Plasma-induced, N-doped, and reduced graphene oxide-incorporated NiCo-layered double hydroxide nanowires as a high-capacity redox mediator for sustainable decoupled water electrolysis.

Although the recent emergence of decoupled water electrolysis prevents typical H2/O2 mixing, the further development of decoupled water electrolysis has been confined by the lack of reliable redox mediator (RM) electrodes to support sustainable H2 production. As energy storage electrodes, layered double hydroxides (LDHs) possess inherently poor conductivity/stability, which can be improved by growing LDHs on graphene substrates in situ. The proper modification of the graphene surface structure can improve the electron transport and energy storage capacity of composite electrodes, while current methods are usually cumbersome and require high temperatures/chemical reagents. Therefore, in this study, dip coating was adopted to grow graphene oxide (GO) on nickel foam (NF). Then, the GO was reduced using nonthermal plasma (NTP) to reduced GO (rGO) in situ while simultaneously implementing N doping to obtain plasma-assisted N-doped rGO on NF (PNrGO/NF). The uniform conductive substrate ensured the subsequent growth of less-aggregated NiCo-LDH nanowires, which improved the conductivity and energy storage capacity (5.93 C/cm2 at 5 mA/cm2) of the NiCo-LDH@PNrGO/NF. For the decoupled system, the composite RM electrode exhibited a high buffering capacity for 1300 s during the decoupled H2/O2 evolution, and in the conventional coupled system, the necessary input voltage of 1.67 V was separated into two lower ones, 1.42/0.33 V for H2/O2 evolutions, respectively. Simultaneously, the RM possessed outstanding redox reversibility and structural stability during long-term cycling. This work could offer a feasible strategy for using NTP to synthesize excellent RM electrodes for application to decoupled water electrolysis.

High buffering capacity cobalt-doped nickel hydroxide electrode as redox mediator for flexible hydrogen evolution by two-step water electrolysis.

Two-step water electrolysis has been proposed to tackle the ticklish H2/O2 mixture problems in conventional alkaline water electrolysis recently. However, low buffering capacity of pure nickel hydroxide electrode as redox mediator limited practical application of two-step water electrolysis system. A high-capacity redox mediator (RM) is urgently needed to permit consecutive operation of two-step cycles and high-efficiency hydrogen evolution. Consequently, a high mass-loading cobalt-doped nickel hydroxide/active carbon cloth (NiCo-LDH/ACC) RM is synthesized via a facile electrochemical method. The proper Co doping can apparently enhance the conductivity and simultaneously remain the high-capacity of the electrode. Density functional theory results further confirms more negative values in redox potential of NiCo-LDH/ACC than Ni(OH)2/ACC on account of the charge redistribution induced by Co doping, which can prevent the parasitic O2 evolution on RM electrode during decoupled H2 evolution step. As a result, the NiCo-LDH/ACC combined the superiorities of high-capacity Ni(OH)2/ACC and high-conductivity Co(OH)2/ACC, and the NiCo-LDH/ACC with 4:1 ratio of Ni to Co presented a large specific capacitance of 33.52F/cm2 for reversible charge-discharge and high buffering capacity with two-step H2/O2 evolution duration of 1740 s at 10 mA/cm2. The necessary input voltage (2.00 V) of the whole water electrolysis was broken into two smaller ones, 1.41 and 0.38 V, for H2 and O2 production, respectively. NiCo-LDH/ACC provided a favorable electrode material for the practical application of two-step water electrolysis system.

Rosmarinic acid, the active component of Rubi Fructus, induces apoptosis of SGC-7901 and HepG2 cells through mitochondrial pathway and exerts anti-tumor effect.

