Search

A new type of internally illuminated honeycomb photoreactor was designed. The honeycomb catalyst prepared by using Ce-doped TiO2 with 1%–2% vanadium and tungsten was employed for mercury removal from simulated industrial flue gas. The adsorption kinetics in the reaction process were studied. The results showed that the internally illuminated honeycomb photoreactor had good mercury removal performance. When the temperature was 25°C and the ultraviolet (UV) light intensity reached 80 µW/cm2, the mercury removal efficiency reached 92.5%. The mercury removal efficiency increased significantly with the doping ratio of Ce. XPS analysis showed that the oxidation state of Ce changed from 4 to 3 in the mercury removal reaction and produced lattice oxygen, which acts as an oxidant. O2 can promote mercury removal by honeycomb catalysts; SO2 and HCl also had positive effects, while NO had an inhibitory effect on mercury removal. Kinetic research in the reaction process showed that the quasi-first-order dynamic model had good fitting results, and the correlation coefficients of the fitting results for multiple sets of experimental data were more than 0.999. [ABSTRACT FROM AUTHOR]

In this study, a simple method combining sol-gel and impregnation techniques was employed to synthesize magnetic Cu/MnFe 2 O 4. The resulting material demonstrated outstanding efficiency in removing mercury, achieving over 90% at reaction temperatures ranging from 150 °C to 200 °C. Through Cu incorporation, the Hg0 removal performance of Cu 0.15 MnFe was significantly enhanced, leading to a high adsorption capacity of 70.1 mg/g. This surpasses the capabilities of many previously reported adsorbents and holds great potential for enhancing the stability of Hg recovery efficiency. Furthermore, the presence of O 2 , HCl, and NO further improved the Hg0 removal. Conversely, H 2 O had an mild inhibitory effect on Hg0 removal. Additionally, the introduction of Cu noticeably mitigated the inhibitory impact of SO 2 on mercury removal characteristics and alleviated the issue of SO 2 poisoning in adsorbents. The primary active sites responsible for the oxidation of elemental mercury are the redox reaction between Cu2+/Cu+ and Mn3+/Mn2+, and adsorbed oxygen species. Through the oxidation process, Hg0 is primarily converted into various compounds, including HgO, Hg(NO 3) 2 , HgCl 2 , and HgSO 4. As a result, the prepared magnetic recyclable adsorbent, with its high mercury adsorption capacity, exhibits promising prospects for industrial application in the low-temperature removal of Hg0 from coal-fired flue gas. [Display omitted] • Magnetic Cu/MnFe 2 O 4 adsorbent was prepared using a simple method. • Cu/MnFe 2 O 4 owned a large Hg adsorption capacity of 70.1 mg/g. • The introduction of Cu greatly alleviated SO 2 poisoning in adsorbents. • Cu2+, Mn3+ and O* play a crucial role as active sites for Hg0 oxidation. [ABSTRACT FROM AUTHOR]

