Simultaneous Removal of NO and Hg(0) from Flue Gas over Mn-Ce/Ti-PILCs

Review on magnetic adsorbents for removal of elemental mercury from coal combustion flue gas

Under the influence of human activities, atmospheric mercury (Hg) concentrations have increased by 450% compared with natural levels. In the context of the Minamata Convention on Mercury, which came into effect in August 2017, it is imperative to strengthen Hg emission controls. Existing Air Pollution Control Devices (APCDs) combined with collaborative control technology can effectively remove Hg2+ and Hgp; however, Hg0 removal is substandard. Compared with the catalytic oxidation method, Hg0 removal through adsorbent injection carries the risk of secondary release and is uneconomical. Magnetic adsorbents exhibit excellent recycling and Hg0 recovery performance and have recently attracted the attention of researchers. This review summarizes the existing magnetic materials for Hg0 adsorption and discusses the removal performances and mechanisms of iron, carbon, mineral-based, and magnetosphere materials. The effects of temperature and different flue gas components, including O2, NO, SO2, H2O, and HCl, on the adsorption performance of Hg0 are also summarized. Finally, different regeneration methods are discussed in detail. Although the research and development of magnetic adsorbents has progressed, significant challenges remain regarding their application. This review provides theoretical guidance for the improvement of existing and development of new magnetic adsorbents.

Three-dimensional porous CuO-modified CeO2-Al2O3 catalysts with chlorine resistance for simultaneous catalytic oxidation of chlorobenzene and mercury: Cu-Ce interaction and structure

Chlorine poisoning effects are still challenging to develop efficient catalysts for applications in chlorobenzene (CB) and mercury (Hg⁰) oxidation. Herein, three-dimensional porous CuO-modified CeO₂-Al₂O₃ catalysts with macroporous framework and mesoporous walls prepared via a dual template method were employed to study simultaneous oxidation of CB and Hg⁰. CuO-modified CeO₂-Al₂O₃ catalysts with three-dimensional porous structure exhibited outstanding activity and stability for simultaneous catalytic oxidation of CB and Hg⁰. The results demonstrated that the addition of CuO into CeO₂-Al₂O₃ can simultaneously enhance the acid sites and redox properties through the electronic inductive effect between CuO and CeO₂ (Cu²⁺+Ce³⁺↔Cu⁺+Ce⁴⁺). Importantly, the synergistic effect between Cu and Ce species can induce abundant oxygen vacancies formation, produce more reactive oxygen species and facilitate oxygen migration, which is beneficial for the deep oxidation of chlorinated intermediates. Moreover, macroporous framework and mesoporous nanostructure dramatically improved the specific surface area for enhancing the contact efficiency between reactants and active sites, leading to a remarkable decrease of byproducts deposition. CB and Hg⁰ had function of mutual promotion in this reaction system. In tune with the experimental results, the possible mechanistic pathways for simultaneous catalytic oxidation of CB and Hg⁰ were proposed.

Influence of SO3 on the MnOx/TiO2 SCR catalyst for elemental mercury removal and the function of Fe modification

Elemental mercury (Hg⁰) is a highly hazardous pollutant of coal combustion. The low-temperature SCR catalyst of MnO_x/TiO₂ can efficiently remove Hg⁰ in coal-burning flue gas. Considering its sulfur sensitivity, the effect of SO₃ on the catalytic efficiency of MnO_x/TiO₂ and Fe modified MnO_x/TiO₂ for Hg⁰ removal was investigated comprehensively for the first time. Characterizations of Hg-TPD and XPS were conducted to explore the catalytic mechanisms of Hg⁰ removal processes under different conditions. Hg⁰ removal efficiency of MnO_x/TiO₂ was inhibited irreversibly from 92% to approximately 60% with the addition of 50 ppm SO₃ at 150 ℃, which resulted from the transformation of Mn⁴⁺ and chemisorbed oxygen to MnSO₄. The existence of H₂O would intensify the inhibitory effect. The inhibition almost disappeared and even converted to promotion as the temperature increased to 250 ℃ and above. Fe modification on MnO_x/TiO₂ improved the Hg⁰ removal performance in the presence of SO₃. The addition of SO₃ caused only a slight inhibition of 1.9% on Hg⁰ removal efficiency of Fe modified MnO_x/TiO₂ in simulated coal-fired flue gas, and the efficiency maintained good stability during a 12 h experimental period. This work would be conducive to the future application of MnO_x/TiO₂ for synergistic Hg⁰ removal.

