Hg0 Removal Efficiency Research Articles

Efficient removal of Hg(II) from dental effluents by thio-functionalized biochar derived from cape gooseberry (Physalis peruviana L.) leaves

Mercury is well known to be highly toxic to humans and aquatic life. Wastewater discharges from dental clinics are the predominant source of mercury species in the environment. Innovative biochar was fabricated by the thio-functionalization of cape gooseberry (Physalis peruviana L.) leaves to produce thio-modified biochar for the sequestration of Hg (II) ions. The removal Hg(II) efficiency for the native and thio-functionalized cape gooseberry biochars were compared. Sulfur impregnation improved the affinity of biochar for Hg(II) uptake via –SH exchange and complexation mechanisms by 54%. The applicability of the novel thio-modified biochars for Hg(II) removal from dental effluents below five ppb levels was tested. The Hg(II) removal efficiency was 96.4% for 3BHS at pH = 5.0 and 25 min of contact time. The results of the present study indicated that thio-modified biochar from cape gooseberry could be a potential low-cost material for the sequestration of Hg(II) ions from acidic wastewater.

Migration and control of mercury in hazardous chemical waste incineration

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 CuBr2, 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.

Mercury removal from flue gas by a MoS2/H2O heterogeneous system based on its absorption kinetics.

An enhanced MoS2/C10TAB/H2O system was built and investigated for Hg0 removal based on strengthening the Hg0 gas-liquid mass transfer. The results showed that adding 7mg/L C10TAB can improve the Hg0 removal efficiency from 76.5 to 88.7% as decrease of the solution surface tension. Keeping 2000rpm of stirring rate accelerated the renewal rate of gas-liquid interface, thereby enhancing Hg0 removal. SO2 slightly promoted the Hg0 removal efficiency to 91% because of the absorption of SO2 causing a decrease in the solution pH from 6.9 to 4.3. NO participated in Hg0 removal reactions but not removed in this system which visibly enhanced the Hg0 removal efficiency to 94%. The Hg mass transfer kinetics were analyzed to determine how C10TAB promoted Hg0 removal. The Hg-TPD, Hg fate, and species results revealed that Hg0 was first oxidized to Hg2+, then bonded with S to generate HgS and enrich on the MoS2. Therefore, improving the Hg0 gas-liquid mass transfer can enhance Hg0 removal in MoS2/H2O system, which can provide reference for purification of other insoluble pollutants in absorption system.

Synergistic removal of NO and Hg0 over Co-Mn/TiO2 catalyst: High efficiency and in-depth reaction mechanism

The key challenge for controlling Hg0 using selective catalytic reduction (SCR) technology is to develop a suitable catalyst capable of operating in a cost-effective manner, so it is necessary to study the in-depth reaction mechanism. Herein, Co-Mn/TiO2 catalysts were fabricated by sol-gel method, excellent stability and high efficiency of Hg0 removal (100%) and NO conversion (99%) are concurrently reached at 180 °C, which are benefited from the abundant active oxygen species on the catalysts. In order to clarify the synergistic reaction process, the mechanism of mutual effects between SCR atmosphere and Hg0 is highly dedicated. Specifically, NO and O2 were beneficial to Hg0 oxidation, while NH3 competitive adsorption with Hg0 and consumption of active oxygen species prevent the Hg0 oxidation. Impressively, the inhibition effect of NH3 was not weakened but also intensified, mainly due to the co-existence of NO and NH3 could induce partial HgO reduction. What's more, the direct evidence for the synergistic reaction mechanism of NO and Hg0 is hypothesized by a combination of XPS and in-situ DRIFTs. These findings thus open up a way to address the simultaneous removal of NO and Hg0 in industry.

Regeneration mechanism of a novel high-performance biochar mercury adsorbent directionally modified by multimetal multilayer loading

