Removal Of Hg Research Articles

Novel optical optode for selective detection and removal of ultra-trace level of mercury ions in different environmental real samples

Owing to the high cost and unavailability of different analytical techniques, there is an urgent need to develop new techniques not only for detecting but also removing mercury ions in real samples. Thus, an optical chemical sensor based on the anchoring of phenanthraquinone monophenylthiosemicarbazone in a plasticized cellulose triacetate membrane was fabricated and applied to the recognition and removal of mercury ions from aqueous solutions. The synthesized optode was characterized by FT-IR, SEM, AFM, and thermal analysis. Several parameters, including the pH, temperature, contact time, washing solvent, and washing time, were optimized. Under optimal conditions, a promising optode film platform was utilized for sensing mercury ions, and the concentrations were calculated based on colorimetric analysis (Histogram, RGB) of digital images, visualization, and spectrophotometry. Also, an optical optode was used for complete adsorption of mercury ions from aqueous solutions. In addition, the regeneration of the synthesized optode was evaluated using 0.1 mol L− 1 nitric acid, which effectively removed all adsorbed mercury ions. The obtained data indicated good linearity in the sensing and adsorption of Hg2+ over a concentration range of 0.005–5000 µgL− 1 with a low limit of detection (LOD = 0.066 µgL− 1) and limit of quantification (LOQ, 0.22 µgL− 1). Furthermore, it showed good distinctions in the presence of coexisting ions, high stability (five months), good applicability, and reproducibility (RSD = 1.31%), making it a promising sensor for Hg2+ detection. On the other hand, the kinetic studies revealed that the pseudo-second-order was the best model for describing the adsorption behavior of mercury ions on the optode surface. Also, the thermodynamic parameters indicate spontaneous (ΔG0 < 0) and endothermic (ΔH0 < 0) reactions. Also, the maximum adsorption capacity was found to be 73.2 mg g− 1. Thus, the optodes were successfully applied for the detection and/or removal of Hg2+ in different real samples, including cucumber, fish, soil, and water samples, with excellent recoveries of 98.1–99.5%.

Melamine-Derived Mesoporous Carbon for Efficient and Selective Removal of Trace Hg(II) from Honeysuckle Decoction

Melamine-Derived Mesoporous Carbon for Efficient and Selective Removal of Trace Hg(II) from Honeysuckle Decoction

Practical Remediation of Hg-Contaminated Groundwater by MoS2: Batch and Column Tests

Trace mercury contamination in groundwater poses a serious threat to ecological systems and human health. The kinetics and isotherms of MoS2 (MS) for Hg removal were studied in batch tests under an unfavorable high salinity and low mercury environment. Flower-like MS with nanosheets can effectively remove Hg in the groundwater matrix, with a shorter equilibrium time (3 h), superior removal efficiency (94.26%), excellent distribution coefficient (5.69 × 106 mL g−1), and higher maximum adsorption capacity (926.10 ± 165.25 mg g−1). Furthermore, the Adams-Bohart model (R2 = 0.9052–0.9416) can accurately describe the dynamic interception process of the initial stage (≤40 PVs), and the Yan model (R2 = 0.9765−0.9941) depicts the whole process (140 PVs) of MS in a fixed column well. A higher dosage of m, but lower C0 and νp facilitate the interception efficiency in column tests. Based on the characterizations of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), which were used to simultaneously consider the species of Hg and the groundwater matrix, surface complexation, electrostatic attraction, ion exchange, and precipitation is a plausible interfacial adsorption mechanism of MS for mercury. The excellent performance demonstrates that MS with nanosheets is a promising candidate for the PRB remediation of trace Hg in saline groundwater.