Heterogeneous agglomeration (HA) is a very potential technology for coal-fired flue gas treatment. In this paper, the distribution and migration mechanisms of trace elements (TEs) such as Se, As and Pb in CFPPs were studied on a 30,000 m3/hr pilot-scale experimental platform. The influences of HA on the removal efficiency of gaseous and particulate TEs were well analyzed. The results showed that Se, As and Pb were enriched in fly ash, and their sensitivity to particle size is quite different. The content of Se was the highest in PM 1 , reaching 193.04 mg/kg at the electrostatic precipitator (ESP) outlet. The average particle size of the total dust before ESP increased significantly from 21.686 to 62.612 µm after injecting the heterogeneous agglomeration adsorbent, conducive to its further removal by ESP. In addition, the concentrations of gaseous Se, As and Pb in the flue gas decreased after adsorbent spray, and accordingly, their contents in the hierarchical particles increased, indicating that the adsorbent could effectively promote the adsorption of gaseous trace elements in fly ash and reduce the possibility of their escape to the atmosphere. Total concentrations of Se, As and Pb emitted by wet flue gas desulfurization (WFGD) are 0.223, 0.668 and 0.076 µg/m3, which decreased by 59.98%, 47.69% and 90.71%, respectively. Finally, a possible HA mechanism model was proposed, where chemical adsorption, physical condensation and collision agglomeration of gaseous TEs and fine particles with adsorbent droplets occurred to form larger agglomerates. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • The La 0.8 Ce 0.2 MnO 3 catalyst was highly active for Hg0 oxidation under SFG condition. • NO and HCl promoted Hg0 oxidation by forming active surface species. • H 2 O changed the catalyst surface chemistry and consumed active chlorine, which weakened the Hg0 oxidation. • NH 3 consumed surface oxygen and induced HgO reduction, hence limiting the Hg0 conversion. Abstract La 0.8 Ce 0.2 MnO 3 perovskite catalyst was employed for elemental mercury (Hg0) oxidation in coal combustion flue gas. The effects of flue gas components, including O 2 , NO, SO 2 , HCl, H 2 O as well as the selective catalytic reduction (SCR) reductant (NH 3), on Hg0 oxidation were investigated systematically. Above 90% Hg0 oxidation was obtained at 200 °C under simulated flue gas (SFG) and SCR atmosphere with a gas hourly space velocity of 60,000 h−1. Gaseous O 2 regenerated and replenished surface oxygen, hence promoting the oxidation of Hg0. NO promoted the Hg0 oxidation because of the formation of active surface species like NO 2. HCl facilitated the Hg0 oxidation, and 98.8% Hg0 oxidation was obtained under the atmosphere containing 10 ppm HCl in the co-presence of O 2. SO 2 inhibited Hg0 oxidation because of the irreversible damage on catalytic activity by reacting with the active species on the catalyst·H 2 O also inhibited Hg0 oxidation due to the change of catalyst surface chemistry as well as the consumption of active surface chlorine species (Cl∗). NH 3 competed active sites with Hg0 and induced oxidized mercury reduction, hence limiting the Hg0 conversion. However, the inhibitive effect of NH 3 could be partly offset by the promotional effect of NO. This work clarified the effects of flue gas compositions on Hg0 oxidation over a novel La 0.8 Ce 0.2 MnO 3 perovskite catalyst, which is essential for further improving the catalyst activity. [ABSTRACT FROM AUTHOR]

Abstract Novel adsorbents with low cost and high efficiency that do not produce secondary pollutants are vital for removing gaseous elemental mercury (Hg0) from coal-fired power plants. In this study, eight diatomite-based adsorbents were developed and used to remove Hg0 in a bench-scale fixed-bed reactor. The effects of active substances, reaction temperature, and gas components on the Hg0 removal performance of diatomite (Dia) and the mechanisms were investigated. After modification, the specific surface area of diatomite increased by 2-to-12 fold, and the Hg0 removal performance was greatly improved. The Hg0 removal efficiencies of the adsorbents decreased in the following order: I-Dia > Br-Dia > Cl-Dia. The Hg0 removal efficiency of CuBr 2 -Dia reached 91% in the simulated flue gas at the optimal reaction temperature (140 °C). The simultaneous presence of O 2 and HCl promoted the Hg0 removal by CuBr 2 -Dia. NO alone also played a significant role in Hg0 removal. However, SO 2 exhibited clear inhibitory effect. The average Hg0 removal efficiencies of CuBr 2 -Dia were 60% under 1200 ppm SO 2 , 87% under 1200 ppm SO 2 + 300 ppm NO, and 93% under 4% O 2 + 1200 ppm SO 2 + 300 ppm NO. The changes in the active adsorption sites caused by NO, and those caused by NO + SO 2 were different and irreversible. During the Hg0 removal process, Hg0 was oxidized to the Hg2+ or Hg+ species, while Cu2+ and Br radicals were reduced to Cu+ and Br−, respectively. Graphical abstract Unlabelled Image Highlights • Low cost and high efficiency adsorbents needed for Hg0 removal from flue gas. • Diatomite-based adsorbents exhibited excellent performance for Hg0 removal. • CuBr 2 -Dia had high Hg0 removal efficiency at 60–180 °C. • NO alleviated the inhibitory effect of SO 2 on Hg0 removal by CuBr 2 -Dia. • NO and NO + SO 2 caused distinct changes in the surface chemistry of adsorbent. [ABSTRACT FROM AUTHOR]

