Mercury Uptake Capacity Research Articles

Direct Ag-Hg amalgamation in the nanoscale on the surface of biosourced amorphous silica

Mercury poses a significant threat to air, soil, and water ecosystems. Mercury-based alloys, aka amalgams, are already known for their effectiveness in mercury capture in water and gaseous streams. However, limited research has been published on direct amalgamation, the process involving a direct redox reaction between two metals, occurring on the surface of amorphous silica. This study investigates the amalgamation process in nanoscale, in particular the direct interaction between silver (Ag⁰) nanoparticles supported on functionalized bio-derived amorphous silicon dioxide (SiO₂) and mercury (Hg2⁺) ions in aqueous solutions. Also, the influence of aqueous mercury speciation on amalgamation is studied in detail. The results reveal that the presence of chloride (Cl⁻), acetate (OAc⁻), and nitrate (NO3⁻) ions significantly influences the interaction between mercury and silver. We propose plausible mechanisms to explain these observations. Our findings demonstrate that the maximum mercury uptake capacity followed the order HgCl2 > Hg(OAc)2 > Hg(NO3)2, while the reaction rate followed the order Hg(OAc)2 > HgCl2 > Hg(NO3)2. These findings hold significant implications for the design of efficient mercury remediation processes. By elucidating the influence of aqueous speciation on amalgamation, our work paves the way for tailored strategies that can maximize mercury capture from water.

A novel Sulfur-functionalized alkynyl carbon material for highly efficient removal of Hg(II) from water

In this work, a novel sulfur-functionalized alkynyl carbon materials (SACMs) were synthesized by mechanochemical reaction of CaC2 and CS2 with rich sulfur and alkynyl functional groups, as well as high porosity and surface area. Their sulfur content varies from 4.1 % to 39.8 %, depending on the stoichiometric ratio of the reactants used. The SACM-2 exhibits extremely high mercury uptake capacity (500 mg-Hg⋅g−1 at ca. 2 μg.g-1 of equilibrium Hg(II) concentration), being one of the best adsorbents, and it showed favorable recyclability after 5 cycles. The adsorption behavior follows the Freundlich and the pseudo second-order kinetic model, respectively. The SACM-2 was examined for aqueous phase adsorption of mercury, cadmium, lead, and copper ions. Its affinity for neat heavy metals was in the order of Hg(II) > Cd (II) > Pb(II) > Cu(II). The high-efficiency adsorption of Hg(II) was mainly attributed to the sulfur and alkynyl functional groups as well as their synergestic effect for specific soft acid-soft base interaction between adsorbent and the heavy metal ions. Overall, our work not only reports a promising material for removal of heavy metals-containing wastewater, but inspires the value-added utilization of CS2 in preparing other highly sulfureted materials.

Sol-gel hybrid silicas as an useful tool to mercury removal

Due to high potential toxicity of mercury species and their characteristics of bioaccumulation and biomagnification, these pollutants have become a huge problem for environment, being able to spread along all trophic levels, including humans. This work describes the influence of hybrid silicas textural characteristics on mercury uptake capacity, revealing the possibility to use different sol-gel routes as a form to produce materials to interact with mercury species. The hybrid silicas prepared by basic catalyzed route showed more efficiency to remove inorganic mercury from aqueous media (1.5–1.9 μg. mg−1 of adsorbed mercury) if compared to those obtained by acid-catalyzed or two-steps routes (zero μg. mg−1 of adsorbed mercury). In addition, the hybrid silicas loaded with amino or sulfur-groups showed the high capacity to adsorb mercury, removing 82–99% from a 10 mg.L−1 Hg(II) solution with only 50 mg of the sorbents.

Study of elemental mercury removal from flue gases using Tetravalent manganese Feroxyhyte

