Hg Adsorption Capacity Research Articles

Ultrafine Au nanoparticles confined in three-dimensional mesopores of MCM-48 for efficient and regenerable Hg0 removal sorbent in H2S and H2O containing natural gas

The H2O and H2S in natural gas are frequently deemed to have inhibitory influences on Hg0 removal performance of most noble metal based Hg0 absorbents, it is extremely significant to develop an efficient and regenerable Hg0 removal absorbent with excellent H2S and H2O tolerance. In the work, the Au/MCM-48 absorbent was controllable synthesized using a facile yet robust method for Hg0 removal in H2S and H2O containing natural gas. The ultrafine Au nanoparticles with a diameter of 1.4 nm were embedded and uniformly dispersed in the three-dimensional channels of MCM-48. The absorbent of 1 wt% Au achieved a complete Hg0 capture performance at 60,000 h−1 and 30 °C by forming Au-Hg amalgam, and its Hg0 adsorption capacity achieved to 7.23 mg∙g−1 at 5% breakthrough. The spent sample could be easily regenerated by thermal treatment without distinct degradation over 5 cycles. The introduction of H2S and H2O in gas flow had an inappreciable impact on Hg0 removal performance over the Au/MCM-48 absorbent. The excellent Hg0 adsorption efficiency, outstanding capture capacity and good regeneration performance of the absorbent due to the nano-confinement of MCM-48 channels, which prevents Au nanoparticles from growing and agglomerating. Excellent H2O tolerance is attributed to the good hydrophobicity of MCM-48 modified by trimethylchlorosilane, and the high H2S tolerance is due to the fact that the Au nanoparticles lack reactivity toward H2S. This work provides a promising method for the preparation of effective and regenerable absorbents for demercuration in H2S and H2O containing natural gas.

Highly dispersed transition metal oxide-supported activated carbon prepared by plasma for removal of elemental mercury

Recently, transition metal oxide-supported activated carbon (MOx/AC) has been extensively investigated for Hg0 removal, due to its high Hg0 adsorption capacity and reproducibility. Non-thermal plasma (NTP) was applied for the preparation of transition metal oxide-supported AC in this work. The obtained adsorbents were investigated for the removal of Hg0. The adsorbents were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), temperature-programmed reduction of H2 (H2-TPR), and so on. The results indicated that the plasma treatment process instead of heat treatment could effectively promote the dispersion of active site and catalytic oxidation property of adsorbent. Consequently, the CeO2/AC-P and Co3O4/AC-P adsorbents prepared by plasma treatment exhibited higher Hg0 removal efficiency than the CeO2/AC and Co3O4/AC adsorbents prepared by conventional heat treatment. The Hg0 removal efficiency of the adsorbent could be recovered by the temperature-programmed desorption (TPD) process at a relatively mild regeneration temperature, while retaining high stability even at higher temperatures. The present work showed that plasma treatment could serve as an efficient method of preparing catalyst.

Mechanistic investigation of elemental mercury adsorption over silver-modified vanadium silicate: A DFT study

Ag-modified vanadium silicate (EVS-Ag) has been regarded as a superior sorbent for elemental mercury (Hg0) capture from coal-fired flue gas. However, the atomic-level reaction mechanism which determines Hg0 adsorption capacity of EVS-Ag sorbent remains elusive. Reaction mechanism and active sites of Hg0 adsorption over EVS-Ag sorbent were studied using density functional theory (DFT) calculations systematically. DFT calculation results indicate that silver exchange shows little effects on the geometric structure of EVS-10 sorbent. Hg0 adsorption on EVS-10 and EVS-Ag surfaces is controlled by the physisorption and chemisorption mechanisms, respectively. Ag2 cluster is determined to be the most active site of Hg0 adsorption over Ag-modified EVS sorbent. The adsorption energy of Hg0 on Ag2 cluster is −51.93 kJ/mol. The orbital hybridization and electron sharing between Ag and Hg atoms are responsible for the strong interaction between EVS-Ag surface and Hg0. HgO prefers to adsorb on Ag2 cluster of EVS-Ag sorbent, and yields an energy release of 306.21 kJ/mol. HgO desorption from EVS-Ag sorbent surface needs a higher external energy, and occurs at the relatively higher temperatures. O2 molecule promotes Hg0 adsorption over EVS-Ag sorbent. HgO species can be easily formed during Hg0 adsorption over EVS-Ag sorbent in the presence of O2.

