Remove elemental mercury from simulated flue gas by CeO2-modified MnOx/HZSM-5 adsorbent.

In this study, we synthesized a Ce-modified Mn/HZSM-5 adsorbent via the ultrasound-assisted impregnation for Hg0 capture. Given the addition of 15% CeO2, ~ 100% Hg0 efficiency was reached at 200 °C, suggesting its promotional effect on Hg0 removal. The doped Ce introduced additional chemisorbed oxygen species onto the adsorbent surfaces, which facilitated the oxidation of Hg0 to HgO. Even though adding CeO2 led to a weakened adsorbent acidity, yet it appeared that this negative affect could be completely overcome by the enhanced oxidative ability, which finally endowed Ce-modified Mn/HZSM-5 with a satisfactory Hg0 removal performance within the whole investigated temperature range. During the Hg0 capture process, chemisorption was predominant with Mn4+operating as the main active site for oxidizing Hg0 to Hg2+. Finally, the 15Ce-Mn/HZSM-5 adsorbent exhibited good recyclability and stability. However, its tolerance to H2O and SO2 appeared relatively weak, suggesting that some modification should be conducted to improve its practicality.

Cascade signal amplification using Hg2+-induced oxidation of silver nanoparticles and cation exchange reaction for ICP-MS bioassay.

Combining the Hg2+-induced oxidization of silver nanoparticles with the cation exchange reaction between Ag+ and CuS nanoparticles for cascade signal amplification, a sensitive, universal and label-free ICP-MS bioassay for nucleic acids and proteins was developed. By replacing the loop sequence of the T-Hg-T hairpin structure with specific sequences or aptamers to different biomarkers, it has great promise for the early detection of biomarkers potentially for diagnosis of cancerous diseases.

Encapsulation of activated carbon into calcium alginate microspheres toward granular-activated carbon adsorbents for elemental mercury capture from natural gas.

Activated carbon (AC) is an effective adsorbent for removing environmental pollutants. However, the traditional powder form of AC shows difficulty in handling during application which widely limits its utilization on the industrial scale. Herein, to avoid such limitation, traditional AC powder was encapsulated into calcium alginate (CA) microspheres. Calcium alginate/activated carbon (CAA) composite microspheres were prepared via cross-linking of sodium alginate/activated carbon composite solutions in a calcium chloride solution. Furthermore, in order to boost adsorption affinity of CAA composite microspheres toward elemental mercury (Hg°), ammonium iodide (NH4I)-treated calcium alginate/activated carbon (NCA) composite microspheres were obtained by a simple impregnation method using NH4I treatment. The morphological, structural, and textural properties of the microspheres were characterized and their Hg° adsorptive capacity was tested at different temperatures. Interestingly, the maximum adsorption capacity of NCA adsorbent composite microspheres was determined as 36,056.5 µg/g at a flow rate of 250 mL/min, temperature of 25 °C, and 500 µg/Nm3 of Hg° initial concentration. The Gibbs free energy (ΔG°) for NCA adsorbent composite microspheres varied from - 8.59 to - 10.54 kJ/mol indicating a spontaneous adsorption process with an exothermic nature. The experimental Hg° breakthrough curve correlated well with Yoon‒Nelson and Thomas models. The breakthrough time (tb) and equilibrium time (te) were found to be 7.5 days and 23 days, respectively. Collectively, the findings of this work indicate a good feasibility of using NCA composite microspheres as potential adsorbents for removing Hg° from natural gas.

Manipulating the monomer-dimer transformation of a heptamethine cyanine ligand: near infrared chromogenic recognition of biothiols.

A novel absorbance recovery method has been developed for the determination of biothiols with a near-infrared reagent. This method employs a two-reagent system composed of cation heptamethine cyanine (CyL) and Hg2+. The absorbance of CyL, with a maximum peak at 760 nm, was decreased due to addition of Hg2+, but recovered when biothiols were added. Under optimal conditions, the reciprocal extent of recovered absorbance was proportional to the concentration of biothiols. The calibration curves are linear over the range of (0.3-7.0) × 10-6 M for cysteine, (1.0-10.0) × 10-6 M for homocysteine and (1.0-9.0) × 10-6 M for glutathione. Because of the specific affinity of Hg2+for biothiols, there is minimal interference from other amino acids. This method has been successfully applied to the determination of homocysteine in human urine samples with satisfactory results.

