Hg0 Removal Efficiency Research Articles

Constructing Heterointerfaces in Dual-Phase High-Entropy Oxides to Boost O2 Activation and SO2 Resistance for Mercury Removal in Flue Gas.

The low O2 activation ability at low temperatures and SO2 poisoning are challenges for metal oxide catalysts in the application of Hg0 removal in flue gas. A novel high-entropy fluorite oxide (MgAlMnCo)CeO2 (Co-HEO) with the second phase of spinel is synthesized by the microwave hydrothermal method for the first time. A high efficiency of Hg0 removal (close to 100%) is achieved by Co-HEO catalytic oxidation at temperatures as low as 100 °C and in the atmosphere of 145 μg m-3 Hg0 at a high GHSV (gas hourly space velocity) of 95,000 h-1. According to O2-TPD and in situ FT-IR, this extremely superior catalytic oxidation performance at low temperatures originates from the activation ability of Co-HEO to transform O2 into superoxide and peroxide, which is promoted by point defects induced from the spinel/fluorite heterointerfaces. Meanwhile, SO2 resistance of Co-HEO for Hg0 removal is also improved up to 2000 ppm due to the high-entropy-stabilized structure, construction of heterointerfaces, and synergistic effect of the multicomponents for inhibiting the oxidation of SO2 to surface sulfate. The design strategy of the dual-phase high-entropy material launches a new route for metal oxides in the application of catalytic oxidation and SO2 resistance.

Porous spherical indium oxide-loaded BiOIO3 nanosheets to construct Z-scheme heterojunction to enhance photocatalytic activity

In this work, In2O3/BiOIO3 Z-scheme heterojunction composites enriched with oxygen vacancies were prepared by hydrothermal and calcination methods. Combining the experimental results with DFT calculations, it is found that the photogenerated electrons of In2O3-loaded BiOIO3 are transferred along the Z-scheme path, which proves that the In2O3/BiOIO3 Z-scheme heterojunction is successfully synthesized. The introduction of In2O3 has resulted in abundant oxygen vacancies on the surface of the composites. Oxygen vacancies construct new carrier transfer channels to accelerate the separation and transfer efficiency of electron-hole pairs. The photocatalytic activity was evaluated by the removal efficiency of the heavy metal mercury in the gas phase. The best sample had a Hg removal efficiency of 98.5 %. Finally, we propose that the synergistic interaction of oxygen vacancies and Z-scheme heterojunction promotes the activation of molecular oxygen and the generation of more ROS (·O2- and·OH) with high redox reactivity and analyze the mechanism in detail.

Effect of natural organic matter (NOM) on the removal efficiency of Hg(ii) by MoS2: dependence on the Hg/MoS2 ratio and NOM properties

In groundwater, the efficiency of MoS2 nanosheets for Hg(ii) removal is significantly hindered by natural organic matter (NOM) at high molar ratios of Hg/MoS2, whereas at low ratios, NOM has minimal impact on Hg(ii) removal.

Enhanced simultaneous oxidation of Hg0 and NO with SO2 resistance by dual single-atom Co-Cu incorporated g-CN nanocomposites

The simultaneous catalytic oxidation of Hg0 and NO within coal-fired plants is crucial in abating diverse pollutants. Nevertheless, conventional catalysts often encounter challenges, such as diminished oxidation efficiency at lower temperatures and competitive adsorption with other gaseous components, particularly SO2, to remove Hg0 and NO. A nanocomposite catalyst, Co-Cu/g-CN, was developed to address these issues, featuring dual single-atom doping of Co and Cu in graphitized carbon nitride (g-CN). Surface characterization techniques and theoretical calculations confirmed that Co and Cu single atoms were successfully incorporated into the g-CN structure. Moreover, this innovative catalyst exhibited a strong metallic interaction between the dual single atoms, which led to an increased production number of superoxides (O2−), albeit with a slightly reduced oxidizing ability. The trade-off in the active centers of O2− ultimately enhanced the oxidation capability of Hg0 and NO owing to the augmented number of O2−. Co-Cu/g-CN demonstrated complete Hg0 removal efficiency and achieved 81.3% NO removal efficiency at 200–250 °C. Both theoretical analysis and DRIFTS investigation revealed that the competitive adsorption of SO2 over O2− was significantly weakened due to the reduced oxidizing ability of O2−. Additionally, the Cu single atoms acted as sacrificial sites for sulfate species, thereby preserving the catalytic activity of Co single atoms for NO oxidation. This research provides a valuable dual single-atom-catalyst fabrication strategy for addressing flue-gas NOx and Hg0 pollution.

