Removal Of Hg Research Articles

Efficient gaseous mercury removal by nano-amorphous red selenium and recycling design of HgSe nanoparticles

Mercury, is a highly toxic chemical that poses serious hazards to both humans and the environment to be controlled. In this paper, Different Se forms have great varying performance of gaseous mercury(Hg0) removal. Nano-amorphous red selenium(ar-Se) has an excellent adsorption effect on Hg0 successfully synthesized by one step oxidation reduction. The factors to ar-Se such as flue gas components, temperature, gas flow rate, and pH affecting mercury removal effect were investigated. The results showed that the ar-Se achieved high utilization (>74.9 %) and mercury affinity (>97 %) at room temperature. Mercury removal rate was almost unaffected by gas components at room temperature, and it kept a stable mercury adsorption in long-time gaseous mercury recovery experiments, which responded to the high electron activity on its surface. Long-range periodic structures with no regular atomic arrangement decide ar-Se in an active state having high specific surface area, surface activity, good dispersion. The HgSe nanoparticles(NPs) was formed by the adsorption of gaseous mercury onto ar-Se. For further recycling of mercury, a recovery route for HgSe has been proposed and oxygen was found having a strong influence on the production of HgSe.

Elemental mercury removal by copper-containing brominated pyrolytic chars derived from waste printed circuit boards

Waste printed circuit boards (WPCBs) containing brominated flame retardants (BFRs) would result in serious environmental pollution without pertinent treatments. However, bromine-containing materials have been proven highly efficient for elemental mercury removal (Hg0). This work proposes a win–win strategy of a cost-effective Hg0 removal method and a highly efficient utilization of WPCB-derived chars. Diverse copper-containing brominated pyrolytic chars of WPCBs were prepared in a fixed bed reactor at 500–700 °C tailored for Hg0 removal from coal-fired flue gas. The resulting copper-containing pyrolytic chars were proven to have a high Hg0 removal efficiency. Various characterizations and adsorption curves insights into the impacts of copper, sorbent weights, pyrolysis and adsorption temperatures, on Hg0 removal efficiency of WPCB-derived chars. The results indicate that copper in WPCBs enhances the fixation of the bromine elements in pyrolytic chars, resulting in improved Hg0 removal performance. The optimal pyrolysis and adsorption temperatures for pyrolytic chars are 600 °C and 140 °C, respectively. Under optimized conditions, a Hg0 removal efficiency exceeding 90 % is realized after 30 min of adsorption. Notably, the results indicating the Hg0 adsorption capacity of WPCB-derived chars rivals that of commercial activated carbons and significantly surpasses that of biochar. Both adsorption kinetics and characterizations affirm that chemisorption is the predominant adsorption method. The C-Br bond and CuO emerge as crucial active sites facilitating the oxidation of Hg0.

Highly efficient and selective nitrate and Hg(II) removal from wet oxidation flue gas purification wastewater using bifunctional MXene nanofiltration membrane

The wet oxidation process is a promising method for simultaneously removing SO2, NO, and Hg0 from coal-fired flue gas. However, the resource utilization of the resulting wastewater, which is enriched with complex ions such as Hg2+, NH4+, NO3−, and SO42−, remains a significant challenge. To achieve the simultaneous goals of concentrating NH4+/NO3−/SO42− ions, adsorbing and separating Hg2+ ions, and reusing wastewater, a bifunctional MXene composite nanofiltration membrane with large interlayer spacing and excellent electrostatic repulsion was developed. The membrane was prepared by co-depositing MXene nanosheets, carboxylated multi-walled carbon nanotubes (MWCNTs), and sodium dodecyl sulfate (SDS) onto an NF-90 membrane. The resulting MXene-MWCNTs-SDS (MMS-COOH) composite membrane demonstrated exceptional salt rejection of 84.4 % for NO3−, 89.0 % for NH4+, 99.8 % for SO42−, and 99.7 % for Hg2+. After 30 cycles, the membrane structure remained stable, maintaining good reusability, with NH4+ and SO42− rejection still reaching 90.0 %. Moreover, the maximum adsorption capacity for Hg2+ was 2869.6 mg g−1, while the capacities for Cr6+ and Pb2+ were 577.6 and 316.8 mg g−1, respectively. The MMS-COOH composite membrane introduces an innovative method for the benign treatment of wet oxidation flue gas purification wastewater and facilitates the recovery of (NH4)2SO4 and NH4NO3 as fertilizers, holding a promising application prospect.