Two Birds with One Stone: Copper-Based Adsorbents Used for Photocatalytic Oxidation of Hg0 (Gas) after Removal of PH3.

CuX/TiO2 adsorbents with CuO as the active component were prepared via a simple impregnation method for efficient purification of phosphine (PH3) under the conditions of low temperatures (90 °C) and low oxygen concentration (1%). The PH3 breakthrough capacity of optimal adsorbent (Cu30/TiO2) is 136.2 mg(PH3)·gsorbent-1, and the excellent dephosphorization performance is mainly attributed to its abundant sur face-active oxygen and alkaline sites, large specific surface area, and strong interaction between CuO and the support TiO2. Surprisingly, CuO is converted to Cu3P after the dephosphorization by CuX/TiO2. Since Cu3P is a P-type semiconductor with high added value, the deactivated adsorbent (Cu3P/TiO2) is an efficient heterostructure photocatalyst for photocatalytic removal of Hg0 (gas) with the Hg0 removal performance of 92.64% under visible light. This study provides a feasible strategy for the efficient removal and resource conversion of PH3 under low-temperature conditions and the alleviation of the environmental risk of secondary pollution.

Selective Chelation of the Exotic Meitner-Auger Emitter Mercury-197 m/g with Sulfur-Rich Macrocyclic Ligands: Towards the Future of Theranostic Radiopharmaceuticals.

Mercury-197 m/g are a promising pair of radioactive isomers for incorporation into a theranostic as they can be used as a diagnostic agent using SPECT imaging and a therapeutic via Meitner-Auger electron emissions. However, the current absence of ligands able to stably coordinate 197m/g Hg to a tumour-targeting vector precludes their use in vivo. To address this, we report herein a series of sulfur-rich chelators capable of incorporating 197m/g Hg into a radiopharmaceutical. 1,4,7,10-Tetrathia-13-azacyclopentadecane (NS4 ) and its derivatives, (2-(1,4,7,10-tetrathia-13-azacyclopentadecan-13-yl)acetic acid (NS4 -CA) and N-benzyl-2-(1,4,7,10-tetrathia-13-azacyclopentadecan-13-yl)acetamide (NS4 -BA), were designed, synthesized and analyzed for their ability to coordinate Hg2+ through a combination of theoretical (DFT) and experimental coordination chemistry studies (NMR and mass spectrometry) as well as 197m/g Hg radiolabeling studies and in vitro stability assays. The development of stable ligands for 197m/g Hg reported herein is extremely impactful as it would enable their use for in vivo imaging and therapy, leading to personalized treatments for cancer.

Zinc detection in oil-polluted marine environment by stripping voltammetry with mercury-free nanoporous gold electrode.

Detection of Zn(II) in oil-polluted seawater via square-wave anodic stripping voltammetry (SW-ASV) utilizing thin gold electrodes sputtered onto nanoporous poly(acrylic acid)-grafted-poly(vinylidene difluoride) (PAA-g-PVDF) membrane is herein reported. Prior to SW-ASV, PAA grafted nanopores demonstrated to efficiently trap Zn(II) ions at open circuit. This passive adsorption followed a Langmuir law. An affinity constant of 1.41 L [Formula: see text]mol[Formula: see text] and a maximum Zn(II) adsorbed mass q[Formula: see text] of 1.21 [Formula: see text]mol g[Formula: see text] were found. Applied SW-ASV protocol implied an accumulation step (- 1.2 V for 120 s) followed by a stripping step (- 1.2 to 1 V; 25 Hz; step: 4 mV; amplitude: 25 mV; acetate buffer (pH 5.5)). It revealed a Zn redox potential at - 0.8 V (Ag/AgCl pseudo-reference). Multiple measurements in synthetic waters close to the composition of production waters exhibited a decreasing precision with the number of readings R (1.65[Formula: see text] (R = 2) and 6.56[Formula: see text] (R = 3)). These membrane-electrodes should be used as disposable. The intra-batch mean precision was 14[Formula: see text] (n = 3) while inter-batches precision was 20[Formula: see text] (n = 15). Linear and linear-log calibrations allow exploitation of Zn(II) concentrations ranging from 10 to 500 [Formula: see text]g L[Formula: see text] and 100 to 1000 [Formula: see text]g L[Formula: see text] respectively. The LOD was 4.2 [Formula: see text]g L[Formula: see text] (3S/N). Thanks to obtained calibration, a detected Zn(II) content of 1 ppm in a raw production water from North Sea oil platform was determined.