Acid treatment for enhancing Hg0 removal efficiency of chlorine-loaded biochar: mechanism and kinetic analysis.

Adsorbents modified solely with chlorine have limited effectiveness in removing mercury at high temperatures. This study aims to investigate the influence of various acid (HNO3, H2SO4, and H2O2) loadings on the removal efficiency of mercury from NH4Cl-modified adsorbents. The objective is to develop rice straw carbon adsorbents that are both more efficient and cost-effective. The experiments were conducted on a fixed bed experimental platform, with SEM and BET to observe the physical property changes of the modified char samples. XPS analysis was employed to analyze the effects of oxygen, chlorine, and sulfur functional groups. Additionally, a kinetic model was used to investigate the interaction mechanism between the adsorbent and mercury. The findings demonstrate that co-modification surpasses the use of NH4Cl alone, with the combination of NH4Cl and HNO3 yielding the best results. Co-modification enhances the development of a more refined and compact pore structure on the char surface, promoting the physical adsorption of mercury. Moreover, an increased presence of chlorine and oxygen functional groups is observed on the char surface, particularly in the NH4Cl and HNO3 co-modified samples, further enhancing the chemical adsorption capacity of the char. The results from the kinetic analysis support this conclusion. Furthermore, the adsorption process of Hg0 relies on both external mass transfer and chemical adsorption, with the chemical adsorption process playing a more significant role as the controlling factor.

Boosting SO2‑tolerant oxidation of Hg0 and chlorobenzene over MnCo2O4@TiO2 catalyst via constructing shielding effects

Currently, it was still challenging to improve the SO2-tolerant catalytic oxidation of Hg0 and chlorobenzene in flue gas. Herein, we developed a MnCo2O4@TiO2 core–shell material that employed a self-shielding mechanism to prevent sulfate deposition. The optimal MnCo2O4@TiO2-2 catalyst achieved 100 % Hg0 removal efficiency at 250 °C under 150–600 ppm SO2, and also showed enhanced SO2 resistance during chlorobenzene conversion at 275 °C. The strong interaction between MnCo2O4 and TiO2 facilitated the electronic transfer from MnCo2O4 to TiO2, thereby producing more Co3+ and maintaining the high reactivity. Further, the mesoporous TiO2 layer facilitated the generation of moderate acid sites, improved the distribution of surface oxygen species, and weakened SO2 adsorption on catalyst. Under the protection of mesoporous TiO2 layer, the generation of Mn/Co sulfates could be inhibited effectively. In particular, the suitable TiO2 shell balanced the chemical adsorption and oxidation processes of Hg0 on the catalyst. This enhancement led to improved single Hg0 removal efficiency and SO2-tolerant Hg0 removal performance. During chlorobenzene degradation in presence of SO2, the oxidation path of chlorobenzene on MnCo2O4@TiO2 occurred via chlorobenzene → phenolates → maleates → formates/acetates → CO2 and H2O. Although sulfate formation would cover the active surface and inhibit the reaction path, the TiO2 shell could attenuate this negative effect. This study provided a new approach for the development of SO2-tolerant transition metal oxide with superior performance, holding significant academic and practical value.