ZIF-7-NH2 functionalized collagen fibers for effective and selective mercury ion capture

Adsorptive removal of mercury ion from wastewater has become a hot topic due to the toxicity and persistence; acquiring adsorbent materials with high-capacity, rapid-kinetic, super-selective while low-cost features are highly demanded. Herein, based on the full functionality of collagen fiber (CF) from the leather waste, we proposed an innovative synthetic approach through exploiting amino-functionalized ZIF-7 (ZIF-7-NH2) as functional groups to facilely in-situ incorporate with CF, affording low-cost but effective adsorbent materials of CF/ZIF-7-NH2 composite maximizing both functions of CF and ZIF-7-NH2 in the Hg(II) capture. Remarkably, it exhibits an ultra-high capacity as high as 909.09 mg g-1, fast kinetics that could remove 99.01 % of 200 mg·L-1 within 20 min, and significant selectivity of SHg/M (KdHg/KdM) as large as 522–1017 over Mg2+, K+, Ca2+, Cd2+, and Mn2+. We understand such an impressive adsorption is contributed by the synergistic action between functional groups including on the CF and ZIF-7-NH2. This study offers an effective method for removing heavy metal ions, achieving efficient removal of Hg(II) ions for pollution control, and promoting the reuse of waste CF to reduce waste accumulation in various aspects.

Global Distribution of Mercury in Foliage Predicted by Machine Learning.

Foliar assimilation of elemental mercury (Hg0) from the atmosphere plays a critical role in the global Hg biogeochemical cycle, leading to atmospheric Hg removal and soil Hg insertion. Recent studies have estimated global foliar Hg assimilation; however, large uncertainties remained due to coarse accounting of observed foliar Hg concentrations, posing a substantial challenge in constraining the global Hg budget. Here, we integrated a comprehensive observation database of foliar Hg concentrations and machine learning algorithms to predict the first spatial distribution of foliar Hg concentrations on a global scale, contributing to the first estimate of global Hg pools in foliage. The global average of foliar Hg concentrations was estimated to be 24.0 ng g-1 (7.5-56.5 ng g-1), and the global total in foliar Hg pools reached 4561.3 Mg (1455.2-9062.8 Mg). The spatial distribution showed the hotspots in tropical regions, including the Amazon, Central Africa, and Southeast Asia. A range of 2268.5-2727.0 Mg yr-1 was estimated for annual foliar Hg assimilation accounting for the perennial continuous assimilation by evergreen vegetation foliage. The first spatial maps of foliar Hg concentrations and Hg pools may aid in understanding the global biogeochemical cycling of Hg, especially in the context of climate change and global vegetation greening.

Analysis of mercury removal and sulfur resistance of CrOx-MnOx-SnOx-TiO2 catalysts

To investigate the ability of CrOx-MnOx-SnOx-TiO2 composite catalysts to adsorb and remove substances, particularly in the presence or absence of SO2, Sn was included in CrMnTi catalysts throughout the production procedure. The incorporation of Sn was found to boost the specific surface area, optimize the pore structure, and augment the number of active sites, as determined using characterization methods such as XRD, XPS, and BET. When Sn metal oxides were included in MnTi catalysts individually, the resulting MnSnTi catalysts showed a limited capacity to remove Hg0. However, adding Sn metal oxides allowed for widening the temperature range in which the catalysts found successful application. This will increase the range of application temperature and is of very successful importance for large-scale commercial applications. They demonstrate that, by incorporating chromium metal oxides, the oxygen Oβ reactivity within the MnSnTi catalyst increases, resulting in a greatly improved capacity for Hg0 removal and its resistance to sulfur. This study details the combined effect of Cr, Mn, and Sn ternary composite oxides on sulfur resistance and mercury removal. The result shows that Sn promotes the strengthening of both the physical properties of the catalyst and the adsorption of mercury while also assisting in the dispersion of the catalyst. Cr enhances the ability of the catalyst to transfer electrons while in oxidation and, at the same time, favours the remaining high valence of Mn. Mn supports the catalyst for oxidizing mercury by changing its multivalent state. The CrMnSnTi catalysts have exceptional efficacy in removing mercury and possess excellent resistance to sulfur, making them an ideal catalytic option for industrial demercury removal. The catalysts exhibited excellent efficacy in removing mercury and showed strong sulfur resistance.