Fly ash fine particles emitted from flue gas during coal combustion are the primary atmospheric pollutants in China. The purpose of this study was to investigate the characteristics of the zeta potential of fine particle suspensions. The relationship between the zeta potential and the fine particle removal efficiency was also discussed. Batch experiments were conducted to evaluate the zeta potential of fine particle aqueous solutions under various pH, ion concentration, surfactant, polymer, and chemical agglomeration solution conditions. A chemical agglomeration system was designed to simulate the removal process of the fine particles. The test results indicated that the zeta potential absolute value of the solution decreased initially and then increased as the pH increased. As the pH increased from 4 to 12, the zeta potential decreased from Zp  = 9.4 mV to Zp  = −45.4 mV. The isoelectric point (IEP) was 4.3. Also at the IEP, the highest fine particle removal efficiency of 25.9% was achieved. The zeta potential increased as the metal cation concentration of the solutions increased. The trivalent cation Al 3+ exhibited the best performance, which increased Zp from −32.1 mV to −11.2 mV and produced the highest fine particle removal efficiency of 9.2%. Polymers significantly impacted the zeta potential. As the concentration of kappa-carrageenan (CAR) increased from 0.01% to 5%, the zeta potential increased from −30.1 mV to 12.6 mV. The highest fine particle removal efficiency of 41.8% was acquired at a concentration of 0.5%, which had the lowest zeta potential absolute value of 3.5 mV. It can be inferred that the increase in the zeta potential induced the growth of the energy barrier, which prevented particle agglomeration. The suspension with a lower zeta potential exhibited a better fine particle removal efficiency. [ABSTRACT FROM AUTHOR]

Samples of magnetic iron–manganese binary oxide supported on activated carbon fiber (Fe 3−x Mn x O 4 /CNF) were prepared for Hg 0 removal from flue gas. The results showed that the Hg 0 removal performance of Fe 3−x Mn x O 4 /CNF was significantly promoted with the increase of Mn incorporating content into Fe 3 O 4 spinel structure. The optimal sample of Fe 2 MnO 4 /CNF, at the optimal reaction temperature of 150–200 °C, attained above 90% of Hg 0 removal efficiency (E a ). CNF played an important role in Hg 0 removal by Fe 3−x Mn x O 4 /CNF due to the disperation of Fe 3−x Mn x O 4 particles and the enhancement for electron transfer process. O 2 enhanced the Hg 0 removal via the Mars-Maessen mechanism, and NO improved the Hg 0 removal performance slightly because of the formation of NO 2 . SO 2 and H 2 O played an inhibitive role in Hg 0 removal due to the competition of active sites for Hg 0 adsorption. A mechanism of Hg 0 removal over Fe 3−x Mn x O 4 /CNF is proposed, in which both Mn cations and lattice/chemisorbed oxygen were thought to the active sites for Hg 0 adsorption/oxidation. Further, the spent Fe 3−x Mn x O 4 /CNF could be regenerated with no obvious decrease of Hg 0 removal performance by water washing followed by thermal treatment at 450 °C in N 2 and calcination at 200 °C in air. [ABSTRACT FROM AUTHOR]