Biochar that is directly obtained by pyrolysis exhibits a low adsorption efficiency; furthermore, the process of recycling adsorbents is ineffective. To solve these problems, conventional chemical coprecipitation, sol-gel, multimetal multilayer loading and biomass pyrolysis coking processes have been integrated. After selecting specific components for structural design, a novel high-performance biochar adsorbent was obtained. The effects of the O2 concentration and temperature on the regeneration characteristics were explored. An isothermal regeneration method to repair the deactivated adsorbent in a specific atmosphere was proposed, and the optimal regeneration mode and conditions were determined. The microscopic characteristics of the regenerated samples were revealed along with the mechanism of Hg0 removal and regeneration by using temperature-programmed desorption technology and adsorption kinetics. The results show that doping multiple metals can reduce the pyrolysis reaction barrier of the modified biomass. On the modified surface of the sample, the doped metals formed aggregated oxides, and the resulting synergistic effect enhanced the oxidative activity of the biochar carriers and the threshold effect of Ce oxide. The optimal regeneration conditions (5% O2 and 600 °C) effectively coordinated the competitive relationship between the deep carbonization process and the adsorption/oxidation site repair process; in addition, these conditions provided outstanding structure-effect connections between the physico-chemical properties and Hg0 removal efficiency of the regenerated samples. Hg0 adsorption by the regenerated samples is a multilayer mass transfer process that involves the coupling of physical and chemical effects, and the surface adsorption sites play a leading role.

Hg0 removal performance and mechanisms of FeOCl regulated by CuCl2

Pure FeOCl has a low Hg0 adsorption capacity and the complex flue gas environment further hinders its practical application to mercury removal. This paper proposes that CuCl2 is used to regulate the Hg0 chemisorption capacity of FeOCl. The experimental results found that when the CuCl2 to FeCl3 mass ratio was 2:1, the efficiency of Hg0 removal reached 100% at 140–160 °C. In addition, the sulfur resistance and O2 adsorption capacity of FeOCl are enhanced by doping with CuCl2. The adaptability of FeOCl-based sorbents to complex flue gas environments was significantly improved. The regulation mechanisms of CuCl2 were clarified by density functional theory. This work addresses the low sulfur resistance and low chemisorption capacity of FeOCl-based sorbents and provides an effective solution for mercury removal in complex flue gas environments.

Three-dimensional ordered zeolite-templated carbon with covalent sulfur for efficient removal of elemental mercury: Experimental study and molecular dynamic simulation

Traditional activated carbon used to remove elemental mercury (Hg0) from coal-fired power plants exhibit an irregular porous structure, showing an adverse effect on the removal of Hg0. To obtain carbon materials with a regular porous structure, zeolite-templated carbon samples (ZTC and S-doped ZTC) with a three-dimensional ordered structure were synthesized via the chemical vapor deposition (CVD) method using C2H2 and H2S as the carbon and sulfur precursor on BEA zeolite. Several techniques including TG-MS, SEM-TEM-EDS, etc. were used to determine that ZTC replicated the regular microporous structure of zeolite and generated turbostratic carbon. Moreover, the Hg0 removal efficiency (MRE) of ZTC samples was investigated. At 30 °C, they removed Hg0 mainly by physisorption, while at 150 °C, chemisorption was the dominant approach for capturing Hg0. The influence of flue gas components (H2O, NH3, and SO2) on the MRE of ZTC-HS was further studied by experimental methods and molecular dynamic (MD). H2O and NH3 weakened the MRE of ZTC-HS due to the competing adsorption. The effect of SO2 on the MRE of ZTC-HS was related to its concentration. Because of its advantages in regeneration features, preparation cost and higher resistance to flue gas components, ZTC-HS exhibited the potential for industrial applications.

The Release and Reduction of Mercury from Solid Fuels through Thermal Treatment Prior to Combustion

The main source of mercury (Hg) anthropogenic emissions is the combustion of hard and lignite coal in power plants. Reduction of Hg emissions from coal-based power production systems involves Hg removal from the fuel before combustion/gasification by thermal treatment (i.e., low-temperature pyrolysis). Herein, we present the results of laboratory and bench-scale studies on Hg removal from coal via thermal fuel treatment. The influence of the process temperature and coal residence time in the reaction zone on Hg removal efficiency and fuel parameters is studied. The properties of the process products are analyzed as follows: proximate and ultimate analysis for solids as well as H2, N2, CO, CO2, CH4, organic compounds C2–C5, density, and HHV for gaseous. The results show a substantial reduction of Hg in the fuel using a low-temperature pyrolysis process. At moderate pyrolysis temperature provided Hg removal efficiencies of up to 50% for hard coal and over 90% for lignite, with a moderate decrease in the chemical enthalpy of the fuel.

A high efficiency and high capacity mercury adsorbent based on elemental selenium loaded SiO2 and its application in coal-fired flue gas

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/SiO2 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/SiO2 was studied. The results showed that O2, NO, and HCl increased the efficiency of Hg removal and SO2 and SO3 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/SiO2 adsorbent carrier was soluble SiO2, 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.

