Co-adsorption enhancement of formaldehyde/carbon dioxide over modified hexagonal boron nitride for whole-surface capture purification.

Simultaneous capture of formaldehyde (HCHO) and carbon dioxide (CO) in indoor air is promising of achieving indoor-air purification. Of all potential adsorbents, hexagonal boron nitride (h-BN) is one of the most suitable species owing to facile formation of attraction points. Therefore, in this study, performances of HCHO and CO being adsorbed over pure/modified h-BN are systematically investigated via density functional theory (DFT) calculations.

Research on nonsteady-state adsorption and regulation towards stabler adsorption for benzene over single-wall carbon materials.

With the intention of separating benzene (CH) from indoor polluted air and collecting it in a cleaner way, it is promising of getting CH adsorbed on activated carbon materials with outstanding physicochemical properties. In this study, how CH is adsorbed over single-wall carbon materials and relevant adsorption processes are enhanced is thoroughly investigated via density functional theory (DFT). Especially, distinction between partial and whole effects of adsorbents on CH adsorption, features of electron distribution across section of adsorption forms, and regulation mechanism of nonsteady-state adsorption for CH are key points.

Comprehensive Effect of Oxidant Addition in an FGD Slurry on the Removal and Distribution of Selenium: A Field Study.

Flue gas desulfurization (FGD) scrubbers capture selenium in coal-fired power plants, leading to a high concentration of selenium in the slurry. This research proves that SO is preferentially oxidized compared to SeO by SO. With the increase in the oxidation-reduction potential (ORP) caused by SO addition, the conversion rate of SO increased and the size of gypsum grains grew from 31.

Fe-Catalyzed CO Adsorption over Hexagonal Boron Nitride with the Presence of HO.

The energy barrier of CO chemically adsorbed on hexagonal boron nitride (h-BN) is relatively big. In order to cut down the energy barriers and facilitate fast adsorption of CO, it is necessary to apply catalysts as a promoter. In this study, single-atom iron is introduced as the catalyst to reduce the energy barriers of CO adsorbed on pure/doped h-BN.

CO adsorption enhancement over Al/C-doped h-BN: A DFT study.

Reducing energy barriers of CO being chemisorbed on hexagonal boron nitride (h-BN) is a kernel step to efficiently and massively capture CO. In this study, aluminum/carbon (Al/C) atoms are used as dopants to alter surface potential fields of h-BN, which aims at lowering energy barriers of adsorption processes. Through theoretical calculations, direct-adsorption structures/properties of CO, joint-adsorption structures/properties of CO/HO, transition state (TS) energy barriers, effects of temperatures on adsorption energies/TS energy barriers and changes of reaction rate constants over different adsorbents are investigated in detail in order to reveal how doping of Al/C atoms promotes CO adsorption strength over doped h-BN.

Arsenic adsorption enhancement performances of Mn-modified γ-AlO with flue gas constituents involved.

Some flue gas constituents have negative effects on AsO adsorption of γ-AlO so promoting arsenic adsorption performances under complicated flue gas conditions is necessary based on previous studies. In this study, γ-AlO is modified with manganous nitrate and then Mn-modified γ-AlO is used as the adsorbents in experiments. Besides, molecular dynamics (MD) simulations and density functional theory (DFT) calculations are performed to explore mechanisms of how loadings of Mn enhance arsenic adsorption features of γ-AlO when being affected by flue gas constituents in microscale and mesoscale, respectively.

Selenium migration mechanism in wet FGD slurry: Experimental and DFT analysis.

Selenium (Se) is one of the hazardous trace elements emitted from coal-fired power plants. The Se migration behavior in wet flue gas desulfurization (FGD) slurry is still unclear, and the species of Se in FGD gypsum remains controversial. In this research, the bubbling experiments using simulated slurry with/without gypsum crystallization process were conducted.

The distribution and conversion of selenite and selenate with the bubbling of simulated flue gas in simulated WFGD slurry.

Selenium is one of the hazardous trace elements emitted from coal-fired power plants. The distribution of selenium in Wet Flue Gas Desulfurization (WFGD) process is still unclear and even in controversial, impeding the development of selenium removal technologies. This research has found that the selenite in simulated slurry could be reduced by SO while selenate has not been affected.

Band application of flue gas desulfurization gypsum improves sodic soil amelioration.