Wet flue gas desulfurization (WFGD) systems have several benefits, including SO 2 removal and Hg pollution control. However, the absorbed ionic mercury may be transformed into insoluble elemental mercury because of the chemical interaction with the aqueous scrubbing solution, which causes mercury re-emission and reduces the mercury capture efficiency of the scrubber. This study investigates the effects of operating temperatures, pH, and O 2 and SO 4 2 − concentrations on the reduction of Hg 2 + in the presence of SO 3 2 − in a simulated desulfurization aqueous solution. The results indicate that excess SO 3 2 − inhibits Hg 2 + reduction due to the formation of the stable Hg(SO 3 ) 2 2 − complex, whereas a low SO 3 2 − concentration (< 2 mM) leads to enhanced mercury re-emission due to the formation of more redox-unstable HgSO 3 . The Hg 0 release increases from 18.6% to 59.6% when the operating temperature increases from 45 °C to 55 °C. A pH decrease in the slurry from 5 to 3 causes a significant increase in the Hg 0 emission from 6.9 to 127.9 μg/m 3 in a simulated desulfurization slurry. In addition, O 2 caused a secondary emission of Hg 0 by damaging the stable redox complexes of Hg 2 + and SO 3 2 − . In the presence of oxygen, the Hg 0 emission decreases; subsequently, a HgSO 3 SO 4 2 − complex is formed. Sulfate (HgSO 4 and HgSO 3 SO 4 2 − ) inhibit the emission of Hg 0 . [ABSTRACT FROM AUTHOR]

Several modified adsorbents were developed by impregnating palygorskite (Pal) with the active substances CuCl 2 , CuBr 2 , NaBr, sulfur (S), MnO 2 and Co 3 O 4 , which were used to conduct experiments via a bench-scale fixed-bed reactor system in simulated flue gas for evaluating their elemental mercury removal capacity. In addition, a variety of characterization methods were applied to understand the physicochemical properties of these adsorbents. Furthermore, adsorbents, namely, CuCl 2 /CuBr 2 -impregnated Pal (Cu-Pal), were chosen for deep exploration under various gas conditions. The results showed that the mercury removal capability of Pal was greatly improved after impregnation. At 120 °C in pure N 2 , the mercury removal efficiency of the adsorbents modified by CuCl 2 and CuBr 2 could reach 90.9% and 95.2%, respectively, while it could be > 80% for the adsorbents modified by the others. The overall trend showed that O 2 and HCl were beneficial to increasing the mercury removal efficiency of Cu-Pal. To be specific, for CuCl 2 -Pal and CuBr 2 -Pal, when adding in 8% O 2 , their efficiencies could be increased by 6.6% and 1.9% respectively, while 50 ppm HCl increased their efficiencies by 2.8% and 2.1%, respectively. Different from O 2 and HCl, SO 2 and NO had negative effects. The removal efficiencies could be reduced by 6.5% for CuCl 2 -Pal and 4.7% for CuBr 2 -Pal with 1200 ppm SO 2 , while they could be reduced by 4.2% and 2.6% with 300 ppm NO. Compared with CuCl 2 -Pal, CuBr 2 -Pal performed better. Combined with the characterization results, Cu 2 + was reduced to Cu + and halogen migrated into new compounds on the surface of Cu-Pal after reaction. Eventually, the mercury removal mechanism of Cu-Pal was analysed and proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Basic reference data for Hg migration and control were obtained. • Removal efficiency of HgT by flue gas purification equipment is 92.40%. • CuBr 2 -modified activated carbon exhibits excellent Hg0 removal performance. • Mechanism of CuBr 2 -modified activated carbon for Hg0 removal were revealed. This study evaluated the emission and control characteristics of mercury during hazardous chemical waste incineration. Meanwhile, for the complex flue gas conditions generated by hazardous chemical waste incineration, the commercial activated carbon used in the incineration system was modified with CuBr 2 , and its Hg0 removal performance was tested. The results showed that the major proportion of Hg was in the fly ash, and the content accounted for 74.53 % of the total Hg. The Hg content in the fly ash increased with decreasing fly ash particle size. In the exhaust flue gas, the Hg content was 11.05 % of the total Hg, in which the mass percentages of Hg2+ and Hg0 were 59.08 % and 40.92 %, respectively. The flue gas purification equipment of the incineration system had a removal efficiency of 92.40 % for HgT. The saturated Hg0 removal capacity of the modified activated carbon was improved by 33.51 times. Under simulated incineration flue gas conditions, the modified activated carbon was able to achieve an Hg0 removal efficiency of 92.85 %. The results can contribute to the understanding of Hg emissions from hazardous chemical incineration systems and provide guidance for efficient Hg removal from activated carbon. [ABSTRACT FROM AUTHOR]