Cysteamine-Anchored MOF through Post-Synthetic Modification Strategy for the Effective Removal of Mercury from Water.

The introduction of cysteamine functionality, referred to as Q-ZIF-67-SH, was successfully achieved through postsynthetic modification while maintaining the structural and thermal stability of the quasi metal-organic framework Q-ZIF-67. By subjecting ZIF-67 to controlled partial deligandation at 310 °C under an air atmosphere, a substantial number of unsaturated cobalt sites were generated within the quasi ZIF-67 (Q-ZIF-67) structure. These unsaturated cobalt sites facilitated effective coordination with cysteamine, resulting in the development of the thiol-functionalized framework Q-ZIF-67-SH. The potential of these metal-organic frameworks (MOFs) for the adsorptive removal of hazardous Hg(II) was investigated. Various factors, such as the type of sorbent, pH, adsorbent dosage, initial concentration of Hg(II), and presence of coexisting ions, were thoroughly examined and comprehensively explained. Thiol-anchored MOF significantly enhanced the efficiency of Hg(II) removal, achieving an impressive removal rate of up to 99.2%. Furthermore, it demonstrated a maximum adsorption capacity of 994 mg g-1 and a distribution coefficient of 2.5 × 106 mL g-1. A good correspondence with pseudo-second-order kinetics and the Langmuir model was observed through the fitting of adsorption kinetics and the isotherm model. The thermodynamic data strongly indicate that the adsorptive removal of Hg(II) is characterized by endothermicity and spontaneity. This signifies that the process is energetically favorable and has potential for efficient Hg(II) removal. Therefore, the Q-ZIF-67-SH sorbent emerges as a promising and advantageous option for the removal of Hg(II) from water.

A novel mercapto-functionalized bimetallic Zn/Ni-MOF adsorbents for efficient removal of Hg(II) in wastewater

Heavy metals, especially mercury ions, pose extreme hazards to human health and environmental sustainability. Receiving significant interest lately, metal-organic frameworks with mercapto-functionalization (SH-MOFs) have shown impressive efficacy in effectively eliminating highly hazardous Hg(II) from wastewater. In this investigation, a novel mercapto-functionalized Zn/Ni bimetallic MOF (ZNM-2) was synthesized utilizing a simple solvothermal technique employing zinc and nickel as metal sources and 2-mercaptobenzimidazole (MBI) as the organic ligand. The Hg(II) adsorption capacity by ZNM-2 reached 744.4 mg/g, surpassing that of a single-nickel MOF (NM) 328.8 mg/g. More impressively, ZNM-2 successfully eliminated 99.99 % of Hg(II) from actual water samples, achieving a concentration level for Hg(II) that is lower than the threshold of 1.0 μg/L specified in the GB 5749–2022 drinking water standard. When the pH of Hg(II) solution ranged from 2.0 to 6.0, it exhibited exceptional adsorption capacity and sustained high removal efficiency throughout four consecutive regeneration cycles. The adsorption mechanisms observed in this study were found to conformity with the Langmuir model and PSO kinetic model, suggesting that the predominant mode of Hg(II) adsorption is through a chemisorption process occurring at a monolayer level. The superior Hg(II) removal rate of ZNM-2 can be attributed to the predominant coordination of Hg(II) to the thiol (-SH) groups, as revealed by a combination of FT-IR, XPS analysis, and DFT calculations. Therefore, ZNM-2 is an efficacious Hg(II) absorbent that provides a novel approach to alleviate mercury contamination in wastewater.

MXene/polyaniline/sodium alginate composite gel: Adsorption and regeneration studies and application in Cu(II) and Hg(II) removal