Boosting SO2-tolerance of Mn-doped CeO2-ZrO2 for Hg catalytic oxidation via NaOH etching

Manganese-doped CeO2-ZrO2 solid solution (CZM) is a prominent sorbent for extracting Hg0 from flue gas, operating optimally around 150 °C, but impaired by SO2 exposure. In this research, we apply a hydrothermal method, employing a sodium hydroxide (NaOH) solution, to enhance CZM's SO2 resilience. The detrimental effect of SO2 on CZM primarily arises from the reduction of active oxygen species, diminishing Hg0 removal efficacy. After conducting a 10-hour test in the atmosphere comprising N2, 6 %O2, and 500ppmSO2, the mercury removal efficiency of the unmodified CZM significantly decreased from ∼99.5 % to ∼26.0 %. Conversely, the modified sorbents, designated as CZM-1M, demontrasted enhanced stability, with its mercury removal efficiency modestly reducing from ∼97 % to ∼60 %. We then conducted comprehensive characterizations of both sorbents to understand the mechanism behind this improved SO2 tolerance. In CZM-1M, we noted an enhanced conversion rate from Ce4+ to Ce3+, a key factor in boosting the production of active oxygen species, necessary for Hg0 oxidation. Additionally, the formation of SO3 - a result of the interaction between the abundant oxygen species and SO2 - emerged as a novel active site that further promoted Hg0 oxidation. This shift in active site offers a pathway for enhancing SO2 resistance in such material.

Integration of cadmium sulfide quantum dots with calcium alginate microbeads for dual-functional mercury (II) ion sensing and removal

Mercury contamination poses human health as well as ecosystem at significant risks. This study introduces a novel approach for the selective detection with removal of Hg2+ ions from aqueous media by developing a dual functional adsorbent that combines calcium alginate microbeads (FMCAB) with capped cadmium sulfide quantum dots (CdS QDs). CdS QDs immobilized on calcium alginate microbeads in magnetite facilitated efficient separation from the adsorption system under an external magnetic field. The fluorescence properties of CdS QDs remain largely unaffected before and after adsorption of Hg2+ ions on FMCAB, enabling selective monitoring of these ions. The adsorbent demonstrated a high adsorption capacity of around 160 μg/g and exhibited a quick and effective process. FMCAB evidenced selectivity over the other metal ions with limits of detection 12.9 μM. The results from this research pave the way for novel applications of FMCAB for heavy metal ions sensing probes and its removal.

Improved mercury removal performance and leaching stability of Fe/Br co-doped biochars synthesized through one-step pyrolysis

Mercury removal from oxyfuel combustion flue gas remains challenging owning to the shortage of cost-effective, sulfur- and water-resistant sorbents without secondary pollution. In this study, Fe/Br co-doped biochars synthesized via one-step pyrolysis of iron-loaded biomass and brominated flame retarded plastic were adopted for Hg0 immobilization from oxyfuel combustion flue gas. After iron doping, the Br content of Fe/Br co-doped biochars was sharply improved. Both highly developed pore structure and abundant active components were acquired because of the catalytic effect of iron. The Fe/Br co-doped biochars presented superior Hg0 removal performance than Br-doped biochars across a broad temperature interval from 25 °C to 240 °C. The optimized pyrolysis temperature and wood /Fe salt mass ratio for the synthesis of Fe/Br co-doped biochars were respectively 500 °C and 8:1. The Fe/Br co-doped biochars exhibited excellent resistance to H2O and SO2. The Hg0 removal mechanism was revealed, where Fe3+, CBr and chemisorbed oxygen served as active components for Hg0 chemisorption. The Hg/Br leaching behavior of Fe/Br co-doped biochars was further compared with Br-doped biochars and traditional brominated activated carbon. Iron doping significantly enhanced the stability of Hg/Br in Fe/Br co-doped biochars because partial inorganic bromine was converted into organic bromine during co-pyrolysis.

Online in-situ modification of biochar for the efficient removal of elemental mercury and co-benefit of SO2/NO removal