• The millimeter-grade Se/SiO 2 adsorbent can be used as a filler in a fixed bed reactor. • The saturated adsorption capacity of mercury is up to 101.04 mg/g. • HgSe is the main product of mercury removal from adsorbent under flue gas conditions. • The carrier of Se/SiO 2 is soluble SiO 2 , and high purity of HgSe can be recovered. Massive Hg emissions from coal-fired units cause serious environmental pollution and result in a substantial waste of Hg resources. In this study, the prepared millimeter-grade Se/SiO 2 adsorbent was applied as a filler to adsorb mercury in a fixed-bed reactor to obtain the high value-added product HgSe, which solved the problem of short contact time and secondary pollution caused by the traditional injection mercury removal adsorbents. Experimental Hg removal showed that the 25 % Se-loaded adsorbent exhibited excellent Hg removal performance at 150 °C, with a saturation adsorption capacity of mercury was as high as 101.04 mg/g, nearly 300 times that of commercial activated carbons. Additionally, the influence of the flue gas composition on the Hg removal performance of Se/SiO 2 was studied. The results showed that O 2 , NO, and HCl increased the efficiency of Hg removal and SO 2 and SO 3 had trivial impact on the Hg removal performance. The Hg temperature-programmed desorption test results showed that the adsorbed Hg appeared predominantly as HgSe on the sample surface. DFT calculations verified that Se loading improved Hg removal performance and defined the adsorption mechanism. Moreover, the prepared Se/SiO 2 adsorbent carrier was soluble SiO 2 , which provided a good condition for the subsequent high-purity collection of HgSe. Finally, the technological process of Hg removal via Se-loaded adsorbents and the recovery of HgSe were proposed, which could offer a new way to achieve the resource utilization of Hg. [ABSTRACT FROM AUTHOR]

• Magnetospheres was modified through H 2 S as an efficient sorbent for Hg0. • Elemental sulfur derived from H 2 S oxidation was responsible high-efficient Hg0 adsorption. • Gaseous Hg0 was immobilized as stable HgS with extremely low leaching ratio. • The application route for Hg0 removal by using magnetospheres with suface sulfidation modification was proposed. Reduction of elemental mercury (Hg0) emission from coal-fired power plants is an enormous challenge. In this work, magnetospheres separated from fly ash was modified through H 2 S as an efficient sorbent (i.e., S-MS) for Hg0. Elemental sulfur with high affinity towards Hg0 was formed on the S-MS surface through selective catalytic oxidation of H 2 S. The sulfidation temperature played an important role in Hg0 adsorption over S-MS, ascribing to the variation of sulfur species on S-MS. The S-MS exhibited above 80% Hg0 adsorption efficiency with a sulfidation temperature of 150 °C for 30 min. The optimal Hg0 adsorption performance was obtained at 50 and 75 °C, implying that the S-MS could be adopted by injecting into the duct upstream of wet electrostatic precipitator (WESP) system. The gaseous Hg0 was immobilized by S-MS as stable mercury sulfide (HgS) owing to the presence of abundant sulfur species that is active for binding Hg0. The leaching ratio of mercury from spent S-MS in WESP effluent was as low as 1%, hence minimizing the secondary mercury pollution from the industrial waste. The cost analysis demonstrates that the mercury removal technology on the basis of magnetospheres adsorbents exhibited much superiority in operation cost compared with commercial activated carbon injection technology. Thus, the S-MS, with specific features, such as high Hg0 adsorption performance, minimized environmental hazardous and recyclability, displayed great potential in Hg0 sequestration. [ABSTRACT FROM AUTHOR]