The imperative to efficiently remove heavy metals from water has heightened the demand for adsorbents capable of co-adsorbing heavy metals and offering robust reusability. A novel composite adsorbent (PANI@SA-SNM) was synthesized with amine/sulfur-modified MXene, in-situ polymerized polyaniline (PANI) and sodium alginate (SA). Cu(II) and Hg(II) were used as model pollutants to test the adsorption capacity and stability of the adsorbent. Results showed that this adsorbent illustrated remarkable stability and adaptability across a pH range of 3 to 7 due to the proton transfer effect in PANI. The pseudo-second-order kinetic and Langmuir model were suitable for describing the physical and chemical adsorption process of Cu(II) and Hg(II). Thermodynamic analysis confirmed the adsorption process to be spontaneous and endothermic. The maximum adsorption capacity calculated by the Langmuir model was 255.81 mg g−1 for Cu(II) and 352.76 mg g−1 for Hg(II) (C0 = 50 ∼ 1000 mg L−1, pH = 4, Dos = 0.02 g/50 mL and T = 303.15 K), outperforming most of the reported adsorbents. In the study of binary systems, we found that the adsorbent exhibited effective co-adsorption capacity, and the differential competitive relationship between two ions was regulated by complex factors. Detailed characterizations revealed the adsorption mechanism, which involved physical adsorption, electrostatic attraction, ion exchange, complexation, and redox reaction. Moreover, the adsorbent maintained high desorption and adsorption efficiency for both ions over eight cycles thanks to strong protonation, Ca2+’s chelation and PANI’s reversibility. This research not only provides a new method for improving gel reusability, but also offers insights for ions co-adsorption study.

Response surface methodology approach for optimization of biosorption process for removal of Hg(II) ions by immobilized Algal biomass Coelastrella sp.

Response surface methodology approach for optimization of biosorption process for removal of Hg(II) ions by immobilized Algal biomass Coelastrella sp.

Bottom-up synthesis of a sulfhydryl-modified heteroporous covalent organic framework for ultrafast removal of trace Hg(Ⅱ) from water

The development of functionalized covalent organic frameworks (COFs) is crucial in expanding their potential for removing toxic heavy metals from drinking water. Here, a new sulfhydryl-modified heteroporous COF (COFDBD-BTA) was prepared using a “bottom-up” approach in which a direct amine-aldehyde dehydration condensation between 2,5-diamino-1,4-benzenedithiol dihydrochloride (DBD) and [1,1′-biphenyl]-3,3′,5,5′-tetracarbaldehyde (BTA) was occurred. The COFDBD-BTA featured a hexagonal kagome (kgm) structure and a sheet-like morphology. Notably, COFDBD-BTA contained densely S atoms that provided high-density Hg(II) adsorption sites for efficient and selective trace Hg(II) removal. COFDBD-BTA exhibited excellent performance in rapidly removing trace Hg(II) from 30 μg L−1 to 0.71 μg L−1 within 10 s, below the World Health Organization's allowable limit of 1 μg L−1. Additionally, COFDBD-BTA exhibited a high Hg (Ⅱ) removal level from water, achieving adsorption capacity of 687.38 mg g−1. Furthermore, the adsorbent exhibited a wide range of applicability for low concentration (6–500 μg L−1) Hg (Ⅱ), a simple and feasible regeneration method, and strong Hg(II) removal ability in real tap water systems. The excellent adsorption efficiency, outstanding recyclability, and one-step room temperature synthesis make S-rich COFDBD-BTA a promising candidate for eliminating Hg (Ⅱ) from drinking water.

Enhanced Hg(II) removal using thiourea-functionalized graphene oxide: Lab to pilot scale evaluation

Here, a thiourea-formaldehyde functionalized graphene oxide (G3DTF) is shown to effectively remove mercury (Hg) from various water sources, including ultrapure, bottled, and seawater. Over 99 % of the Hg in each water source is removed with only 10 mg/L of G3DTF resulting in a residual Hg concentration < 1 μg L−1. This concentration falls within the permissible limits established by the European drinking water guidelines. Notably, the presence of chlorocomplexes in seawater does not reduce the sorption efficiency of G3DTF. The sorption process across all water matrices can be accurately described by pseudo-second-order kinetics, with an R2 > 0.99 suggesting chemical interactions between Hg ions and G3DTF functional groups. The equilibrium isotherms demonstrate a remarkably high maximum adsorption capacity (qm) of 1039 mg g−1, exceeding the values reported in literature for the sorption of Hg on carbon-based materials. Remarkably, G3DTF retains its performance in the presence of other metal ions such as Cu, Cd, and Pb. Incorporating G3DTF into commercially activated carbon (AC) at a concentration as low as 2 wt % significantly enhances the efficiency of Hg(II) removal in fixed bed adsorption. The breakthrough curve exhibits enhanced absorption, attaining a 99.7 % removal of Hg(II) within a span of 2 h, surpassing the efficiency of AC. This relevant result represents a substantial advancement towards the adoption of graphene-based nanocomposites as effective commercial remediation materials.