In this study, non-thermal plasma discharge was proposed for online in-situ modification of biochar injected into coal-biomass co-combustion flue gas, aiming to achieve the combined removal of elemental mercury (Hg0), NO, and SO2 from flue gas. After plasma discharge, the pore structure of biochar was slightly improved whereas the surface morphology of biochar was almost unchanged. After plasma discharge under O2, SO2, and HCl atmospheres, the oxygen, sulfur, and chlorine contents of biochar were obviously increased. More exactly, additional functional groups were formed on the modified biochar surface, such as CO, C(O)OC, CS, and CCl. Compared with raw biochar, the biochar modified under HCl, SO2, O2, H2O and CO2 atmospheres exhibited higher Hg0 removal efficiency, and longer modification time resulted in better Hg0 removal performance. The optimal modification atmosphere and reaction temperature were the simulated flue gas (SO2 + HCl + CO2 + O2 + H2O + NO + N2) and 20 ℃-100 ℃, respectively. The modified biochar exhibited excellent resistance to SO2 and H2O. The addition of HCl, CO2, NO, and O2 contributed to Hg0 removal. The removal efficiency of NO and SO2 attained a maximum of 100 %. The Hg0 removal mechanism was further revealed, where CO, C(O)OC, CS, and CCl served as active components.

Experimental and DFT studies of mercury adsorption and oxidation on CuCo2O4(110) surface

Elemental mercury (Hg0) is a typical toxic pollutant in flue gas from coal-fired power plants. The specific role of oxygen transfer on Hg0 oxidation over CuCo2O4 oxygen carrier and the involved reaction mechanisms were systematically studied by experimental and theoretical methods. In this study, the CuCo2O4 oxygen carrier with spinel-structure was prepared with salt-assisted combustion method. To reduce the grain size and increase the specific surface area of the oxygen carrier, the optimal KCl: CuCo2O4 ratio of 1:1 was obtained. Oxygen uncoupling ability of CuCo2O4 oxygen carrier was very strong, and the oxygen-releasing performance was slightly decreased after ten cyclic processes. Simulation based on density functional theory (DFT) shows that CuCo2O4 has relative low oxygen vacancy formation energy and oxygen transport energy barrier, and the oxygen vacancy is the preferred O2 adsorption site. Hg0 removal experiments show that CuCo2O4 has a strong ability to remove Hg0. The proportion of Hg2+ increases with the temperature, and the proportion of HgP decreases accordingly. Simulation shows that the 3-Co site on the surface of the CuCo2O4 oxygen carrier is the optimum Hg0 adsorption site. CuCo2O4 is found as a strong oxygen-releasing oxygen carrier, which can effectively promote the oxidation of Hg0.

Synergetic effect of pyrrhotite and zero-valent iron on Hg(Ⅱ) removal in constructed wetland: Mechanisms of electron transfer and microbial reaction

Effective removal of mercury (Hg) from wastewater is significant due to its high toxicity, especially methylmercury (MeHg). Reducing of Hg(II) to Hg(0) in constructed wetlands (CWs) using iron-based materials is an effective strategy for preventing the formation of MeHg. However, the surface passivation of zero-valent iron (ZVI) limits its application. Herein, synergetic ZVI and pyrrhotite were utilized to enhance Hg removal in CWs. Results indicated that the removal of total Hg, dissolved Hg, and particulate Hg in CWs with ZVI and pyrrhotite were improved by 21.68 ± 0.76 %, 13.02 ± 0.88 %, and 22.27 ± 0.76 % compared to that with single ZVI or pyrrhotite. Pyrrhotite increased the surface corrosion of ZVI, thereby facilitating the process of iron reduction. The redox of iron promoted the generation of EPS, which could provide electrons for Hg(II) reduction. The sulfur also participates in electron transfer by driving the methylation of Hg and provides sulfides to form FeS-Hg complexes and HgS precipitation. The abundance of key enzymes that involved in iron reduction and Hg transformation was enhanced with the addition of ZVI and pyrrhotite. The synergetic of pyrrhotite and ZVI enhances the removal of Hg in CW, offering a promising technology for high-efficiency treatment of Hg.