Rosmarinic acid (RA) is a well-known phenolic acid widely present in over 160 species of herbal plants and known to exhibit anti-tumor effects on breast, prostate, and colon cancers in vitro. However, its effect and mechanism in gastric cancer and liver cancer are unclear. Moreover, there is no RA report yet in the chemical constituents of Rubi Fructus (RF). In this study, RA was isolated from RF for the first time, and the effect and mechanism of RA on gastric and liver cancers were evaluated using SGC-7901 and HepG2 cells models. The cells were treated with different concentrations of RA (50, 75, and 100 µg/mL) for 48 h, and the effect of RA on cell proliferation was evaluated by the CCK-8 assay. The effect of RA on cell morphology and mobility was observed by inverted fluorescence microscopy, cell apoptosis and cell cycle were determined by flow cytometry, and the expression of apoptosis-related proteins cytochrome C, cleaved caspase-3, Bax, and Bcl-2 was detected by western blotting. The results revealed that, with an increase in the RA concentration, the cell viability, mobility, and Bcl-2 expression decreased, while the apoptosis rate, Bax, cytochrome C, and cleaved caspase-3 expression increased, and SGC-7901 and HepG2 cells could be induced to arrest their cell cycle in the G0/G1 and S phases, respectively. These results together indicate that RA can induce apoptosis of SGC-7901 and HepG2 cells through the mitochondrial pathway. Thus, this study supplements the material basis of the anti-tumor activity of RF and provides an insight into the potential mechanism of RA-inducing apoptosis of gastric cancer SGC-7901 cells and liver cancer HepG2 cells, thereby facilitating further developmental studies on and the utilization of the anti-tumor activity of RF.

Pd-doped HKUST-1 MOFs for enhanced hydrogen storage: effect of hydrogen spillover.

Extensive research has been devoted to developing metal nanoparticle (NP) doped porous materials with large hydrogen storage capacity and high hydrogen release pressure at ambient temperature. The ultra-sound assisted double-solvent approach (DSA) was applied for sample synthesis. In this study, tiny Pd NPs are confined into the pore space of HKUST-1, affording Pd@HKUST-1-DS with minimizing the aggregation of Pd NPs and subsequently the formation of Pd NPs on the external surface of HKUST-1. The experimental data reveal that the obtained Pd NP doped Pd@HKUST-1-DS possessed an outstanding hydrogen storage capacity of 3.68 wt% (and 1.63 wt%) at 77 K and 0.2 MPa H2 (and 298 K and 18 MPa H2), in comparison with pristine HKUST-1 and impregnated Pd/HKUST-1-IM. It is found that the storage capacity variation is not only ascribed to the different textural properties of materials but is also illustrated by the hydrogen spillover induced by different electron transport from Pd to the pores of MOFs (Pd@HKUST-1-DS > Pd/HKUST-1-IM), based on X-ray photoelectron spectroscopy and temperature desorption spectra. Pd@HKUST-1-DS, featuring high specific surface area, uniform Pd NP dispersion and strong interaction of Pd with hydrogen in the confined pore spaces of the support, displays the high hydrogen storage capacity. This work highlights the influence of spillover caused by Pd electron transport on the hydrogen storage capacity of metal NPs/MOFs, which is governed by both physical and chemical adsorption.

Mechanisms and degradation pathways of doxycycline hydrochloride by Fe3O4 nanoparticles anchored nitrogen-doped porous carbon microspheres activated peroxymonosulfate.

Peroxymonosulfate (PMS) based advanced oxidation processes have gained widespread attention in refractory antibiotics treatment. In this study, Fe3O4 nanoparticles anchored nitrogen-doped porous carbon microspheres (Fe3O4/NCMS) were synthesized and applied to PMS heterogeneous activation for doxycycline hydrochloride (DOX-H) degradation. Benefitting from synergy effects of porous carbon structure, nitrogen doping, and fine dispersion of Fe3O4 nanoparticles, Fe3O4/NCMS showed excellent DOX-H degradation efficiency within 20 min via PMS activation. Further reaction mechanisms revealed that the reactive oxygen species including hydroxyl radicals (•OH) and singlet oxygen (1O2) played the dominant role for DOX-H degradation. Moreover, Fe(II)/Fe(III) redox cycle also participated in the radical generation, and nitrogen-doped carbonaceous structures served as the highly active centers for non-radical pathways. The possible degradation pathways and intermediate products accompanying DOX-H degradation were also analyzed in detail. This study provides key insights into the further development of heterogeneous metallic oxides-carbon catalysts for antibiotic-containing wastewater treatment.

