Fabrication of a magnetic metal-organic framework/covalent organic framework composite for simultaneous magnetic solid-phase extraction of seventeen trace quinolones residues in meats.

Effective capture of quinolones (QNs) in animal-derived food is a vital procedure for food safety monitoring. However, the lack of adsorption specificity and difficult to recycle in complex substrate conditions have been major problems for most of the adsorbents. In this work, a magnetic Fe3O4/MOF/COF composite (named Fe3O4@NH2-MIL-125@TpPa-SO3H) was successfully synthesized with good magnetic responsiveness and conspicuous affinity towards QNs. The Fe3O4/MOF/COF composite was used as a magnetic solid-phase extraction (MSPE) adsorbent for pretreatment and determination of QNs in meat samples. Under optimal MSPE conditions in combination with high performance liquid chromatography-quadrupole orbitrap high resolution mass spectrometer (HPLC-Q-Orbitrap HRMS), the proposed method had good linearity (R2 ≥ 0.9978) from 0.01 to 100ng g-1, low limits of detection (0.0016 to 0.0940ng g-1), good precision with relative standard deviations lower than 5.8%. This method was effectively applied to the detection of 17 QNs in the spiked pork, chicken and beef samples with satisfactory recoveries from 83.9 to 106.2%. The separation selectivity mainly due to the π-π interaction, hydrogen bonding, and electrostatic attraction between QNs and the sulfonic acid and amino functional groups of the composite. After verification, the stability and reusability of the composite meet the requirements of complex matrix sample pretreatment. The developed MSPE method based on the magnetic Fe3O4/MOF/COF composite provided an ideal sample pretreatment alternative for determining trace QNs in complex matrixes with selectivity, simplicity, rapidity, and efficiency.

Energy efficient portable air cathode electrochlorinator for point-of-use disinfection of toilet wastewater.

Active chlorine is the most widely used disinfectant for water disinfection as well as surface sterilization. Here, we report an air cathode electrochlorinator for point-of-use disinfection of toilet wastewater. The air cathode dominated by a four-electron pathway to reduce O2 to OH- was more suitable for chlorine synthesis than through a two-electron pathway to H2O2, which could reduce chlorine back to chloride ions. The minimum driving potential of the air cathode electrochlorinator was as low as 0.94 V, which made it possible to be directly powered by a piece of commercial mini photovoltaic solar panel without electronic converter. Under the cell voltage of 2 V, the Faraday current efficiency was 82.0 % and the electrical energy required to produce 1 kg active chlorine was estimated to be only 1.75 kWh. The normalized energy consumption to disinfect simulated toilet wastewater with a pathogen concentration of 107 CFU/mL was estimated to be 7.2 W h/m3. Moreover, the material cost for fabrication of the electrochlorinator was estimated to be less than $ 0.62. These features guarantee the air cathode electrochlorinator of high potential for point-of-use disinfection of toilet wastewater.

Facile synthesis of triazine-based microporous organic network for high-efficient adsorption of flumequine and nadifloxacin: A comprehensive study on adsorption mechanisms and practical application potentials.

Flumequine (FLU) and nadifloxacin (NAD), as emerging contaminants, have received extensive attention recently. In this study, a triazine-based microporous organic network (TMON) was synthetized and developed as an excellent adsorbent for FLU and NAD. The adsorption behavior and influence factors were investigated in both single and binary systems. Insight into the adsorption mechanisms were conducted through experiments, models, and computational studies, from macro and micro perspectives including functional groups, adsorption sites, adsorption energy and frontier molecular orbital. The results showed that the maximum adsorption capacities of TMON for FLU and NAD are 325.27 and 302.28 mg/g under 30 °C higher than records reported before. TMON exhibits the better adaptability and anti-interference ability for influence factors, leading to the preferable application effect in kinds of real water samples. TMON also shows the application potentials for the adsorption of other quinolone antibiotics and CO2 capture. Hydrogen-bonding interaction played the most critical role compared to π-π stacking effect, π-π electron-donor-acceptor interaction, CH-π interaction, and hydrophobic interaction during the adsorption. TMON could be regarded as a promising environmental adsorbent for its large surface area, stable physical and chemical properties, excellent recyclability, and wide range of applications.

Enhanced removal of tetracycline via advanced oxidation of sodium persulfate and biochar adsorption.

Advanced oxidation of antibiotic tetracycline (TC) is becoming an accessible and efficient technology. The removal of TC from the complex wastewater needs to be lucubrated. In this study, a TC removal system involving degradation and adsorption was established. TC degradation was accomplished by enhanced advanced oxidation via the addition of sodium persulfate (SP) and biochar into simulated wastewater containing Mn2+ and TC wastewater. The adsorption of TC and its derivatives was removed by biochar. The results indicate that the optimized reaction parameters were 3.0 g/L of biochar prepared at 600 °C (B600) and 400 mg/L of SP under acidic condition, and the removal percentage of TC was 87.48%, including 74.23% of degradation and 13.28% of adsorption; the anions Cl-, NO3-, and H2PO4- had negligible effects on the removal of TC in this Mn2+/B600/SP system. The system also functioned well with an aqueous solution with a high chemical oxygen demand (COD) concentration. Electron paramagnetic resonance (EPR) analysis indicated that ·OH and SO4- free radicals were present in the Mn2+/B600/SP system. Based on the testing and analysis results, a removal mechanism and potential TC degradation pathway for this system were proposed. TC can be degraded by ·OH and SO4- via three degradation pathways. Mn2+ can be precipitated as MnO2, and a part of the TC and its derivatives can be adsorbed on the biochar surface. The Mn2+/B600/SP system also performed satisfactorily for a complex aqueous solution with various cations and antibiotics.

