughout its life cycle, which is higher than that of nuclear power (12.4 ± 1.5 g CO2-eq/kWh) and hydropower (3.5 ± 0.4 g CO2-eq/kWh). In addition, this study revealed that the the manufacturing stage is the largest contributor of environmental impacts for wind and hydropower. By contrast, the decommissioning stage is most significant for nuclear power in terms of environmental impacts. The comparative life cycle assessment method proposed in this study provides useful tool for the future environmental assessment of electricity production technologies. Findings of this study provide useful inputs for the sustainable transformation of the energy sector.
Carbonyl oxides, or Criegee intermediates, are important transient species formed in the reactions of unsaturated hydrocarbons with ozone. Although direct detection of Criegee intermediates has ...recently been realized, the main atmospheric sink of Criegee intermediates remains unclear. We report ultraviolet absorption spectroscopic measurements of the lifetime of the simplest Criegee intermediate, CH2OO, at various relative humidity levels up to 85% at 298 kelvin. An extremely fast decay rate of CH2OO was observed at high humidity. The observed quadratic dependence of the decay rate on water concentration implied a predominant reaction with water dimer. On the basis of the water dimer equilibrium constant, the effective rate coefficient of the CH2OO + (H2O)2 reaction was determined to be 6.5 (±0.8) × 10–12 cubic centimeters per second. This work would help modelers to better constrain the atmospheric concentrations of CH2OO.
In this study, a series of Ce-OMS-2 catalysts were synthesized by a hydrothermal method, their physicochemical properties and catalytic activity for ozone decomposition were evaluated. The results ...show that suitable grain size and morphology can be formed as needed by tuning the hydrothermal conditions. In this way, the content of surface oxygen in the catalyst can be increased to enhance the reduction performance of the samples. At the same time, the quantity of low-valent manganese (Mn2+ and Mn3+) can be increased to raise the oxygen vacancy concentration, and finally improve the O3 elimination performance of the catalyst. On the basis of this study, we screened out a suitable range of hydrothermal conditions, namely 95–100 °C and 8–24 h, which showed a higher ozone conversion rate than manganese oxide catalysts reported to date. The durability of the preferred catalyst under harsh conditions shows that preferred Ce-OMS-2 catalysts can meet the requirements of engineering applications.
Traditional ozone sensing and removal materials still suffer from high energy consumption and low efficiency. Thus, seeking new ozone‐responsive materials with high efficiency and broad working ...conditions is of great significance. Herein, we first developed covalent organic frameworks (COFs) for smart sensing and efficient removal of ozone. Notably, imine‐based COFs possess dramatically fast optical responses (<1 s) to ozone as low as 0.1 ppm under broad working conditions (e.g., in the presence or absence of moisture, room temperature). Moreover, we found that imine‐based COFs can also be applied as excellent ozone removers that can efficiently reduce the ozone concentration below the recommended safety limit (<0.1 ppm) for humans. The mechanism for the performance of imine‐based COFs was unveiled in‐depth by various characterization techniques and analyses. This study not only provides a new type of advanced materials for ozone sensing and removal but also broadens the application scope of COFs.
We demonstrated the first example to use imine‐based covalent organic frameworks (COFs) for smart sensing and efficient removal of ozone, and showed that the COFs’ performance could surpass traditional materials. The mechanism for the performance of imine‐based COFs is unveiled.
This work investigated degradation (measured by qPCR) and biological deactivation (measured by culture-based natural transformation) of extra- and intracellular antibiotic resistance genes (eARGs and ...iARGs) by free available chlorine (FAC), NH2Cl, O3, ClO2, and UV light (254 nm), and of eARGs by •OH, using a chromosomal ARG (blt) of multidrug-resistant Bacillus subtilis 1A189. Rate constants for degradation of four 266–1017 bp amplicons adjacent to or encompassing the acfA mutation enabling blt overexpression increased in proportion to #AT+GC bps/amplicon, or in proportion to #5′-GG-3′ or 5′-TT-3′ doublets/amplicon, with respective values ranging from 0.59 to 2.3 (×1011 M–1 s–1) for •OH, 1.8–6.9 (×104 M–1 s–1) for O3, 3.9–9.2 (×103 M–1 s–1) for FAC, 0.35–1.2(×101 M–1 s–1) for ClO2, and 2.0–8.8 (×10–2 cm2/mJ) for UV at pH 7, and from 1.7–4.4 M–1 s–1 for NH2Cl at pH 8. For FAC, NH2Cl, O3, ClO2, and UV, ARG deactivation paralleled degradation of amplicons approximating a ∼800–1000 bp acfA-flanking sequence required for natural transformation in B. subtilis, whereas deactivation outpaced degradation for •OH. At practical disinfectant exposures, eARGs and iARGs were ≥90% degraded/deactivated by FAC, O3, and UV, but recalcitrant to NH2Cl and ClO2. iARG degradation/deactivation always lagged cell inactivation. These findings provide a quantitative framework for evaluating ARG fate during disinfection/oxidation, and support using qPCR as a proxy for tracking ARG deactivation under carefully selected circumstances.