Mechanistic investigations into the removal of Hg0 over Pt-based sorbents by warm syngas cleanup

Commercial sorbents for Hg0 removal from syngas operate at low temperatures (<120 ºC), which impacts the thermal efficiency of integrated gasification and chemical production processes. For the first time, supported Pt-based sorbents with different supports, viz., Pt/SBA-15, Pt/S-40, Pt/ZrO2, Pt/CeO2, and Pt/TiO2 are synthesized for high-temperature (≥200 ºC) Hg0 removal. Pt/SBA-15 shows the highest cumulative Hg0 removal efficiency (>99%) at 270 ºC in N2, which is retained for much higher durations (>20h) compared to the best-reported Pd-based and metal oxide sorbents. Besides amalgam formation, Hg0 removal on Pt/ZrO2 and Pt/CeO2 occurs via oxidation at high temperatures (> 270 ºC), which explains the reduced negative effect of high temperature over these sorbents. In contrast to other supports, the removal efficiency over Pt/SBA-15 is above 99% even in the presence of H2, H2O, and CO2, and is attributed to the hydrophobic mesoporous silica support. DRIFTS studies indicate CO adsorption on the active Pt sites over all sorbents. Based on the inferences obtained, a kinetic model is developed and integrated into a reactor-scale model which effectively simulates the spatio-temporal features of Hg0 sorption over Pt/SBA-15.

Fluorescent cellulose hydrogels based on corn stalk of double sulfhydryl functional group modification for Hg(II) removal and detection

Ions of mercury, one of the most hazardous heavy metals in nature, pose serious risks to the environment and human health. Blue sulfur-doped carbon dots (SCDs) from corn stalks were utilized as material. The SCDs were incorporated into a carboxylated hydrogel modified with sulfur, and a compound gel (SCDs–KTOCS gel) was successfully fabricated for simultaneous fluorescence detection and Hg(II) adsorption. This enabled the effective identification and removal of Hg(II) from contaminated water. The chemical content, fluorescence properties, and adsorption behaviors of the SCDs–KTOCS–gels were analyzed. The results demonstrate that the SCDs–KTOCS–gels exhibited effective Hg(II) adsorption (193 mg/g) and an extensive linear spectrum for Hg(II) fluorescence emission (150–500 mg/L; detection limit = 1.5668 mg/L). The adsorption values fit well with the Temkin models and pseudo-second-order kinetics. Additionally, Hg(II) detection and adsorption in the SCDs–KTOCS–gels were examined. By exchanging the existing probe for a suitable one that fits various relevant applications, this study suggests an environmentally friendly and sustainable method of producing materials for removing and detecting Hg(II) and constructing a fluorescence hydrogel for the detection and adsorption of different metals.

Synergistic effects of multi-walled carbon nanotubes and Mn0.4Cu0.6Fe2O4 on mercury removal with high efficiency and sulfur resistance

Although ferrite-based adsorbents are the potential mercury removal materials for the high thermal stability, they usually suffer from a low efficiency in flue gas environment, especially under SO2 condition. In the present paper, the multi-walled carbon nanotubes (MWCNTs) are utilized to improve the adsorption capacity of the Mn0.4Cu0.6Fe2O4 adsorbents as well as inhibit the influence of flue gas composition. The influences of temperature, adsorbent type and the flue gas composition on Hg0 removal efficiency are evaluated by experiments. The physical adsorption property of MWCNTs provides a platform for Hg0 oxidation by Mn0.4Cu0.6Fe2O4. The synergistic effect between MWCNTs and Mn0.4Cu0.6Fe2O4 enhances the mercury removal efficiency as well we the sulfur resistance. The results find that the adsorbent of Mn0.4Cu0.6Fe2O4 containing 14 % MWCNTs has a high mercury removal efficiency of 95.6 % at 120 °C even under 1000 ppm SO2 concentration. The kinetic behaviors of adsorbent adsorption are analyzed by theoretical models. The mechanisms of porous carbon-containing modifier to improve the mercury removal performance of Mn0.4Cu0.6Fe2O4 are explored carefully. The present ferrite-based adsorbent exhibits promising prospects for the practical industrial applications of the low temperature mercury removal from coal-fired flue gas.

