Hg Adsorption Research Articles

Reticular poly(pyrrole methylene)s synthesized by synchronous-cross-linking process for the capture of Hg(ll) from water: Adsorption performance and mechanism

The development of novel high-capacity porous materials is critical to advancing the treatment of mercury-containing wastewater. In this study, two reticular poly(pyrrole methylene) adsorbent materials (PPB2E and PPD2E) were synthesized by a synchronous cross-linking method and successfully employed for Hg(II) adsorption in water. Their adsorption performance on Hg(II) in water was investigated. The results showed that PPB2E and PPD2E have large specific surface areas (535.43 m2/g and 523.23 m2/g, respectively) and are abundant microporous, with the molecular chains partially cross-linked and partially oxidized to form a conjugated structure. The adsorption of Hg(II) by the two adsorbents could reach equilibrium within 120 min, and the adsorption behavior followed the pseudo-second-order model. The adsorption isotherms were more in line with the Langmuir model, and the maximum adsorption capacities of PPB2E and PPD2E for Hg(II) were up to 1537.46 mg/g and 1511.94 mg/g (298 K, pH = 4), respectively. The two adsorbents exhibited excellent adsorption selectivity for Hg(II) in mixed metal salt solutions with good cycling stability. The primary adsorption mechanism of the synthesized materials for Hg(II) was jointly verified by characterization and DFT calculations: Hg(OH)2 molecules were adsorbed by forming hydrogen bonds with pyrrole N and carboxyl O in the adsorbents. Compared with other metal ions, the materials have more active sites for Hg(II) adsorption, higher utilization, and easier formation of stable adsorption configurations, thus exhibiting highly selective adsorption.

Adsorption of Hg2+/Cr6+ by metal-binding proteins heterologously expressed in Escherichia coli

BackgroundRemoval of heavy metals from water and soil is a pressing challenge in environmental engineering, and biosorption by microorganisms is considered as one of the most cost-effective methods. In this study, the metal-binding proteins MerR and ChrB derived from Cupriavidus metallidurans were separately expressed in Escherichia coli BL21 to construct adsorption strains. To improve the adsorption performance, surface display and codon optimization were carried out.ResultsIn this study, we constructed 24 adsorption engineering strains for Hg2+ and Cr6+, utilizing different strategies. Among these engineering strains, the M’-002 and B-008 had the strongest heavy metal ion absorption ability. The M’-002 used the flexible linker and INPN to display the merRopt at the surface of the E. coli BL21, whose maximal adsorption capacity reached 658.40 μmol/g cell dry weight under concentrations of 300 μM Hg2+. And the B-008 overexpressed the chrB in the intracellular, its maximal capacity was 46.84 μmol/g cell dry weight under concentrations 500 μM Cr6+. While in the case of mixed ions solution (including Pb2+, Cd2+, Cr6+ and Hg2+), the total amount of ions adsorbed by M’-002 and B-008 showed an increase of up to 1.14- and 4.09-folds, compared to the capacities in the single ion solution.ConclusionThe construction and optimization of heavy metal adsorption strains were carried out in this work. A comparison of the adsorption behavior between single bacteria and mixed bacteria systems was investigated in both a single ion and a mixed ion environment. The Hg2+ absorption capacity is reached the highest reported to date with the engineered strain M’-002, which displayed the merRopt at the surface of chassis cell, indicating the strain’s potential for its application in practical environments.

Hypersensitized electrochemical sensing of Hg(II) based on phase engineering of Co doped MoSe2 nanosheets: Insight in dynamic phase change induced by the chemical interaction between Se and Hg(II)

