Hg Adsorption Capacity Research Articles

Selenium–phosphorus modified biochar reduces mercury methylation and bioavailability in agricultural soil

Biochar is a frequently employed for solidifying and stabilizing mercury (Hg) contamination in soil. However, it often results in an elevated presence of soil methylmercury (MeHg), which introduces new environmental risks. Consequently, there is a necessity for developing a safer modified biochar for use in Hg-contaminated soil. This study employed sodium selenite (at a safe dosage for soil) and hydroxyapatite to modify straw biochar (BC) based on the interaction between selenium (Se) and phosphorus (P). This process led to the formation of Se-modified biochar (Se-BC), P-modified biochar (P-BC), and Se and P co-modified biochar (Se-P-BC). Additionally, solvent adsorption experiments and pot experiments (BC/soil mass ratio: 0.5 %) were conducted to investigate the impacts of these soil amendments on soil Hg methylation and bioavailability. Se and P co-modification substantially increased the surface area, pore volume, and Hg adsorption capacity of BC. BC treatment increased the simulated gastric acid-soluble Hg, organo-chelated Hg, and MeHg in the soil. Conversely, Se-P-BC significantly reduced these forms of Hg in the soil, indicating that Se-P-BC can transform soil Hg into less bioavailable states. Among the different biochar treatments, Se-P-BC exhibited the most pronounced reductions in soil MeHg, total Hg, and MeHg in water spinach, achieving reductions of 63 %, 71 %, and 70 %, respectively. The co-modification of Se and P displayed a synergistic reduction effect in managing soil Hg pollution, which is associated with the increase of available Se in the soil due to phosphorus addition. The significantly reduced dissolved organic carbon and the abnormally high SO42− concentration in the soil of Se-P-BC treatment also inhibited Hg methylation and bioavailability in the soil. In summary, Se-P-BC substantially increased reduction percentage in plant Hg content while mitigating the risk of secondary pollution arising from elevated soil MeHg.

Facile synthesis of new metal-organic framework/chitosan composite sponge for Hg(II) removal: Characterization, adsorption efficiency, and optimization using Box-Behnken design

The objective of this research was to develop a novel adsorbent to eliminate mercury (Hg(II)) from water. A unique citrate-crosslinked La-MOF/citrate crosslinked chitosan composite sponge (La-MOF@CSC composite sponge) was successfully synthesized in an acidic environment using a one-step technique. Modifying the composition of adsorbent materials is a commonly employed strategy to enhance adsorption capacity, particularly for materials composed of metal-organic frameworks. The study investigated the impact of the composite sponge on the adsorption and removal of Hg(II). The composite sponge exhibited a maximum adsorption capacity (qmax) for Hg(II) at 765.22 mg/g and an impressive high surface area of 1208 m2/g. Various factors influencing the adsorption capacity were taken into account in this study. The adsorption isotherm and kinetics were modeled using Langmuir and pseudo-second-order equations, respectively. Consistent with thermodynamics, the adsorption process was identified as spontaneous and endothermic. The quantities of adsorbed substances increased with rising temperature. The La-MOF@CSC composite sponge demonstrated the ability to be reused up to five times with satisfactory efficiency, retaining its chemical composition and exhibiting similar XRD and XPS data before and after each reuse. The interaction between heavy metals and the La-MOF/CSC composite sponge was examined. Optimization of the adsorption outcomes was conducted using the Box-Behnken design (BBD).