An innovative material, namely Tetravalent Manganese Feroxyhyte (TMFx), was synthesized and tested for its capacity to capture elemental mercury, Hg(0), from boiler flue gases. TMFx presents characteristics well-suited for this purpose, since it incorporates high oxidation capacity, high surface area and high negative surface charge density. Results show that the Hg(0) uptake capacity (Q50) at break through concentration equal to the EU emission limit (50μg/m3) was essentially affected by synthesis pH, temperature and Empty Bed Contact Time (EBCT). The significantly high Hg(0) uptake capacity of 13.9mgHg/g, was determined for the material prepared at pH 9, and tested in a fixed bed reactor at T=120°C and EBCT=40ms. Uptake capacity was reduced at higher temperatures of 150–180°C, due to the exothermic nature of the process and degradation of the TMFx’s surface properties. An XPS study and regeneration tests indicated oxidation of Hg(0) in its bivalent form that allows for regeneration of spent TMFx samples under mild chemical conditions (KI solution) at room temperature. These mild regeneration conditions result in preserving TMFx uptake capacity. The presence of flue gas constituents affected positively the TMFx’s uptake capacity for Hg(0). Oxygen alone increased adsorption yield by 180%, NO by 80%, and HCl by 64%. In contrast, SO2 had a strong negative effect, almost zeroing the Hg(0) uptake. The effect became positive when oxygen was added and yield increased by 25%. Contact time significantly influenced mercury uptake capacity, since by increasing the EBCT from 40ms to 90ms at 150°C, the Q50 value almost tripled.

MoS2 Nanosheets with Widened Interlayer Spacing for High‐Efficiency Removal of Mercury in Aquatic Systems

Molybdenum disulphide (MoS2) has been an attractive target for investigations in the fields of catalysis, sensing, energy storage, electronics, and optoelectronics. However, its potential application in the important area of environmental cleanup has not yet been effectively explored. With an intrinsically sulfur‐rich characteristic and unique 2D structure, MoS2 should be capable of mercury capture and removal. However, successful attempts to apply MoS2 to mercury removal are quite rare, presumably because the vast majority of sulfur atoms are located inside the bulk of MoS2 and are therefore inaccessible for mercury ions. Here, the first experimental evidence that MoS2 nanosheets with widened interlayer spacing are capable of mercury capture, with an extremely high mercury uptake capacity closely matching the theoretically predicted value (2506 mg g−1) and the largest distribution coefficient value (3.53 × 108 mL g−1) is provided. Remarkably, a single treatment of industrial wastewater (polyvinyl chloride industry) with this modified MoS2 could efficiently reduce the mercury concentration (126 p.p.b.) below U.S. Environmental Protection Agency limits for drinking water standards. The findings open up the possibility of expanding the applications of transition metal dichalcogenides in environmental remediation.

Mercury nano-trap for effective and efficient removal of mercury(II) from aqueous solution.

Highly effective and highly efficient decontamination of mercury from aqueous media remains a serious task for public health and ecosystem protection. Here we report that this task can be addressed by creating a mercury 'nano-trap' as illustrated by functionalizing a high surface area and robust porous organic polymer with a high density of strong mercury chelating groups. The resultant porous organic polymer-based mercury 'nano-trap' exhibits a record-high saturation mercury uptake capacity of over 1,000 mg g(-1), and can effectively reduce the mercury(II) concentration from 10 p.p.m. to the extremely low level of smaller than 0.4 p.p.b. well below the acceptable limits in drinking water standards (2 p.p.b.), and can also efficiently remove >99.9% mercury(II) within a few minutes. Our work therefore presents a new benchmark for mercury adsorbent materials and provides a new perspective for removing mercury(II) and also other heavy metal ions from contaminated water for environmental remediation.

Mercury Uptake by Modified Mackinawite

This study investigated the mercury uptake capacity of synthetic mackinawite regarding its surface modification with L-cysteine. Mackinawite (FeS) is an excellent material for mercury uptake from anoxic-contaminated sediments. However, one limitation to its use is the low oxidation stability; it is easily transformed when applied to natural sediments. The modification of mackinawite with L-cysteine improves its oxidation stability, making it a promising material to be used in sediment remediation by in-situ capping. The results showed that L-cysteine does not affect the mercury-uptake capacity of mackinawite (around 490 mg/g for modified and unmodified mackinawite). The Hg (II) uptake decreased as the solution pH changed from acid to alkaline range, especially in solutions with low Hg (II) concentrations. Sorption curves for Hg (II) on modified mackinawite, as a function of initial concentration of Hg (II) and mackinawite, showed the same pattern as that on unmodified mackinawite, indicating no significant difference in the mercury-sorption mechanism. The solids before and after Hg (II) uptake were analyzed by X-ray powder diffraction (XRPD) by noting the composition of both modified and unmodified mackinawite, and the results were in agreement with the sorption experiments.

