It is possible to remove volatile organic compounds containing chlorine (CVOCs, such as chlorobenzene) in a single device designed for selective catalytic reduction of NOx with NH3 for the industries ...containing CVOCs and NOx. Breaking the efficiency‐selectivity trade‐off in chlorobenzene oxidation remains a major challenge due to the conjugation of halogen atoms with the benzene ring and the reducing nature of NH3. A stepwise synthesis strategy is demontrated to disperse dual Ru/Cu Lewis acid sites outside and inside the zeolite channel. Under the confinement of zeolite, the Ru4+ Lewis acid site on the external surface of the zeolite promotes chlorobenzene oxidation by weakening the p‐π conjugate structure of Cl and benzene ring, while the Cu2+ Lewis acid site within the internal channel converts NOx and NH3 to N2. The mutual interference between catalytic oxidation and reduction is successfully avoided. Therefore, the low toxic CO2 and HCl selectivity experience a considerable increase from 21% to 86%, and from 51% to 94% with 91% conversion of chlorobenzene, while maintaining excellent elimination performance for NO (with N2 selectivity exceeding 90%). The incorporation of separated active sites and reaction spaces into the design may offer potentials for other energy and environmental applications.
A dual Ru/Cu Lewis acid sites dispersing respectively on the external surface and in the internal channel of zeolite is developed by a shape‐selective regulation strategy. The separated active site and reaction space, inhibiting the mutual interference of CBCO and SCR reactions, make Ru/Cu‐SSZ‐13 exhibit high CO2, HCl, and N2 selectivity for synergistic elimination of CB and NO.
Manganese oxide supported Pt single atoms (Pt1/MnOx) are prepared by the molten salt method. Catalytic oxidation of toluene and iso-hexane, typical emissions from furniture paints industry, is ...tested. Pt1/MnOx shows poor and high catalytic stability for toluene and iso-hexane oxidation, respectively. Enhancement in the catalytic stability for toluene oxidation is observed after the hydrogen reduction treatment of Pt1/MnOx at 200 °C. The hydrogen treated catalyst possesses the weaker Mn–O bonds and lower coordination number of PtO, with superior mobility of lattice oxygen and appropriate toluene adsorption. Balancing lattice oxygen mobility and volatile organic compounds adsorption is important for the catalytic stability of Pt1/MnOx. For the oxidation of toluene and iso-hexane mixture, owing to the competitive adsorption, iso-hexane oxidation is greatly inhibited, while toluene oxidation is not influenced. The present Pt1/MnOx catalyst holds promising prospect in furniture paints industry applications because of high catalytic stability and water resistance ability.
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•Single-atom Pt catalyst is synthesized via a novel one-pot molten salt strategy.•Simple H2 reduction treatment enhances the catalytic stability of single-atom Pt catalyst.•Balancing oxygen mobility and VOCs adsorption is the key for catalytic stability.•Single-atom Pt catalyst exhibits high performance for VOCs mixture removal in the presence of water.
To improve the desalination performance, the coconut shell-based activated carbon electrodes were prepared by using a two-stage activation method. Both the specific surface area and the ratio of ...mesopore to micropore can be successfully manipulated by the activation process of KOH etching plus CO2 gasification. The results showed that the activated carbon electrodes with controlled mesoporosity exhibited higher specific capacitance and better rate capability as compared to the commercial one. The coexistence of mesopores and micropores can provide large surface area for ions to form an electrical double layer, while the enlarged mesoporosity can not only facilitate the ion transport but also improve the accessible surface area, suggesting the improved capacity of capacitive ion storage. From the desalination experiments at 1.0V, the activated carbon electrode, associated with a specific surface area of 2105m2g−1 and a 70.7% ratio of mesopore to total pore volume, presented an electrosorption capacity of 9.72mgg−1 and electrosorption rate constant of 0.060min−1, which were considerably higher than the micropore-dominant carbon electrodes. Therefore, the significantly improved desalination performance can be ascribed to the high surface area and the high ratio of mesoporosity in the activated carbon-based capacitive deionization.
•A tunable ratio of mesopore to micropore can be achieved by combined chemical/physical activation process.•A coconut shell-based activated carbon electrode was prepared for capacitive deionization.•Enhanced desalination performance is ascribed to high specific surface area and high mesoporosity.