Steering electrophilic N center in ionic liquid for efficient oxidative capture of elemental mercury

Ionic liquids (ILs) show promise for flue gas purification, but suffer from the insufficient oxidation ability for elemental mercury (Hg0) removal. In light of the critical role of electrophilic structure in the oxidation process, we proposed a novel strategy to enhance Hg0 oxidative capture by steering electrophilicity of positively charged N center in the cation of IL. We screened ILs containing cations with N centers featuring varied hybridization and localization, and thioacetate anions that aid in immobilizing the resulting mercury ions. The electrophilicity of ILs, as determined by quantum chemical calculations, adheres to the following hierarchy: [Bpy][ThAc] (highly delocalized sp2-hybridized N) > [Bmim][ThAc] (low delocalized sp2-hybridized N) > [Bpyrr][ThAc] (sp3-hybridized N) ≈ [Bpip][ThAc] (sp3-hybridized N). This hierarchy correlated positively with experimental oxidation activity and Hg0 removal performance. Specifically, the Hg0 adsorption capacity of [Bpy][ThAc] (23.0 mg/g) was 3.6 times larger than that of [Bmim][ThAc]. Hg-TPD, XPS, and theoretical calculations corroborated that the highly delocalized sp2-hybridized N with a stable π system in [Bpy][ThAc] constitutes a strong electrophilic center, boosting electron transfer from Hg0 to the cation. Subsequently, the oxidized Hg2+ was immobilized through coordination with the anion. Furthermore, beyond the specific mercury removal process, the integration of Hg0 capture with desulfurization was successfully achieved by introducing [Bpy][ThAc] into the IL employed for desulfurization, highlighting its adaptability and practicability. This work not only develops an effective remediator for Hg0 removal from the flue gas but also offers design guidelines for ILs used in the oxidative degradation of other contaminants.

The design of high-entropy metal sulfides promising high-performance gaseous elemental mercury removal

Regulating the surface coordination environment and improving the formation of active species represent the key factor in designing high-performance metal sulfide-based sorbents for gaseous Hg0 capture. This paper reported the Hg0 adsorption by high entropy metal sulfides for the first time, and clarified the mechanisms involved in the evolutions of active species as well as the Hg0 adsorption. The multiple metal components of the high entropy metal sulfides have great significance in improving the surface chemistry. The addition of Ce helps not only the formation of chemically homogeneous structure, but also the generation of high valence state metal cations and unsaturated sulfur species, thereby improving obviously the Hg0 removal ability. The synthesized CeNiCoMnCuSx has a high Hg0 adsorption capacity of 10.52 mg·g−1 at 80 %-breakthrough, and a Hg0 adsorption rate of 4.31 μg·g−1·min−1. The high valence state metal cations (Ni3+, Co3+, Mn4+, Cu2+ and Ce4+) and unsaturated Sx2− and S22− species can directly oxidize Hg0 and convert it into HgS. In comparison, the quaternary sulfide counterpart (NiCoMnCuSx) cannot form a main phase structure, and has obviously lower percentages of high valence state metal cations and unsaturated sulfur species. This work provides a new space for developing metal sulfides for Hg0 adsorption.

Facile fabrication of regenerable spherical La0.8Ce0.2MnO3 pellet via wet-chemistry molding strategy for elemental mercury removal

Perovskite-based sorbents have received extensive attention in the field of mercury abatement. However, the excellent Hg0 adsorption performance on the lab scale hardly transforms into industrial-scale utilization because of the elutriation and microcrystalline nature of powdery perovskite sorbent. Hence, the granulation of perovskite into pellets is a strongly solicited and urgent demand. In this work, a universal granulation strategy is exploited for fabricating perovskite sorbent pellets for Hg0 capture from coal combustion flue gas (CCFG) based on a facile wet-chemistry method. This route takes advantages of the unique thermal sensitivity and thermal decomposition characteristics of agar powder and surface tension of medium to simultaneously trade off the molding, pore creation, and mechanical property of perovskite-based sorbent pellets. Besides, silica sol was also added to further enhance the physical strengths of sorbent pellets. The obtained perovskite sorbent pellet (i.e., LCMO-A-Z-2) with a favorable BET surface area of 113.16 m2 g−1 and pore diameter of 8.81 nm, largely facilitating Hg0 diffusion and capture over sorbent pellets. LCMO-A-Z-2 was further employed to Hg0 adsorption experiment under simulated CCFG, which exhibited satisfactory Hg0 adsorption capacity of 2.07 mg g−1 and nearly identical Hg0 adsorption performance after 5 cycles. The weight loss was approximately 13 % after 1000 rotations in the anti-attrition ability experiment suggesting its outstanding mechanical strength. It is reasonable to deduce this granulation method can be readily extended to other powdery sorbents. This work makes first step towards the application of sorbent pellets under application-relevant conditions and support the ultimate implementation of traditional sorbents in various large-scale industrial scenarios.