High-efficiency removal of low-concentration Hg(II) from aqueous solution by bentonite nanocomposite: Batch and fixed-bed column adsorption study

ABSTRACT A nanocomposite based on bentonite was synthesized. Its adsorption properties for Hg(II) were evaluated by batch and fixed-bed column adsorption experiments. The results showed that the nanocomposite was an efficient adsorbent for the treatment of wastewater containing low-concentration Hg(II). It removed more than 92% of Hg(II) from aqueous solution with a pH ranged from 4.00 to 12.00. Its adsorption capacity for Hg(II) increased linearly with the increase of mercury concentration. The nanocomposite had excellent reusability. HCl solution can be used to elute Hg(II) ions loaded. The developed Bohart–Adams model can be used for the design of adsorption column.

Synthesis and Application of Recyclable Core-Shell Structure Microspheres Mcts-G-At in Detection of Hg(Ⅱ) in Aquatic Products

The MCTS-g-AT was developed as a novel magnetic adsorbent with core-shell structure. Its unique synthesis route endows MCTS-g-AT with green, convenient, economical and safe characteristics, and also good selective adsorption of Hg(Ⅱ). The material was characterized using an appropriate set of spectroscopic and analytical techniques (SEM, EDS, XRD, VSM, FTIR and TGA). Its adsorption kinetics fits the pseudo-secondary model well and adsorption isotherm fits the Langmuir equation well, suggesting the main adsorption mechanism of chemisorption with monolayer adsorption. The results of the thermodynamic parameters indicate that the adsorption process is spontaneous and endothermic. Column adsorption experiments showed that the maximum adsorption capacity of Hg(II) was 207.6 mg/g (298 K). Moreover, the Hg(II) adsorbed on composite microspheres was completely eluted by 3 mol/L HNO 3 or 4 mol/L HCl. Furthermore, MCTS-g-AT adsorption column combined with spectrophotometer can achieve more accurate detection of Hg(II) in aquatic products.

Detection of Hg(II) in adsorption experiment by a lateral flow biosensor based on streptavidin-biotinylated DNA probes modified gold nanoparticles and smartphone reader

The increased occurrence of Mercury (Hg II) contaminant has caused environmental and health concerns worldwide. Removal of Hg(II) from water is of significant interest, in particular if these can be coupled in a manner of detection. Here, a novel activated carbon (AC) adsorbent and a fast detection device to form a closed-cycle strategy was developed. The synthesis of conjugates of streptavidin-biotinylated DNA probes modified gold nanoparticle was used with lateral flow biosensors for Hg(II) detection. A quantification was completed via a self-developed smartphone app and its limit of detection was 2.53 nM. Moreover, AC was activated with a new activating agent of diammonium hydrogen phosphate. The adsorbent was characterized and determined to have an amorphous microporous structure with a high surface area (1076.5 m2 g−1) and demonstrated excellent removal efficiency (99.99%) and adsorption capacity (∼100 mg g−1) for Hg(II). The kinetics of the pseudo-second-order model and the mechanisms of electrostatic adsorption, ion exchange, and complex reactions are provided. The proposed closed-cycle strategy can be useful for early, fast, and mobile detection of Hg (II) pollution, followed by its effective removal during water treatment.

Green Graphene-Chitosan Sorbent Materials for Mercury Water Remediation.