Design and fabrication of chitosan cross-linked bismuth sulfide nanoparticles for sequestration of mercury in river water samples.

The existence of heavy metals in ecological systems poses great threats to living organisms due to their toxicant and bio-accumulating properties. Mercury is a known toxicant with notable malignant impacts. It has long been known to cause toxic threats to the health of living organisms since the break out of Minamata disease. The turbulent expulsion of mercury-based pollutants from the industrial sector, requires a proper solution. Many attempts have been made to design a greener and more efficient route for a satisfactory removal of mercury. In the current study, bismuth sulfide nanoparticles (BiSNPs) have been synthesized via the co-precipitation method. The BiSNPs were supported with crosslinked chitosan to enhance their sorption capacity and avoid leaching. The average size of the BiSNPs was 42 nm based on SEM micrographs. The SEM analysis of the bismuth sulfide chitosan-crosslinked beads (BiS-CB) showed that the beads possessed a spherical and smooth morphology with a size of 1.02 mm. The FTIR analysis showed that the beads possessed the characteristics bands of imine groups of chitosan, bismuth, sulfur, and glycosidic linkages present in the molecules. The XRD analysis confirmed the phase crystallinity of the BiS-CB with an average crystallite size of 11 nm. The BiS-CB was employed for the sorption of mercury from water samples. The maximum sorption capacity of 65.51 mg/g was achieved at optimized conditions of pH 5, concentration 80 ppm, in 45 min at 30 °C. The mechanism studied for mercury removal showed that sorption followed the complexation mechanism according to the SHAB concept. In conclusion, the results showed that the BiS-CB sorbent exhibited an excellent sorption capacity to remove mercury.

Resource utilization of pig hair to prepare low-cost adsorbents with high density of sulfhydryl for enhanced and trace level removal of aqueous Hg(II).

Pig hair (PH), a keratinous waste, was modified by ammonium thioglycolate in a ball milling to promote its performance of Hg(II) sequestration. The ball milling broke the hydrophobic cuticle sheath and enhanced the reduction of disulfide bond, which increased the sulfydryl content of the modified PH (BTPH) from 0.07 to 11.05 µmol/g. BTPH exhibited a significantly higher capture capacity of Hg(II) (415.4 mg/g) than PH (3.1 mg/g), as well as the commercial activated carbon (219.7 mg/g), and persisted its performance over a wide range of solution pH. Meanwhile, BTPH with a distribution coefficient of 5.703 × 105 mL/g could selectively capture Hg(II) from the water with the coexisting metal ions such as Mg(II), Cd(II) and Pb(II). Moreover, the low-cost BTPH could reduce the Hg(II) from 1.0 mg/L to well below the limit of drinkable water (2 µg/L) in real-world samples. Density functional theory (DFT) calculations and state-of-the-art characterizations illustrated that the binding of Hg(II) to sulfydryl groups was the main adsorption mechanism. Notably, BTPH decreased the mercury content of water spinaches from 24.1 to 0.50 mg/kg and thereby significantly reduced the phytotoxicity of Hg(II). This work therefore provides a sustainable way to utilize keratinous wastes for the remediation of aqueous Hg(II).

Particle-Bound Hg(II) is Available for Microbial Uptake as Revealed by a Whole-Cell Biosensor.