Efficient removal of Hg0 by regulating the bonding degree between CuO and carrier Nb2O5

Nb2O5 is introduced to act as a novel carrier of CuO using for Hg0 removal, presenting the excellent performance compared to niobium combined with other metal oxides (MnO2, CeO2, Fe2O3). By regulating the calcination temperature and CuO load amount, it was found that the formative stage of CuNb2O6 was the optimum binding degree of CuO and Nb2O5, which was beneficial for strong interaction of active component and carrier. Hg0 removal behaviors showed Cu0.5/Nb2O5 exhibited the high Hg0 adsorption capacity, about 0.32 mg/g for 200 min at 150 ℃, and had a wide temperature range (100–250 ℃). SO2 and H2O have slight toxic effects on Hg0 capture, while O2 plays an important role in Hg0 capture. Studies on the structure and properties of samples manifested CuO was homogeneously dispersed on the surface of Nb2O5, and Cu0.5/Nb2O5 had good thermal stability and abundant surface acid property, besides, Cu+ specie can be more easily generated, which was beneficial for Hg0 removal in the flue gas. Furthermore, the removal mechanism of Hg0 was also studied, manifested Cu0.5/Nb2O5 can be considered as a promising mercury adsorbent for various applications.

Tailored Zeolitic Imidazolate Framework (TSC‐ZIF) for water purification: Evaluating TSC‐ZIF affinity towards heavy metal ions in multi‐metal solutions

In response to the growing concerns surrounding water pollution and the presence of multiple metal ions in environmental matrices, we conducted a comprehensive study to explore the potential of a thiosemicarbazone Schiff base in the Zeolitic Imidazolate Framework (TSC‐ZIF‐1) as an efficient adsorbent for removing harmful metal ions from aqueous solutions. Our investigation assessed the adsorption capacity and efficiency of TSC‐ZIF 1 towards three key metal ions—Hg(II), Ag(I), and Pb(II)—in homo‐ionic, tertiary, and multi‐metal ion systems. TSC‐ZIF 1 exhibited unprecedented adsorption behavior towards all three metal ions in the homo‐ionic system, with the Langmuir isotherm models fitting well (R2 ~ 0.98 to 0.99). The maximum adsorption capacities were found to be 1,667 mg/g for Hg(II), as previously reported; 285 mg/g for Ag(I); and 769 mg/g for Pb(II); these values serve as baseline values. Subsequently, we conducted a comparative analysis for a tertiary system, Hg(II)/Ag(I)/Pb(II), where the three metals co‐existed in one solution. The adsorption capacity for each metal ion was reduced to varying extents; notably, the adsorption capacity for Pb(II) experienced the most significant reduction, reaching a qm value of 57 mg/g, representing an ~93% decrease compared to the homo‐ionic metal system. Conversely, the adsorption capacity for Ag(I) exhibited a minor decrease of ~3%. Despite a decrease in the adsorption capacity for Hg(II) by approximately 34%, the removal capacity remains the highest among the other metals. Our investigation of the competitive adsorption among the metal ions in the Hg(II)/Ag(I)/Pb(II) system revealed an antagonistic effect, indicating strong adsorption competition for available sites on TSC‐ZIF 1. When extending this study to a more complex multi‐metal ion system containing six metal ions, TSC‐ZIF 1 exhibited high selectivity (higher than 60% removal) towards Hg(II), Ag(I), and Pb(II) in a multi‐ionic system, including Hg(II), Ag(I), Pb(II), Cd(II), Ni(II), and Mg(II).