The development of new graphene-based nanocomposites able to provide synergistic effects for the adsorption of toxic heavy metals in realistic conditions (environment) is of higher demand for future applications. This work explores the preparation of a green nanocomposite based on the self-assembly of graphene oxide (GO) with chitosan (CH) for the remediation of Hg(II) in different water matrices, including ultrapure and natural waters (tap water, river water, and seawater). Starting at a concentration of 50 μg L–1, the results showed that GO–CH nanocomposite has an excellent adsorption capacity of Hg (II) using very small doses (10 mg L–1) in ultrapure water with a removal percentage (% R) of 97 % R after only two hours of contact time. In the case of tap water, the % R was 81.4% after four hours of contact time. In the case of river and seawater, the GO–CH nanocomposite showed a limited performance due the high complexity of the water matrices, leading to a residual removal of Hg(II). The obtained removal of Hg(II) at equilibrium in river and seawater for GO–CH was 13% R and 7% R, respectively. Our studies conducted with different mimicked sea waters revealed that the removal of mercury is not affected by the presence of NO3– and Na+ (>90% R of Hg(II)); however, in the presence of Cl–, the mercury removal was virtually nonexistent (1% R of Hg(II)), most likely because of the formation of very stable chloro-complexes of Hg(II) with less affinity towards GO–CH.

Development of mercaptosuccinic anchored MOF through one-step preparation to enhance adsorption capacity and selectivity for Hg(II) and Pb(II)

A novel Zr-MOF adsorbent was synthesized by one-step method and was used to selectively adsorb Hg(II) and Pb(II) from wastewater. The adsorbent can reduce the concentration of mercury and lead to less than the national standard (Hg is 50 μg/L and Pb is 1 mg/L). The entire adsorption process conforms to the pseudo second-order kinetic and Hill isotherm models. At pH 4, the adsorbent removed more than 90% of mercury (to 22 μg/L) and lead (to 0.732 mg/L) in 10 min and 960 min, and the maximum adsorption capacity was 1080 mg/g and 510 mg/g, respectively. In addition, the practical application in wastewater proved that the adsorbent can selectively adsorb Hg(II) and Pb(II) from the mixed ion solution and it still meets national standards for wastewater discharge. The research of repeated experiments proves that the adsorbent can be used repeatedly. The adsorption mechanism was clarified by FTIR, XPS spectroscopy before and after adsorption, and density functional theory (DFT) calculation. In summary, the adsorbent is stable in aqueous solution and has great potential for the efficient removal of trace heavy metal ions (mercury and lead) in future treatment of wastewater.

Zinc concentrate internal circulation technology for elemental mercury recovery from zinc smelting flue gas

As most of the purposed synthesized mercury sorbents are expensive and insufficient for capturing mercury from the flue gas with ultrahigh concentration of Hg0 and SO2 in smelting processes, the application of sorbent injection for mercury removal in zinc smelting was extremely restricted. In this work, Zinc concentrate (ZC) ore, one of the raw materials for smelting, was developed to capture gaseous Hg0 from zinc smelting flue gas. The average Hg0 adsorption capacity of ZC was greater than 2 mg·g−1, even better than some synthetic binary sulfide sorbents. Meanwhile, ZC presented a good resistance to H2O and SO2 at 60–100 °C. Higher ratio of Cu element in ZC ores can result in better Hg0 adsorption performance due to the increase of active site Sn2− derived from the oxidation of S2− by Cu2+. After capture Hg0, spent ZC can be reused as raw material for zinc production, eliminating the generation of waste sorbent. This technology can as a co-benefit of condensation device to deeply purify mercury pollutants, and the excessive gaseous Hg0 will be removed from the system by condensing into liquid mercury. Moreover, such ZC cycles offers a specific strategy for gaseous Hg0 recovery in other nonferrous smelting industries.

Electrodeposition of layered double hydroxide intercalated with 2,3-dimercaptopropane sulfonate on carbon cloth and application for effective uptake of heavy metals