Thermally robust chelating adsorbents for the capture of gaseous mercury: Fixed-bed behavior

Thermally robust chelating adsorbents for the capture of vapor-phase mercuric chloride (HgCl 2) have been developed, to address the issue of mercury removal from flue gases from coal-fired power plants. The adsorbents are mesoporous silica substrates functionalized with a chelating agent and coated with an ionizing surface nano-layer. This architecture enables selective, multi-dentate adsorption of mercury directly from the gas phase with high capacity. The capture efficiency of the adsorbents was evaluated in the fixed-bed mode for oxidized mercury at 160 °C. Two chelating adsorbents, one functionalized with 3-mercaptopropyltrimethoxysilane (MPTS) and the other with 2-mercaptobenzothialzole (MBT), were studied. For both adsorbents a high mercury uptake capacity was observed, several times higher than that of commercial activated carbon. The mechanism for mercury uptake in the two adsorbents is different. The effect of pore size on uptake was also evaluated. It was found that pore size does not have a significant effect on the mercury adsorption, and mercury diffusion through the ionic coating is believed to be the rate-limiting step for capture.

Removal of low concentration Hg 2+ from natural waters by microporous and layered titanosilicates

Mercury is one of the most toxic heavy metals present in aquatic systems, exhibiting a complex behaviour in the environment, where it may persist for decades after the source of pollution is stopped. Hence, it is important to, both, study the complex phenomena that control the transference of mercury to the environment, and develop new techniques for its removal from the aquatic systems. In this context, a particularly promising line of research is the synthesis of materials capable of uptaking mercury from aqueous systems. Microporous and layered titanosilicates have unique physical and chemical properties due to their structure. Here, the microporous materials ETS-10, ETS-4, AM-2 and layered AM-4 have been prepared and their capacity to uptake Hg 2+ from aqueous media found to be ETS-4 > ETS-10 > AM-2 and AM-4. For these four materials, the kinetics of the Hg 2+ removal from water is better described by a pseudo second-order model. The presence of the competitive Ca 2+, Na + and Mg 2+, which are the dominant cations in freshwater, does not reduce the ETS-4 mercury uptake capacity, even when their concentrations are much larger than the concentration of Hg 2+. Although the presence of these ions slows down slightly the kinetics of Hg 2+ sorption by ETS-4, this process is still second-order. High Cl − concentrations greatly reduce the Hg 2+ sorption capacity of ETS-4 and slow down the uptake kinetics, due to the formation of neutral or negatively charged mercury chloro-complexes. Thus, ETS-4 may not be efficient in the remediation of salty or sea waters.

Sulfurization of a carbon surface for vapor phase mercury removal – II: Sulfur forms and mercury uptake

Sulfur forms deposited on carbonaceous surfaces after exposure to hydrogen sulfide were analyzed using XPS and XANES. Higher temperatures promote the formation of organic sulfur and the presence of H 2S during the cooling process increased elemental sulfur content. Temperatures between 400–600 °C were found to be optimal for producing effective mercury uptake sorbents. The increased amount of sulfur deposited during the cooling process in the presence of H 2S was very effective towards Hg uptake in nitrogen. Correlation of mercury uptake capacity and the content of each sulfur form indicated that elemental sulfur, thiophene, and sulfate are likely responsible for mercury uptake, with elemental sulfur species being the most effective.

Adsorption and desorption characteristics of mercury(II) ions using aminated chitosan bead

Adsorption and desorption characteristics for mercury ions using aminated chitosan bead which showed very high affinity to mercury ions were studied. The adsorption of mercury ions using aminated chitosan bead was an exothermic process since binding strength each other increased as the temperature decreased. And the adsorption of mercury ions was almost completed in 100 min at 150 rpm. In case that adsorbent dose increased, mercury uptake capacity decreased, while, removal efficiency increased. The beads were not greatly affected by the ionic strength, organic material and alkaline-earth metal ions. Mercury ions adsorbed on aminated chitosan bead were desorbed effectively about 95% by EDTA and the adsorption capacity of the recycled beads can still be maintained at 90% level at the 5th cycle.

