The efficiency and mechanism of heterogeneous catalytic O3 and UV/O3 for municipal solid waste (MSW) incineration leachate advanced treatment was systematically compared. Prior to comparison, catalyst used in heterogenous catalytic O3 and operation parameters for each technology were optimized. The COD removal of CuO@Al2O3/O3 under its optimal parameters was 57.2%, which failed to meet the standard (≥75%). In contrast, the COD removal by UV/O3 could be 82.3%. The superior efficiency of UV/O3 over CuO@Al2O3/O3 could be summarized into three aspects: (I) Cu bounded ·OH (≡Cu–O·) preferentially attacked hydrophilic groups, while free hydroxyl radical (·OH) was non-selective, thus UV/O3 exhibited a unique three-stage mechanism; (II) The oxidation potential of ≡Cu–O· was higher than that of ·OH, therefore was more vulnerable to the negative effect of radical self-quenching; (III) The existence of UV-induced excited states made organics in UV/O3 more active than in CuO@Al2O3/O3 system, thus high concentration of anions enhanced COD removal in UV/O3 but affected that in CuO@Al2O3/O3. The study further revealed the characteristics of heterogeneous catalytic O3 and UV/O3, and UV induced excited state should be considered in UV-based advanced oxidation processes (AOPs).
The development of digital economy and expansion of digital trade has become an inherent requirement for China to seize the high ground of digital industry revolution, and to build a new development pattern in which the domestic circulation is the mainstay and the domestic and international double circulation promote each other. Clarifying China’s position, especially its advantages and disadvantages relative to the USA and the EU in the international competition of digital economy and trade, is crucial to judge and guide the future development of China’s digital economy in both domestic and international double circulation. At present, there are various methods to define and measure the digital economy and digital trade, but there is a lack of connection and comparison between different methods as well as between different countries from a global perspective. Based on the solid statistical measurements and comparative analysis of relevant data，we make in-depth research on scale pattern, structural pattern, dynamic pattern, competition pattern, dependency pattern, etc. between China, the USA and the EU, and find that China’s digital economy and trade is“big but not excellent, fast but not first, surplus but not winning”. Therefore, we propose policy suggestions for the sustainable development of China’s digital economy and trade such as comprehensively optimizing the digital economic structure, promoting strengths and avoiding weaknesses in the electronic equipment manufacturing industry, cultivating a new pillar of the information service industry, and reversing the disadvantages in the digital media industry.
The occurrence of antibiotics in drinking water resources, like reservoirs, is of considerable concern due to their potential risks to ecosystem, human health, and antimicrobial resistance development. Here, we quantified 83 antibiotics in water and sediments of wet and dry seasons from the Miyun reservoir and its inflow rivers in Beijing, China. Twenty-four antibiotics were detected in water with concentrations of ND-11.6 ng/L and 19 antibiotics were observed in sediments with concentrations of ND-6.50 ng/g. Sulfonamides (SAs) were the dominated antibiotics in water in two seasons. SAs and quinolones (QNs) in wet season and macrolides (MLs) and QNs in dry season predominated in sediments. The reservoir and inflow rivers showed significant differences in antibiotic concentrations and compositions in water and sediments. As an important input source of reservoir, the river water showed significantly higher total antibiotic concentrations than those in the reservoir. In contrast, the reservoir sediments are the sink of antibiotics, and had higher total antibiotic concentrations compared with rivers. A prioritization approach based on the overall risk scores and detection frequencies of antibiotics was developed, and 3 (sulfaguanidine, anhydroerythromycin, and sulfamethoxazole) and 5 (doxycycline, sulfadiazine, clarithromycin, roxithromycin, and flumequine) antibiotics with high and moderate priority, respectively, were screened. The study provides a comprehensive insight of antibiotics in the Miyun Reservoir and its inflow rivers, and is significant for future monitoring and pollution mitigation of antibiotics.