Hg0 Removal by V2O5 Modified Palygorskite in Simulated Flue Gas at Low Temperature

The V2O5-modified palygorskite (V2O5/PG catalysts) were prepared and used for Hg0 removal in simulated flue gas at low temperature. It was found that the V2O5/PG catalyst had excellent performance for Hg0 removal at 150 °C. O2 exhibited a positive effect on Hg0 removal over V2O5/PG, while SO2 and H2O showed an inhibiting effect. However, Hg0 removal efficiency showed a promotion trend in the presence of H2O, SO2, and O2. The Brunauer–Emmett–Teller (BET) method, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were applied to characterize the physicochemical properties of the V2O5/PG catalyst. Mercury temperature-programmed desorption (Hg-TPD) experiments were also conducted to identify the mercury species adsorbed on the V2O5/PG catalyst, and the pathway of Hg0 removal over V2O5/PG was also discussed. The used V2O5/PG catalyst after Hg0 removal was regenerated, and its capability for Hg0 removal can be completely recovered. The V2O5/PG-Re-300 °C catalyst showed excellent performance and good stability for Hg0 removal after regeneration.

Role of impurity components and pollutant removal processes in catalytic oxidation of o-xylene from simulated coal-fired flue gas

Volatile organic compounds (VOCs) emitted from coal-fired flue gas of thermal power plants have reached unprecedented levels due to lack of understanding of reaction mechanisms under industrial settings. Herein, inhibition mechanisms for catalytic oxidation of o-xylene in simulated coal-fired flue gas are elucidated with in-situ and ex-situ spectroscopic techniques considering the presence of impurity components (NO, NH₃, SO₂, H₂O). MnCe oxide catalysts prepared at Mn: Ce mass ratios of 6:4 are demonstrated to promote 87% o-xylene oxidation at 250 °C under gas hourly space velocities of 60,000 h^-1. Reaction intermediates on the catalyst surface are revealed to be o-benzoquinones, benzoates, and formate and they were stably formed under O₂/N₂ atmospheres. When either NO or NH₃ was introduced into the simulated flue gas, the formed species shifted toward formate in minutes, which indicated that changes in catalyst surface chemistry are directly related to impurity components. Presence of NH₃ in the simulated flue gas inhibited o-xylene oxidation by reducing Mn and lowering Brønsted acidity of the catalyst. Impurity components associated with pollutant removal processes (Hg⁰ oxidation and selective catalytic reduction of NO) lowered o-xylene removal efficiency. Presence of o-xylene in the flue gas had little effect on the efficiency of pollutant removal processes. Layered catalytic beds located downstream from Hg⁰/NO pollutant removal processes are proposed to lower VOC emissions from coal-fired flue gases of thermal power plants in industrial settings.

MIL-100(Fe) supported Mn-based catalyst and its behavior in Hg0 removal from flue gas

A novel magnetic composite catalyst of MnOx loaded on MIL-100(Fe) was prepared for the removal of Hg⁰ from flue gas, via incipient wetness impregnation followed with calcination at 300 °C. The MIL-100(Fe) supported catalyst showed greater capacity of Hg⁰ adsorption and oxidation than Fe₂O₃ supported catalyst at all test temperatures, showing Hg⁰ removal efficiency of 77.4% at 250 °C with high GHSV of 18,000 h^-1. Besides the merit of high BET surface area and developed porous, the ultra-highly dispersed and homogeneous Fe sites on MIL(Fe) significantly promoted Hg⁰ adsorption and oxidation via the synergy effect with MnOx. Furthermore, the catalyst exhibited magnetic property, which allowed easy separation of the catalyst from fly ash with a recovery of 104%. SO₂, H₂O and NH₃ in flue gas were proved inhibited Hg⁰ removal via different mechanisms. SO₂ and H₂O competed and desorbed Hg²⁺ on the surface of catalyst, while NH₃ was more likely to compete adsorption sites with Hg⁰.