New insight into the co-adsorption of oxytetracycline and Pb(II) using magnetic metal-organic frameworks composites in aqueous environment: co-adsorption mechanisms and application potentials.

The present study aimed to investigate the co-adsorption and application of water stabilized Fe3O4@ZIF-8 composite with magnetic cubic crystal structure. This new material was successfully prepared by facile modification strategy and rational design, which was used for simultaneous adsorption of oxytetracycline (OTC) and Pb(II) in aqueous solution. The co-adsorption behavior and mechanism of the composite for OTC and Pb(II) were systematically investigated by characterization techniques and batch experiments, and its application potential was effectively evaluated. The results showed that the synthesized Fe3O4@ZIF-8 composite innovatively retained the cubic crystal structure of ZIF-8 and was successfully loaded on the surface of Fe3O4 particles with small particle size to form a core-shell structure. The Fe3O4@ZIF-8 composite possessed a large specific surface area (1722 m2/g), magnetic separation performance (13.4 emu/g), and rich functional groups. The co-adsorption of OTC and Pb(II) on Fe3O4@ZIF-8 had fast reaction kinetics (equilibrium within 90 min) and large adsorption capacity (310.29 mg/g and 276.06 mg/g respectively). The adsorption process for both contaminants followed pseudo-second order kinetics and Langmuir isotherm models and had synergistic and competitive effects at the same time. π-π stacking and electrostatic interaction were the main mechanisms of adsorption. Fe3O4@ZIF-8 had good adsorption performance after cyclic adsorption for 4 times and it performed well in the treatment of real waste water. This study provided a new sight for the control of combined pollution of OTC and Pb(II) and proved Fe3O4@ZIF-8 composites have great application potentials for complex wastewater treatment.

Stepwise hollow Prussian blue/carbon nanotubes composite as a novel electrode material for high-performance desalination.

As a promising intercalation material for capacitive deionization (CDI), Prussian blue (PB) and its analogues (PBAs) have the superiority of high theoretical capacity and easy synthesis. But they often suffer from low conductivity and severe crystal phase transition, resulting in inferior desalination capacity and poor cycling stability. Herein, the dual strategy of structural optimization and carbon-based materials introduction is proposed to enhance the desalination performance of PBAs. Stepwise hollow structure formed by surface etching has been proved to be more outstanding than cubic structure. Enlarged the specific surface area, the contact area with the electrolyte increases, therefore, more active sites are exposed. Besides, the etching of external surfaces provides more buffer space, improves the tolerance to crystal phase transition, and enhances the cycling stability. The introduction of carbon nanotubes brings high conductivity. Specifically, the desalination test shows that stepwise hollow Prussian blue/carbon nanotubes composite delivers a high desalination capacity of 103.4 mg g-1 with outstanding cycling stability. Moreover, the low energy consumption of 0.23 Wh g-1 is also suitable for practical application. The dual strategy opens a window to design advanced electrode materials for CDI.

Pollution characteristics of metal pollutants in PM2.5 and comparison of risk on human health in heating and non-heating seasons in Baoding, China.

PM2.5 particles were collected to study the distribution, accumulation and health risk assessment of metal pollutants. The concentrations of 11 kinds of metal elements in PM2.5 during heating period and non-heating period were analyzed. Based on the American health risk assessment model as well as the human exposure parameters in China, the human health risk was assessed. The concentrations of metal components in PM2.5 during the heating period were, in descending order, Pb, Mn, Cr, As, Sb, Se, Ni, Cd, Tl, Hg, and Be, while during the non-heating period, they were basically in the same order, except Cd and Ni, as the concentration of the former was a little higher than that of the latter. The concentrations of As, Cd, Hg, Ni, Se, and Tl were quite different in the heating period and non-heating period. The non-carcinogenic risks caused by metal elements were lower than the minimum acceptance 10-6 per year during both the heating period and non-heating period. The non-carcinogenic results of a descending order were Pb, Mn, Sb, Tl, Se, and Hg. The carcinogenic risks of a descending order were Cr, As, Cd, Ni, and Be. The risks of As and Cr to children were over 10-6. Hence, As and Cr should be considered as priorities.

Boosted activity of graphene encapsulated CoFe alloys by blending with activated carbon for oxygen reduction reaction.

The slow oxygen reduction reaction (ORR) hampers the efficiency of microbial fuel cells (MFCs) to a large extent, which usually requires catalysts to facilitate the electron transfer. The major challenge of the existed non-precious metals in place of the noble metal catalysts (Pt, Pd, Au et al.) for ORR is their low efficiency, which urgently needs special route to tackle this issue. Herein, we report a simple and convenient technique using prussian blue analogues as precursor to directly synthesize the N-doped graphene encapsulated CoFe alloy which is present in "Core-Shell" structure via calcination of Co2Fe(CN)6 in inert condition. The encapsulation of metal alloy within graphene shell immensely promotes the electron transfer from the encapsulated metals to the graphene surface. It efficiently optimizes the electronic structure of the as-synthesized catalyst and thereby triggers high ORR activity. The surrounding activated carbon (AC) contributes to the large pore structure and further offers a commodious route for the oxygen to gain electron. Therefore, the total resistance of air cathodes is significantly reduced from 17.300â€¯Ω to 9.551â€¯Ω and the electrochemical activity is greatly improved. The power performances of MFCs indicate that CoFe/C-10% presents the highest maximum power density (MPD) of 1616 mW m-2, which is 5 times larger than that of the bare AC. It is well concluded that the graphene encapsulated CoFe alloy can be recognized as potential ORR catalyst for MFCs.