Blending flue gas desulfurization (FGD) gypsum with surface sodic soil is a universally recognized method for the rapid amelioration of sodic soils; however, little information is available on whether other application methods (band application) will reclaim sodic soil. Three FGD gypsum application methods (single-band, dual-band and blend applications) and a control treatment (non-FGD gypsum) were carried out using sodic soil in soil bins to investigate the effects of the application method on the wetting front, major cations in the leachate during the process of water infiltration and soluble and exchangeable cations in the soil profile after infiltration. The results showed that the wetting fronts in the band treatments were denser in the horizontal direction than in the vertical direction, but the blend and control treatments only had vertical migration.

Effects of O, SO, HO and CO on AsO adsorption by γ-AlO based on DFT analysis.

In order to reveal the affecting mechanisms of flue gas on AsO adsorption by γ-AlO and to enhance the adsorbing capacities of γ-AlO, the influences of flue gas constituents on AsO adsorption on γ-AlO(0 0 1) surface are investigated theoretically via density functional theory (DFT) in this study. The flue gas constituents selected include O, HO, SO and CO. O converts nearly all of the physisorption structures into chemisorption structures except one structure, in which the O electron cloud does not interact with AsO molecule and therefore does not enhance the capture of AsO.

Research on the removal of AsO by γ-AlO adsorption based on density functional theory.

In order to protect selective catalytic reduction (SCR) catalysts for flue gas denitration in coal-fired power plants, the adsorption of AsO on γ-AlO(0 0 1) surface is investigated theoretically through density functional theory (DFT) in this study. The adsorption sites, adsorption structures, adsorption energies, electronic clouds, transition processes, and intermediate and transition structures are investigated. The theoretical results indicate that the adsorption of AsO molecule on the surface of γ-AlO(0 0 1) could be either physical or chemical, depending on the sites the molecule hangs over.

Kinetic study on elemental mercury release from fly ashes and hydrated fly ash cement pastes.

The kinetics of elemental mercury (Hg) release from fly ashes and hydrated fly ash cement pastes was investigated using a homemade Hg measurement system. Three types of fly ash (FA) and ordinary Portland cement (OPC) were used to prepare cement pastes. After standard curing for 28 days, the hydrated cement paste (HCP) was ground into a fine powder for Hg emission measurements.

Theoretical Study of As₂O₃ Adsorption Mechanisms on CaO surface.

Emission of hazardous trace elements, especially arsenic from fossil fuel combustion, have become a major concern. Under an oxidizing atmosphere, most of the arsenic converts to gaseous As₂O₃. CaO has been proven effective in capturing As₂O₃.

The promotion effect of manganese on Cu/SAPO for selective catalytic reduction of NO with NH.

The activity and hydrothermal stability of Cu/SAPO and Mn-2Cu/SAPO for low-temperature selective catalytic reduction of NO with ammonia were investigated. An ion-exchanged method was employed to synthesize Mn-2Cu/SAPO, which was characterized by N adsorption, ICP-AES, X-ray diffraction (XRD), NH-temperature programmed desorption (NH-TPD), NO oxidation, X-ray photoelectron spectrum (XPS), UV-vis, H-temperature programmed reduction (H-TPR) and diffuse reflectance infrared Fourier transform spectra (DRIFTS). 2Mn-2Cu/SAPO and 4Mn-2Cu/SAPO showed the best SCR activity, in that at 150 °C NO conversion reached 76% and N selectivity was above 95% for the samples.

Zerovalent Selenium Adsorption Mechanisms on CaO Surface: DFT Calculation and Experimental Study.

Zerovalent Se (Se atom and small Se molecule) adsorption mechanisms on a CaO surface were studied by both density functional theory (DFT) calculations and adsorption experiments. Nonvalent Se adsorption on the CaO(001) surface was simulated using a slab model. The adsorption energy, adsorption structure, electron density clouds, and electron properties were calculated.

Fate of mercury in flue gas desulfurization gypsum determined by Temperature Programmed Decomposition and Sequential Chemical Extraction.

A considerable amount of Hg is retained in flue gas desulfurization (FGD) gypsum from Wet Flue Gas Desulfurization (WFGD) systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition (TPD) and Sequential Chemical Extraction (SCE) were applied to FGD gypsum to identify the Hg species in it.

Influence of Flue Gas Desulfurization Gypsum Amendments on Heavy Metal Distribution in Reclaimed Sodic Soils.

Although flue gas desulfurization (FGD) gypsum has become an effective soil amendment for sodic soil reclamation, it carries extra heavy metal contamination into the soil environment. The fate of heavy metals introduced by FGD gypsum in sodic or saline-alkali soils is still unclear. This work aims to investigate the effects of FGD gypsum addition on the heavy metal distributions in a sodic soil.