Transition metal dichalcogenides (TMDs) are regarded as promising nanomaterials for electrochemical detection to heavy metal ions due to their variable performance. However, their detection performances are still limited by inferior conductivities and adsorption ability. In this work, the defects and phase engineering strategy are proposed to utilize cobalt (Co) doped MoSe2 nanosheet for electrochemical detection of Hg ion (Hg(II)). Through Co doping, we successfully achieved the phase transition of MoSe2 from the 2 H phase of semiconductor to the 1 T phase of conductor. Moreover, the 1 T MoSe2 is demonstrated to show a better adsorption and catalytic ability for Hg(II) detection than that of 2 H MoSe2. As a result, the MoSe2 containing atomic ratio of Co is 10% (named CM10) owning suitable content of 1 T phase has a superior sensitivity of 52.17 μA μM−1 and a low LOD of 3.96 nM for Hg(II). More importantly, combining with the characterization of X-ray photoelectron spectroscopy (XPS) and density-functional theory (DFT) calculation, it is found that the Hg(II) adsorption will also lead to the phase change of MoSe2, and the change state in the samples after the adsorption of Hg(II) will be more accurate to be responsible for the improvement of catalytic ability.

Study on adsorption properties and DFT calculations using ethylenediamine-functionalized Zr-based MOF as adsorbent for Hg(II)

Given the considerable toxicity of mercury and its persistent environmental presence, mercury pollution ranks among the most detrimental contaminants. In this study, thiol-functionalized zirconium-based metal-organic frameworks (MOF, UiO66-BAT-SH) were synthesized through click chemistry, and their potential for adsorbing Hg(II) ions from water was investigated. The composition, structure, and morphology of the adsorbent were characterized using scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The adsorption performance and adsorption mechanism of the material were investigated. The best adsorption effect was obtained at pH 4, with a maximum removal efficiency of 97.2 % and an adsorption capacity of 243.1 mg/g. The adsorption obeyed the proposed two-stage kinetic model, and the Langmuir isotherm model was in good agreement with the experimental isotherm. Density functional theory (DFT) calculation revealed that the adsorption of Hg(II) on UiO66-BAT-SH depends on electron exchange, electron sharing, electrostatic, and covalent interactions between metal ions. In conclusion, UiO66-BAT-SH demonstrated stability and recyclability, highlighting its potential as an adsorbent for Hg(II) remove.

Electrostatically directed assembly of macroporous skeleton structured copper selenide for elemental mercury sequestration from coal-fired flue gas

Decontamination of Hg0 from coal-fired flue gas remains an enormous challenge. It is an imperative pursuit to design adsorbents bearing an abundance of accessible chelating sites with a high affinity toward mercury, thus achieving both rapid uptake and high capacity for Hg0. Herein, an electrostatically directed assembly strategy was designed to construct Cu2Se decorated commercial polyurethane sponge (Cu2Se/PUS) as an efficient Hg0 trap. The surface coverage of Cu2Se on the Cu2Se/PUS can be rationally adjusted by turning the charge density of Cu2Se and PUS. The saturated Hg0 adsorption capacity of Cu2Se/PUS was achieved at 217.04 mg g−1 (normalized to the Cu2Se coating amount), which was much higher than that of powdery Cu2Se (43.66 mg g−1). Multiform selenium active sites (Se- and Se2-) and copper-terminated active centers of Cu2Se/PUS co-participated in Hg0 adsorption, instead of the individual role of Se- over powdery Cu2Se. The macroporous skeleton structure and the highly dispersed Cu2Se boosted the diffusion of mercury to the active sites for immobilization, thus accelerating the consumption of multiple active sites on the Cu2Se/PUS. This work not only provided an efficient Hg0 trap but also showed great inspiration for the potential of electrostatically directed assembly methods in constructing adsorbents for diverse environmental remediations.

Co-removal of CO2 and Hg using corn straw and pine biochar pretreated by hydrothermal technology

To reduce CO2 and Hg0 emission, the comparative research about CO2 and Hg0 co-removal performance of corn straw and pine biochar pretreated by hydrothermal technology was carried out. The results show that the specific surface area of corn straw and pine biochar can reach 448.24 m2/g and 397.86 m2/g, respectively. But in the range of 700–900 °C, pyrolysis temperature has opposite effects on the physical structure of the two types of biochar. Although iron ions can regulate the growth of ultra-micropores through the reduction reaction with matrix carbon during pyrolysis, too high pyrolysis temperature can also cause matrix collapse and ion sintering to hinder the construction of ultra-micropores of biochar. The ultra-microporous homogeneity and volume are main factors affecting the physical adsorption of CO2 and Hg0. The pine biochar prepared at 700 °C (PCH-700) performed the better CO2 adsorption capacity and mercury removal efficiency (5.35 wt% and around 100 %) at room temperature. The CO2 trapped on the biochar can be linked to the biochar matrix and form oxygen-containing functional groups, thereby promoting the release of free radical oxygen to achieve the co-removal of CO2 and Hg0.