Review on Mercury Control during Co-Firing Coal and Biomass under O2/CO2 Atmosphere

Combining biomass co-firing with oxy-fuel combustion is a promising Bioenergy with Carbon Capture and Storage (BECCS) technology. It has the potential to achieve a large-scale reduction in carbon emissions from traditional power plants, making it a powerful tool for addressing global climate change. However, mercury in the fuel can be released into the flue gas during combustion, posing a significant threat to the environment and human health. More importantly, mercury can also cause the fracture of metal equipment via amalgamation, which is a major risk for the system. Therefore, compared to conventional coal-fired power plants, the requirements for the mercury concentration in BECCS systems are much stricter. This article reviews the latest progress in mercury control under oxy-fuel biomass co-firing conditions, clarifies the impact of biomass co-firing on mercury species transformation, reveals the influence mechanisms of various flue gas components on elemental mercury oxidation under oxy-fuel combustion conditions, evaluates the advantages and disadvantages of various mercury removal methods, and finally provides an outlook for mercury control in BECCS systems. Research shows that after biomass co-firing, the concentrations of chlorine and alkali metals in the flue gas increase, which is beneficial for homogeneous and heterogeneous mercury oxidation. The changes in the particulate matter content could affect the transformation of gaseous mercury to particulate mercury. The high concentrations of CO2 and H2O in oxy-fuel flue gas inhibit mercury oxidation, while the effects of NOx and SO2 are dual-sided. Higher concentrations of fly ash in oxy-fuel flue gas are conducive to the removal of Hg0. Additionally, under oxy-fuel conditions, CO2 and metal ions such as Fe2+ can inhibit the re-emission of mercury in WFGD systems. The development of efficient adsorbents and catalysts is the key to achieving deep mercury removal. Fully utilizing the advantages of chlorine, alkali metals, and CO2 in oxy-fuel biomass co-firing flue gas will be the future focus of deep mercury removal from BECCS systems.

ZIF-67 loaded thio-groups modified chitosan hydrogel for high efficient Hg(II) removal from water

In the past few years, there has been an increasing worry about the pollution of water caused by the presence of heavy metals. To address this environmental issue, a highly effective adsorbent called ZIF-67/CS-SH was developed. This adsorbent was prepared by grafting thioglycolic acid and loading a metal-organic framework called ZIF-67 onto chitosan, to remove Hg(II) from water. Confirmation of the ZIF-67/CS-SH was achieved by employing a range of techniques including FTIR, XRD, TGA, SEM, EDS, BET, and XPS. Due to the presence of abundant active sites (-SH, O/N-containing functional groups) and ZIF-67, ZIF-67/CS-SH exhibited a high adsorption capacity (949 mg/g at 298 K) and rapid adsorption kinetics (20 min for 91 % removal). The optimal pH for the adsorption process was found to be 5. The adsorption process followed a pseudo-second-order kinetics and Langmuir isotherm, with chemisorption being the main adsorption mechanism. The adsorption process was determined to be spontaneous and endothermic. Additionally, ZIF-67/CS-SH demonstrated selective adsorption in the presence of other metal cations at concentrations of 100 mg/L. Furthermore, ZIF-67/CS-SH exhibited excellent regenerative properties, with only a 10 % decrease in adsorption capacity after ten cycles. The key adsorption sites were identified as the –SH groups, O/N-containing functional groups, and ZIF-67 in ZIF-67/CS-SH through FTIR, EDS, and XPS analyses. Considering its outstanding performance in removing Hg(II), ZIF-67/CS-SH shows promise for application in industrial wastewater treatment.

Investigation of elemental mercury removal performance and mechanism of rice straw biochars from a fluidized bed pyrolysis system impregnated by NH4Br