Thioether-functionalized covalent organic framework for mercury removal

Post-synthetic modification of COFs via pendant groups or secondary functional groups of the skeleton structure is an important strategy to introduce new properties or enhance existing properties of COFs. Herein, we take advantage of the inherent advantages of COFs and introduce thioether functional groups into a reasonably designed novel COF (TAPA-TFPD) through a post-synthetic modification strategy to create a promising thioether functionalized adsorbent for mercury removal. The thioether functionalized COF material, TAPA-TFPD-S-S, exhibited high mercury removal efficiency from aqueous solution, and the adsorption capacity of Hg2+ was up to 593 mg/g. This efficient mercury removal performance can be attributed its well-defined pore channel sufficient to facilitate Hg2+ diffusion together with high concentration of sulfide chelating sites distributed uniformly throughout the pore wall. The strong interaction between Hg2+ and the thioether groups of TAPA-TFPD-S-S was confirmed by XPS. In addition, TAPA-TFPD-S-S also has the ability to capture Hg0 from the air. The efficient capture of mercury species from aqueous solution and air and the excellent reusability make the prepared thioether-functionalized COFs have great development potential in practical applications. Our work not only demonstrates the utilization of thioether-functionalized COFs in the removal of heavy metal contaminants, but also highlights the exceptional potential of post-synthetic modification strategies in the development of environmental remediation materials.

Homogeneous synthesis of Schiff base modified PAMAM dendrimers/silica for efficient adsorption of Hg(II)

Water pollution caused by Hg(II) is a serious environmental issue and poses great risk to human health. Adsorption is a promising method for decontaminating aqueous Hg(II). Therefore, a family of Schiff base modified polyamidoamine (PAMAM) dendrimer/silica (G0-T1/x-S, G1-T1/x-S and G2-T1/x-S (x = 2, 4, 6)) were synthesized by homogeneous method for removing Hg(II) from water solution. The adsorption property of the adsorbents for Hg(II) was comprehensively evaluated. The adsorption capacity for Hg(II) was found to depend on the dendrimer generation. The effects of solution pH, time, temperature, and interfering metal ions on the adsorption property for Hg(II) were determined by selecting G0-T1/2-S, G1-T1/2-S and G2-T1/2-S as models. The optimal pH for the adsorption of Hg(II) is 6. Adsorption kinetic shows that the adsorption is fast at initial, and the equilibrium can be reached at 400 min. Adsorption isotherm demonstrates the increase of temperature and concentration can promote the adsorption for Hg(II). The kinetic and isotherm process can be fitted by pseudo-second-order kinetic model and Langmuir model, respectively. The adsorbents display good adsorption selectivity for Hg(II) and the functional groups of CONH, C-N, C = N and OH dominate the adsorption. The adsorbents exhibit good removal efficiency for Hg(II) from simulated industrial wastewater with the coexistence of multiple pollutants. Moreover, the adsorbents show excellent reusability as the regeneration rate of G2-T1/2-S can still maintain 92.45 % after the tenth adsorption–desorption cycles. The research work provides a feasible method for the preparation of efficient adsorbents to remove aqueous Hg(II) with practical values.

Cupric ion stabilized iron sulfide as an efficient trap with hydrophobicity for elemental mercury sequestration from flue gas

Iron sulfides (FeSx) characterized by the nonstoichiometric coordination between iron and sulfur are promising sorbents for elemental mercury (Hg0) adsorption from industrial flue gas. However, the unstable nature of FeSx tending to self-combust under ambient conditions impedes its scalable synthesis. To overcome this critical challenge, this work developed a cupric ion incorporation method to stabilize FeSx. When the compositional ratios of cupric ion and FeSx both equaled 50%, the composite sorbent as synthesized (50Cu-FeSx) exhibited ultra-high Hg0 adsorption capacity and uptake rate that reached 433.2 mg g−1 and 847.4 μg g−1 min−1, outperforming those benchmark metal sulfides as reported in previous studies for practical uses. In this sample, the copper ion well-incorporated into the lattice of amorphous FeSx was an indispensable fundamental that contributed to its outstanding performance and hydrophobic ability. The stabilized FeSx thus enriched its surface with abundant under-coordinated sulfur due to the nonstoichiometric coordination environment, which acted as the primary active sites for the conversion of Hg0 because only under-coordinated sulfur could accept electrons Hg0 donated. The main product after 50Cu-FeSx adsorbed Hg0 was HgS, an extremely stable mercury form in nature. From these perspectives, it is proper to declare that this work not only proposed an efficient sorbent holding great potential for Hg0 removal from high-humidity industrial flue gas but also provided a novel method for the rational design of FeSx-based materials with extensive applicability in the future.