Enhancement of CeO2 modified commercial SCR catalyst for synergistic mercury removal from coal combustion flue gas

CeO₂ modification improves the synergistic Hg⁰ removal performance of commercial SCR catalyst.

Cost-Effective Manganese Ore Sorbent for Elemental Mercury Removal from Flue Gas

Mercury capture from flue gas remains a challenge for environmental protection due to the lack of cost-effective sorbents. Natural manganese ore (NMO) was developed as a cost-effective sorbent for elemental mercury removal from flue gas. NMO sorbent showed excellent Hg⁰ removal efficiency (>90%) in a wide temperature window (100-250 °C) under the conditions of simulated flue gas. O₂, NO, and HCl promoted Hg⁰ removal due to the surface reactions of Hg⁰ with these species. SO₂ and H₂O slightly inhibited Hg⁰ removal under the conditions of simulated flue gas. O₂ addition could also weaken the inhibitory effect of SO₂. NMO sorbent exhibited superior regeneration performance for Hg⁰ removal during ten-cycle experiments. Quantum chemistry calculations were used to identify the active components of NMO sorbent and to understand the atomic-level interaction between Hg⁰ and sorbent surface. Theoretical results indicated that Mn₃O₄ is the most active component of NMO sorbent for Hg⁰ removal. The atomic orbital hybridization and electrons sharing led to the stronger interaction between Hg⁰ and Mn₃O₄ surface. Finally, a chemical looping process based on NMO sorbent was proposed for the green recovery of Hg⁰ from flue gas. The low cost, excellent performance, superior regenerable properties suggest that the natural manganese ore is a promising sorbent for mercury removal from flue gas.

Effect of SCR Atmosphere on the Removal of Hg0 by a V2O5-CeO2/AC Catalyst at Low Temperature

A series of V₂O₅-xCeO₂/AC (noted as V-Ce/AC) catalysts were synthesized by the impregnation method, which combined the advantage of AC and V-Ce. The effects of SCR atmosphere on Hg⁰ removal were systematically investigated at low temperature. The experimental results indicated that NO had a positive effect on Hg⁰ removal. In addition, an interesting experimental phenomenon was found that NH₃ also showed a positive effect on Hg⁰ removal, which is different from many studies that have reported a negative effect of NH₃ on Hg⁰ removal by other catalysts. NH₃-TPD experiment showed that there was no apparent competition between NH₃ and Hg⁰. An FT-IR gas analyzer and in situ DRIFTS were used to study the mechanism for the effect of NH₃ on the catalyst surface and found that a small part of NH₃ was overoxidized to NO₂ in this catalytic system. O₂ acted as a promoter in the whole process of NO and Hg⁰ removal. However, H₂O showed an inhibiting effect on Hg⁰ and NO removal over V-Ce/AC catalysts, which may be caused by the competitive adsorption of H₂O and pollutants (NO and Hg⁰). Additionally, 1 V-8Ce/AC catalyst exhibited high stability ( E_Hg = 87.6%, E_NO = 82.84%) after 72 h reaction in SCR atmosphere at 150 °C.