Particle-bound mercury (HgP), ubiquitously present in aquatic environments, can be methylated into highly toxic methylmercury, but it remains challenging to assess its bioavailability. In this study, we developed anEscherichia coli-based whole-cell biosensor to probe the microbial uptake of inorganic Hg(II) and assess the bioavailability of HgP sorbed on natural and model particles. This biosensor can quantitatively distinguish the contribution of dissolved Hg(II) and HgP to intracellular Hg. Results showed that the microbial uptake of HgP was ubiquitous in the environment, as evidenced by the bioavailability of sorbed-Hg(II) onto particulate matter and model particles (Fe2O3, Fe3O4, Al2O3, and SiO2). In both oxic and anoxic environments, HgP was an important Hg(II) source for microbial uptake, with enhanced bioavailability under anoxic conditions. The composition of particles significantly affected the microbial uptake of HgP, with higher bioavailability being observed for Fe2O3 and lower for Al2O3 particles. The bioavailability of HgP varied also with the size of particles. In addition, coating with humic substances and model organic compound (cysteine) on Fe2O3 particles decreased the bioavailability of HgP. Overall, our findings highlight the role of HgP in Hg biogeochemical cycling and shed light on the enhanced Hg-methylation in settling particles and sediments in aquatic environments.

Mercury Reduction, Uptake, and Species Transformation by Freshwater Alga Chlorella vulgaris under Sunlit and Dark Conditions.

As a major entry point of mercury (Hg) to aquatic food webs, algae play an important role in taking up and transforming Hg species in aquatic ecosystems. However, little is known how and to what extent Hg reduction, uptake, and species transformations are mediated by algal cells and their exudates, algal organic matter (AOM), under either sunlit or dark conditions. Here, using Chlorella vulgaris (CV) as one of the most prevalent freshwater model algal species, we show that solar irradiation could enhance the reduction of mercuric Hg(II) to elemental Hg(0) by both CV cells and AOM. AOM reduced more Hg(II) than algal cells themselves due to cell surface adsorption and uptake of Hg(II) inside the cells under solar irradiation. Synchrotron radiation X-ray absorption near-edge spectroscopy (SR-XANES) analyses indicate that sunlight facilitated the transformation of Hg to less bioavailable species, such as ß-HgS and Hg-phytochelatins, compared to Hg(Cysteine)2-like species formed in algal cells in the dark. These findings highlight important functional roles and potential mechanisms of algae in Hg reduction and immobilization under varying lighting conditions and how these processes may modulate Hg cycling and bioavailability in the aquatic environment.

Satisfactory Anti-Interference and High Performance of the 1Co-1Ce/Mn@ZSM-5 Catalyst for Simultaneous Removal of NO and Hg0 in Abominable Flue Gas.

The removal performance of NO and Hg0, the operating temperature window, and the resistance of SO2 and H2O on Mn@ZSM-5 catalyst, which was synthesized by a one-step hydrothermal method with manganese oxide as the active component, were improved by doping different molar ratios of Co/Ce. Co and Ce doping increased the content of Mn4+ as well as of chemisorbed oxygen and promoted the NO and Hg0 removal performance, which reached 96.7 and 98.9%, respectively, in flue gas over the 1Co-1Ce/Mn@ZSM-5 catalyst. Furthermore, with SO2 and H2O addition, it decreased slightly to 88.4 and 89.3%, respectively, and then remained stable. The coexistence of SO2 and H2O had a synergistic poisoning effect on the activity of the catalyst, while the doping of Co and Ce had a positive influence on the tolerance to SO2 and H2O. The excellent anti-interference and high performance of the 1Co-1Ce/Mn@ZSM-5 catalyst in the abominable flue gas were mainly due to the outer surface modification of organosilane and because the sacrificial element Co protected the active sites of Ce and Mn from poisoning, which prevented the redox ability of the catalyst from getting affected.

Removal and Recovery of Gaseous Elemental Mercury Using a Cl-Doped Protonated Polypyrrole@MWCNTs Composite Membrane.