“Concentrate-and-degrade” is an effective strategy to promote mass transfer and degradation of pollutants in photocatalytic systems, yet suitable and cost-effective photocatalysts are required to practice the new concept. In this study, we doped a post-transition metal of Indium (In) on a novel composite adsorptive photocatalyst, activated carbon-supported titanate nanotubes (TNTs@AC), to effectively degrade perfluorooctanoic acid (PFOA). In/TNTs@AC exhibited both excellent PFOA adsorption (>99% in 30 min) and photodegradation (>99% in 4 h) under optimal conditions (25 °C, pH 7, 1 atm, 1 g/L catalyst, 0.1 mg/L PFOA, 254 nm). The heterojunction structure of the composite facilitated a cooperative adsorption mode of PFOA, i.e., binding of the carboxylic head group of PFOA to the metal oxide and attachment of the hydrophobic tail to AC. The resulting side-on adsorption mode facilitates the electron (e‒) transfer from the carboxylic head to the photogenerated hole (h+), which was the major oxidant verified by scavenger tests. Furthermore, the presence of In enables direct electron transfer and facilitates the subsequent stepwise defluorination. Finally, In/TNTs@AC was amenable to repeated uses in four consecutive adsorption-photodegradation runs. The findings showed that adsorptive photocatalysts can be prepared by hybridization of carbon and photoactive semiconductors and the enabled “concentrate-and-degrade” strategy is promising for the removal and degradation of trace levels of PFOA from polluted waters.
A novel Z-scheme Ag/AgVO3/carbon-rich g-C3N4 heterojunction with excellent solar-light-driven photocatalytic activity was constructed via a facile hydrothermal-calcining method. The Ag/AgVO3/carbon-rich g-C3N4 composites displayed superior performance for the photocatalytic degradation of sulfamethiadiazole (SFZ) under solar irradiation. The optimal composite with a 10 wt% Ag/AgVO3 content showed the highest photocatalytic activity, its degradation rate constant (k) for SFZ degradation was ∼13 and 30 times than that of carbon-rich g-C3N4 (CCN) and Ag/AgVO3, respectively. Furthermore, •O2– was identified as the most crucial reactive species in the Z-scheme photocatalysis system. The greatly improved photocatalytic activities are derived from the built-in electric field (BIEF) of CCN and efficient Z-scheme charge transfer with Ag nanoparticles as charge transmission-bridge. The possible photocatalytic degradation mechanism and pathway over Ag/AgVO3/carbon-rich g-C3N4 were proposed based on LC-MS analysis and density functional theory (DFT) calculation, and the toxicity of intermediates was evaluated by Quantitative structure–activity relationship (QSAR) based prediction. In summary, this work provides new insight into constructing highly efficient Z-scheme photocatalyst, which is promising for implementation in surface water remediation.
Geological carbon storage and utilization is commonly-accepted as the most feasible approach to mitigate carbon emissions in energy transition period. Shale reservoirs attract special attentions due to their huge amounts of reserves and wide distributions worldwide. In the meantime, improved technologies are required to implement the production and storage projects in the shale reservoirs because dramatic changes of phase and production properties occur and most conventional methods become inapplicable. Here, first, a field-scale numerical reservoir simulation is developed to model the miscible CO2 utilization in the fractured shale reservoirs. Second, an analytical nanoscale-extended theory model is proposed to calculate a series of basic physiochemical properties and production parameters by including the intermolecular interactions and confinement effects. Third, the CO2 post-production storage is specifically investigated in fractured shale reservoirs. All models developed in this study are compared with and verified by the literature data. Continuous CO2 injection is applied for an 800-day EOR process in the fractured shale reservoir. With the production time, the reservoir oil saturations and pressures become lower, while the gas saturations and cumulative oil productions/oil recovery factors become higher. Moreover, the confinement effect is beneficial to enhance oil productions. The miscible CO2 injection is achieved through, at least in majority, the vaporization process based on the compositional analysis results. On the other hand, in comparison with the conventional reservoirs, the shale reservoirs with nanopores are proven to be more promising for the post-production CO2 storage due to larger caprock sealing pressure, maximum storage height, and storage capacity. The amount of CO2 trapped in the reservoir with confinement is three time as large as that without confinement. Overall, this study provides numerical simulation and analytical theory for the investigation and application of the coupled processes of miscible CO2 utilization and post-production geological storage in fractured shales.
More than two billion people worldwide have suffered thyroid disorders from either iodine deficiency or excess. By creating the national map of groundwater iodine throughout China, we reveal the spatial responses of diverse health risks to iodine in continental groundwater. Greater non-carcinogenic risks relevant to lower iodine more likely occur in the areas of higher altitude, while those associated with high groundwater iodine are concentrated in the areas suffered from transgressions enhanced by land over-use and intensive anthropogenic overexploitation. The potential roles of groundwater iodine species are also explored: iodide might be associated with subclinical hypothyroidism particularly in higher iodine regions, whereas iodate impacts on thyroid risks in presence of universal salt iodization exhibit high uncertainties in lower iodine regions. This implies that accurate iodine supply depending on spatial heterogeneity and dietary iodine structure optimization are highly needed to mitigate thyroid risks in iodine-deficient and -excess areas globally.