Using CuO-MnOx/AC-H as catalyst for simultaneous removal of Hg° and NO from coal-fired flue gas

A series of CuO-MnO_x modified catalysts were prepared, and proposed for simultaneous removal of Hg° and NO from flue gas. As Mn loading value was 5%, the high value of 90% Hg and 60% NO_x were removed efficiently. With gradual increasing of reaction temperature, the mercury removal efficiency (Mercury RE) first increased to 92% then decreased slightly, while NO_x removal efficiency (NO_x RE) exhibited a trend of continuous increase. O₂ had promotional effect on the double pollutants removal, while NH₃ had slightly negative effect on Hg° removal. As 5% O₂ was added into system, the removal efficiency of Hg and NO_x rose by 30% and 47%, respectively. Unfortunately, Mercury RE decreased to 90% in the presence of 500 ppm NH₃. Overall, superior Mercury RE (>90%) and NO_x RE (78%) were performed over 8%CuO-5%MnO_x/AC-H at 200 °C. XRD results revealed calcination affected catalysts activity by playing a role in active components formation at different temperature. In XPS spectra, new formation of HgO and Hg° adsorption on spent catalysts revealed the possible reaction processes that the conversion of CuO and MnO₂ on fresh catalyst to other species benefited HgO formation. The removal mechanism might be a combination of Langmuir-Hinshelwood and Mars-van-Krevelen mechanism.

Suppression of N2O formation by H2O and SO2 in the selective catalytic reduction of NO with NH3 over a Mn/Ti–Si catalyst

Proposed mechanism of NO reduction and N₂O formation as well as H₂O/SO₂ suppression effects with participation of (a) Lewis acid sites and (b) Brønsted acid sites over a Mn/Ti–Si catalyst.

Removal of Hg0 from simulated flue gas over silver-loaded rice husk gasification char

Mercury released into the atmosphere from coal combustion is harmful to humans and the environment. Rice husk gasification char (RHGC) is an industrial waste of biomass gasification power generation, which is silver-loaded to develop a novel and efficient sorbent for mercury removal from simulated flue gas. The experiment was carried out in a fixed-bed experimental system. The Hg⁰ adsorption performance of RHGC was improved significantly after loading silver. Hg⁰ adsorption capacity and mercury inlet concentration were found to be nonlinear. The adsorption capacity of RHGC decreased with the increase of reaction temperature. SO₂ inhibited mercury removal, NO and HCl promoted mercury removal; the Hg⁰ adsorption capacity in the simulated flue gas was higher than that in pure N₂. The silver-loaded rice husk gasification char (SRHGC) could be recycled about five times without significantly losing its removal efficiency. The SRHGC will not only reduce the cost of mercury removal but also save energy and reduce environmental pollution. At the same time, it provides a new way for the resource utilization of RHGC.

Low-temperature co-purification of NOx and Hg0 from simulated flue gas by CexZryMnzO2/r-Al2O3: the performance and its mechanism

In this study, series of Ce_xZr_yMn_zO₂/r-Al₂O₃ catalysts were prepared by impregnation method and explored to co-purification of NO_x and Hg⁰ at low temperature. The physical and chemical properties of the catalysts were investigated by XRD, BET, FTIR, NH₃-TPD, H₂-TPR, and XPS. The experimental results showed that 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ yielded higher conversion on co-purification of NO_x and Hg⁰ than the other prepared catalysts at low temperature, especially at 200-300 °C. 91% and 97% convert rate of NO_x and Hg⁰ were obtained, respectively, when 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ catalyst was used at 250 °C. Moreover, the presence of H₂O slightly decreased the removal of NO_x and Hg⁰ owing to the competitive adsorption of H₂O and Hg⁰. When SO₂ was added, the removal of Hg⁰ first increased slightly and then presented a decrease due to the generation of SO₃ and (NH₄)₂SO₄. The results of NH₃-TPD indicated that the strong acid of 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ improved its high-temperature activity. XPS and H₂-TPR results showed there were high-valence Mn and Ce species in 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃, which could effectively promote the removal of NO_x and Hg⁰. Therefore, the mechanisms of Hg⁰ and NO_x removal were proposed as Hg (ad) + [O] → HgO (ad), and 2NH₃/NH₄⁺ (ad) + NO₂ (ad) + NO (g) → 2 N₂ + 3H₂O/2H⁺, respectively. Graphical abstract ᅟ.