In situ activation synthesis of tire-derived sorbents for efficient immobilization of elemental mercury from flue gas

Mercury removal from coal combustion flue gas remains a daunting challenge because of the lack of cost-effective sorbents. In this study, the in situ activation synthesis of tire chars was realized through SO2 induction and the tire-derived sorbents were used for elemental mercury (Hg0) removal from the simulated flue gas. Therein the sulfur species in tire chars are regulated. The results indicated that the specific surface area of tire chars was slightly decreased whereas more micropores were generated after SO2 activation. Compared with raw tire char, the sulfur content of tire-derived sorbents was obviously increased. The tire-derived sorbents also contained more sulfur- and oxygen-containing functional groups. For this reason, the Hg0 removal performance of tire-derived sorbents was dramatically increased after SO2 activation. The optimum pyrolysis temperature for the synthesis of tire-derived sorbents was 600 °C. The SO2 concentration in activation atmosphere had little effect on the Hg0 removal performance of tire-derived sorbents. The presence of SO2, NO and O2 was beneficial for Hg0 removal·H2O had little effect on Hg0 removal. The Hg0 adsorption capacity of tire-derived sorbents was further compared with the previously reported sorbents through adsorption dynamic simulations. Furthermore, the mechanism of Hg0 removal over tire-derived sorbents was revealed through XPS analysis and mercury temperature programmed desorption. It was found that the Hg0 removal process was mainly dominated by chemisorption, where organic sulfur species, CO group and COOH/C(O)–O–C group served as active sites for Hg0 capture.

Adsorption/desorption of mercury (II) by artificially weathered microplastics: Kinetics, isotherms, and influencing factors

While both mercury (Hg) and microplastics (MPs) are well-studied global pollutants, comparatively little is known about the interactions between them and the mobilization of Hg from MPs into organisms. We examined the affinity of Hg(II) to artificially weathered MPs, including polyamide (w-PA), polyethylene (w-PE), polyethylene terephthalate (w-PET), polyester fibers (w-PEST), polyvinyl chloride (w-PVC), and polylactic acid (w-PLA), along with crumb rubber (CR) and PE collected from a wastewater treatment plant (WWTP-PE). WWTP-PE, CR, and w-PEST had particularly high Hg(II) affinities, which can be attributed to electrostatic interaction and pore filling. The adsorption followed a pseudo-second-order kinetic process and fitted the Freundlich model, suggesting multi-step (mass transfer and intraparticle diffusion) and heterogeneous adsorptions. Hydrochemical conditions (pH, dissolved organic matter (DOM), salinity and co-existent metal ions) all impacted Hg-MP behavior. Changes in Hg speciation and MP surface properties contributed to the different Hg(II) adsorption capacities for the MPs. Weathering of MPs generally increased the adsorption of Hg(II) onto MPs, but CR, PET and PEST did not follow this trend. Less than 3% of adsorbed Hg(II) was mobilized from the MPs in freshwater, but that increased up to 73% under simulated avian digestive conditions, suggesting increased bioavailability of Hg(II) from ingested MPs. Overall, weathered MPs adsorb and retain Hg(II) under environmentally relevant conditions but desorb much of it in simulated avian digestion fluid, suggesting that birds that ingest MPs may have increased Hg(II) exposure.