Efficient removal of Hg0 by the combination of CuO and excellent carrier Ta2O5

A carrier Ta2O5 was introduced and combined with CuO for the removal of Hg0 in flue gas This combination exhibited an excellent performance and demonstrated robust resistance to both water and SO2 when compared to commonly used carriers (TiO2, Al2O3, etc.). CuO0.35/Ta2O5 manifested the highest Hg0 removal efficiency and excellent stability among all synthesized samples, reaching nearly 95 % in the initial stage. The introduction of O2 can improve the removal rate of Hg0, and the present of SO2 did not lead to catalyst poisoning. Physicochemical characterization revealed that CuO0.35/Ta2O5 possessed a high specific surface area and good thermal stability. Besides, copper was evenly distributed on the catalyst surface, and the combination of CuO and Ta2O5 enhanced the oxidation property of the catalyst. The removal mechanism of Hg0 was investigated and it was found that Hg0 binded to lattice oxygen on the catalyst after oxidation. A portion of the bound mercury was adsorbed on the catalyst, while the remainder was released into the flue gas.

Cu incorporating into OMS-2 lattice creates an efficient Hg0 removal sorbent in natural gas with ambient-temperature H2S/H2O tolerance

Removing mercury in wet natural gas containing acidic components is essential to developing the natural gas purification industry and mitigating corrosion in aluminum heat exchangers. In this work, the Cu-doped manganese oxide octahedral molecular sieve (OMS-2) nanorods were designed for oxidation of Hg0 in wet natural gas. The Hg0 removal efficiency over Cu(0.05)-OMS-2 reached 98.2 % under a high space velocity of 24 × 104 h−1 and a complex atmosphere containing H2O, CO2, and H2S. Surface reactive oxygen species produced by strong electronic interactions owing to Mn-O-Cu hybridization was the main active sites for Hg0 oxidation. The reactive oxygen species on Cu(0.05)-OMS-2 reacted with H2S to form active sulfur species, which could combine with Hg0 to form HgS. Cu(0.05)-OMS-2 exhibited excellent ambient-temperature water resistance, which was attributed to the good redox properties caused by Cu incorporation. This work provided a new strategy for designing efficient sorbents to remove Hg0 from wet natural gas.

Plasma-assisted synthesis of nano-sulfur adsorbent for efficient removal of mercury from flue gas

Adsorbents injection technology is one of the most promising strategies to control mercury emission from flue gas. However, existing literature has shown leaching risk of mercury and halogen from commercial halogen impregnated adsorbents. Therefore, we proposed a novel and convenient fabrication method for nano-sulfur adsorbent assisted with nonthermal plasma technology in order to address these issues. The morphology, number concentration and size distribution of as-obtained nano-sulfur particles was determined by High Resolution Transmission Electron Microscopy (HRTEM) and Scanning Mobility Particle Sizer (SMPS). The mercury adsorption experiments showed nano-sulfur adsorbent (removal efficiency: 88.2 %) was more effective than micron-sized elemental sulfur (less than 10 %). Furthermore, the chemical composition of elemental sulfur allotropes (S6, S7 and S8) was determined using High-performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). It was found that nano-sulfur particles contained higher proportions of S6 (1.53 %) and S7 (1.29 %) allotropes, which are the active materials in elemental sulfur. To investigate the effects of adsorption temperature and simulated flue gas on the performance of nano-sulfur adsorbent, the optimal adsorption temperature of 110 °C was determined, indicating its suitability for coal-fired power plants equipped with a low-temperature electrostatic precipitator system. Additionally, it was observed that simulated flue gas had slight inhibitory effects on the adsorbent performance, with a reduction of approximately 5 % in Hg0 removal efficiency. In summary, this research proposed a novel method for synthesizing nano-sulfur adsorbent and revealed the differences in sulfur allotropes' reactions with mercury, thereby deepening our understanding of the mercury-sulfur reaction mechanism.