Comparison of Elemental Mercury Oxidation Across Vanadium and Cerium Based Catalysts in Coal Combustion Flue Gas: Catalytic Performances and Particulate Matter Effects

This paper discussed the field test results of mercury oxidation activities over vanadium and cerium based catalysts in both coal-fired circulating fluidized bed boiler (CFBB) and chain grate boiler (CGB) flue gases. The characterizations of the catalysts and effects of flue gas components, specifically the particulate matter (PM) species, were also discussed. The catalytic performance results indicated that both catalysts exhibited mercury oxidation preference in CGB flue gas rather than in CFBB flue gas. Flue gas component studies before and after dust removal equipment implied that the mercury oxidation was well related to PM, together with gaseous components such as NO, SO₂, and NH₃. Further investigations demonstrated a negative PM concentration-induced effect on the mercury oxidation activity in the flue gases before the dust removal, which was attributed to the surface coverage by the large amount of PM. In addition, the PM concentrations in the flue gases after the dust removal failed in determining the mercury oxidation efficiency, wherein the presence of different chemical species in PM, such as elemental carbon (EC), organic carbon (OC) and alkali (earth) metals (Na, Mg, K, and Ca) in the flue gases dominated the catalytic oxidation of mercury.

Novel CeMo x O y -clay hybrid catalysts with layered structure for selective catalytic reduction of NO x by NH3

A facile method is to prepare novel CeMo_xO_y-clay hybrid catalysts with layered structures by using organic cation modified clay as support. During the preparation process, cerium cations and molybdate anions are easily adsorbed and impregnated into the interlamellar space of the organoclay, and after calcination they undergo transformation to highly dispersed CeMo_xO_y nanoparticles within the interlamellar space of the clay. As expected, the prepared CeMo_0.15O_x-OC-T catalysts with layered structures had high selective catalytic reduction (SCR) activity such as high NO_x conversion of >90% in the wide temperature range of 220–420 °C. Meanwhile, they also exhibit high stability and tolerance to water vapor (5 vol%) and SO₂ (200 ppm), demonstrating that these novel catalysts could serve as a good alternative for NH₃-SCR in practical application.

A facile method is to prepare novel CeMo_xO_y-clay hybrid catalysts with layered structures by using organic cation modified clay as support.

Cu/Mn Double-Doped CeO2 Nanocomposites as Signal Tags and Signal Amplifiers for Sensitive Electrochemical Detection of Procalcitonin

Nanomaterials themselves as redox probes and nanocatalysts have many advantages for electrochemical biosensors. However, most nanomaterials with excellent catalytic activity cannot be directly used as redox probe to construct electrochemical biosensor because the redox signal of these nanomaterials can only be obtained in strong acid or alkali solution at high positive or negative potential, which greatly limits their applications in biologic assay. In this study, Cu/Mn double-doped CeO₂ nanocomposite (CuMn-CeO₂) was synthesized to use as signal tags and signal amplifiers for the construction of electrochemical immunosensor for sensitive assay of procalcitonin (PCT). Herein, CuMn-CeO₂ not only possesses excellent catalytic activity toward H₂O₂ for signal amplification, but also can be directly used as redox probe for electrochemical signal readout achieved in neutral mild buffer solution at low positive potential. Importantly, since doping Cu, Mn into CeO₂ lattice structure can generate extra oxygen vacancies, the redox and catalytic performance of obtained CuMn-CeO₂ was much better than that of pure CeO₂, which improves the performance of proposed immunosensor. Furthermore, CuMn-CeO₂ can be implemented as a matrix for immobilizing amounts of secondary antibody anti-PCT by forming ester-like bridging between carboxylic groups of Ab₂ and CeO₂ without extra chemical modifications, which greatly simplifies the preparative steps. The prepared immunosensor exhibited a wide linear range of 0.1 pg mL^-1 to 36.0 ng mL^-1 with a low detection limit of 0.03 pg mL^-1. This study implements nanomaterial themselves as redox probes and signal amplifiers and paves a new way for constructing electrochemical immunosensor.