Mercury transformation and distribution across a polyvinyl chloride (PVC) production line in China.

The production of polyvinyl chloride (PVC) via the calcium carbide process utilizes a catalyst containing large amounts of mercury (Hg) and is therefore one of the most important sources of anthropogenic Hg in China. To measure the emission of Hg from PVC production, we established a flowchart for the calcium carbide process, for which we quantified the Hg content of the material/product at each step. Results indicated that 71.

DRIFTS study of ammonia activation over CaO and sulfated CaO for NO reduction by NH3.

CaO catalyzes NH(3) oxidation, while sulfated CaO catalyzes NO reduction by NH(3) in the presence of O(2), and the adsorption and transformation of ammonia over CaO and sulfated CaO has been investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to understand their catalytic mechanism. It has been found that ammonia is first adsorbed over Lewis or Brönsted acid sites, and later undergoes hydrogen abstraction giving rise to either NH(2) amide or NH imide intermediates. The intermediates react with NO or lattice O to produce N(2) or NO.

[Effects of sulfur compounds on Pb partitioning in a simulated MSW incinerator].

The effect of sulfur compounds (including sulfur, sulfide, sulfite and sulfate), initial concentration of heavy metal and operating conditions on Pb emission in MSW incineration were investigated using a simulated tubular furnace with the simulated MSW. Operating conditions of the experiment included combustion chamber temperature and MSW residence time. The concentration of Pb was measured by ICP-AES after the digesting of samples including bottom ash, fly ash and flue gas according to related USEPA methods.

[Effects of chlorides on Cd partitioning and speciation in a simulated MSW incinerator].

The effects of chlorides (including inorganic chloride NaCl and organic chloride PVC) on Cd emission in MSW (municipal solid waste) incineration was investigated using a simulated tubular furnace and the simulated MSW spiked with heavy metals. The concentrations of heavy metals were measured by ICP-AES after the digesting of samples including bottom ash, fly ash and flue gas according to related USEPA Methods. Heavy metal species in bottom ash and fly ash were identified by X-ray diffraction technique and the spectra of elements distributed and micrographs of bottom ash and fly ash were detected by energy dispersive X-ray system and scanning electron microscope, respectively.

Simultaneous removal of SO2 and trace As2O3 from flue gas: mechanism, kinetics study, and effect of main gases on arsenic capture.

Sulfur dioxide (SO2) and trace elements are pollutants derived from coal combustion. This study focuses on the simultaneous removal of S02 and trace arsenic oxide (As2O3) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range. Experiments have been performed on a thermogravimetric analyzer (TGA).

Simultaneous removal of SO2 and trace SeO2 from flue gas: effect of SO2 on selenium capture and kinetics study.

Sulfur dioxide (SO2) and trace elements are all pollutants derived from coal combustion. This study relates to the simultaneous removal of SO2 and trace selenium dioxide (SeO2) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range, especially the effect of SO2 presence on selenium capture. Experiments performed on a thermogravimetric analyzer (TGA) can reach the following conclusions.

Simultaneous removal of SO2 and trace SeO2 from flue gas: effect of product layer on mass transfer.

Sulfur dioxide (SO2) and trace elements are all pollutants derived from coal combustion. This study relates to the simultaneous removal of sulfur and trace selenium dioxide (SeO2) by calcium oxide (CaO) adsorption in the medium temperature range, especially the mass transfer effect of sulfate product layer on trace elements. Through experiments on CaO adsorbing different concentrations of SO2 gases, conclusions can be drawn that although the product layer introduces extra mass transfer resistance into the sorbent-gas reaction process, the extent of CaO adsorption ability loss due to this factor decreases with decreasing SO2 concentration.

Size-exclusion chromatography of large molecules from coal liquids, petroleum residues, soots, biomass tars and humic substances.

Size-exclusion chromatography (SEC) using 1-methyl-2-pyrrolidinone (NMP) as eluent has been calibrated using various standard polymers and model compounds and applied to the analysis of extracts of coal, petroleum and kerogens, to petroleum vacuum residues, soots, biomass tars and humic substances. Three separate columns of different molecular mass (MM) ranges were used, with detection by UV absorption; an evaporative light scattering detector was used for samples with no UV absorption. Fractionation was useful to separate signal from the less abundant high-mass material, which was normally masked by the strong signal from the more abundant low-mass material in the absence of fractionation.