Cubic SAPO-34 supported MnOx for low-temperature gaseous mercury oxidation and adsorption from coal-fired flue gas

Gaseous elemental mercury (Hg0) from industrial flue gas is difficult to be synergistically removed by existing flue gas purification equipment. In this paper, Mn-based oxides were used for the modification of SAPO-34 molecular sieve to enhance Hg0 oxidation and adsorption performances. The results showed that when 5 % Mn dropped on the surface of SAPO-34, it had the highest Hg0 removal efficiency and exhibited a better Hg0 removal performance at lower temperature (<150 °C). SO2 would compete for active adsorption sites of Hg0, while H2O vapor had little influence on Hg0 removal. The Hg0 removal mechanism was discussed based on experiment and characterization results and density functional theory calculation. The larger surface area and pore volume of Mn/SAPO-34 benefited the physical adsorption process. The surface MnOx particles enhanced the oxidation of Hg0 to Hg2+ and the oxygen site can further bond with Hg2+ to form stable HgO. In addition, the larger desorption peak of HgO (487 °C) and the more negative adsorption energy (-1.21 eV) revealed the dominant role of chemical adsorption of Hg0 over Mn/SAPO-34. Thus, the Mn/SAPO-34 is a potential catalyst for Hg0 removal from industrial flue gas.

The novel magnetic adsorbent derived from MIL-100 (Fe) loading with bimetallic Cu and Mn oxides for efficient Hg0 removal from flue gas

A novel magnetic adsorbent derived from MIL-100(Fe) loading with bimetallic Cu and Mn oxides, namely CuMnOx/MIL-100(Fe), was easily synthesized and used to remove elemental mercury (Hg0) from flue gas. Different mass loadings of CuMnOx (3%, 6%, and 9%) were impregnated on MIL-100(Fe) and calcinated at 200–500 °C to form CuMnOx/MIL-100(Fe), which was used to inspect Hg0 removal efficiencies at different reaction temperatures (40–200 °C). The Hg0 removal performance was studied through a variety of characterizations, including XRD, BET, SEM-EDS, TGA, XPS, VSM, H2-TPR, and Hg-TPD. 6%CuMnOx/MIL-100(Fe) calcined at 500 °C had a superior Hg0 removal efficiency of 92.4% and capacity of 1.16 mg/g at 120 °C, indicating that high-temperature calcination and bimetal loading were capable of improving the catalytic activity of MIL-100(Fe) and thereby improving the removal efficiency of Hg0 at a relatively low operating temperature of 120 °C. Under different flue conditions, the increase in O2 and NO concentrations can obviously promote the removal efficiency of Hg0, while SO2 and H2O had an opposite trend. The Hg0 removal efficiency remained above 90% after 8 cycles, which exhibits potential for industrial application. Furthermore, the Hg0 removal mechanism was attributed to the reaction with chemisorbed oxygen or lattice oxygen to form HgO on CuMnOx/MIL-100(Fe), which follows the Langmuir-Hinshelwood and Mars-Maessen mechanism.

Catalytic performance and sulfur resistance of OMS-2 modified by copper for mercury removal at low temperature

Cu-doped manganese oxide molecular sieve catalysts (Cu-OMS-2) are prepared by hydrothermal synthesis method, and their Hg0 removal ability and sulfur resistance are investigated experimentally under simulated flue gas conditions. It indicated that appropriate proportion of Cu doped could increase both the content of Mn4+ active sites on the catalyst surface and the BET specific surface area. The maximum specific surface area of these catalysts is 260.49 m2/g, with the Cu/Mn molar ratio of 0.025. A highest Hg0 removal efficiency of 93.6 % is achieved by the catalyst with Cu/Mn molar ratio of 0.05. SO2 in flue gas significantly inhibits the Hg0 removal ability of OMS-2-H120, but its suppression ability is relatively weak after the addition of Cu to OMS-2-H120. The Hg0 removal efficiency of Cu0.05-OMS-2 can reach 92 % even in the presence of 1000 ppm SO2. The doping of Cu on OMS-2 enhances SO2 adsorbed by CuO, inhibiting the reaction of SO2 with the active center on the catalyst surface. It reduces the generation of sulfate and enhances the sulfur resistance ability of Cu0.05-OMS-2. The process of Hg0 oxidation by O2 over Cu0.05-OMS-2 is found to follow Mars-Maessen mechanism based on the characteristics of fresh and spent catalysts. Elemental mercury is firstly chemisorbed on the Cu0.05-OMS-2 catalyst surface and then oxidized.