Efficient and Environmentally Friendly Synthesis of AlFe-PILC-Supported MnCe Catalysts for Benzene Combustion

An efficient and environmentally friendly synthesis of AlFe-pillared clay (AlFe-PILC)-supported MnCe catalysts was explored. Mixed AlFe pillaring agents were prepared by a one-step method using Locron L and ferric nitrate solutions at a high temperature and high pressure. Montmorillonite was treated with the AlFe pillaring agents to synthesize AlFe-PILC. MnO _x and CeO₂ with different Mn/Ce atomic ratios were loaded onto the AlFe-PILC support by an impregnation method. The catalysts were characterized using X-ray diffraction, N₂ adsorption, and high-resolution transmission electron microscopy-energy dispersive spectrometry and were tested for the catalytic combustion of benzene and temperature-programmed surface reaction using a microreactor. Compared to conventional methods, this method is simpler and less costly and results in a larger specific surface area, pore volume, and basal spacing, with the ability to control the structure of the catalytic materials. MnCe(6:1)/AlFe-PILC has the highest catalytic activity and can completely degrade benzene (600 ppm in air) at 250 °C. The activity of the catalyst is stable, and no obvious deactivation is observed at 230 °C after 1000 continuous hours. The catalyst is resistant to water and Cl-poisoning. The amount of CeO₂ added is critical to the dispersion of MnO _x on the support and the creation of optimum number of oxygen vacancy defect sites for the benzene oxidation reaction. The AlFe-PILC-supported MnCe catalyst is a promising porous material; the support structure, proper dispersion of active species, and addition of Ce are essential for achieving complete degradation of organic toxic chemicals at relatively low temperatures.

Gaseous Heterogeneous Catalytic Reactions over Mn-Based Oxides for Environmental Applications: A Critical Review

Manganese oxide has been recognized as one of the most promising gaseous heterogeneous catalysts due to its low cost, environmental friendliness, and high catalytic oxidation performance. Mn-based oxides can be classified into four types: (1) single manganese oxide (MnOx), (2) supported manganese oxide (MnOx/support), (3) composite manganese oxides (MnOx-X), and (4) special crystalline manganese oxides (S-MnOx). These Mn-based oxides have been widely used as catalysts for the elimination of gaseous pollutants. This review aims to describe the environmental applications of these manganese oxides and provide perspectives. It gives detailed descriptions of environmental applications of the selective catalytic reduction of NOx with NH₃, the catalytic combustion of volatile organic compounds, Hg⁰ oxidation and adsorption, and soot oxidation, in addition to some other environmental applications. Furthermore, this review mainly focuses on the effects of structure, morphology, and modified elements and on the role of catalyst supports in gaseous heterogeneous catalytic reactions. Finally, future research directions for developing manganese oxide catalysts are proposed.

Simultaneous removal of NO and Hg0 over Ce-Cu modified V2O5/TiO2 based commercial SCR catalysts

A series of novel Ce-Cu modified V₂O₅/TiO₂ based commercial SCR catalysts were prepared via ultrasonic-assisted impregnation method for simultaneous removal of NO and elemental mercury (Hg⁰). Nitrogen adsorption, X-ray diffraction (XRD), temperature programmed reduction of H₂ (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. 7% Ce-1% Cu/SCR catalyst exhibited the highest NO conversion efficiency (>97%) at 200-400°C, as well as the best Hg⁰ oxidation activity (>75%) at 150-350°C among all the catalysts. The XPS and H₂-TPR results indicated that 7% Ce-1% Cu/SCR possess abundant chemisorbed oxygen and good redox ability, which was due to the strong synergy between Ce and Cu in the catalyst. The existence of the redox cycle of Ce⁴⁺+Cu¹⁺↔Ce³⁺+Cu²⁺ could greatly improve the catalytic activity. 7% Ce-1% Cu/SCR showed higher resistance to SO₂ and H₂O than other catalysts. NO has a promoting effect on Hg⁰ oxidation. The Hg⁰ oxidation activity was inhibited by the injection of NH₃, which was due to the competitive adsorption and oxidized mercury could be reduced by ammonia at temperatures greater than 325°C. Therefore, Hg⁰ oxidation could easily occurred at the outlet of SCR catalyst layer due to the consumption of NH₃.