In-situ synthesis of dual functionalized MOF by engineering modulator induced defect for efficient remediation of aqueous mercury through adsorption

UiO-66 is an extremely versatile metal organic framework (MOF) due to its remarkable water stability and high specific surface area. The incorporation of modified chemical and structural defects (missing linker and missing cluster defects) into the crystalline UiO-66 by the simultaneous use of an amino modified ligand and a thiol containing monocarboxylic acid modulator (thioglycolic acid, TGA) during synthesis resulted in developing a novel dual-functional MOF, designated as NH2-UiO-66-SH_C. This material was characterized using FTIR, XRD, FESEM, EDX, XPS, BET and Zetasizer to explore the morphological integrity and chemical composition. NH2-UiO-66-SH_C crystals demonstrated irregular nano-sized morphology (< 100 nm) and microporous nature with specific surface area of 519.6 m2/g. The material was subsequently tested to adsorb the highly toxic aqueous mercury (Hg) which is responsible for severe damages to human health. The maximum adsorptive capacity for aqueous inorganic mercury was 885 mg/g at 303 K. The optimum adsorbent dose and solution pH were 0.3 g/L and 5, respectively. The adsorption was endothermic and followed pseudo-second order kinetics. The developed nano-adsorbent illustrated enhanced sorption capacities which were far higher compared to its parent MOFs (UiO-66 as well as NH2-UiO-66) and other reported modified forms of UiO-MOFs. A regeneration method that was effective over 5 cycles (Hg removal efficiency > 90%) was also reported. Overall, this study reports the development of a newly modified nano-crystalline MOF, by manipulation of the synthetic chemistry (with defect modulation), which is a promising adsorbent for Hg (II) in aqueous phase.

Study of mercury resistance and Fourier transform infrared spectroscopy-based metabolic profiling of a potent Bacillus tropicus strain from forest soil.

Mercury (Hg) is a highly toxic heavy metal and Hg-resistant indigenous bacterial isolates may offer a green and cost-effective bioremediation strategy to counter Hg contamination. In this study, a potent Hg-resistant bacterium was isolated from the forest soil of a bird sanctuary. Identification using matrix-assisted laser desorption ionization-time of flight mass spectrometry depicted the isolate as a strain of Bacillus tropicus, validated by morphological, biochemical, and molecular studies. The isolate demonstrated biological Hg removal efficiency and capacity of 50.67% and 19.76 mg g-1 , respectively. The plasmid borne resistance determinant, merA, encoding mercuric reductase, was detected in the bacterium endowing it with effective Hg volatilization and resistance capability. A Fourier-transform infrared spectroscopic comparative metabolic profiling revealed the involvement of various functional groups like -COOH, -CH2 , -OH, PO4 - and so on, resulting in differential spectral patterns of the bacterium both in control and Hg-exposed situations. A temporal variance in metabolic signature was also observed during the early and mid-log phase of growth in the presence of Hg. The bacterium described in this study is the first indigenous Hg-resistant strain isolated from the Uttar Dinajpur region, which could be further explored and exploited as a potent bioresource for Hg remediation.

Mechanistic study on the enhanced SO2-tolerant ability of CuCl2-promoted MnOx-CeOx mixed oxide for Hg0 removal

SO2, a typical component in coal-fired flue gas, always results in a decreased Hg0 removal efficiency of the catalysts/adsorbents. Therefore, developing a catalyst/adsorbent with satisfactory sulfur resistance constitutes an important step in achieving the goal of mercury emission reduction. In this study, we modified MnOx-CeOx mixed oxide with CuCl2, aiming to enhance its SO2-tolerant ability and reveal the relevant promotional mechanisms. As 200 ppm SO2 was introduced, MnOx-CeOx suffered from deactivation with its Hg0 removal efficiency decreasing from ∼100% to ∼80%. With increasing the SO2 concentration, this deactivation phenomenon was more pronounced. This was because SO2 had a greater affinity to MnOx-CeOx, which would drive the adsorbed Hg0 away from the active sites. Besides, SO2 was able to rob the oxygen atoms from HgO formed on the MnOx-CeOx surface, which increased the Hg0 concentration in the working gas and thus explained the decreased Hg0 removal efficiency with SO2. Given the doping of CuCl2, the highly active Cl− favored the efficient oxidation of Hg0, making the adverse factors arising from the Hg0-SO2 competitive behaviors less influencing. Moreover, the produced HgCl2 tended to emit into the working gas instead of being stabilized on the material surface, which could be free from the reduction to Hg0 by SO2. As a result, CuCl2-promoted MnOx-CeOx exhibited superior sulfur resistance; >95% Hg0 removal efficiency was well-retained during the 320-min deactivation cycle. This result was vital to the stable operation of the MnOx-CeOx-based materials in coal-fired flue gas.