In this work, Cu Cr-layered double hydroxide nanosheet intercalated with 2,3-dimercaptopropane sulfonate (DMPS-LDH) has been synthesized on a carbon cloth via a simple two-electrode electrodeposition method. The DMPS-LDH coated on the carbon cloth was used for the effective uptake of heavy metal ions and exhibits superior selectivity as well as a good adsorption capacity for Hg(II) ions in the presence of interfering ions. The selective Hg(II) ions-thiol groups interactions are the basis for the high selectivity of adsorbent. The adsorption isoterm of Hg(II) fitted with the Langmuir isotherm model and thus suggests a monolayer adsorption. The DMPS-LDH coated on the carbon cloth exhibits a high record saturation Hg(II) uptake capacity of over 2500 mg g−1 and distribution coefficients of 4.10 × 106 mL g−1, which place it at the top of adsorbents known for the uptake of Hg(II). The sorption kinetics for Hg(II) conform a pseudo-second-order model, that this model proposes a chemisorption reaction with the adsorption mechanism via M-S and M-SO4 bindings. Moreover, we observed efficient Hg(II) removal from tap water, well water, river water, and seawater samples. The excellent efficiency in recycling studies and good stability of the coating are other properties of the adsorbent.

Efficient Separation of Heavy Metals by Magnetic Nanostructured Beads

This study reports the ability of magnetic alginate activated carbon (MAAC) beads to remove Cd(II), Hg(II), and Ni(II) from water in a mono-metal and ternary system. The adsorption capacity of the MAAC beads was highest in the mono-metal system. The removal efficiency of such metal ions falls in the range of 20–80% and it followed the order Cd(II) > Ni(II) > Hg(II). The model that best fitted in the ternary system was the Freundlich isotherm, while in the mono-system it was the Langmuir isotherm. The maximum Cd(II), Hg(II), and Ni(II) adsorption capacities calculated from the Freundlich isotherm in the mono-metal system were 7.09, 5.08, and 4.82 (mg/g) (mg/L)1/n, respectively. Lower adsorption capacity was observed in the ternary system due to the competition of metal ions for available adsorption sites. Desorption and reusability experiments demonstrated the MAAC beads could be used for at least five consecutive adsorption/desorption cycles. These findings suggest the practical use of the MAAC beads as efficient adsorbent for the removal of heavy metals from wastewater.

Preparation of ultra-lightweight and surface-tailored cellulose nanofibril composite cryogels derived from Date palm waste as powerful and low-cost heavy metals adsorbent to treat aqueous medium

In this study, new bio-based crogels as adsorbents were prepared from date palm tree waste (Phoenix dactylifera L). Cellulose nanofibrills (CNFs) and cellulose nanofibrills cryogels modified with 10 % GO and Fe3O4 nanoparticle as filler (CNFs/GO/Fe3O4) were prepared by facile freeze drying methodology. The unmodified and modified cryogels were characterized by fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), energy-dispersive X-ray spectroscopy (EDAX), specific surface area (BET), thermogravimetric analysis (TGA) and mechanical test. In the following, CNFs/GO/Fe3O4 cryogels were achieved with low density (0.0139 (g/cm3)), ultra-porosity (99.46 %), appropriate specific surface area (SBET = 55 (m2/g)) with more significant thermal and mechanical properties than unmodified cryogel. Furthermore, the adsorptive removal of chromium (VI), lead (II) and mercury (II) ions was investigated by response surface methodology (RSM) with central composite design (CCD), on to CNFs/GO/Fe3O4 cryogels. Optimal conditions resulting from the effective parameters such as pH, adsorbent dosage and contact time were assessed via RSM for this novel adsorbent. The adsorption kinetics were fitted well with pseudo-second-order model and the adsorption capacity of Pb(II), Hg(II) and Cr(VI) on CNFs/GO/Fe3O4 cryogels by Langmuir model concluded 126.58, 36.70 and 73.52 mg/g, respectively at 298 ±1°K. In addition, CNFs/GO/Fe3O4 cryogels could be successfully reused even after four cycles.