Three-dimensional ordered macroporous molybdenum doped NiCoP honeycomb electrode for two-step water electrolysis.

Two-step alkaline water electrolysis is considered a safe and efficient method for producing hydrogen from renewable energy. Reversal of the current polarity in a bifunctional electrocatalyst used as a gas evolution electrode (GEE) in two-step water electrolysis can generate H2/O2 at different times and in different spaces. The design of a bifunctional electrocatalyst with high durability and excellent activity is imperative to achieving continuous, safe, and pure H2 generation via two-step alkaline water electrolysis. Here, we present for the first time a novel 3D Mo-doped NiCo phosphide honeycomb electrocatalyst that was grown on nickel foam (3D Mo-NiCoP/NF) and fabricated using polystyrene as a template. The electrocatalyst exhibited extremely low overpotentials in both the hydrogen evolution reaction (HER; 117 mV at 10 mA/cm2) and the oxygen evolution reaction (OER; 344 mV at 100 mA/cm2). As a bifunctional electrocatalyst for two-step alkaline water electrolysis, the device had a 1.784 V cell voltage at 10 mA/cm2, 95% decoupling efficiency, and ∼83% energy conversion efficiency. Taken together, the use of 3D Mo-NiCoP/NF as a GEE reduced the complexity and lowered the cost of the electrolyzer. The latter could be used to construct highly competitive water-splitting systems for continuous H2 production and green energy harvesting.

Highly Effective H2/D2 Separation within the Stable Cu(I)Cu(II)-BTC: The Effect of Cu(I) Structure on Quantum Sieving.

Realizing ideal deuterium separation from isotopic mixtures remains a daunting challenge because of their almost identical sizes, shapes, and physicochemical properties. Using the quantum sieving effect in porous materials with suitable pore size and open metal sites (OMSs) enables efficient hydrogen isotope separation. Herein, synthetic HKUST-1-derived microporous mixed-valence Cu(I)Cu(II)-BTC (BTC = benzene-1,3,5-tricarboxylate), featuring a unique network of distinct Cu(I) and Cu(II) coordination sites, can remarkably boost the D2/H2 isotope separation, which has a high selectivity (SD2/H2) of 37.9 at 30 K, in comparison with HKUST-1 and other porous materials. Density functional theory (DFT) calculations indicate that the introduction of Cu(I) macrocycles in the framework decreases the pore size and further leads to relatively enhanced interaction of H2/D2 molecules on Cu(II) sites. The significantly enhanced selectivity of Cu(I)Cu(II)-BTC at 30 K can be mainly attributed to the synergistic effect of kinetic quantum sieving (KQS) and chemical affinity quantum sieving (CAQS). The results reveal that Cu(I) OMSs exhibit counterintuitive behaviors and play a crucial role in tuning quantum sieving without a complex structural design, which provides a deeper insight into quantum sieving mechanisms and a new strategy for the intelligent design of highly efficient isotope systems.

Volatile organic compounds degradation by nonthermal plasma: a review.

Volatile organic compounds (VOCs) have posed a severe threat on both ecosystem and human health which thus have gained much attention in recent years. Nonthermal plasma (NTP) as an alternative to traditional methods has been employed to degrade VOC in the atmosphere and wastewater for its high removal efficiency (up to 100%), mild operating conditions, and environmental friendliness. This review outlined the principles of NTP production and the applications on VOC removal in different kinds of reactors, like single/double dielectric barrier discharge, surface discharge, and gliding arc discharge reactors. The combination of NTP with catalysts/oxidants was also applied for VOC degradation to further promote the energy efficiency. Further, detailed explanations were given of the effect of various important factors including input/reactor/external conditions on VOC degradation performance. The reactive species (e.g., high-energy electrons, HO·, O·, N2+, Ar+, O3, H2O2) generated in NTP discharge process have played crucial roles in decomposing VOC molecules; therefore, their variation under different parameter conditions along with the reaction mechanisms involved in these NTP technologies was emphatically explained. Finally, a conclusion of the NTP technologies was presented, and special attention was paid to future challenges for NTP technologies in VOC treatment to stimulate the advances in this topic.