• Heterogeneous agglomeration reduce the emission of fine particles and trace elements. • The mechanism of heterogeneous agglomeration on fine particles and trace elements. • Combined removal of pollutants by heterogeneous agglomeration and ESP. • Migration and transformation of trace elements in the tail gas of power plants. For a domestic 350 MW coal-fired power plant, the effect of heterogeneous agglomeration technology on the migration and emission of three trace elements of arsenic, selenium and lead in tail flue gas was studied. The results show that heterogeneous agglomeration technology can promote the attachment of gaseous harmful trace elements to particulate matter effectively. The reduction rates of gaseous As, Se and Pb concentrations at the ESP outlet were 24.10%, 61.08%, and 70.38%, respectively. Under the synergistic effect of ESP, more As, Se, and Pb are enriched in fly ash, and the concentration of As, Se, and Pb in fine particles below 10 μm at the ESP outlet is reduced by 54.48%, 56.47%, and 75.17%, respectively. In addition, after spraying the agglomerating agent, the final As, Se, and Pb concentrations in the atmosphere were 1.29 μg/m3, 2.01 μg/m3, and 1.12 μg/m3, which were far lower than those of the relevant EPA emission limits. [ABSTRACT FROM AUTHOR]

Abstract: Effect of SO2 on elemental mercury (Hg0) oxidation over a highly active CeO2–TiO2 catalyst was systematically investigated. SO2 was found to have different, even contrary, effects on Hg0 oxidation under different flue gas conditions. In pure N2 atmosphere, SO2 inhibited Hg0 oxidation. In N2 plus O2 atmosphere, low concentration of SO2 promoted Hg0 oxidation, while high concentration of SO2 deteriorated Hg0 oxidation. The promotional effect of SO2 on Hg0 oxidation was probably due to SO3 generated from SO2 oxidation, and the inhibitive effect of SO2 on Hg0 oxidation was attributed to the competitive adsorption between SO2 and Hg0. The results suggest a balance point for SO2 concentration, where the promotional effect on Hg0 oxidation by SO3 originated from SO2 is equal to the inhibitive effect of SO2 on Hg0 adsorption and subsequent oxidation via the Langmuir–Hinshelwood mechanism. In the presence of NO, SO2 with the aid of O2 exhibited promotional effect on Hg0 oxidation through NO-catalyzed oxidation to form SO3 and hence a balance point of higher SO2 concentration. However, without O2, SO2 greatly limited Hg0 oxidation in the presence of NO. When HCl was present, most Hg0 oxidation was due to reactions between active chlorine species and adsorbed Hg0. SO2 inhibited Hg0 adsorption and therefore deteriorated Hg0 oxidation by chlorine species. When both NO and HCl were present, NO accelerated the conversion of SO2 to SO3, and hence relieved the prohibitive effect of SO2 on Hg0 oxidation by HCl. [Copyright &y& Elsevier]