Aminated Hydroximoyl Camelthorn Residues as a Novel Adsorbent for Extracting Hg(II) From Contaminated Water: Studies of Isotherm, Kinetics, and Mechanism

Camelthorn, a desert plant, has been utilized as an adsorbent material for the extraction of Hg(II) ions from aqueous solution after grafting with acrylonitrile followed by amination with hydroxylamine hydrochloride in basic medium to obtain aminated hydroximoyl camelthorn (AHCT). AHCT were found to exhibit excellent adsorption capacity over a wide range of Hg(II) concentration. The surface functional groups and morphology of AHCT were determined. The influences of time (0–60 min), pH (2–6), and dose (0.3–8 g/L) were also evaluated. The adsorption data were analyzed using the Langmuit, Freundlich and Temkin tr models at 30 °C using nonlinear regression analysis. The maximum adsorption capacity (qmax) of Hg(II) onto AHCT was 272.9 mg/g at an initial pH of 6 and a temperature of 30 °C and the Freundlich constants, KF and n, at 30 °C were found to be 25.47 mg/g and 3.2, respectively. The value of n (3.2), which being in the range 0–10 indicate that adsorption of Hg(II) ions onto AHCT is favorable. Various kinetics models including the pseudo-first-order, pseudo-second-order and intraparticle diffusion models have been applied to the experimental data to predict the adsorption kinetics. Kinetic study was carried out by varying initial concentration of Hg(II) at constant temperature and it was found that pseudo-second-order rate equation was better obeyed than pseudo-first-order and intraparticle diffusion supporting that chemisorption process was involved. The examination of R2 values and error analysis method (ARE) showed that the Langmuir model provide the best fit to experimental data than other isotherms and follow the following order: Langmuir > Freundlich > Temkin. The results revealed that the AHCT-Hg(II) ions adsorption system was promoted by the high density of active sites and the adsorption process is independent of the adsorbent surface area. Consequently, AHCT residues can offer an effective method of Hg (II) ion removal from aqueous solutions, demonstrating its potential role in water remediation processes.

Insight into the interfacial stability and reaction mechanism between gaseous mercury and chalcogen-based sorbents in SO2-containing flue gas

Chalcogen-based materials have been confirmed to possess large adsorption capacities for gaseous elemental mercury (Hg0) from SO2-containing flue gas. However, the interface reaction mechanisms and the interfacial stability are still ambiguous. Here, we selected some commonly used chalcogen-based sorbents (e.g., X, ZnX, CuX. X = S, Se) to investigate the in-depth reaction mechanisms. The adsorption capacities, structure effect on thermal and surface mercury stability, and interfacial reaction mechanism in the absence/presence of SO2 were evaluated. The experimental results indicated that Cu-chalcogenide had higher Hg0 adsorption capacity and surface Hg-X bonding stability compared with zinc one, while they exhibited an opposite degree of thermal stability. Moreover, all the chalcogenides showed well SO2 tolerance but with a slight difference. Chalcogenides with the same crystal structures, like ZnX or CuX, exhibited similar properties in stability and interfacial Hg0 and SO2 reaction mechanism. X− in chalcogenides have a better affinity to mercury, while in the Hg0 capture process, the existence of multivalent metal elements (like Cu2+ and Cu+) can faster the Hg0 oxidation for the further chemical-adsorption. This work provides a basic understanding of the application for efficiently enriching and recycling gaseous Hg0 from industrial SO2-containing flue gas.

Versatile MoS2 hollow nanoroses for a quick-witted removal of Hg (II), Pb (II) and Ag (I) from water and the mechanism: Affinity or Electrochemistry?

In this paper, a nano Molybdenum disulphide with an open cavity at the centre (hollow) and a rose flower-shaped structure (MoS2HNR) has been synthesized using a novel, micelle assisted hydrothermal method and has been successfully demonstrated the ability of the nano MoS2 for the simultaneous removal of the toxic metal ions: Hg (II), Pb (II) and Ag (I) from water. A single treatment of contaminated real water samples with MoS2HNR can rapidly (in ∼5- 30 min) decrease the concentration of Hg (II), Pb (II) and Ag (I) simultaneously from 10,000 ppb to 0.49, 20.5, and 11.62 ppb respectively, the levels less than the safe limits suggested by the U.S Environmental Protection Agency (USEPA) with an efficiency of ≥ 99% at a V/m ratio of 10,000, in real water samples. The adsorption capacities for Hg (II), Ag (I) and Pb (II) are ∼1991, 1350 and 1267 mg/g, respectively at pH 7.0 and exhibited high distribution coefficients (Kd) values of ∼108 mL/g. The rose-like morphology and the open cavity of the material attributed to the excellent removal property as the structure offers a large number of active S2− sites for adsorption. A possible mechanism for the high-efficiency removal and the order of adsorption Hg (II) >Ag (I) >Pb (II) is explained based on the affinity between S2− and metal ions and the electrochemistry factor. The MoS2HNR retains its morphology even after six trails of reuse.