Cobalt sulfide nanosheets synthesized by anion exchange method for efficient Hg0 removal from flue gas

Transition metal sulfide adsorption has been recognized as a potential method for Hg0 removal, and the physicochemical properties of the adsorbent can significantly affect the Hg0 removal efficiency. The nanosheet structure with abundant unsaturated surface atoms can result in lower mass transfer resistance and give more adsorption sites. Thus, in the present work, cobalt sulfide nanosheet adsorbents with different Co/S ratio were synthesized by anion exchange method. Characterization results show that CS-10 has the lowest crystallinity and the highest Co3+/Co2+ and S22−/S2− ratio. These results give CS-10 the best Hg0 removal efficiency of nearly 100 % at a high GHSV of 180 000 h−1 at 60 °C. In addition, CS-10 has a good resistance to SO2 whose Hg0 removal efficiency decrease after SO2 introduction but recover to original level after SO2 cutting off. After being impregnated in Na2S solution, the adsorption efficiency of the used CS-10 can be easily regenerated. XPS results show that HgS can resolve in Na2S solution via HgS(ad) + S2− → [HgS2]2−. Furthermore, Co3+ and S22− as the main active sites for Hg0 removal can be replenished during the impregnation in Na2S solution. Kinetic study points that Hg0 adsorption characteristics on CS-10 obey pseudo-first-order and pseudo-second-order kinetic models, suggesting that the Hg0 diffusion on the external surface and the reaction at the adsorption site can both influence the Hg0 removal process.

Efficient Hg0 catalytic removal by direct S-scheme heterostructure of two-dimensional Bi2MoO6 (2 0 0)/g-C3N4 nanosheets under visible light

The gaseous elemental mercury (Hg0) emitted from coal-fired flue gas is extremely harmful to the atmospheric environment and human health. In this study, a 2D/2D Bi2MoO6(2 0 0)/g-C3N4 heterojunction photocatalyst was synthesized and exhibited a high visible-light driven Hg0 removal efficiency up to 99.5% in an atmosphere consisting of N2, O2 (6%), CO2 (12%), NO (100 ppm), SO2 (800 ppm), and H2O (5%). The introduction of surfactant CTAB led to further exposure of the highly active (2 0 0) crystal facet of Bi2MoO6, with a higher reactive oxygen species ratio than the original mainly exposed (1 3 1) crystal facet, and inhibited the agglomeration of Bi2MoO6, thereby greatly reducing the micro-thickness and improving the specific surface area. The smaller thickness effectively promoted the separation of photoinduced carriers and the speed of transfer to the interface. Additionally, through EPR characterization and work function calculation, we observed that the change in the exposed crystal facet regulated the Fermi level of Bi2MoO6 nanosheets, altering the direction of the built-in electric field at the interface with g-C3N4. This formation of an S-scheme 2D/2D Bi2MoO6(2 0 0)/g-C3N4 heterostructure further facilitated the recombination of unintentional carriers and strengthened the separation and catalysis of effective photogenerated carriers. To a certain extent, this work provides a guidance for the research of photocatalysis to achieve efficient and sustainable mercury removal from coal-fired flue gas.