Abstract: MnO x -CeO2 mixed-oxide supported on TiO2 (Mn-Ce/Ti) was synthesized by an ultrasound-assisted impregnation method and employed to oxidize elemental mercury (Hg0) at 200°C in simulated coal combustion flue gas. Over 90% of Hg0 oxidation was achieved on the Mn-Ce/Ti catalyst at 200°C under simulated flue gas representing those from burning low-rank coals with a high gas hourly space velocity of 60,000h−1. Gas-phase O2 regenerated the lattice oxygen and replenished the chemisorbed oxygen, which facilitated Hg0 oxidation. HCl was the most effective flue gas component responsible for Hg0 oxidation. 10ppm HCl plus 4% O2 resulted in 100% Hg0 oxidation under the experimental conditions. SO2 competed with Hg0 for active sites, thus deactivating the catalyst''s capability in oxidizing Hg0. NO covered the active sites and consumed surface oxygen active for Hg0 oxidation, hence limiting Hg0 oxidation. Water vapor showed prohibitive effect on Hg0 oxidation due to its competition with HCl and Hg0 for active adsorption sites. This study provides information about the promotional or inhibitory effects of individual flue gas components on Hg0 oxidation over a highly effective Mn-Ce/Ti catalyst. Such knowledge is of fundamental importance for industrial applications of the Mn-Ce/Ti catalyst in coal-fired power plants. [Copyright &y& Elsevier]

Abstract: High surface area SiO2–TiO2–V2O5 (STV) catalysts of various titania loadings were synthesized by a sol–gel method. The STV catalysts were tested for oxidation of elemental mercury (Hg0) and its capture in simulated coal combustion flue gas representing those from combustion of low-rank coals (sub-bituminous and lignite). Experiments were conducted in a fixed-bed reactor at temperatures ranging from 26 to 400°C. In simulated flue gas, Hg0 oxidation efficiency over the STV catalysts was found to decrease dramatically from 135 to 300°C. At typical selective catalytic reduction (SCR) operating temperatures, the catalyst''s oxidation activity increased as titania loading of the STV catalysts increased up to 18wt%. The reaction mechanisms over the STV catalysts at SCR operating temperatures were investigated using individual flue gas components (HCl, NO, SO2 and H2O) with O2 balanced in N2. Hg0 oxidation over STV catalysts follows the Eley–Rideal mechanism where active surface species generated from adsorbed flue gas components react with gas-phase or weakly adsorbed Hg0. Fresh STV catalysts had some capability for adsorbing oxidized mercury (Hg2+) at 350°C, and no obvious effect of the adsorbed Hg2+ on subsequent Hg0 oxidation was observed. The presence of HCl with O2 had excellent oxidation and capture efficiency; however, without O2 it remarkably inhibited Hg0 adsorption on the STV catalysts. NO and SO2 promoted Hg0 oxidation and capture in the presence of O2, but their promotional effects were insignificant in the absence of O2. Water vapor showed prohibitive effects on Hg0 oxidation due to its competition with reactive species such as HCl and NO for active adsorption sites. This study demonstrates the feasibility of using STV catalysts for Hg0 removal at typical SCR operating temperatures. The identification of the reaction mechanism provides critical information for developing effective SCR catalysts for Hg0 oxidation in coal combustion flue gas. [Copyright &y& Elsevier]

• Modified tonstein (CuBr 2 -TCS) effectively removed Hg0 from simulated flue gas. • O 2 significantly facilitated Hg0 removal by the spent adsorbent after the cycle. • The adding order of NO and SO 2 had a large effect on the performance of CuBr 2 -TCS. • Both Cu2+ and Br played key roles in the process of Hg0 removal. Tonstein in coal seam (TCS) is a kind of mining solid waste, which was developed to a novel adsorbent (CuBr 2 -TCS) by using copper bromide modification. In this paper, CuBr 2 -TCS was subjected to elemental mercury (Hg0) removal experiment in simulated coal-fired flue gas (SFG). Several characterization methods were used to determine the mineralogical characteristics of TCS and reaction mechanisms. In-depth, the Hg0 removal performances of CuBr 2 -TCS under different flue gas components were explored. The results revealed that CuBr 2 -TCS exhibited 92.1% and 78.3% Hg0 removal efficiency in dry and wet SFG, respectively. HCl and O 2 facilitated Hg0 removal performance of CuBr 2 -TCS by supplementing oxygen atoms and halogens, respectively, accompanying some intermediate transition products such as Cu 2 OBr 2. SO 2 played a serious suppressive role. SO 2 acting alone or NO and SO 2 acting simultaneously caused irreversible changes in the surface functional groups that formed active sites with NO. However, the thermal stability of the adsorbed mercury on the adsorbent which was spent in N 2 + SO 2 + O 2 atmosphere became better. In addition, the spent adsorbent that first went through the Hg0 removal process in N 2 + NO atmosphere, exhibited higher Hg0 removal efficiency in N 2 + SO 2 + NO atmosphere than that first reacted in N 2 + SO 2 atmosphere. CuBr 2 -TCS is a cost-effective adsorbent for the Hg0 abatement from the coal-fired flue gas (CFG). [ABSTRACT FROM AUTHOR]