Radiation grafting mediated tailoring of a mercury (Hg(II)) selective adsorbent “RAdMer”: Mechanistic insights, uptake performance and reusability evaluation in artificially contaminated groundwater

The presence of mercury (Hg(II)) in water bodies poses a pressing threat not only to aquatic life forms but also human health. This work proposes the fabrication of a novel thiol (-SH), amine (–NH–) and carboxylic (-COOH) group containing trifunctional adsorbent based on a radiolytically surface engineered biodegradable platform for selective sequestration of Hg(II) from aqueous media. Polyacrylonitrile (PAN) was gamma radiolytically incorporated onto cotton fabric via Radiation Induced Graft Polymerization (RIGP) process, followed by chemical conversion of the nitrile groups using dl-Cysteine as the trifunctional agent. The developed adsorbent RAdMer was characterized by FTIR, TGA, SEM-EDX, EDXRF, XRD, CHNS, 13C NMR and XPS techniques, and tested for Hg(II) removal in batch and continuous flow adsorption modes. Adsorption kinetics and equilibrium characteristics were validated using various theoretical models as well column adsorption models. Density Functional Theory (DFT) calculations performed to determine the complexation mechanism revealed the binding to be occurring predominantly in a 1:2 metal to ligand ratio with calculated binding affinity of −19.63 kcal.mol−1. RAdMer demonstrated fast uptake kinetics with over 60 % of total Hg(II) adsorption occurring within the first 30 min, while peak adsorption capacity was calculated at 174.3 mg.g−1. Moreover, RAdMer could be reused for >5 iterative cycles using an optimized HCl-Thiourea eluent system. Acting upon the UNOs SDG6 principle of providing “clean water and sanitation for all”, RAdMer efficiency was demonstrated with Hg(II) spiked ground water samples to successfully achieve the WHO permissible limit of <1.0 μg.L−1, and can therefore be potentially upscaled as an efficient methodology for remediation of Hg(II) ions in contaminated water.

Tailored rapid recognizer and adsorbent of ultra-trace Hg2+ with novel benzothiazol-group decorated covalent organic polymers

Porous materials for fast detection and adsorption of Hg2+, due to their good sensitivity and high adsorption capacity, were currently developed as one of the best ways to solve Hg2+ pollution. Inspired by the structure of small-molecule B-1 demonstrating specific recognition towards Hg2+, the covalent organic polymers (COPs) material TB-COP was constructed for a better demonstration of Hg2+ detection and adsorption. The results indicated that TB-COP could accomplish rapid detection of Hg2+ in about 90 s, with a good linearity (R2 = 0.9993) and high sensitivity (LOD = 36 nM). Because the electron transfer between N and S atoms in the benzothiazole moiety, the recognition of TB-COP towards Hg2+ was achieved, which was further proved by DFT calculation. Though the COPs possess its excellent fluorescence properties, the saturated adsorption capacity for Hg2+ by TB-COP reached 150.38 mg·g−1 at pH = 7. More importantly, TB-COP could be approximately recycled 5 times in the Hg2+ adsorption-desorption cycle at room temperature, providing a new strategy to solve Hg2+ pollution.