Wet flue gas desulfurization (WFGD) simultaneously removes Hg and SO2 from coal-fired power plant flue gas streams. Hg0 re-emission occurs when the dissolved Hg(II) is converted to a volatile form ...(i.e., Hg0) that can be subsequently emitted into the ambient air from WFGD wastewater aeration basins. Others have shown that Hg0 re-emission depends on pH, temperature, ligands (Cl, Br, I, F, SO32-, SO42-, NO3-, SCN-, and ClO-), O2, minerals (Se and As), and metals (Fe and Cu) in WFGD wastewater. Still others have shown Hg0 re-emission restriction via inhibitor addition (adsorbents and precipitators). This is the first review that summarizes the complex and inconsistently reported Hg0 re-emission mechanisms, updates misconceptions related to Hg(II) complexation and reduction, and reviews applications of inhibitors that convert aqueous Hg(II) into stable solid forms to prevent gaseous Hg0 formation and release.
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•Hg0 wet flue gas desulfurization (WFGD) re-emission mechanisms were summarized.•Effects of various aqueous parameters on Hg0 re-emission were reviewed.•Inhibitor applications on Hg0 re-emission restriction were compared.•Misconceptions related to Hg(II) complexation and reduction were updated.•Critical and future perspectives on Hg0 re-emission from WFGD water were presented.
Electrode materials are a crucial component for achieving high desalination performance via capacitive deionization (CDI). In the present work, we have successfully fabricated a manganese dioxide ...(MnO2)/activated carbon (AC) composite electrode using an anodic electrodeposition technique. Surface characterization confirms the presence of electrodeposited MnO2 on the AC surface with an amorphous structure and improved wetting behavior. Cyclic voltammetry and galvanostatic charge/discharge measurements indicate that the MnO2/AC composite electrode exhibits a high specific capacitance (77.6 F g–1 at 5 mV s–1), rate capability, and excellent cycling reversibility for capacitive charge storage. Furthermore, the salt electrosorption capacity is investigated using batch mode experiments at a working voltage of 1.0 V in a 0.01 M NaCl solution. The MnO2/AC composite electrode presents a superior electrosorption capacity of 9.3 mg g–1, which is approximately 1.6-fold higher than that of the pure AC electrode (5.7 mg g–1). This significant improvement can be attributed to the mixed capacitive-Faradaic process, corresponding to the combination of the double-layer charging of the high specific surface area (625 m2 g–1) and the pseudocapacitive redox reaction of MnO2. Therefore, the electrodeposited MnO2/AC composite is a potential electrode material for high-performance CDI.
The elimination of volatile organic compounds (VOCs) emitted from the process of industry production is of great significance to improve the atmospheric environment. Herein the catalytic oxidation of ...the toluene and iso-hexane mixture, as the typical components from furniture paint industry, and the enhancement in the catalytic stability for toluene oxidation were investigated in detail. The formation rate of active oxygen species was very important for the development of the catalyst with high catalytic stability. Compared with the Pt/M catalyst, the Pt-Cu/M catalyst owned stronger ability of VOCs adsorption and gaseous oxygen activation by introducing additional sites for activating O2. The Langmuir–Hinshelwood (adsorbed oxygen) and Mars–van Krevelen (lattice oxygen) mechanism existed in toluene oxidation over the present Pt/M and Pt-Cu/M catalysts, respectively. The change in the involved active oxygen species during toluene oxidation was resulted from the Pt-Cu alloy structure. In addition to the adsorption of O2, a part of active lattice oxygen species can also be replenished by the migration of bulk lattice oxygen over Pt-Cu/M. With a rise in the reaction temperature, weakly adsorbed iso-hexane could be timely reacted with the more active lattice oxygen species to keep the catalytic stability over the Pt/M and Pt-Cu/M catalysts. Generally, we not only prepared a promising material for the catalytic removal of VOCs from the furniture paint industry, but also provided a new strategy for the generation of active oxygen species, making the catalyst exhibit high catalytic oxidation stability.
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•Formation rate of active oxygen species is very important for catalytic stability.•Pt-Cu/M catalyst owns stronger ability of gaseous oxygen activation.•Toluene oxidation over Pt/M or Pt-Cu/M follows L-H or MvK mechanism.•Pt-Cu alloy structure makes active lattice oxygen involved in toluene oxidation.