Due to complicated ozone formation regimes controlled by both ozone precursors and meteorological conditions, the underlying drivers for soaring ozone concentrations in Beijing were limitedly ...examined. With ground observation and remotely sensed data, the variation of ground ozone concentrations at an urban AT (Aoti) station and a rural YF (Yufa) station in Beijing was examined and a notable upward trend of ozone concentrations at both stations was found from 2006 to 2017. Following this, through a statistical model, the relative contribution of meteorological conditions to long-term ozone variations at both stations was calculated as 2%–3%, indicating anthropogenic emissions were the major cause for long-term ozone variations in Beijing. Meanwhile, short-term ozone variations could be influenced significantly by seasonal and synoptic meteorological conditions. Furthermore, the long-term variations of ozone formation regimes across Beijing were analyzed using OMI (Ozone Monitoring Instrument) retrieved HCHO VCDs (Vertical Column Densities)/NO2 VCDs, which were strongly correlated with ozone concentrations. The results suggested that the ozone formation regime for the AT urban station and YF rural station had changed from VOCs-limited and NOx-limited to VOCs-NOx-limited respectively. In this case, NOx-oriented emission-reduction measures for reducing PM2.5 concentrations might conversely enhance ozone concentrations in Beijing. Given the increasingly heterogeneous distribution of different ozone formation regimes across Beijing, emission-reduction strategies that balanced consider the reduction of VOCs and NOx emissions should be better designed and implemented according to local ozone formation regimes.
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•Zn-S catalyst improves DB22 decolonization and mineralization rate by heterogeneous catalytic ozonation.•Zn, Ca constituents in Zn-S improve OH* generation in heterogeneous catalytic ...ozonation of DB22.•DB22′s mineralization by Zn-S catalytic ozonation was highest in alkaline condition.•Mineralization kinetic of DB22 follows pseudo-first order kinetic model.
This study developed a low cost catalyst, namely, zinc slag (Zn-S) for the ozonation process of Direct Black 22 (DB22) from aqueous solutions. Among five different kind of low cost metal slags including Fe-S, Cu-S, Cd-S, Pb-S and Zn-S, the Zn-S slag was selected as an efficient catalyst in this study. Zn-S contained mainly zinc (Zn) and calcium (Ca) discharged from zinc slag waste in Vietnam. It was found that Zn-S could effectively decolonize and mineralize DB22 through heterogeneous catalytic ozonation. The degradation kinetic of DB22 followed the pseudo-first order model. The best removal efficiency of DB22 (Zn-S/O3/H2O2 (76%) > Zn-S/O3 (69%) > O3/H2O2 (66%) > O3 (55% for COD) occurred at pH 11 for heterogeneous catalytic ozonation processes with Zn-S as the catalyst as well as ozone alone and perozone processes due to fast decomposition of O3 in alkaline solution to generate powerful and non-selective OH radicals. An increase in decolonization and mineralization rate was observed when increasing the Zn-S dosage from 0.125 g/L to 0.75 g/L for Zn-S/O3 and 0.125 g/L to 1.0 g/L for Zn-S/O3/H2O2. The K values of the pseudo-first order model followed the same sequence as mineralization rates of DB22 in term of COD removal. Ca and Zn constituents in the Zn-S catalyst contributed to the increase in O3 decomposition and improvement of reaction rate with H2O2. Subsequently, the degradation of DB22 by the ozonation process with Zn-S catalyst was enhanced through the enrichment mechanism of hydroxyl radicals (*OH) and surface adsorption. The degradation mechanism of DB22 by hydroxyl radicals was surely affirmed by tests with the decrease in degradation percentage of DB22 in case of the presence t-butanol, Cl− and CO32−.
A significant overpotential necessary for the electrochemical oxygen evolution reaction (OER) is one of the most serious disadvantages in water electrolysis, which, on the contrary, gives the ...probability to electrochemically produce ozone alternative to the common corona discharge. To effectively suppress the competitive OER and improve gaseous ozone escaping, here we present a capillary effect-enabled electrolysis strategy by employing an unusual partial-submersed mode of anode composed of a β-PbO2 cuboids-loaded bulk porous Pb, and realize a much enhanced electrocatalytic gaseous ozone production in comparison to the cases of solid Pb counterpart and/or usual submersion operation. Detailed study reveals a capillary pressure-induced “molecular oxygen-locking effect” in the electrolyte fully filled in the porous structure of the electrode area above the electrolyte pool level, which unexpectedly leads to the production of unusual ·O3 – intermediate. Distinctive from the traditional electrochemical ozone production (EOP) mechanism dependent on the essential reaction between the atomic oxygen and molecular oxygen, the ·O3 – intermediate generation favors the EOP process in the special case where the capillary action is relevant for a porous bulk anode.
•This paper presents the high efficiency of gas supply and mass transfer in water using MNBs.•The ozone MNBs technique was applied for in situ groundwater remediation of an organics-contaminated ...site.•Ozone MNBs show considerable advantages in contaminant cleanup and time efficiency.•Ozone MNBs potentially represent an innovative technology for in situ remediation of organics-contaminated groundwater.
Ozone is widely used for water treatment because of its strong oxidation ability. However, the efficiency of ozone in groundwater remediation is limited because of its relatively low solubility and rapid decomposition in the aqueous phase. Methods for increasing the stability of ozone within the subsurface are drawing increasing attention. Micro-nano-bubbles (MNBs), with diameters ranging from tens of nanometres to tens of micrometres, present rapid mass transfer rates, persist for a relatively long time in water, and transport with groundwater flow, which significantly improve gas concentration and provide a continuous gas supply. Therefore, MNBs show a considerable potential for application in groundwater remediation. In this study, the characteristics of ozone MNBs were examined, including their size distribution, bubble quantity, and zeta potential. The mass transfer rate of ozone MNBs was experimentally investigated. Ozone MNBs were then used to treat organics-contaminated water, and they showed remarkable cleanup efficiency. Column tests were also conducted to study the efficiency of ozone MNBs for organics-contaminated groundwater remediation. Based on the laboratory tests, field monitoring was conducted on a trichloroethylene (TCE)-contaminated site. The results showed that ozone MNBs can greatly improve remediation efficiency and represent an innovative technology for in situ remediation of organics-contaminated groundwater.
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