Efficient and selective capture of various mercury species from water using an exfoliated thiocellulose

The primary challenge in mercury (Hg) adsorbents for large-scale practical applications is to achieve the balance between performance and economy. This work attempts to address this issue by synthesizing an exfoliated thiocellulose (CU-SH) with high thiol density and hierarchical porosity using in-situ ligands grafting combined with chemical stripping. The prepared CU-SH shows remarkable physical stability and chemical resistance, and the micron sized fiber is conducive to separation from water. Hg(II) adsorption tests in water demonstrate that CU-SH has broad working pH range (1−12), fast kinetics (0.64 g/(mg‧min)), high adsorption capacity (652.9 mg/g), outstanding selectivity (Kd = 6.2 × 106 mg/L), and excellent reusability (R > 95 % after 20 cycles). Importantly, CU-SH exhibits good resistance to various coexisting ions and organic matter, and can efficiently remove Hg(II) from different real water. CU-SH can be made into a Point of Use (POU) device for continuous and efficient removal of Hg(II) from drinking water. 0.1 g CU-SH filled device can purify 3.2 L of Hg(II) (0.5 ppm) contaminated tap water before the breakthrough point of 2 ppb. Moreover, CU-SH also reveals good adsorption affinity for Hg-dissolved organic matter complexes (Hg(II)-DOM) in water, chloro(phenyl)mercury (PMC) in organic media and Hg0 vapor in air, suggesting the great practical potential of CU-SH.

Biomimetic mercury immobilization by selenium functionalized polyphenylene sulfide fabric

Highly efficient decontamination of elemental mercury (Hg0) remains an enormous challenge for public health and ecosystem protection. The artificial conversion of Hg0 into mercury chalcogenides could achieve Hg0 detoxification and close the global mercury cycle. Herein, taking inspiration from the bio-detoxification of mercury, in which selenium preferentially converts mercury from sulfoproteins to HgSe, we propose a biomimetic approach to enhance the conversion of Hg0 into mercury chalcogenides. In this proof-of-concept design, we use sulfur-rich polyphenylene sulfide (PPS) as the Hg0 transporter. The relatively stable, sulfur-linked aromatic rings result in weak adsorption of Hg0 on the PPS rather than the formation of metastable HgS. The weakly adsorbed mercury subsequently migrates to the adjacent selenium sites for permanent immobilization. The sulfur-selenium pair affords an unprecedented Hg0 adsorption capacity and uptake rate of 1621.9 mg g−1 and 1005.6 μg g−1 min−1, respectively, which are the highest recorded values among various benchmark materials. This work presents an intriguing concept for preparing Hg0 adsorbents and could pave the way for the biomimetic remediation of diverse pollutants.

Hg0 chemisorption of magnetic manganese cobalt nano ferrite from simulated flue gas

Mercury (Hg) emissions from the flue gas of coal-fired power plants constituted the primary source of atmospheric mercury pollution, manifesting in three distinct forms: granular mercury, oxidized mercury, and elemental mercury. This pollution posed significant threats to the ecological environment. There was an urgent demand for a more effective and economically viable mercury removal technology. The magnetic Mn0.5Co0.5Fe2O4 nanoparticles were prepared via a rapid combustion process. Their capacities for mercury adsorption and regeneration were scrutinized through a fixed-bed experimental system. The outcomes revealed that Mn0.5Co0.5Fe2O4 nanoparticles, prepared at a calcination temperature of 400 °C with 20 ml of anhydrous ethanol, exhibited the most proficient adsorption of Hg°. Under these specific conditions, the average particle size of the Mn0.5Co0.5Fe2O4 nanoparticles was approximately 26.8 nm. These nanoparticles demonstrated a superior adsorption capacity of 9.48 μg·g−1 for Hg° at an adsorption temperature of 30 °C under a space velocity of 2.4 × 104 h−1. Elevating the permeation temperature to 70 °C resulted in an impressive adsorption capacity for Hg°, reaching 560.59 μg·g−1. The Hg-TPD (Hg-Temperature Programmed Desorption) and XPS (X-ray photoelectron spectroscopy) analyses revealed the involvement of chemisorbed oxygen (Oads), Mn3+, and Fe3+ in the adsorbent, facilitating the oxidation of Hg° and generating HgO on the adsorbent surface. Following six cycles of adsorption and desorption, the adsorption capacity of Mn0.5Co0.5Fe2O4 nanoparticles for Hg° retained 71% of the first adsorption capacity, which indicated that magnetic Mn0.5Co0.5Fe2O4 nanoparticles held great promise as an adsorbent for mercury removal.