Nitrate removal under low carbon to nitrogen ratio by modified corn straw bioreactor: Optimization and possible mechanism.

ABSTRACTThe removal of nitrate (NO3--N) from water bodies under the conditions of poor nutrition and low carbon to nitrogen (C/N) ratio is a widespread problem. In this study, modified corn stalk (CS) was used to immobilize Burkholderia sp. CF6 with cellulose-degrading and denitrifying abilities. The optimal operating parameters of the bioreactor were explored. The results showed that under the hydraulic retention time (HRT) of 3 h and the C/N ratio of 2.0, the maximum nitrate removal efficiency was 96.75%. In addition, the organic substances in the bioreactor under different C/N ratios and HRT were analyzed by three-dimensional fluorescence excitation-emission mass spectrometry (3D-EEM), and it was found that the microorganisms have high metabolic activity. Scanning electron microscope (SEM) showed that the new material has excellent immobilization effects. Fourier transform infrared spectrometer (FTIR) showed that it has potential as a solid carbon source. Through high-throughput sequencing analysis, Burkholderia sp. CF6 was observed as the main bacteria present in the bioreactor. These research results showed that the use of waste corn stalks waste provides a theoretical basis for the advanced treatment of low C/N ratio wastewater.

Efficient adsorption and reduction of Cr(VI) from aqueous solution by Santa Barbara Amorphous-15 (SBA-15) supported Fe/Ni bimetallic nanoparticles.

Nanoscale zero-valent iron (nZVI or Fe0) can rapidly reduce Cr(VI) contaminants in the water environment, but the agglomeration and passivation of the Fe0 system have adverse effects on its application. In this study, a novel mesoporous Santa Barbara Amorphous-15 supported Fe/Ni bimetallic composite (SBA-15@Fe/Ni) is proposed to remove Cr(VI). The proposed material can enhance the stability and removal capacity of the nZVI system. The results show that the unique six-way through-hole structure of SBA-15 provides a place for the dispersion of Fe0 particles. Meanwhile, SBA-15 effectively alleviates the accumulation of Fe0 particles. The removal efficiency of SBA-15@Fe/Ni is better than two single systems (SBA-15 and Fe/Ni). The removal efficiency of SBA-15@Fe/Ni towards Cr(VI) can reach 97.62% after 60 min at pH 4.0. SBA-15@Fe/Ni still maintains excellent performance in the presence of various competitive ions (Cl-, SO42-, CO32-, NO3-). At 298 K, the maximum removal capacity of SBA-15@Fe/Ni towards Cr(VI) is 180.99 mg/g. The possible removal process of SBA-15@Fe/Ni towards Cr(VI) is divided into the following steps: First, Cr(VI) is attracted into the vicinity of the SBA-15@Fe/Ni channel by the electrostatic attraction; Second, the reduction of Cr(VI) occurs after contacting with the Fe/Ni system, and its driving force mainly comes from nZVI and Fe(II); Furthermore, the introduction of Ni can promote Cr(VI) reduction through electron transfer and catalytic hydrogenation. In conclusion, adopting SBA-15@Fe/Ni to treat chromium contamination is an effective and promising approach.

Correction: Graphene oxide-iron oxide and reduced graphene oxide-iron oxide hybrid materials for the removal of organic and inorganic pollutants.

[This corrects the article DOI: 10.1039/C2RA20885G.].

Correction: Synthesis of porous Fe3O4 hollow microspheres/graphene oxide composite for Cr(VI) removal.

Correction for 'Synthesis of porous Fe3O4 hollow microspheres/graphene oxide composite for Cr(VI) removal' by Mancheng Liu et al., Dalton Trans., 2013, 42, 14710-14717, https://doi.org/10.1039/C3DT50955A.

A rare potassium-rich zirconium fluorophosphonate with high Eu3+ adsorption capacities from acidic solutions.