Wet removal of elemental mercury by acid-assisted electrochemical oxidation method

As a global pollutant, mercury emission is increasingly restricted in recent years. It is urgent to explore a new and efficient mercury removal technology for coal-fired power plants. A new acid-assisted electrochemical oxidation (AEO) technique for mercury removal was proposed using platinum plate as cathode and fluorine-doped tin dioxide (FTO) glass as anode. The effects of acid type, acid concentration, applied direct current (DC) voltage, electrolyte type, SO2, NO and O2 on the Hg0 removal efficiency were carried out. The results indicated that the mercury removal efficiency increased with the increase of DC voltage and nitric acid concentration. When the concentration of nitric acid increased to 0.15 mol/L, the mercury removal efficiency remained unchanged. SO2 and NO inhibited the removal of Hg0 in AEO system, but the inhibition was reversible. Compared with the mercury removal efficiency under single experimental conditions, the mercury removal efficiency of electrochemical oxidation can reach 96% under the experimental conditions of 0.1 mol/L nitric acid and 4V DC voltage, suggesting that the synergistic effect of nitric acid and DC voltage plays a key role. According to the experimental results, the mechanism of Hg0 removal in AEO system was analyzed. At the anode, Hg0 was oxidized by hydroxyl radical (.OH) generated by the oxidation reaction on the anode surface. At the cathode, dissolved oxygen or O2 adsorbed on the surface of Pt is reduced to form anionic superoxide radicals (.O−2). Moreover, parts of .O−2 would produce .OH with the aid of electron at acidic condition. Free radicals capture experiments showed that .O−2 and .OH were the main active substances for the removal of Hg0 by acid-assisted electrochemical method. The research is helpful for the development of effective electrochemical techniques for industrial mercury removal and recycling of industrial acid waste.

Rational amelioration of redox equilibrium by constructing hollow nanotube Co-Mn/TiO2 catalyst to boost simultaneous removal of NO and Hg0

Simultaneous removal of NO and Hg0 in one purification unit is cost-effective, while the conflicting redox environmental requirements remains extremely challenging. Herein, hollow nanotube Co-Mn/TiO2 was elaborately fabricated by reconstructing nanoparticles to ameliorate the redox equilibrium, allowing the catalysts to sustain the excellent synergistic catalytic performance, which delivered more than 98 % NOx conversion with above 95 % N2 selectivity and nearly 100 % Hg0 removal efficiency within 150–240 °C. Abundant oxygen vacancies and strong surface acidity were synchronously generated after the formation of unique hollow nanotube, improving the mobility of oxygen species and facilitating the adsorption and activation of reactants, and the cooperation of oxygen vacancy and surface acidity resulted in superior simultaneous removal activity. Strikingly, in situ DRIFTS and kinetic results revealed that the reaction rate was obviously accelerated on hollow nanotube Co-Mn/TiO2. This study provided new insights toward engineering efficient catalysts for simultaneous removal of NO and Hg0.

0D/2D catalyst for photocatalytic mercury removal under visible light

Photocatalytic technology has the advantages of environmental friendliness, low energy consumption, and fast reaction speed, which can be applied in the field of visible light mercury removal. High stability and narrow bandgap are fundamental factors for ideal semiconductor photocatalysts. A novel method of hydrothermal synthesis of CQDs/2D-BWO composite catalyst to improve the oxidation efficiency of elemental mercury was proposed. The morphology, physicochemical properties, and optical performance of the materials were fully characterized. The experiment of Hg oxidation efficiency under visible light showed that C2/2D-BWO exhibited a Hg removal efficiency of was as high as 86.3 % under visible light and adequate cyclic stability. The effects of SO2 and NO on Hg oxidation were also studied, and the reasons for the improved of photocatalytic activity of CQDs on 2D-BWO were analyzed based on DFT calculations. The reaction mechanism of the catalytic oxidation of Hg by C2/2D-BWO was proposed, and C2/2D-BWO was found to be an efficient and stable visible light catalyst.