Effect of additives on mercury partitioning in wet-limestone flue-gas desulfurization

AbstractThe wet-flue-gas desulfurization (FGD) process plays an important role in removing water-soluble flue-gas components such as sulphur dioxide (SO2) and oxidized mercury compounds. Under the reducing environment of the FGD, there is the possibility of re-emission of the already absorbed mercury (Hg) to the gas phase, which may be diminished by the utilization of specific additives. In this study, the effect of two different additives on Hg re-emission from the aqueous phase and Hg partitioning in gypsum and filtrate of a lab-scale wet-limestone FGD is investigated. Furthermore, the behaviour of additives in the presence of different halides is studied. The studied additives are TMT 15® as a sulphidic precipitating agent, which forms non-soluble mercury compounds, and activated lignite (AL) as a carbon-based sorbent, which adsorbs Hg compounds from the aqueous phase. TMT 15® has no significant effect on SO2 absorption; on the other hand, addition of AL improves the SO2-removal efficiency by up to 30%. Using both additives, Hg re-emission is suppressed in all the experimented cases except for AL in the absence of halides, in which Hg re-emission shows no change. Thus, the need to form nucleophilic oxidized mercury compounds in the slurry for the adsorption of oxidized mercury on AL can be concluded. Usage of both additives improves Hg retention in the slurry to different extents. It is shown that, for the additive-free slurries, the Hg-adsorption capacity of the solid fraction of the slurry is the limiting parameter. Moreover, the utilization of both additives results in a significant increase in the Hg concentration of solid fraction. The correlation between redox potential and partitioning of Hg in the slurry is presented by comparing the change in the redox potential of slurries when additives are used.

Improvement of NH3 resistance over CuO/TiO2 catalysts for elemental mercury oxidation in a wide temperature range

In this study, the effects of ammonia (NH3) were explored for catalytic oxidation of elemental mercury (Hg0) over CeO2/TiO2, CuO/TiO2, Fe2O3/TiO2, and V2O5-WO3/TiO2 catalysts. In the presence of 50 ppm NH3, the results showed that CuO/TiO2 catalysts could still maintain 98–100 % of Hg0 conversion in the range of 100–400 °C, while the catalytic performance of other catalysts was significantly inhibited by NH3 in the same temperature range. NH3 resistance was observed on CuO/TiO2 catalysts. The catalysts were further characterized by means of XRD, H2-TPR, XPS, NH3-TPD, BET, and in-situ DRIFTS. For the CuO/TiO2 catalysts, Cu(II) was the primary Cu species that conducive to the strong reducibility properties which beneficial for the catalytic performance. The mechanism of NH3 resistance in Hg0 oxidation over CuO/TiO2 catalysts was proposed. At low-temperature range (lower than about 250 °C), abundant weak acidic sites contributed to the superior Hg0 adsorption capacity. The Hg0 oxidation activity was enhanced correspondingly. At high-temperature range (about 250–400 °C), the Hg0 oxidation performance was mainly affected by the oxidation of NH3 and the products. The main product of NH3 oxidation was NO2, which could promote Hg0 oxidation activity.