Copper selenide anchored on Ti3C2 MXene via Lewis acidic etching route for efficient removal of gaseous elemental mercury

A fundamental obstacle that restricts the use of metal selenides for gaseous elemental mercury (Hg0) immobilization is the failure to take both the optimization of intrinsic structure favorable for Hg0 diffusion and adequate exposure of metal selenide towards Hg0 into consideration. In this work, a Ti3C2 MXene/Cu2Se sorbent for Hg0 sequestration was synthesized via a Lewis acid etching route combined with room-temperature selenization pathway. During this strategy, copper chloride plays a dual role, i.e., an etching agent for the Ti3C2 MXene synthesis and a precursor for Cu0 decoration. Cu2Se precursors (Cu0) were dispersedly and firmly pre-anchored on the substrate, effectively avoiding the agglomeration and warranting excellent dispersion of Cu2Se. Compared with pristine Cu2Se, Ti3C2 MXene/Cu2Se exhibits advantageous structural characteristics fully boosting Hg0 diffusion kinetics. Meanwhile, the enhanced dispersion of Cu2Se from the prefixation of Cu0 largely enhances the exposure and utilization of selenide. Consequently, Ti3C2 MXene/Cu2Se shows a Hg0 adsorption capacity of 147.64 mg g−1, which is much higher than those of Cu2Se and most other metal selenides. Impressively, its uptake rate of 688.99 μg g−1 min−1 is the highest record rate in metal selenides. Moreover, Ti3C2 MXene/Cu2Se still maintained outstanding Hg0 adsorption performance under relatively high reaction temperature with the shelter of Ti3C2 MXene. Typical fuel gas situations including coal combustion flue gas, smelting flue gas, natural gas have negligible influences on its Hg0 adsorption performance, indicating its extensive applicability and flexibility for actual industrial situations. This work also provides valuable hints for the trade-off of structural properties and ligands exposure to design Hg0 sorbents with satisfactory Hg0 sequestration performances.

Synthesis of salicylaldehyde tailored PAMAM dendrimers/chitosan for adsorption of aqueous Hg(II): Performance and mechanism

Water pollution caused by Hg(II) exerts hazardous effect to environmental safety and human health. Herein, a family of salicylaldehyde tailored poly(amidoamine) (PAMAM) dendrimers/chitosan composites (G0-S/CTS, G1-S/CTS, and G2-S/CTS) were prepared and used for the removal of Hg(II) from water solution. The adsorption performance of the as-prepared composites for Hg(II) was thoroughly demonstrated by determining various influencing factors. G0-S/CTS, G1-S/CTS and G2-S/CTS exhibited competitive adsorption capacity and good adsorption selective property for Hg(II). The maximum adsorption capacity of G0-S/CTS, G1-S/CTS and G2-S/CTS for Hg(II) were 1.86, 2.18 and 4.47 mmol‧g−1, respectively. The adsorption for Hg(II) could be enhanced by raising initial Hg(II) concentration and temperature. The adsorption process was dominated by film diffusion processes with monolayer adsorption behavior. The functional groups of NH2, CONH, CN, OH, CO and CN were mainly responsible for the adsorption of Hg(II). G0-S/CTS, G1-S/CTS and G2-S/CTS displayed good regeneration property and the regenerate rate maintained 95.00 % after five adsorption-desorption cycles. The as-prepared adsorbents could be potentially used for the efficient removal of Hg(II) from aqueous solution.

Mechanochemical activation of natural metal sulfide minerals for Vapor-Phase mercury immobilization