Mercury(II) Adsorption from Wastewaters Using a Thiol Functional Adsorbent

The removal of mercury(II) from wastewaters (coal-fired utility plant scrubber solutions) using a thiol functional organoceramic composite (SOL-AD-IV) is investigated. A simulant is employed as a surrogate to demonstrate the removal of mercury from real waste solutions. Equilibrium studies show a mercury uptake capacity of 500 mg/g at a low mercury concentration of 0.5 mg/L and 726 mg/g at saturation. Adsorption is observed to be independent in the pH range 3−5. The kinetic performance assessed on a recycle batch reactor shows a rapid rate of adsorption. Selectivity is found to be in the order Hg(II) > Pb(II) ∼ Cd(II) > As(V) > Cr(III). Regeneration of SOL-AD-IV is accomplished using 12 M HCl. Effluent mercury concentrations of <0.001 mg/L are achieved using a fixed-bed adsorption column. A stability test operated for 25 cycles indicates a capacity loss of <10%. A high potential is demonstrated for application for mercury cleanup of wastewaters.

Impact of Flue Gas Conditions on Mercury Uptake by Sulfur-Impregnated Activated Carbon

Novel sulfur-impregnated activated carbons (SIACs) have shown excellent mercury uptake capacity when pure nitrogen was used as a carrier gas. This study investigated the impact of various gas constituents found in a real flue gas on the performance of SIACs. Fixed-bed adsorber tests showed that CO2 (up to 15%) had no impact on mercury uptake by SIAC, while the presence of O2 (up to 9%) increased the adsorptive capacity up to 30%. Increase in the amount of oxygen-containing acidic surface functional groups had no impact on mercury uptake, and it is postulated that the enhanced performance was due to the formation of HgO catalyzed by SIAC. Moisture presence (up to 10%) can decrease SIAC's capacity for mercury uptake by as much as 25% due to competitive adsorption and additional internal mass transfer resistance. SO2 (1600 ppm) and NO (500 ppm) exhibited no impact on mercury uptake by SIAC even in the presence of 10% moisture. Adsorptive capacity of SIAC decreased significantly when the reaction temperature increased from 140 to 250 and 400 °C due to the pronounced exothermic nature of HgS formation, but increasing the empty-bed contact time can partially offset this loss of capacity.

Optimization of Sulfur Impregnation Protocol for Fixed-Bed Application of Activated Carbon-Based Sorbents for Gas-Phase Mercury Removal

Novel sulfur-impregnated activated carbons for vapor phase mercury uptake (BPL-S series) were designed and developed in this study. Temperature and the initial sulfur to carbon ratio (SCR) during impregnation were the two control parameters for the impregnation procedure. By adjusting these two variables, a series of sulfur-impregnated carbons was created. These new materials together with commercially available sulfur-impregnated activated carbon (HGR) and coal samples were evaluated for the uptake of vapor phase elemental mercury using nitrogen as a carrier gas. The results showed that carbons impregnated with sulfur at high temperature exhibited the highest efficiency for mercury removal. As the impregna tion temperature decreased, the performance of the carbons deteriorated. When SCR was varied from 4:1 to 1:2, the sulfur content decreased only slightly, which resulted in a small decrease in mercury uptake capacity. Therefore, the impregnation temperature is the most important factor influencing the e...

Biosorption of mercury by the inactivated cells of pseudomonas aeruginosa PU21 (Rip64)

Biomass of a mercury-resistant strain Pseudomonas aeruginosa PU21 (Rip64) and hydrogen-form cation exchange resin (AG 50W-X8) were investigated for their ability to adsorb mercury. The maximum adsorption capacity was approximately 180 mg Hg/g dry cell in deionized water and 400 mg Hg/g dry cell in sodium phosphate solution at pH 7.4, higher than the maximum mercury uptake capacity in the cation exchange resin (100 mg Hg/g dry resin in deionized water). The mercury selectivity of the biomass over sodium ions was evaluated when 50 mM and 150 mM of Na(+) were present. Biosorption of mercury was also examined in sodium phosphate solution andphosphate-buffered saline solution (pH 7.0), containing 50mM and 150 mM of Na(+), respectively. It was found that the presence of Na(+) did not severely affect the biosorption of Hg(2+), indicating a high mercury selectivity ofthe biomass over sodium ions. In contrast, the mercury uptake by the ion exchange resin was strongly inhibited by high sodium concentrations. The mercury biosorption was most favorable in sodium phosphate solution (pH 7.4), with a more than twofold increase in the maximum mercury uptake capacity. The pH was found to affect the adsorption of Hg(2+)bythe biomass and the optimal pH value was approximately 7.4. The adsorption of mercury on the biomass and the ion exchange resin appeared to follow theLangmuir or Freundlich adsorption isotherms. (c) 1994 John Wiley & Sons, Inc.