To remove Hg0 from flue gas efficiently and economically, the rice straw biochars prepared in a fluidized bed pyrolysis system and then modified with NH4Br are employed as the sorbents. The mercury adsorption capacity of Br-modified biochar (1786.85 μg/g) is superior to that of activated carbon (207 μg/g), which indicates Br-modified rice straw biochar sorbent displays higher Hg0 adsorption efficiency and can replace high-cost activated carbon. The sorbents are characterized by Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of pyrolysis temperature, pyrolysis atmosphere, reaction temperature, the components of flue gas (O2, NO and SO2) on mercury removal efficiency, kinetics, thermodynamics and mercury removal mechanism are investigated. The results indicate elevating pyrolysis temperature and oxygen content significantly enhance the Hg0 removal efficiency. The Hg0 adsorption process is better fitted by pseudo-second-order kinetic model and proves a spontaneous endothermic process. The presence of O2 and NO in flue gas enhances Hg0 adsorption, while the presence of SO2 restrains it. After Hg0 adsorption, the peak area ratio of C=O (288.5 eV) and C-Br (69.1 eV) by Br-modified rice straw biochars produced under 8 %O2 and 500 °C atmosphere decreases from 17.03 % and 70.14 % to 6.55 % and 50.50 %, respectively, while that of Br− (68.1 eV) increases from 29.86 % to 48.50 %, indicating the surface O* and Br* species are responsible for Hg0 removal, and the products are mainly HgO and HgBr2. This work provides a kind of cost-effective Hg0 removal sorbent and explores the mechanism of Hg0 removal by Br-modified biochars.

Microcosmic insights into Hg0-SO2 interaction on CuFe2O4 catalyst

CuFe2O4 is considered as a very promising kind of catalysts for Hg0 oxidation in the industrial flue gas. The flue gas produced by solid-fuel combustion usually contains acid gas component SO2, which can exhibit the versatile effects on Hg0 oxidation. However, the effects of SO2 on Hg0 oxidation catalyzed by CuFe2O4 catalyst and its reaction mechanism remain elusive. Herein, the reaction mechanism governing the effects of SO2 on Hg0 oxidation was investigated via the Hg0 oxidation experiments and density functional theory (DFT) calculations. The experimental results show that the temperature change and SO2 presence can affect the Hg0 removal efficiency of CuFe2O4 catalyst. SO2 has a certain degree of inhibition effect on the Hg0 oxidation of CuFe2O4 catalyst. The inhibition effect of SO2 is relatively weak in the low temperature range of 50–150 °C, which is closely associated with the competitive adsorption between SO2 and Hg0. SO2 exhibits a relatively strong inhibition effect on Hg0 oxidation in the high temperature range of 200–350 °C, which is related to the high-temperature sulfation of CuFe2O4 catalyst surface. Mercury species on the CuFe2O4 catalyst surface mainly exists in the forms of HgSO4 and HgO in the presence of SO2. The DFT-calculation results indicate that the conversion process of SO2 to SO3 includes two steps: SO2 adsorption and SO2 oxidation. The activation energy barrier of SO2 oxidation reaction is 216.42 kJ/mol. The oxidation of Hg0 on the surface of CuFe2O4 catalyst includes four steps: Hg0 adsorption, Hg* oxidation into HgO*, HgO*-to-HgSO4* conversion and HgSO4 desorption. HgSO4 is formed by the bimolecular reaction of HgO* and SO3* on CuFe2O4 catalyst. Hg* oxidation into HgO* is found to be the rate-determining step of HgSO4 formation.

Tuning the coordination environment of sulfur on carbon surface via doping with iron for high-capacity gaseous elemental mercury capture

Enhancement of the formation of unsaturated short-chain sulfur represents the key point in enhancing the gaseous elemental mercury (Hg0) capture by sulfur-based sorbents, and yet the sulfur often agglomerates into long-chain species. Herein, by doping with iron cation as the regulator of the coordination environment of sulfur, the long-chain sulfur was successfully converted into short-chain sulfur on carbon. The iron-sulfur loaded carbon shows a high Hg0 adsorption capacity of 72.8 mg·g−1 (80 % breakthrough) and a low cost of $42.09/kg Hg, which are superior to various sulfur modified carbons and metal sulfides. The iron can not only immobilize more amount of sulfur on carbon surface, but also break the S-S bonds. The double interaction of iron and carbon with sulfur facilitates the formation of short-chain sulfur species for Hg0 adsorption. Density functional calculations suggest that S, Fe and C sites on surface are active centers for Hg adsorption. The Hg can tri-coordinate with S, Fe and C sites, which gives a high adsorption energy of − 219.3 kJ‧mol−1, confirming the strong reaction. This work provides a new in insights into the regulation of the coordination environment of sulfur, which allows the designing of high-capacity and low-cost sorbents for gaseous Hg0 removal.