Facile fabrication of 3D spherical Ag2WO4 doped BiOI/BiOCl double S-scheme heterojunction photocatalyst with efficient activity for mercury removal

The novel ternary Ag2WO4/BiOI/BiOCl microspherical photocatalysts were successfully fabricated by a facile one-pot coprecipitation method to accelerate the separation performance of photogenerated electron-hole (e–-h+) pairs of BiOCl and BiOI materials. The as-prepared materials were characterized by multiple methods, and the effects of various parameters such as Ag2WO4 content, fluorescent light irradiation, pH value and inorganic anions on photocatalytic removal of Hg0 were studied in detailed. The characterization results showed that the three-dimensional (3D) microspherical BiOI/BiOCl composite provided a suitable carrier for Ag2WO4, and Ag2WO4 material was evenly dispersed on the Ag2WO4/BiOI/BiOCl surface. The ternary composite possessed a larger surface area than Ag2WO4 and BiOI/BiOCl with the addition of Ag2WO4. Meanwhile, the separation efficiency of e–-h+ pairs in Ag2WO4/BiOI/BiOCl composite was greatly enhanced. The experimental results showed that Ag2WO4 content, fluorescent light irradiation, CO32− and SO2 all exhibited remarkable influences in the photocatalytic process. The Hg0 removal efficiency of Ag2WO4/BiOI/BiOCl photocatalyst was still up to 94 % after four cycles, indicating a superior stability of photocatalyst. Superoxide radical (•O2–) and hole (h+) were proved to be the main reaction substances for Hg0 removal. In view of the characterization analysis, free radicals capture test results and Density functional theory (DFT) calculation, the charge transfer route of Ag2WO4/BiOI/BiOCl composite and its mechanism for gaseous Hg0 removal were proposed with a double S-scheme mode.

Tunning active oxygen species for boosting Hg0 removal and SO2-resistance of Mn-Fe oxides supported on (NH4)2S2O8 doping activated coke

Active oxygen species (AOS) play an essential role in modulating the activity of activated coke (AC) based samples. In this paper, AC was endowed with abundant AOS by modifying with (NH4)2S2O8 and MnOx-FeOx for Hg0 removal. (NH4)2S2O8 treatment induced abundant micropores and oxygen-containing functional groups, and thus provided more anchoring sites for the dispersion of MnOx-FeOx. The synergy of MnOx-FeOx and interaction between MnOx-FeOx and NAC support contributed to a larger surface area, highly-dispersed active components, stronger reducibility, and more metal ions with high valence of MnFe/NAC. The optimal MnFe/NAC exhibited superior Hg0 removal efficiency above 90% at 120∼180 ℃, as well as excellent performance for simultaneous removal of Hg0 and NO, and 600 ppm SO2 and 8 vol.% H2O addition led to a slight deterioration. XPS and Hg-TPD revealed that mercury adsorbed on MnFe/NAC included phy-Hg, C=O-Hg, COO-Hg, and OL-HgO. Besides, the priority of AOS for Hg0 chemisorption was C=O > COO- > OL, and Hg2+ was also detected in the outlet. Moreover, the SO2-poisoning effect was ascribed to the sulfation of MnOx and the occupation of COO- and C=O, and FeOx incorporation enhanced the SO2-resistance through weakening SO2 adsorption on C=O and COO-. The motivation of O2 mainly contributed to the regeneration of AOS, especially OL. The excellent regeneration performance and stability further affirmed the application potential of MnFe/NAC for Hg0 capture from coal-fired flue gas.

Enhanced photocatalytic Hg0 removal over Z-scheme CeO2/Bi5O7I nanorod composite under fluorescent light irradiation