Due to the restrictions on mercury mining, recovering the mercury from mercury-containing waste is attracting increasing attention. This study successfully achieved the removal and recovery of gaseous elemental mercury (Hg0) by using membrane technology. A novel composite membrane of Cl-doped protonated polypyrrole-coated multiwall carbon nanotubes (Cl-PPy@MWCNTs) was fabricated in which MWCNTs acted as the framework to support the active component Cl-PPy. The morphology, structure, and composition of the prepared membranes were determined by field emission scanning electron microcopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, etc. The composite membrane exhibited an excellent performance in Hg0 removal (97.3%) at a high space velocity of 200,000 h-1. The dynamical adsorption capacity of Hg0 was 3.87 mg/g when the Hg0 breakthrough reached 10%. The adsorbed Hg0 could be recovered/enriched via a leaching process using acidic NaCl solution; meanwhile, the membrane was regenerated. The recovered mercury was identified in the form of Hg2+, with a recovery efficiency of over 99%. Density functional theory calculations and mechanism analysis clarified that the electrons of Hg0 transported to the delocalized electron orbits of protonated PPy and then combined with Cl- to form Hg2Cl2/HgCl2. Finally, we first demonstrated that the analogous protonated conductive polymers (e.g., polyaniline) also possessed good Hg0 removal ability, implying that such species may offer more outstanding answers and attract attention in future.

Organic mercury solid phase chemoselective capture for proteomic identification of S-nitrosated proteins and peptides.

Cysteine S-nitrosation mediates NO signaling and protein function under pathophysiological conditions. Herein, we provide a detailed protocol regarding the organic mercury chemoselective enrichment of S-nitrosated proteins and peptides. We discuss key aspects of the enrichment strategy and provide technical tips for the best performance of the experimental protocol.

Structural Insights for the Stronger Ability of Shrimp Ferritin to Coordinate with Heavy Metal Ions as Compared to Human H-Chain Ferritin.

Although apoferritin has been widely utilized as a new class of natural protein nanovehicles for encapsulation and delivery of nutraceuticals, its ability to remove metal heavy ions has yet to be explored. In this study, for the first time, we demonstrated that the ferritin from kuruma prawns (Marsupenaeus japonicus), named MjF, has a pronouncedly larger ability to resist denaturation induced by Cd2+ and Hg2+ as compared to its analogue, human H-chain ferritin (HuHF), despite the fact that these two proteins share a high similarity in protein structure. Treatment of HuHF with Cd2+ or Hg2+ at a metal ion/protein shell ratio of 100/1 resulted in marked protein aggregation, while the MjF solution was kept constantly clear upon treatment with Cd2+ and Hg2+ at different protein shell/metal ion ratios (50/1, 100/1, 250/1, 500/1, 1000/1, and 2500/1). Structural comparison analyses in conjunction with the newly solved crystal structure of the complex of MjF plus Cd2+ or Hg2+ revealed that cysteine (Cys) is a major residue responsible for such binding, and that the large difference in the ability to resist denaturation induced by these two heavy metal ions between MjF and HuHF is mainly derived from the different positions of Cys residues in these two proteins; namely, Cys residues in HuHF are located on the outer surface, while Cys residues from MjF are buried within the protein shell. All of these findings raise the high possibility that prawn ferritin, as a food-derived protein, could be developed into a novel bio-template to remove heavy metal ions from contaminated food systems.

Dithiolated peptides incorporating bis(tryptophan)s for cooperative mercury(II) binding.

The indole side chain of tryptophan is a versatile π-donor that can participate in various types of cation-π interactions. An understanding of how it may contribute as an auxiliary binding group in mercury(II) complexes can provide valuable insights toward the design of effective chelators for optimal mercury immobilization. In this study, we investigate how the incorporation of two tryptophan residues in model dicysteinyl peptides might participate in peptide-mercury(II) complex stabilization. Two pentapeptides consisting of a Cys-Trp-Cys sequence motif containing a second tryptophan residue at the N-terminal (BT1) or C-terminal (BT2) were designed. An analogous cyclohexapeptide (BT3) was included to evaluate how tryptophan residues, restricted in constrained peptidic turn motifs, might take part in mercury(II) complexation. Their interactions with mercury(II) were investigated by spectroscopic methods and computational modeling. UV-vis studies indicate the formation of 1:1 dithiolated mercury(II) complex, which is corroborated by ESI-MS analysis. Spectroscopic studies reveal that the tryptophan indole group(s) in BT1 and BT3 can participate in mercury(II) cation-π interactions. Optimized 1:1 mercury(II)-BT3 structures indicate that both indole rings are very close to the mercury(II) coordination site and could stabilize it by shielding it from ligand exchange. These findings provide some useful insights toward use of aromatic donor groups as hydrophobic shields in designing more effective metal chelating agents.