• Mechanism of Hg0 adsorption on GO and Zn/Cu/Ni-GO is elucidated by DFT method. • Zn/Cu/Ni greatly enhances Hg0 adsoption on GO surface, of which Ni is the best one. • ZnGO/CuGO/NiGO can be used as an efficient catalyst for elemental mercury removal. Mercury emissions from coal-fired power plants are a major cause of severe environmental issues, and elemental mercury is the most difficult form to remove from combustion flue gases. Based on density functional theory (DFT) calculations, the adsorption effects of elemental mercury on primary and three transition metals (Zn, Cu and Ni)-decorated graphene oxides (GO) have been studied. The larger adsorption energies, smaller adsorption distances and stronger charge transfer demonstrate the combination of Hg0 atom on primary GO and ZnGO/CuGO/NiGO surfaces have a significant change from physical adsorption to chemical adsorption. The enhancement order of three modified metal elements for mercury removal is Zn < Cu < Ni, and the maximum values of adsorbed mercury atoms are 2, 3 and 3. Hence, this study exhibits that ZnGO, CuGO and NiGO have favorable mercury removal performance, among which NiGO has the best mercury capture capacity. [ABSTRACT FROM AUTHOR]

• This review discusses the development of mineral adsorbents for Hg0 removal. • Species, physicochemical characteristics and modification methods are summarised. • Mercury removal performance, influence factors and mechanisms are also summarised. • Modified mineral adsorbents are low-cost and effective in removing mercury. Mercury emissions from coal-fired power plant flue gas (CFFG 1 1 CFFG is an abbreviation for coal-fired power plant flue gas.) threaten the natural environment and human health, and this has attracted the attention of environmental protection departments and scientific researchers in recent years. Mineral adsorbents perform well at mercury removal and extensive studies on them have been conducted. This review discusses the progress in researching the application of mineral adsorbents to mercury emission control technologies applied to CFFG. The species and physicochemical characteristics of some common mineral adsorbents are briefly introduced and various modification methods, mainly including high temperature activation, acid activation, organic modification, inorganic modification and combinations of modifications, are summarised. As well, the mercury removal performance of various mineral adsorbents is evaluated, and the results indicate that removal performance relates to the actions of the mineral carrier combined with modification methods which are able to improve the physical structure of minerals and/or increase the number of active sites for mercury removal on the mineral surfaces. The effects of the main process parameters, including reaction temperature and flue gas components (O 2 , HCl, SO 2 , NO, H 2 O, Hg0, etc.), on mercury removal by different mineral adsorbents are also systematically reviewed. Moreover, the possible adsorption and oxidation approaches involved in the process of mercury removal by mineral adsorbents are discussed. This review indicates that the chemical active site is the key factor for mercury removal. Our economic evaluation indicates that the cost of mineral adsorbent is much lower than that of activated carbon, showing that mineral adsorbents have promise in terms of industrial applications. Finally, future work necessary for the continued development of mineral adsorbent injection technology for CFFG mercury control is proposed. [ABSTRACT FROM AUTHOR]