Preparation and Characterization of a Starch‐Based Adsorbent for the Effective Removal of Environmental Pollutants Hg (II)

AbstractIn this work, a dialdehyde starch cysteine (DASC) Schiff base is synthesized by the reaction of dialdehyde starch (DAS) and l‐cysteine, and subsequently tested to remove Hg (II) from aqueous solution using the batch method. It is also characterized by elemental analysis, Fourier transform infrared (FT‐IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscope (SEM), Brunner–Emmet–Teller (BET) measurements, and X‐ray photoelectron spectroscopy (XPS) techniques. The results reveal that the DASC is a kind of starch‐based Schiff base containing thiol group, which holds excellent adsorption capacity for Hg (II) due to the interaction between sulfur atoms and Hg (II). At 25 °C, the equilibrium can be achieved within 2 h and the maximal adsorption capacity of DASC with the substitution degree of 1.14 can be reached at 884.6 mg g−1 at initial pH 5. A relatively high temperature is favorable for the adsorption process of Hg (II). The kinetic and isotherm data are well fitted with the linear forms of pseudo‐second order equation and Freundlich model. Additionally, the DASC shows good regenerative adsorption efficiency of 87.07% after four recycles. Owing to the advantages of economical, eco‐friendly, high adsorption capacity, and recyclability, DASC may provide valuable information for the treatment of Hg (II) contaminated water.

Development of selenized magnetite (Fe3O4−xSey) as an efficient and recyclable trap for elemental mercury sequestration from coal combustion flue gas

Abatement of elemental mercury (Hg0) pollution in coal combustion flue gas remains a challenging task especially for the optimal trade-off among effectiveness, environmental-friendliness and cost. In this work, magnetite (Fe3O4) was simply selenized (Fe3O4−xSey) as an efficient and recyclable sorbent for Hg0 sequestration from coal combustion flue gas. The Fe3O4−xSey as obtained exhibited an advantageous core-shell like spherical structure, in which the interior Fe3O4 core kept unchanged during the selenization process and warranted the recyclability of Fe3O4−xSey, while the exterior part exposed to Hg0 was selenized into iron diselenide (FeSe2) that has high affinity towards Hg0. Moreover, the selenization process introduced more mesopores that were favorable for Hg0 migration and accommodation. Co-benefitted from these perspectives, the Fe3O4−xSey exhibited a Hg0 adsorption capacity and uptake rate as high as 8.8 mg g−1 and 3.7 μg g−1 min−1, respectively, far exceeding the capacity and rate of bare Fe3O4 and traditional Hg0 remediators. The Hg0 stably immobilized by Fe3O4−xSey primarily as mercury selenide (HgSe) indicates the Hg-laden Fe3O4−xSey has negligible mercury re-emission concerns when it is dumped and landfilled. The spent Fe3O4−xSey can also be effectively retrieved and regenerated for reusing purpose with mercury recovery simultaneously, which could dramatically save the operation costs. Thus, the Fe3O4−xSey can be expected to be a promising alternative to traditional sorbents for Hg0 sequestration from coal combustion flue gas considering its high efficiency, negligible environmental risk and decent recyclability and reusability.

Co-doped ZnS with large adsorption capacity for recovering Hg0 from non-ferrous metal smelting gas as a co-benefit of electrostatic demisters.

The installation of electrostatic demisters (ESDs) makes possible the use of sorbent injection technology for recovering Hg0 from non-ferrous smelting gas. ZnS, as a typical smelting raw material, could be a promising candidate due to the sulfur boding site for mercury. However, the low reaction rate and poor adsorption capacity limited its application. In this study, Co was incorporated into ZnS to enhance adsorption activity for recovering Hg0. Co0.2Zn0.8S exhibited the best Hg0 capture performance among the modified sorbents. The Hg0 adsorption capacity was up to 46.01mg/g at 50°C (with 50% breakthrough threshold), and the adsorption rate was as high as 0.017mg/(gmin). Meanwhile, SO2 and H2O had no poison effects on Hg0 adsorption. The chemical adsorption mechanism was proposed, which was Co3+, and sulfur active sites could immobilize Hg0 in the form of stable HgS, following a Mars-Maessen reaction pathway. The spent sorbent will release ultrahigh concentration mercury-containing vapor through the heating treatment, which facilitated centralized recovery of Hg0. Meanwhile, inactivated sorbent can be used as smelting raw material to recover sulfur resources. Therefore, the control of Hg0 emission from non-ferrous smelting gas by Co-adopted ZnS was cost-effective and did not form secondary pollution. Graphical abstract.