Multifunctional Ni-MOF (3D) with N-rich structures for self-generated reactive oxygen species and enhanced electron transfer for synergistic degradation of organic pollutants and removal of Hg(II)

Metal–organic frameworks (MOFs) can effectively adsorb or remove pollutants; however, their application to water treatment remains limited. Herein, we report the preparation of two novel multifunctional Ni-based MOFs (2D and 3D), via the design and synthesis of multi-nitrogen-like ligands. The introduction of polynitrogen-containing organic macrocyclic ligands improved the structure and electron transfer capability of the MOF, and its adsorption and synergistic degradation performance were further enhanced via coordination with Ni. The 3D MOF (MOF-2) had a maximum adsorption capacity of 948 mg/g for Hg(II). The adsorption and synergistic degradation capacities of MOF-2 for tetracycline (TC, 18 mg/L), 17α-ethynylestradiol (EE2, 3 mg/L), rhodamine B (RhB, 6 mg/L), and methylene blue (MB, 6 mg/L) were 98.54%, 97.32%, 91.08%, and 85.02%, respectively. The addition of KHSO5 (PMS, 0.01 g/L) resulted in nearly 100% degradation of the organic pollutants within 100 min. MOF-2 alone simultaneously degraded more than 90.73% (360 min Hg(II) adsorption equilibrium) of five pollutants in ultrapure water, tap water, and lake water. MOF-2+PMS degraded 99.13% of TC within 60 min, and the remaining four pollutants were completely adsorbed and degraded. DFT calculations and experiments indicated that the efficient adsorption of Hg(II) and efficient degradation of the organic pollutants by MOF-2 were mainly attributed to its abundant N atoms, which provide active sites for Hg(II) capture; and the structure itself has strong electron transfer ability and self-produced reactive oxygen species (ROS), which can effectively degrade organic pollutants and activate PMS to enhance the degradation efficiency. MOF-2 also exhibited 100% antibacterial activity against Escherichia coli and Staphylococcus aureus. This work provides a basis for designing synthesis pathways for MOFs and elucidates the electron-transfer mechanism underlying the enhanced synergistic removal of complex pollutants from water.

Enhancing the activity and sulfur resistance of CuFeAlOx catalyst via the structure effect for the simultaneous removal of Hg0 and NO at wide temperature

The efficient strategy for improving SO2 resistance and catalytic activity is structural modification. Herein, the CuFeAlOx catalysts with different structures, including one-dimensionally disordered mesoporous nanoparticles structure (CuFeAl-N), one-dimensionally ordered mesoporous nanoparticles structure (CuFeAl-C), three-dimensionally ordered porous honeycomb-like structure (CuFeAl-P) and three-dimensionally ordered porous flower-like structures (CuFeAl-CP), were synthesized via a template method to investigate structure effect on activity and sulfur resistance of the catalyst for simultaneously removing NO and Hg0 at wide temperature. The results showed that the various surface characteristics resulted in distinct behaviours with regards to SO2 tolerance. CuFeAl-CP and CuFeAl-C exhibits excellent SO2 resistance, but CuFeAl-N catalyst presents poor SO2 resistance. The CuFeAl-CP with the flower-like structure possesses large specific surface area, which can expose more active sites and exhibited highly dispersed active component. More importantly, it reacts with SO2 to generate reactive sulfate providing additional acid sites, which significantly promotes high-temperature catalytic performance. One-dimensionally ordered mesoporous and three-dimensionally ordered porous effectively facilitates mass transfer of reactants and ammonium sulphate decomposition, thereby inhibiting surface sulfation and ammonium sulfate species deposition. This work lays the foundation for developing highly efficient SCR catalysts that are tolerant to SO2.

Synthesis and characterization of chitosan Schiff base grafted with formaldehyde and aminoethanol: As an effective adsorbent for removal of Pb(II), Hg(II), and Cu(II) ions from aqueous media