Novel CeO2 modified Bi5O7I nanorod composites were synthesized via a coprecipitation subsequent calcination method, which were employed to oxidize gaseous Hg0 in a photocatalytic bubbling reactor. The porosity properties, crystal structures, morphologies, elemental composition and optical absorption properties of the composites were investigated using various characterization methods. CeO2/Bi5O7I showed a significantly improved photoactivity of Hg0 removal under fluorescent light irradiation. The optimal mass percentage of CeO2 to CeO2–Bi5O7I was 10% and its photocatalytic removal efficiency of Hg0 reached as high as 97%. In comparison to NO, SO2 exhibited significant inhibition on Hg0 removal because of its easy reactivity with active species. The XRD, HRTEM and XPS results indicated the tight contact between Bi5O7I and CeO2, implying that a heterojunction between Bi5O7I and CeO2 was produced. The UV–vis DRS, PL and transient photocurrent test demonstrated that an enhanced activity of 10% CeO2/Bi5O7I for Hg0 removal could be assigned to the broad visible-light-absorption property, much superior separation of photoexcited electron-hole pairs. The scavenging experiments exhibited the superoxide radicals (•O2−) was the major oxidants in the process of Hg0 removal. Moreover, a proposed Z-scheme charge transfer path in CeO2/Bi5O7I nanorod composite was put forward according to the characterization and DFT calculation results.

Effects of Coal-Fired Flue Gas Components on Mercury Removal by the Mechanochemical S-Modified Petroleum Coke.

In this work, the effects of coal-fired flue gas components (O2, CO2, SO2, and NO) on the Hg0 removal by the promising mercury removal adsorbent mechanochemical S-modified petroleum coke were characterized and analyzed in terms of the Hg0 removal efficiency, mercury adsorption capacity, and mercury mass balance. The results show that the mechanochemical S-modified petroleum coke with a theoretical sulfur content of 21% (named TSC-21) is the best candidate for mercury removal based on the Hg0 removal efficiency, Hg0 removal capacity, and difference ratio of Hg0 removal capacity (anti-interference ability) in the basic and full-component simulated flue gas atmosphere (N2 + O2 + CO2, N2 + O2 + CO2 + SO2 + NO). The maximum value (MV) and stable value (SV) of the Hg0 removal efficiency of TSC-21 in the basic simulated flue gas atmosphere are 99.25% (MV) and 91.17% (SV), respectively. O2, CO2, and NO all promote the Hg0 removal by the adsorbent, but they benefit the Hg0 oxidation while inhibiting the Hg0 adsorption. The promoting effect of O2 on the Hg0 removal by TSC-21 is affected by the reaction time, which is especially obvious after 1 min. The presence of SO2 inhibits the oxidation and adsorption of Hg0, which in turn reduces the Hg0 removal performance of the adsorbent. The improving effects on the oxidative escape of Hg0 by CO2 is higher than that by NO and O2. TSC-21 acts more as an oxidant than an adsorbent for Hg0 removal.

Effect mechanism of SO2 on Hg0 adsorption over CuMn2O4 sorbent

SO2 is an important acid flue gas component during solid fuel combustion. The effects of SO2 on the Hg0 removal performance of CuMn2O4 sorbent and its reaction mechanism were investigated by conducting the mercury adsorption experiments and theoretical calculations. The results showed that SO2 concentration coupling with the high temperature was the predominant factor affecting the Hg0 removal performance of CuMn2O4 sorbent. At a relatively high temperature (≥200 °C), the presence of SO2 significantly inhibited Hg0 removal by CuMn2O4 sorbent, and the inhibitory effect was significantly enhanced with the increase of temperature. Hg0 removal efficiency decreased from 88.2 % at 200 ℃ to 17.98 % at 350 °C due to the SO2 sulfation of sorbent surface. Hg0 removal performance of CuMn2O4 sorbent was not sensitive to the variation of SO2 concentration at the low temperature of 150 °C. DFT calculation results showed that SO2 is chemically adsorbed on the sorbent surface, and the adsorption energy of the most stable configuration is −111.78 kJ/mol. The chemisorption of SO2 on the sorbent surface is attributed to the orbital hybridization among Cu, Mn and O atoms. The adsorption energy of Hg0 on the CuMn2O4 surface decreased in the presence of SO2. The transformation pathway of Hg0 in the presence of SO2 includes three steps: Hg0 adsorption, O2 adsorption, and Hg*-to-HgO conversion. The presence of SO2 increased the activation energy barrier of Hg* oxidation into HgO.