A novel 3D potassium-containing zirconium fluorophosphonate K2Zr[CH2(PO3)2]F2 (SZ-8) was successfully synthesized as single crystals via a solvothermal method using a mixture of nitric acid and potassium nitrate as mineralizers. SZ-8 can adsorb 110.6 and 57 mg g-1 of Eu3+ in pH 2 and pH 1 solutions respectively, highlighting its potential remediation for radionuclides with high charges. SZ-8 not only possesses superior Eu3+ removal capacity under strongly acidic conditions, but also provides a universal synthesis strategy for crystalline zirconium phosphonates with inorganic counterions.

Insight into UV-induced simultaneous photocatalytic degradation of Ti3C2Tx MXene and reduction of U(VI).

With the development of MXene as the efficient adsorbent for U(VI), the tendency of MXene coming into contact with U(VI) in wastewaters increases. Motivated by UV light irradiation applied in wastewater treatments, the UV light induced photochemical co-transformation of Ti3C2Tx MXene and U(VI) is studied. To clarify the role of U(VI) induced Ti3C2Tx aggregation in phototransformation of Ti3C2Tx, the aggregation kinetics of Ti3C2Tx in the presence of various valent radioactive ions are investigated, obtaining the critical coagulation concentrations (CCC) of Ti3C2Tx for Cs+, Sr2+, UO22+, Eu3+, and Th4+. Besides, the colloidal stability of UV-induced Ti3C2Tx as a function of standing time is discussed. The results show that the aggregation behavior of Ti3C2Tx induced by radioactive ions follows the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and the Schulze-Hardy rule. The UV irradiation will change the physicochemical properties and colloidal stabilities of Ti3C2Tx. Furthermore, the degradation of Ti3C2Tx can be accelerated by UV irradiation and further promoted by the presence of U(VI). The removal of U(VI) is highest in the case of Ti3C2Tx combined with UV irradiation via adsorption and reduction. This study provides an example demonstrating that the simultaneous transformation of Ti3C2Tx (adsorbent) and U(VI) (adsorbate) to mild toxic components.

Interconnected hierarchical nickel-carbon hybrids assembled by porous nanosheets for Cr(VI) reduction with formic acid.

Magnetic carbon materials promise distinct advantages in the decontamination of heavy metal ions. In this work, a novel interconnected hierarchical nickel-carbon (Ni@IHC) hybrid was synthesized by combining the solvothermal method with a one-step pyrolysis under argon atmosphere. Benefitting from 3D flower-like morphology, interconnected porous nanosheets, large surface area, and abundant Ni nanoparticles, Ni@IHC hybrids can remove Cr(VI) within 25 min by using formic acid (FA) as a reductant at 25 ℃. Furthermore, the experimental parameters that can affect the material catalytic performance such as initial Cr(VI) concentration, catalyst dosage, FA concentration, and temperature were also investigated in detail. It was found that highly dispersed Ni nanoparticles contributed significantly to the reduction process. More importantly, the embedded Ni nanoparticles favor fast separation by a magnet and were helpful for the recycles use. This Ni@IHC hybrid was obtained by a facile and easy scale-up method, resulting in the fast transformation of Cr(VI) into Cr(III).

Efficient Sr-90 removal from highly alkaline solution by an ultrastable crystalline zirconium phosphonate.

We report here a distinct case of strontium removal under 1 M NaOH solution by an ultrastable crystalline zirconium phosphonate framework (SZ-7) with high adsorption capacity (183 mg g-1) and in-depth removal performance (Kd = 3.9 × 105 mL g-1), demonstrating the potential application of SZ-7 for 90Sr removal in highly alkaline nuclear waste.

Pseudomonas stutzeri GF2 augmented the denitrification of low carbon to nitrogen ratio: Possibility for sewage wastewater treatment.

A denitrifying strain with high efficiency at low carbon to nitrogen (C/N) ratio of 2.0 was isolated and characterized. It belongs to the genus Pseudomonas. Scanning electron microscopy (SEM) showed that GF2 was rod-shaped. The nitrate removal efficiency reached up to 92.41% (1.85 mg L-1 h-1) with the C/N ratio of 2.0 and the nitrite accumulation eventually decreased to 0.88 mg L-1. By response surface method (RSM) method, three reaction conditions of strain GF2 were optimized, including pH, C/N ratio, and nitrate concentration. Nitrogen balance and gas detection revealed that 88.03% of nitrogen was removed in gaseous form (included 98.80% nitrogen gas), which confirmed its efficient denitrification ability and pathway. 3D fluorescence spectrum (3D-EEM) manifested that in the absence of organic matter, strain GF2 can utilize extracellular polymeric substance (EPS) as carbon source for efficient denitrification. This research strived to provide new research ideas for low C/N ratio sewage treatment.