Man-made metal sulfides (MSs) have been proven to be effective traps for permanent elemental mercury (Hg0) immobilization from anthropogenic sources. However, the fabrication of MSs generally involves complex steps and adopts hazardous precursors, hence compromising its cost-effectiveness and environmental-friendliness. The earth-abundant natural MS minerals might be optimal alternatives to the synthetic MSs, while most of them suffer from limited Hg0 adsorption capacity. Herein, a mild mechanochemical approach under a solid state with the aid of cupric chloride (CuCl2) was developed to modify pyrrhotite (Fe7S8) from calcination of natural pyrite for Hg0 capture from flue gas. After the CuCl2 aided mechanical milling, the Hg0 adsorption capacity and uptake rate of the CuCl2 modified pyrrhotite (CuCl2@Fe7S8) reached as high as 283.3 mg g−1 and 188.75 μg g−1min−1, approximately 400 folds higher than that of raw pyrrhotite. The characterization and density functional theory calculation results reveal that the superior performance of CuCl2@Fe7S8 was primarily attributed to the mechanochemical approach which not only introduced hetero-ligands (i.e., Cl) to the adsorbent to combine with Hg0 but also generated extremely active copper sulfide for binding Hg0. The excellent resistance to temperature fluctuation and flue gas interference and its magnetic separation recyclability warrant the application of CuCl2@Fe7S8 in real-world conditions. Integrated Hg0 removal technologies based on the performance-enhanced recyclable CuCl2@Fe7S8 were also proposed for potential applications in different industrial scenarios including coal combustion flue gas.

Polypyrrole-Modified Nanocellulose Exhibits Superior Performance for Hg(II) Adsorption.

Cellulose, a kind of polymer containing abundant functional groups, has widespread use in the adsorptive removal of environmental pollutants. An efficient and environmental friendly polypyrrole (PPy) coating approach is employed to modify the agricultural by-product straw derived cellulose nanocrystal (CNC) into excellent property adsorbents for removing the heavy metal ion of Hg(II). The FT-IR and SEM-EDS results demonstrated that PPy is formed on the surface of CNC. Consequently, the adsorption measurements proved that the obtained PPy-modified CNC (CNC@PPy) possesses a remarkably enhanced Hg(II) adsorption capacity of 1095 mg g-1, owing to a plentiful functional group of doped Cl element on the surface of CNC@PPy by forming Hg2Cl2 precipitate. The results of the study suggest that the Freundlich model is more effective than the Langmuir model at describing the isotherms, while the pseudo-second order kinetic model is better suited to correlating with the experimental data compared to the pseudo-first order model. Further, the CNC@PPy exhibits an outstanding reusability, capable of maintaining 82.3% of its original Hg(II) adsorption capacity after five successive adsorption cycles. The findings of this work reveal a method to convert the agricultural by-product into high performance environmental remediation materials.

Edge-Enriched Molybdenum Disulfide Ultrathin Nanosheets with a Widened Interlayer Spacing for Highly Efficient Gaseous Elemental Mercury Capture.

Transition metal sulfides have exhibited remarkable advantages in gaseous elemental mercury (Hg0) capture under high SO2 atmosphere, whereas the weak thermal stability significantly inhibits their practical application. Herein, a novel N,N-dimethylformamide (DMF) insertion strategy via crystal growth engineering was developed to successfully enhance the Hg0 capture ability of MoS2 at an elevated temperature for the first time. The DMF-inserted MoS2 possesses an edge-enriched structure and an expanded interlayer spacing (9.8 Å) and can maintain structural stability at a temperature as high as 272 °C. The saturated Hg0 adsorption capacities of the DMF-inserted MoS2 were measured to be 46.91 mg·g-1 at 80 °C and 27.40 mg·g-1 at 160 °C under high SO2 atmosphere. The inserted DMF molecules chemically bond with MoS2, which prevents possible structural collapse at a high temperature. The strong interaction of DMF with MoS2 nanosheets facilitates the growth of abundant defects and edge sites and enhances the formation of Mo5+/Mo6+ and S22- species, thereby improving the Hg0 capture activity at a wide temperature range. Particularly, Mo atoms on the (100) plane represent the strongest active sites for Hg0 oxidation and adsorption. The molecule insertion strategy developed in this work provides new insights into the engineering of advanced environmental materials.