A comparative study of manganese–cerium doped metal–organic frameworks prepared via impregnation and in situ methods in the selective catalytic reduction of NO

Impregnation and in situ doping were applied for the preparation of MnCe loaded MOFs and the behavior of the catalysts in the SCR was investigated.

Mercury Removal by Magnetic Biochar Derived from Simultaneous Activation and Magnetization of Sawdust

Novel magnetic biochars (MBC) were prepared by one-step pyrolysis of FeCl₃-laden biomass and employed for Hg⁰ removal in simulated combustion flue gas. The sample characterization indicated that highly dispersed Fe₃O₄ particles could be deposited on the MBC surface. Both enhanced surface area and excellent magnetization property were obtained. With the activation of FeCl₃, more oxygen-rich functional groups were formed on the MBC, especially the C═O group. The MBC exhibited far greater Hg⁰ removal performance compared to the nonmagnetic biochar (NMBC) under N₂ + 4% O₂ atmosphere in a wide reaction temperature window (120-250 °C). The optimal pyrolysis temperature for the preparation of MBC is 600 °C, and the best FeCl₃/biomass impregnation mass ratio is 1.5 g/g. At the optimal temperature (120 °C), the Fe_1.5MBC₆₀₀ was superior in both Hg⁰ adsorption capacity and adsorption rate to a commercial brominated activated carbon (Br-AC) used for mercury removal in power plants. The mechanism of Hg⁰ removal was proposed, and there are two types of active adsorption/oxidation sites for Hg⁰: Fe₃O₄ and oxygen-rich functional groups. The role of Fe₃O₄ in Hg⁰ removal was attributed to the Fe³⁺(t) coordination and lattice oxygen. The C═O group could act as act as electron acceptors, facilitating the electron transfer for Hg⁰ oxidation.

Analytical and mineralogical study of a Ghana manganese ore: Quantification of Mn speciation and effect of mechanical activation

In-depth understanding of the manganese ore would be beneficial to make the best use more environmental-friendly. A Ghana manganese ore before/after mechanical activation (MA) was therefore extensively characterized in our investigation. Surface Mn(4+)(35.5%), Mn(3+)(35.9%), Mn(2+)(28.6%) were detected by XPS, though XRD only revealed the presence of Mn(2+)-containing minerals. Thermal decomposition curve of manganese ore obtained by TG-DSC was divided into four stages from 373.15 K to 1273.15 K, which were quite consistent with the pattern of generated gases obtained by TG-FTIR and the theoretical thermodynamics analysis of the incorporated components involving ΔGT(θ) and Kp(θ). Mn species distribution showed no difference for manganese ores before/after MA, but quantitative analysis showed the decrease of residual Mn content (cannot be extracted effectively by acid, from about 12% to 1%), and thereby the increased contents of other four Mn species (exchangeables, carbonates, oxides, organics), which was suggested to be correlated with the dissociation of Mn-containing flocs and SiO2 particles witnessed by SEM-EDS. It was also found that MA could obviously promote the Mn dissolution kinetics in acid condition, though the dissolution of manganese ore before/after MA were both diffusion controlled. This investigation gives benignant inspiration for the resource utilization of manganese ore, taking the increasingly severer situation of Mn resource supply into consideration.

Preparation of novel CeMo(x) hollow microspheres for low-temperature SCR removal of NOx with NH3

A series of novel Mo doped CeO₂ hollow microspheres have been successfully synthesized using carbon microspheres as templates, which were characterized by XRD, SEM, TEM, BET and used to remove NO_x upon NH₃-SCR at lower temperature.

The adsorption and catalytic oxidation of the element mercury over cobalt modified Ce–ZrO2 catalyst

Co modification dramatically enhances Hg⁰ removal efficiency because of the increased surface active oxygen species.