Lithium manganite anchored on mesoporous ceria photocatalyst for removal of Hg(II) ions from aqueous solution under visible illumination

The development of effective photocatalysts is critical for the photo/redox reaction of noxious Hg(II) ions and Hgo in environmental engineering and purification. In this contribution, Li2MnO3 nanoparticles (NPs) were anchored mesoporous CeO2 networks to design photocatalysts with high harvest of visible light, and the obtained Li2MnO3/CeO2 nanocomposites were utilized for photoreduction of Hg(II) ions under visible illumination. The TEM and XRD results showed the formation of Li2MnO3 and CeO2 with the monoclinic and cubic fluorite structures, and the particle size is about 10–20 nm. The enhancement of light absorption of Li2MnO3/CeO2 nanocomposites could create considerable photoinduced carriers during the photocatalytic reactions. The incorporation of Li2MnO3 and CeO2 NPs demonstrated outstanding photocatalytic performance compared with pristine CeO2 NPs, and the optimum 9%Li2MnO3/CeO2 nanocomposite achieved 98 % of the reduction Hg(II) ability within 60 min. The rate constant for 9 % Li2MnO3/CeO2 photocatalyst is ∼ 6.47 and 3.85 times greater than Li2MnO3 and CeO2 NPs. The superior photocatalytic performance of Li2MnO3/CeO2 nanocomposites was ascribed to the efficient separation of photocarriers due to the formation of S-scheme heterojunction, the large surface area, and mesoporous structures. The obtained Li2MnO3/CeO2 nanocomposite was highly stable and efficient for the Hg(II) photoreduction runs up to five successive experiments under similar conditions. Moreover, the possible mechanism over heterojunctions Li2MnO3/CeO2 nanocomposites toward the reduction of Hg(II) ions is examined as well. The formation of S-scheme heterojunction photocatalyst provides better photocatalytic applications in terms of air purification, hydrogen production, and water treatment.

Efficient remediation of mercury-contaminated groundwater using MoS2 nanosheets in an in situ reactive zone

Mercury contamination in groundwater is a serious global environmental issue that poses threats to human and environmental health. While MoS2 nanosheets have been proven promising in removing Hg from groundwater, an effective tool for in situ groundwater remediation is still needed. In this study, we investigated the transport and retention behavior of MoS2 nanosheets in sand column, and employed the formed MoS2in situ reactive zone (IRZ) for the remediation of Hg-contaminated groundwater. Breakthrough test revealed that high flow velocity and MoS2 initial concentration promoted the transport of MoS2 in sand column, while the addition of Ca ions increased the retention of MoS2. In Hg removal experiments, the groundwater flow velocity did not influence the Hg removal capacity due to the fast reaction rate between MoS2 and Hg. With an optimized MoS2 loading, MoS2IRZ effectively reduced the Hg effluent concentration down to <1 μg/L without apparent Hg remobilization. Additionally, flake-like MoS2 employed in this study showed much better Hg removal performance than flower-like and bulk MoS2, as well as other reported materials, with the Hg removal capacity a few to tens of times higher than those materials. These results suggest that MoS2 nanosheets have the potential to be an efficient IRZ reactive material for in situ remediation of Hg in contaminated groundwater.

In situ self-activation strategy for the synthesis of double-layered S/Cl co-doped sorbents for elemental mercury removal from oxy-fuel combustion flue gas

Mercury capture from oxy-fuel combustion flue gas remains an enormous challenge for carbon capture and storage because of the lack of cost-effective, sulfur-resistant and water-resistant sorbent. In this work, double-layered S/Cl co-doped sorbents (CDSs) were synthesized through an in situ self-activation method i.e. co-pyrolysis of waste tire and PVC plastic, which were adopted for elemental mercury (Hg0) immobilization from oxy-fuel combustion flue gas. A synergistic effect between waste tire and PVC plastic was observed during co-pyrolysis. For this reason, chlorine was successfully doped into the CDSs in the form of covalent chlorine and ionic chlorine. The CDSs showed high Hg0 removal efficiency (>80 %) over a wide temperature range (20–140 °C) and excellent sulfur and water resistance. Both the initial Hg0 adsorption rate and adsorption capacity of CDSs were far higher compared with raw tire char. The Hg0 removal mechanisms were further proposed, where Hg0 preferentially reacted with covalent chlorine instead of active sulfur species. Density functional theory calculations revealed that the Hg0 adsorption over CDSs was chemisorption with an adsorption energy of −249.85 kJ/mol. The synergistic effect between sulfur and chlorine was beneficial for the formation of HgCl2 whereas it had negligible effect on the formation of HgCl.