Effect of Pyrolysis Temperature on Removal Efficiency and Mechanisms of Hg(II), Cd(II), and Pb (II) by Maize Straw Biochar

Pyrolysis temperature significantly affects the properties of biochar, which in turn can affect the removal of heavy metal ions and the underlying mechanism. In this work, biochars from the pyrolysis of maize straw at 300, 400, and 500 °C (BC300, BC400, and BC500, respectively) and wheat straw at 400 °C (WBC400) were investigated. The influence of production temperature on the adsorption of Hg2+, Cd2+, and Pb2+ by maize straw biochar was investigated by the characterization of the biochars and by adsorption tests. The adsorption capacities of maize and wheat straw biochar were compared in an adsorption experiment. Biochar BC400 showed the best physical and chemical properties and had the largest number of surface functional groups. The pseudo-second-order kinetic model was more suitable for describing the adsorption behavior of metal ions to biochar. The Langmuir model better fit the experimental data. Biochar BC400 had a higher adsorption speed and a stronger adsorption capacity than WBC400. The sorption of Pb2+ and Hg2+ to maize straw biochar followed the mechanisms of surface precipitation of carbonates and phosphates and complexation with oxygenated functional groups and delocalized π electrons. The adsorption mechanism for Cd2+ was similar to those of Hg2+ and Pb2+, but precipitation mainly occurred through the formation of phosphate. In the multi-heavy-metal system, the adsorption of Cd2+ by BC400 was inhibited by Pb2+ and Hg2+. In summary, BC400 biochar was most suitable for the adsorption effect of heavy metals in aqueous solution.

Facile synthesis of ternary AgBr/BiOI/Bi2O2CO3 heterostructures via BiOI self-sacrifice for efficient photocatalytic removal of gaseous mercury

Ternary AgBr/BiOI/Bi2O2CO3 heterojunction materials, which were synthesized by BiOI self-sacrifice and deposition-precipitation method, were explored for photocatalytic removal of Hg0 from simulated flue gas. Numerous analytical techniques were used to characterize the properties of photocatalysts. The AgBr content, photocatalyst dosage, solution temperature, pH value, fluorescent lamp (FSL) irradiation, SO2 and NO were also implemented to evaluate Hg0 removal performance in detail. The results indicated that AgBr-BiOI/Bi2O2CO3 was successfully prepared with the sacrifice of BiOI and AgBr was uniformly loaded onto the surface of BiOI/Bi2O2CO3. The Hg0 removal efficiency by optimum 2 %AgBr-BiOI/Bi2O2CO3 could reach about 97%, which was 1.38, 1.49 and 3.59 times that of pure AgBr, Bi2O2CO3 and BiOI, respectively. FSL irradiation was essential for an efficient mercury removal and the supply of SO2 significantly exerted inhibition of mercury removal activity. According to the density functional theory (DFT) calculations, a double Z-scheme heterojunction was constructed among AgBr, Bi2O2CO3 and BiOI materials, in which the photo-induced electrons in Bi2O2CO3 combined with holes from AgBr and BiOI, tremendously inhibiting the combination of carriers. According to trapping experiments and electron spin (ESR) test, superoxide radical (O2−) and hole (h+) were testified to make major contributions in the process of an efficient Hg0 removal.

The Synthesis of FeCl3-Modified Char from Phoenix Tree Fruit and Its Application for Hg0 Adsorption in Flue Gas

A sample of FeCl3-modified phoenix tree fruit char (MPTFC) was prepared using pyrolysis and a facile chemical immersion method; it was proposed as an effective sorbent for Hg0 adsorption in flue gas. The BET, SEM, FTIR, and XPS methods were adopted for the characterizations of the sorbents, and a series of Hg0 adsorption tests were conducted on a bench-scale Hg0 removal setup in the lab. The morphological analysis of the sorbent indicated that the hollow fiber in phoenix tree fruit (PTF) shifted to organized directional porous tubular columns in phoenix tree fruit char (PTFC) after pyrolysis. The surface area of MPTFC increased slightly in comparison with PTF and PTFC. The MPTFC showed excellent performance for Hg0 adsorption at 200 °C in flue gas ambiance, and the Hg0 removal efficiency approached 95% with 5% (wt.%) FeCl3 modification. The presence of O2 may help to activate the MPTFC for Hg0 adsorption in flue gas, thus greatly promoting Hg0 adsorption capability. NO had a positive effect on Hg0 adsorption, while the presence of SO2 in flue gas restrained Hg0 adsorption by MPTFC. Functional groups, such as C-Cl and Fe-O, were successfully decorated on the surface of PTFC by FeCl3 modification, which contributed greatly to Hg0 adsorption. In addition, C=O, lattice oxygen (Oα), and adsorbed oxygen (Oβ) also contributed to Hg0 adsorption and oxidization.