Investigation of the Hg(II) biosorption from wastewater by using garlic plant and differential pulse voltammetry.

In this work, the bio sorption of mercury ion by garlic bio-adsorbent was studied. A batch and a continuous up-flow fixed-bed column system were used in this report. Differential pulse voltammetry was used to detecting the amount of mercury ion. Using Differential pulse voltammetry prevents the production of carcinogenic mercury vapor. In the batch system, various doses of bio-adsorbent were investigated. After that, the experimental data was fitted using Langmuir and Freundlich models. The experimental data were also fitted to the Thomas, Bohart-Adams, and Yan models for the continuous mode in a fixed bed of garlic bio-adsorbent. The maximum adsorption capacity estimated by the Thomas models was 23.5 mg g-1 and τ was 135.3 min. This adsorbent is also suitable for absorbing mercury from a real-life well water sample. It is renewable and can be used to absorb mercury several times.

A cysteine-selective fluorescent probe for monitoring stress response cysteine fluctuations.

Rare studies provided evidence for the real-time monitoring of stress response cysteine fluctuations. Here, we have successfully designed and synthesized a cysteine-selective fluorescent probe 1 to monitor stress response Cys fluctuations, providing visual evidence of Hg2+ regulated cysteine fluctuations for the first time, which may open a new way to help researchers to reveal the mechanism of heavy metal ion poisoning.

Identification of metal binding motifs in protein frameworks to develop novel remediation strategies for Hg2+ and Cr(VI).

Amino acid sequences in metal-binding proteins with chelating properties offer exciting applications in biotechnology and medical research. To enhance their application in bioremediation studies, we explicitly aimed to identify specific metal-binding chelating motifs in protein structures for two significant pollutants, such as mercury (Hg2+) and chromium Cr(V1). For this purpose, we have performed an extensive coordination chemistry approach by retrieving Hg2+ and Cr(V1) binding protein structures from the protein database and validated using the B-factor, a term defining uncertainty of the atoms and with occupancy to obtain the best binding motifs. Our analysis revealed that acidic amino acids like aspartic acid, glutamic acid, and basic amino acids such as cysteine and histidine are predominant in coordinating with these metals. The order of preference in Hg2+-bound structures is predicted to be Cys > His > Asp > Glu, and for Cr(V1) is His > Asp > Glu. Examination of the atomic coordinates and their distance from each metal revealed that the sulfur atoms of cysteine showing more preference towards Hg2+coordination with an atomic distance ranging from 1.5 to 2.9 Å. Likewise, oxygen atoms of aspartic acid, glutamic acid and nitrogen atoms of histidine are within 2 Å of Cr(V1) coordination. Based on these observations, we obtained C-C-C, C-X(2)-C-C-(X)2-C, H-C-H motifs for Hg2+, and D-X(1)-D, H-X(3)-E motif for Cr(V1) to be shared within the coordination space of 3 Å. As a future scope, we propose that the identified metal-binding chelating motifs are oligopeptides and can display on the surface of microorganisms such as Escherichia coli and Saccharomyces cerevisiae for effective removal of natural Hg2+ and Cr(V1) through biosorption. Hence, our results will provide the basis for futuristic bioremediation.

Development of Armillae mellea immobilized nanodiamond for the preconcentrations of Cr(III), Hg(II) and Zn(II).

In this study, we present an environmental friend and easy procedure for simultaneous preconcentration of Cr(III), Hg(II) and Zn(II) by solid-phase extraction before their determination by inductively coupled plasma optical emission spectrometry. Armillae mellea immobilized nanodiamond was used as sorbent. During the study, critical parameters influencing the extraction performance were investigated in detail. The best parameters were found as pH 5.0, 2.0 mL min-1 of flow rate, 200 mg of Armillae mellea, 300 mL of sample volume. LOD values were found as 0.025, 0.13 and 0.038 ng mL-1, respectively for Cr(III), Hg(II) and Zn(II). By applying the developed procedure, sensitivities of ICP-OES were improved for 60 fold for Cr(III), Hg(II) and Zn(II). Their concentrations in different food samples were measured after microwave digestion and solid-phase extraction.