► The Hg0 adsorption of S-impregnated carbon highly influenced by acidic gases. ► The effectiveness of enhancing Hg0 adsorption was NO>HCl>O2>SO2. ► The presence of SO2 had deteriorating effects on ...Hg0 adsorption. ► Factorial analysis supports NO having the largest effects on Hg0 adsorption. ► Carbon with a large equilibrium adsorption in general had poor adsorption kinetics.
The impacts of O2, HCl, SO2, and NO existing in simulated coal-combustion flue gases on Hg0 adsorption equilibrium and kinetics of sulfur-impregnated activated carbon were evaluated. The adsorption capacities increased when one acidic/oxidizing gas component coexisted with the baseline components, including CO2, H2O, and N2. The effectiveness of enhancing Hg0 adsorption capacity for these components, in a declining order, was NO, HCl, O2, and SO2. When two acidic/oxidizing gas components were present in the baseline gases, especially when NO coexisted, sulfur-impregnated activated carbon had increasing Hg0 adsorption capacities compared to that obtained at the baseline condition. In contrast, the presence of SO2 with O2 had deteriorating effects on Hg0 adsorption. The reduction in Hg0 adsorption capacity may be attributed to the formation of SO3 known to compete for adsorption sites. When the flue gas contained at least three acidic/oxidizing components, the baseline/O2/HCl/NO gas resulted in the largest Hg0 adsorption capacity. Full factorial analysis further suggested that NO possessed the greatest effects on enhancing the Hg0 adsorption capacity in the simulated coal-combustion flue gases. Kinetic results also showed that sulfur-impregnated activated carbon with a larger equilibrium adsorption capacity under a given gas condition in general possessed poor adsorption kinetics.
Most metals dissolve in aqueous solution in ionic form that tasks of purifying contaminated environments are always challenging for us, and the accurate prediction in the adsorption process is ...essential to identify determinants in surface science. We propose the simple representations of parameters described by Conceptual Density Functional Theory for hydrated metal ions. Different calculation methods through density functional theory (DFT) are developed and corresponding performance is revealed that the high correlation occurs between the global electronegativity and inner-sphere adsorption energy of hydrated metal ions by carboxyl-functionalized single-walled carbon nanotubes, in particular, the calculation concept involving fractional occupation numbers that
R
-square is above 0.8. The hydration energy is not negligible when determining the adsorption energy and it promotes the stability of the complexes in aqueous phase. That metal ions with trivalent charge exhibit stronger hydration energy than those with divalent charge is found. Meanwhile, the efficient system simulated by the meaningful fractional occupation methods for the wastewater treatment and optimal materials designing could be rationalized and accelerated.
Due to public health threats resulting from mercury (Hg) and its distribution in the food chain, global restrictions have been placed on Hg use and emissions. Biochar is a porous, carbonaceous ...adsorbent typically derived from waste biomass or organic matter, making it an eco-friendly material for aqueous mercury (Hg(II)) control. Functionalization of biochar can improve performance in pollution control applications. In this work, carbonization, magnetization, and sulfurization of biochar were combined into a single heating step to prepare sulfurized magnetic biochar (SMBC) for Hg(II) removal from water. Results indicate that SMBC prepared at 600 °C adsorbed 8.93 mg/g Hg(II), more than materials prepared at 400, 500, 700, 800, and 900 °C. Additionally, Hg(II) adsorption onto SMBC was 53.0% and 11.5% greater than onto magnetic biochar (MBC) and biochar (BC), respectively. Hg(II) adsorption is shown to be favorable in acidic conditions (pH 3.5–5), thermodynamically spontaneous, and endothermic. Adsorption results fit the pseudo-second-order (R2 = 0.990 and the sum of squared error (SSE) = 5.382) and external mass transfer (R2 = 0.971 and SSE = 9.422) models. The partitioning coefficients were 4.964 mg/g/μM in freshwater, 0.176 mg/g/μM in estuary water, and 0.275 mg/g/μM in seawater, highlighting the importance of salinity in environmental remediation applications. In summary, SMBC can be readily prepared with minimal processing steps. The product is a robust adsorbent for Hg(II), and it can potentially be applied to remediate contaminated water/sediment/soil in the future.
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•Sulfurized magnetic biochar (SMBC) was developed via a single heating step.•SMBC pyrolyzed at 600 °C had high surface area, microporosity, and Hg(II) adsorption.•CS of SMBC is the key adsorptive site for Hg(II) adsorption.•Partitioning coefficients of Hg(II) adsorption in environmental waters were obtained.