Grafted chitosan materials show the characteristics of high stability, easy separation and recovery, and good heavy metal adsorption capacity, and have received much attention in the adsorption process. Therefore, in this work, novel grafted chitosan-based adsorbent CS-EHBSB@F-AE was prepared by a one-pot reaction of chitosan (CS), 3-ethoxy-4-hydroxybenzaldehyde (EHB), formaldehyde (F) and aminoethanol (F). The microstructure and morphology of the as-prepared composite CS-EHBSB@F-AE were characterized by FT-IR, TGA, DSC, FE-SEM, and BET analyses. The adsorption performance of the as-prepared CS-EHBSB@F-AE composite on Pb(II), Hg(II), and Cu(II) ions from aqueous was investigated using batch experiment and the effects of the initial pH of the solution, contact time, and initial metal ions concentration and temperature on the adsorption efficiency were investigated and discussed. At the best conditions, CS-EHBSB@F-AE exhibited remarkable adsorption capacity of 246.7 mg/g, 203.9 mg/g, and 234.4 mg/g in absorbing Pb(II), Hg(II), and Cu(II), respectively. The adsorption equilibrium and the kinetic studies confirmed that the ions adsorption process fits well with the Langmuir isotherm and pseudo-second-order (PSO) models. Additionally, the adsorption efficiency of Pb(II), Hg(II), and Cu(II) metal ions by the composite CS-EHBSB@F-AE was reduced by increasing the temperature from 298 K to 318 K. In addition, after the sixth ads/des cycles, the as-prepared adsorbent still exhibited high removal efficiency with a decrease in adsorption efficiency of Pb(II) (5.53 %), Hg(II) (15.43 %) and Cu(II) (8.27 %). Finally, we proposed that the ions adsorption by CS-EHBSB@F-AE has happened using the coordination of active groups containing nitrogen and oxygen atoms on the surface of the adsorbent with the Pb(II), Hg(II), and Cu(II) metal ions.

One-step utilizing of waste acidic Cu-containing etching solution to prepare hierarchical Cu-ZSM-5 for efficient flue gas Hg0 removal

Developing mercury adsorbents could mitigate environmental risk of mercury pollution. In this study, waste acidic Cu-containing etching solution from PCBs etching industry was utilized for the simultaneous porosity etching and Cu/Cl sites loading to prepare WA-ZSM for Hg0 removal via a one-step method. WA-ZSM synthesized with different waste acid concentrations exhibited over 94 % Hg0 removal efficiency within 60 min. The long-term stability of 5WA-ZSM under 110 μg/m3 Hg0 within 300 min was higher than 90 %. The dealumination process significantly affected the formation of micropores and Cu loading into the pore structure. The EFAl-Al3+ and “Si-O-Cu” structures formed by dealumination greatly enhanced the strong acid sites and the Cu sites improved the medium strong acidity. Isolated [Cu-OH]+ sites and [Cu–O-Cu]2+ sites are the main active sites in Hg0 removal. This method successfully synthesizes low-cost, high-efficiency Hg0 adsorbents using hazardous wastes, presenting a significant advancement in sustainable waste utilization and mercury pollution control.

Mechanisms of mercury removal from water with highly efficient MXene and silver-modified polyethyleneimine cryogel composite filters

Safeguarding aquatic ecosystems and human health requires effective methods for removing pollutants. Mercury (Hg) is a very toxic pollutant with a global presence and is highly mobile and persistent. Here, innovative materials were prepared for separating Hg(II) from water, and the mechanisms underlying the efficient uptake of Hg species have been investigated. The sorbents include silver (Ag) nanoparticles and multilayered Ti3C2Tx MXene, both incorporated into the structure of a three-dimensional polyethyleneimine porous cryogel (PEI) that acts as a scaffold holding and exposing nano active sites involved in the removal of Hg. Specifically, Ag particles were deposited onto MXene phases, and the resulting composite was embedded in the macroporous PEI polymer (PEI/MXene@Ag cryogel). The composite has beneficial properties regarding Hg removal: 99% of Hg was separated from waste within 24 h in batch studies. The maximum removal capacity of Hg reached 875 mg/g from HgCl2, and 761 mg/g and 1280 mg/g from Hg(OAc)2 and Hg(NO3)2 salts by PEI/MXene@Ag. The Hg uptake stems from the composite’s relatively large specific surface area, layered porous channels, and highly dispersed Ag nanoparticles in the multilayered Ti3C2Tx MXene. The matrix in the water samples that were treated with the composite did not hinder the uptake of Hg by PEI/MXene@Ag. The high effectiveness achieved for the removal of Hg, combined with rapid adsorption kinetics, high efficiency, and selectivity, positions it as an efficient solution. Future work should address upscaling its preparation for increasing readiness towards mitigating Hg in surface water.

A Novel Composite Material UiO-66-Br@MBC for Mercury Removal from Flue Gas: Preparation and Mechanism.