Polyethyleneimine (PEI) and Chitosan (CS) grafted with L-cysteine were used as effective materials for Hg(II) adsorption

Naturally derived polymer materials have attracted extensive attention due to their abundant and environmentally friendly characteristics, and have been modified by more and more scholars to meet specific properties. As a global pollutant that seriously affects human health and ecosystems, Hg(II) is posing a great threat to human and environmental safety. Therefore, it is of great practical significance and commercial value to develop cheap, easily available and excellent Hg(II) adsorbent materials. In this paper, two kinds of effective porous materials for Hg(II) adsorption were successfully prepared by using the water-soluble polymer polyethyleneimine(PEI) and chitosan(CS) as raw materials and modified with L-cysteine(L-Cys), which is simple in structure and environmentally friendly. The maximum Hg(II) adsorption capacities of PEI-Cys and CS-Cys were 231.2 mg/g and 407.4 mg/g. This work provides a new and reliable idea for the practical application of Hg(II) pollution removal.

Adsorption of Hg(II) on polyethyleneimine-functionalized carboxymethylcellulose beads: Characterization, toxicity tests, and adsorption experiments

Mercury (Hg) is widely used in many industrial processes and is released into the environment. Therefore, efficient removal of Hg from water is of vital importance worldwide. Here, we explored the adsorption characteristics of Hg(II) on polyethyleneimine-functionalized carboxymethylcellulose (PEI-CMC) beads and studied the toxicity of the beads toward Daphnia magna and Pseudokirchneriella subcapitata. The PEI-CMC beads had an average particle size of 2.04 ± 0.25 mm, a point of zero charge (pHpzc) of 5.8, and a swelling ratio of 2.45. Acute toxicity tests demonstrated that the PEI-CMC beads had no toxic effects on D. magna. The growth inhibition tests revealed that growth inhibition of P. subcapitata could be attributed to adsorption of trace elements in growth media on the PEI-CMC beads. The adsorption experiments exhibited that the Matthews and Weber model best described the kinetic data, whereas the Redlich–Peterson model was well fitted to the isotherm data. The theoretical maximum Hg(II) adsorption capacity of the PEI-CMC beads was 313.1 mg/g. The thermodynamic experiments showed endothermic nature of the Hg(II) adsorption on the PEI-CMC beads at 10–40 °C. The adsorption experiments exhibited that the Hg(II) adsorption capacity decreased gradually as pH increased from 2 to 12. The adsorption of Hg(II) on the PEI-CMC beads can occur through chelation and electrostatic attraction. The FTIR and XPS spectra before and after Hg(II) adsorption confirmed that chelation of neutral Hg(II) species (HgCl2, HgClOH, and Hg(OH)2) can occur with amino and oxygen-containing functional groups on the PEI-CMC beads. Considering species distribution of Hg(II) and the pHpzc of the PEI-CMC beads, electrostatic attraction between the positively-charged beads and anionic Hg(II) species (HgCl3− and HgCl42−) can take place in highly acidic solutions. The PEI-CMC beads were regenerated and reused for Hg(II) adsorption using 0.1 M HCl.

Achieving Large-Capability Adsorption of Hg0 in Wet Scrubbing by Defect-Rich Colloidal Copper Sulfides under High-SO2 Atmosphere.

This paper reports on a novel method to remove Hg0 in the wet scrubbing process using defect-rich colloidal copper sulfides for reducing mercury emissions from non-ferrous smelting flue gas. Unexpectedly, it migrated the negative effect of SO2 on mercury removal performance, while also enhancing Hg0 adsorption. Colloidal copper sulfides demonstrated the superior Hg0 adsorption rate of 306.9 μg·g-1·min-1 under 6% SO2 + 6% O2 atmosphere with a removal efficiency of 99.1%, and the highest-ever Hg0 adsorption capacity of 736.5 mg·g-1, which was 277% higher than all other reported metal sulfides. The Cu and S sites transformation results reveal that SO2 could transform the tri-coordinate S sites into S22- on copper sulfides surfaces, while O2 regenerated Cu2+ via the oxidation of Cu+. The S22- and Cu2+ sites enhanced Hg0 oxidation, and the Hg2+ could strongly bind with tri-coordinate S sites. This study provides an effective strategy to achieve large-capability adsorption of Hg0 from non-ferrous smelting flue gas.