Adsorption isotherm model of Hg2+ with biochar from young coconut waste

Biochar is a carbon-rich byproduct of biomass pyrolysis that may be used to restrict Hg mobility in soil by utilizing amelioration technology. This study examines the ability of biochar from young coconut waste to adsorb Hg in solution. Isothermal adsorption of Hg by batch equilibrium method. The basic principle of Hg adsorption behavior with biochar from young coconut waste (B-YCW) processed through the Kon-Tiki method at a temperature of 682 0C, moisture of 81.27%, and a yield ratio of 20.87% at a size of 0.5 mm. The adsorption of Hg2+ on B-YCW increased with increasing Hg concentration and decreasing pH. The capacity and adsorption coefficient of Hg2+ by biochar from young coconut waste was 312.88 mg g−1 and 69.64 L Kg−1 at a pH of 1.55 and a concentration of 100 mg L−1 Hg2+. The adsorption isotherm of Hg2+ occurs in the Freundlich and Langmuir models (Freundlich > Langmuir). The Freundlich model (y = 1.0375x - 1.2523; R² = 1) with a value of n of 0.96 and KF of 17.78 (L mg−1)1/n, and the Langmuir II model (y = 17.126x - 0.0244; R² = 1), with average Qm was 18.57 mg g−1; KL 68.198 L mg−1 and RL 0.0054 (favorable) from the Langmuir isotherm model.

Preparation of amino-silane and thiosemicarbazide modified graphene oxide composite for high uptake adsorption of Hg(II) and Pb(II)

Seeking new modification adsorbents of graphene oxide with high uptake for some heavy metal ions is still the current hot-pot in adsorption technique. An amino-silanized and thiosemicarbazide modified graphene oxide adsorbent (TSCGO) was synthesized by silanized and crosslinking reaction of graphene oxide. The structure, morphology and thermostability of TSCGO were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and BET methods. The characteristic results verified that TSCGO was successfully acquired. The adsorption experiments of TSCGO for Hg2+, Pb2+, Cd2+, Zn2+ and Cu2+ showed that TSCGO owned higher uptake for Hg2+ and Pb2+ than the other ions. Main factors affecting adsorption of TSCGO for Hg2+ and Pb2+ were analyzed. The adsorption kinetics was studied using pseudo-first-order, pseudo-second-order, Elovich, Boyd, Weber and Morris models. The adsorption followed the pseudo-second-order kinetic and Weber and Morris intraparticle diffusion models. The adsorption isotherms were fitted using Langmuir, Freundlich, Temkin, Redlich-Peterson and Hill models. The best isothermal models should be Hill model for Hg2+ and Redlich-Peterson model for Pb2+. The maximum uptakes of Hg2+ and Pb2+ obtained from the Hill model were 933.2 and 890.4 mg g−1, respectively, which were much higher than those of some reported adsorbents from the Langmuir model. The adsorption of TSCGO for Hg2+ and Pb2+ was an endothermic and spontaneous chemical process. TSCGO could be effectively regenerated with EDTA. Hence, TSCGO would be a promising adsorbent for removal of Hg2+ and Pb2+ from wastewaters.

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).