To reduce the mercury content in flue gas from coal-fired power plants and to obtain high-performance, low-cost mercury adsorbents, a novel composite material was prepared by structural design through the in situ growth method. Functionalization treatments such as the modification of functional groups and multilayer loading of polymetallic were conducted. These materials include the MOF material UiO-66 and modified biochar doped with Fe/Ce polymetallic, both of which contain unsaturated metal centrals and oxygen-containing functional groups. On the basis of obtaining the effects of adsorption temperature and composite ratio on the Hg0 removal characteristics, coupling and synergistic mechanisms between the various types of active centers included were investigated by using a variety of characterization and analysis tools. The active adsorption sites and oxidation sites were identified during this process, and the constitutive relationship between the physicochemical properties and the performance of Hg0 removal was established. The temperature-programmed desorption technique, Grand Canonical Monte Carlo simulation, and adsorption kinetic model were employed to reveal the mechanism of Hg0 removal. The results showed that the UiO-66-Br@MBC composite adsorbent possessed an excellent Hg0 removal performance at adsorption temperatures ranging from 50 to 250 °C, and targeted construction of adsorption and oxidation sites while maintaining thermal stability. The Hg0 removal by the composites is the result of both adsorption and oxidation. The micropores and small pore mesopores in the samples provide physical adsorption sites. The modified biochar acts as a carrier to facilitate the full exposure of the central metal zirconium ions, the formation of more active sites, and the process of electron transfer. The doping modification of the Br element can enhance the overall redox ability of the sample, and the introduced Fe and Ce polymetallic ions can work in concert to promote the oxidation process of Hg0. The excellent regulation of the ratio between adsorption and oxidation sites on the surface of the composite material finally led to a significant boost in the samples' capacity to remove Hg0.

Tb3+-functionalized covalent organic framework for simultaneous detection and removal of Hg2+

Hg2+ is a common heavy metal ion contaminant in the environment, as well as one of the most hazardous metal ions on the earth, posing a serious threat to the ecosystem and human health. As a result, it is vital to develop materials that can detect or remove Hg2+. In this work, we fabricated a Tb3+-functionalized covalent organic framework (Tb@COF) platform capable of both detecting and removing Hg2+ for the fluorescence enhancement of Tb3+ and the presence of thiol groups in COF. Tb@COF exhibited good selectivity and sensitivity during the detection of Hg2+, with a linear range of 0.2–50 μmol/L(R2 = 0.9985) and a limit of detection (LOD) of 0.076 μmol/L. We employed Tb@COF to detect Hg2+ in lake water with excellent results, and we developed a smartphone-assisted Tb@COF-based agar slice detection platform that could identify Hg2+ both visually and quantitatively. We discussed the sensing mechanism of Tb@COF for Hg2+. Furthermore, we found that Tb@COF displayed good removal efficiency of Hg2+. The adsorption of Hg2+ by Tb@COF followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. Our research provided a novel method for simultaneously detecting and eliminating Hg2+ from the environment.

Use of Activated and Modified Pumice Stone for Removal of Mercury (II) and Arsenic (III) Ions From Aqueous Solution

Removal of Hg (II) and As (III) ions from aqueous solutions using activated and modified pumice stone were investigated. The pH, temperature, initial metal ion concentration which are very important for removal studies, were investigated by batch method. The experiments demonstrated that the equilibrium adsorption data fit the Freundlich isotherm model well for Hg (II) and As (III) ions. The negative value of ΔH° = -199.92 kJ mol-1 and -78,15 kJ mol-1 for mercury (II) and arsenic (III) ions indicates that the adsorption process is exothermic. ΔS° were calculated as -267.85 J K-1 mol-1 for As (III) ions and the positive value of ΔS° = 0.69 kJ K-1 mol-1 for Hg (II) ions. The negative value of ΔG°=-405.14 kJ mol-1 for Hg (II) ions and -1.67 kJ mol-1 for As (III) ions indicates that adsorption is voluntary. EDTA has been found to be a good desorbent in desorption studies to recover arsenic and Hg ions. The experiments show that pumice stone can be used for Hg (II) and As (III) removal in aqueous solution.