Investigation into enhanced performance of toluene and Hg0 stimulative abatement over Cr-Mn oxides co-modified columnar activated coke

In this study, a string of Cr-Mn co-modified activated coke catalysts (XCryMn1-y/AC) were prepared to investigate toluene and Hg0 removal performance. Multifarious characterizations including XRD, TEM, SEM, in situ DRIFTS, BET, XPS and H2-TPR showed that 4%Cr0.5Mn0.5/AC had excellent physicochemical properties and exhibited the best toluene and Hg0 removal efficiency at 200℃. By varying the experimental gas components and conditions, it was found that too large weight hourly space velocity would reduce the removal efficiency of toluene and Hg0. Although O2 promoted the abatement of toluene and Hg0, the inhibitory role of H2O and SO2 offset the promoting effect of O2 to some extent. Toluene significantly inhibited Hg0 removal, resulting from that toluene was present at concentrations orders of magnitude greater than mercury's or the catalyst was more prone to adsorb toluene, while Hg0 almost exerted non-existent influence on toluene elimination. The mechanistic analysis showed that the forms of toluene and Hg0 removal included both adsorption and oxidation, where the high-valent metal cations and oxygen vacancy clusters promoted the redox cycle of Cr3+ + Mn3+/Mn4+ ↔ Cr6+ + Mn2+, which facilitated the conversion and replenishment of reactive oxygen species in the oxidation process, and even the CrMn1.5O4 spinel structure could provide a larger catalytic interface, thus enhancing the adsorption/oxidation of toluene and Hg0. Therefore, its excellent physicochemical properties make it a cost-effective potential industrial catalyst with outstanding synergistic toluene and Hg0 removal performance and preeminent resistance to H2O and SO2.

Elemental mercury removal over MnOx-CoOx-modified HZSM-5 adsorbents: Performance and characterizations

In this study, MnOx-CoOx-modified HZSM-5 sorbents were prepared via the ultrasound-assisted impregnation method for Hg0 removal from the coal-fired flue gas. With the introduction of MnOx-CoOx, the Hg0 removal performance exhibited an increasing trend. Given that the mass content of MnOx-CoOx and the molar ratio of Mn/Co were fixed to 12 wt% and 1:3, the sorbent exhibited a relatively high Hg0 removal efficiency of 81% at 150 °C. Compared to virgin MnOx- or CoOx-modified HZSM-5 sorbent, the synergistic effect between MnOx and CoOx generated abundant surface acid sites and active oxygen species, which facilitated the adsorption of Hg0 and accelerated the oxidation of the adsorbed Hg0. Throughout the Hg0 capture cycles, Mn4+ and Co3+ acted as the active sites with HgO being the end product. Among the various gas constitutes, both O2 and NO demonstrated promotional effect on Hg0 removal, while SO2 interfered with the reaction to some degree. With the co-introduction of NO and SO2, an Hg0 removal efficiency of ∼94% was attained. Given its excellent recyclability, this sorbent system shows promising application potential.

Synergistic effect of HCl, SO2 and O2 on mercury removal by Mn0.5Cu0.5Fe2O4 adsorbent

Ferrite-structured adsorbents have demonstrated high potential for adsorbing zero-valent mercury (Hg0), but their performance in complex flue gas is not well understood. This study investigated the effects of HCl, O2, and SO2 on Hg0 oxidation capacity using Mn0.5Cu0.5Fe2O4 adsorbent. The morphology and microstructure of Mn0.5Cu0.5Fe2O4 were examined, and mass transfer theoretical analysis and X-ray photoelectron spectroscopy experiments were conducted to explore the synergistic effect of HCl, SO2, and O2 on mercury removal. The results indicated that the adsorbent achieved a high Hg0 removal efficiency of approximately 98% when HCl, SO2, and O2 coexisted in the flue gas at 120 °C. The reaction can be separated into three steps. In the first step, HCl dominates the reaction, resulting in the formation of HgCl2 and H2O. In the second step, oxygen defect sites accelerate the breakdown of O2 into chemisorbed oxygen. In the third step, the chemisorbed oxygen combines with Hg0 and SO2 to generate HgO and HgSO4. This study has important implications for the development of ferrite-structured adsorbents in complex flue gas.