Application Study on the Activated Coke for Mercury Adsorption in the Nonferrous Smelting Industry

The massive release of mercury undermines environmental sustainability, and with the official entry into force of the Minamata Convention, it is urgent to strengthen the control of mercury pollution. The effectiveness of activated coke (AC) in removing elemental mercury (Hg0) from high temperatures and sulfur nonferrous smelting flue gas before acid production was studied. Experimental results indicated that the optimal temperature for Hg0 adsorption by AC was 150 °C. And the adsorption of Hg0 by AC was predominantly attributed to physical adsorption. Flue gas components (SO2 and O2) impact studies indicated that O2 did not significantly affect Hg0 adsorption compared to pure N2. Conversely, SO2 suppressed the adsorption capacity, while the simultaneous presence of SO2 and O2 exhibited a synergistic effect in facilitating the removal of Hg0. The characterization results of X-ray photoelectron spectroscopy (XPS) indicated that the SO2 molecule favored to anchor at the Oα site, leading to the formation of SO3. This subsequently oxidized the mercury to HgSO4 instead of HgO. The study demonstrates that cheap and easily accessible AC applications in the adsorption of mercury technology may help improve the sustainability of the circular economy and positively impact various environmental aspects.

Co0 anchored on Co/N co-doped porous carbon material induces H migration to accelerate sulfite oxidation and Hg(ii) adsorption in flue gas desulfurization

The low oxidation rate of (NH4)2SO3 and the coexistence of Hg(ii) in desulfurization liquids restrict sulfur recovery for use as a high-value fertilizer.

Asynchronous variations of mercury accumulation since the last deglaciation in the eastern and western Nanling mountains in South China

There are differences in the response of long-term mercury (Hg) deposition to climate change, so it is necessary to clarify the influencing factors of Hg deposition in different locations. The Dahu and Daping Swamps are located in the eastern and western parts of the Nanling Mountains in South China, respectively. They are asynchronous variations of Hg deposition reflected by the two swamps since the last deglaciation. Based on the comprehensive comparative analysis of physical, chemical, and biological proxies, it is indicated that Hg deposition changes in the Dahu and Daping mainly record the changes in Hg content in the catchment input from organic matter. The differences in organic matter sources, core surrounding environment, Hg sources and atmospheric sedimentation contribution are reasons associated with the catchment environment for the observed differences in swamp Hg deposition and the response to climate. In cold/dry periods, Hg adsorption by terrestrial organic matter in Dahu Swamp were more significant, while in warm/humid periods, Hg adsorption by endogenous organic matter in Daping Swamp and wet deposition of nearby Hg sources, were the main climate-related processes for their asynchronous response. In addition, Dahu and Daping Swamps show similarities and differences in their Hg deposition variations. In both swamps, multi-millennial (∼1000−2200yr) and multi-centennial cycles (∼300–500yr) were observed and may be related to the harmonic period of the Earth's precession cycle and the solar activity cycle. This study helps to understand the differences in response between sedimentary Hg and climate, and to understand the regional and global proxies used to record climate and environmental changes.

In situ growth of Zr-based metal-organic frameworks on cellulose sponges for Hg2+ and methylene blue removal

Metal-organic frameworks (MOFs) are characterised by high porosity levels and controllable structures, making them ideal adsorbents for wastewater. However, obtaining substrate materials with mechanical stability, excellent pore accessibility, and good processability for compositing MOF crystal powders to adsorb multiple pollutants in complex aqueous environments is challenging. In this study, porous MOFs@ modified cellulose sponge (MCS) composites were fabricated using MCS as a scaffold to provide anchoring sites for the coordination of Zr4+ ions and further in situ synthesis of MOFs, namely UiO-66@MCS and UiO-66-NH2@MCS, which effectively removed heavy metal ions and organic dyes. MOFs@MCS composites exhibit excellent water and dimensional stability, maintaining the pore structure by ambient drying during reuse. Compared with UiO-66@MCS composite, UiO-66-NH2@MCS composite exhibited a higher adsorption capacity of 224.5 mg·g−1 for Hg2+ and 400.9 mg·g−1 for methylene blue (MB). The adsorption of Hg2+ onto the MOFs@MCS composites followed the Langmuir and pseudo-second-order models, whereas the Freundlich and pseudo-second-order models were more suitable for MB adsorption. Moreover, the MOFs@MCS composites exhibited excellent reusability and were selective for the removal of Hg2+. Overall, this approach effectively combines Zr-based MOFs with mechanically and dimensionally stable porous cellulose sponges, rendering the approach suitable for purifying complex wastewater.

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.