Role of porous polymer carriers and iron-carbon bioreactor combined micro-electrolysis and biological denitrification in efficient removal of nitrate from wastewater under low carbon to nitrogen ratio.

In the current research, a novel bioreactor composed of porous polymer carriers and iron-carbon (PPC@FeC) was established through bacterial immobilized technology. The influence of key factors was studied on the nitrate removal performance of the PPC@FeC bioreactor. The experimental results showed that the highest removal rate of nitrate (7.33 mg L-1 h-1) can be obtained with short hydraulic retention times (HRT = 2.0 h) and low carbon-to-nitrogen ratio (C/N = 2.0). The results of high-throughput sequencing revealed that Zoogloea sp. L2 was the dominant strain in bioreactor responsible for nitrate removal. Moreover, the SEM and XRD analyses elucidated that Fe2O3 was the final product produced by the interaction of FeC and strain L2. These findings showed that the PPC@FeC bioreactor successfully combined micro-electrolysis and biological denitrification, which exhibited great potential in removing nitrate effectively from wastewater under low C/N ratio and short HRT conditions.

Three dimensional flower-like magnetic polyethyleneimine@MoS2 composites for highly efficient removal of Cr(VI) and Pb(II) ions.

Magnetic Fe3O4 nanoparticles were coated by polyethyleneimine (PEI), and then Fe3O4@PEI was further modified with MoS2 by the hydrothermal method to fabricate 3D flower-like structured magnetic polyethyleneimine@MoS2 (MP@MoS2) composites, and the composites were served as efficient adsorbents to capture Cr(VI) and Pb(II) from aqueous solution. The effects of temperature, pH, shaking time and environmental conditions on adsorption performance of MP@MoS2 towards Cr(VI) and Pb(II) have been conducted by batch adsorption experiments. The prepared MP@MoS2 exhibited high adsorption capacities (192.30 mg/g for Cr(VI) at pH 3.0 and 256.41 mg/g for Pb(II) at pH 6.0) and the adsorption equilibrium could be achieved in a short time. Moreover, MP@MoS2 composites with high saturation magnetization could be simply separated under an external magnet. Combined experiments and spectral analysis, the underlying adsorption mechanism for Cr(VI) on MP@MoS2 was mainly attributed to the reduction of Cr(VI) to Cr(III), and the removal of Pb(II) was due to the complexation with sulfur groups and amino-groups. Consequently, the prepared 3D flower-like structured MP@MoS2 has a great potential for the practical application in removing Cr(VI) and Pb(II) from the aquatic environment.

Magnetic metal organic frameworks/graphene oxide adsorbent for the removal of U(VI) from aqueous solution.

A well-defined magnetic metal organic frameworks (MOFs)/graphene oxide (Fe3O4@HKUST-1/GO) consisting of magnetic Fe3O4 nanoparticles, HKUST-1 nanocrystal and GO was synthesized through a simple and environmentally friendly approach. Characterizations of Fe3O4@HKUST-1/GO adsorbing U(VI) with high-resolution transmission electron microscopy suggested that the Fe3O4@HKUST-1/GO possessed good stability. The introduction of GO enhanced the ability of particles to uptake U(VI) from aqueous solution. The effects of solution pH, contact time and temperature on U(VI) adsorption were systematically tested by intermittent experiments. The adsorption process can be better described by the Langmuir model and the pseudo-second-order kinetic model. The results showed that the Fe3O4@HKUST-1/GO exhibited good adsorption capacity towards U(VI) at the initial solution pH value of 4.0 and T = 318 K. The X-ray photoelectron spectroscopy was used to analyze the U(VI) removal mechanism. This work represents the application of Fe3O4@HKUST-1/GO as a novel adsorbent to extract U(VI) from contaminated water.