Mercury Ions In Aqueous Solution Research Articles

On the mechanism and energetics of electrochemical alloy formation between mercury and platinum for mercury removal from aqueous solutions

Mercury pollution is an acute global concern threatening the health of humans and wildlife. Thus, there is a need for new and improved techniques to reduce emissions and remove toxic mercury from aqueous environments. Electrochemical alloy formation, specifically between mercury ions in aqueous solution and a platinum electrode, emerges as a promising solution. Through analysis of reaction mechanisms and energetics related to the formation and dissolution of the PtHg4 alloy, this study aims to deepen our understanding of the underlying processes of effective electrochemical mercury removal. Potentiodynamic measurements indicate rapid alloy formation at a clean platinum surface, proceeding with only trace amounts of metallic mercury on the surface. However, once the electrode surface has sufficient mercury coverage with an alloy thickness of around 1.5 nm, clear evidence of metallic mercury on the surface is observed. Furthermore, the amount of absorbed mercury on the cathode increases linearly in time. The onset potential for the alloy formation is experimentally determined using electrochemical quartz crystal microbalance with dissipation monitoring to be approximately 0.64 V vs. SHE, and the alloy dissolution (oxidation) onset potential is found to be approximately 0.98 V vs. SHE, at a mercury ion concentration of 10 mg/L. Density functional theory calculations are used to provide a theoretical value for the reversible potential from a thermodynamics perspective, yielding a value of 0.78 V vs. SHE at a mercury ion concentration of 10 mg/L. This value is in excellent agreement with the experimental results, suggesting an overpotential of about 0.14 and 0.20 V for the alloy formation and oxidation, respectively. These findings provide important information on the reaction mechanisms and overpotentials of the PtHg4 alloy formation and dissolution, which are key factors for development of large-scale mercury removal based on this technique, as well as fundamental understanding of the electrochemical alloy formation between mercury ions and platinum.

Fluorescent turn-on detection of inorganic mercury and methylmercury in aqueous solution with PC micelles and live cells using fluorescent chemosensors based on Trp amino acid and cycloalkylamine-7-sulfonyl-2,1,3-benzoxadiazole

Mercury species are well-known to be toxic to humans. Particularly, methylmercury is a highly toxic substance that can readily penetrate lipid membranes, accumulating in human body and causing lethal effects. Thus, the sensitive detection of methylmercury in aquatic environments and live cells is crucial. In this study, we synthesized fluorescent chemosensors (1–5), primarily composed of a tryptophan amino acid (Trp) and cycloalkylamine-7-sulfonyl-2,1,3-benzoxadiazole fluorophores bearing a different size of cyclic amine moiety and developed new sensing systems for Hg2+ and CH3Hg+ by combining the fluorescent chemosensors with lyso-phosphatidylcholine (PC) micelles to resemble cytoplasmic lipid membranes of human cells. Fluorescent chemosensors (1–5) with visible light excitation (>450 nm) exhibited significant enhanced emissions to Hg2+ among various metal ions in purely aqueous solutions. In PC micelles, the chemosensors (1–5) showed significant enhanced green and red emissions (500 ∼ 670 nm) to CH3Hg+ and Hg2+ among various metal ions. Interestingly, the chemosensors have different binding affinities and fluorescent signal changes for CH3Hg+ depending on the size of cyclic amine moiety. Among them, chemosensor 5 with 7-membered cyclic amino group, exhibited the largest fluorescence change for CH3Hg+ and demonstrated the highest binding affinity for CH3Hg+ (Kd = 24.1 μM) and Hg2+ (Kd = 15.8 nM). Chemosensor 5 exhibited a significant enhancement of emission as well as an extremely fast response (<20 sec) for methylmercury in aqueous solution with PC micelles. Thus, we investigated the binding mode of chemosensor 5 with the mercury species in PC micelles using UV/visible absorbance titration, pH titration, and NMR titration experiments. Furthermore, chemosensor 5 was successfully applied to detect sensitively CH3Hg+ and Hg2+ in live cells through increase in both green and red emissions. Fluorescent chemosensors in combination with PC micelles might serve as a promising new fluorescent sensing method for methylmercury and inorganic mercury ions in aqueous solutions and live cells.

Structure affinity of the Langmuir monolayer and the corresponding Langmuir-Blodgett film revealed by X-ray techniques.

The possibility of reproducing the structural organization and functional abilities of a Langmuir monolayer in a film formed from it is one of the fundamental problems of ultrathin film science. This work is devoted to the comparison of monolayer and Langmuir-Blodgett (LB) film characteristics using the example of 2D systems based on the dithia-aza-crown substituted hemicyanine dye HCS. As was shown earlier, the investigated systems are promising for the preparation of selective sensors and extractors for mercury ions in aqueous solutions with a subnanomolar sensitivity threshold. Therefore, the study of the analyte binding mechanism by such a film is of great importance. The study carried out using an ultra-highly brilliant X-ray source (ESRF) allows the application of highly sensitive techniques such as X-ray reflectometry (XRR) and X-ray standing wave (XSW). Comparison of the electron density depth profile of the HCS Langmuir monolayer at the air/water interface and the HCS film transferred to a silicon substrate shows the preservation of the film structure and its functional features. The XSW measurements in turn reveal the similarities in the fine structure of preorganized Langmuir monolayers and Langmuir-Blodgett films of HCS. The integration of X-ray techniques with molecular modeling methods allowed us to show that the crown-ether groups of HCS molecules in the pre-organized monolayer and in the corresponding LB film lie on the surface of water or silicon, and the bound mercury ion is located above the crown-ether, partially binding to the nitrogen atom. The latter loses conjugation to the chromophore group, thereby altering the UV-vis spectrum and providing a response signal. The revealed mechanism of imprinting preorganization allows the proposed approach to be extended to other crown-substituted amphiphilic dyes to significantly enhance the sensory response.

Structural Parameters of the Nearest Environment of Zinc, Cadmium, and Mercury Ions in Aqueous Solutions of Their Salts (A Review)

Structural Parameters of the Nearest Environment of Zinc, Cadmium, and Mercury Ions in Aqueous Solutions of Their Salts (A Review)

A coumarin-based fluorescent probe for highly selective detection of hazardous mercury ions in living organisms

In recent years, heavy metal mercury (II) pollutants have caused serious harm to human health and ecosystems. It has become critical to develop simple and highly selective sensing solutions for monitoring mercury (II). In this work, we designed and developed a novel fluorescent probe Coa-SH using the Hg2+-induced chemical reaction as a sensing mechanism. The probe Coa-SH showed high selectivity for the detection of Hg2+ by desulfurization reactions in solution. The test strips prepared with this probe could be applied to detect mercury ions in aqueous solutions. In addition, the probe Coa-SH provided a tool to detect Hg2+ in living systems. In living cells and zebrafish, the probe turned on bright red fluorescent signals in the presence of mercury ions. Importantly, the probe Coa-SH enabled Hg2+ detection in plant onion roots. This work provides an effective method for monitoring mercury ions in the environment and in living organisms.

Bis-Schiff base cellulosic nanocrystals for Hg (II) removal from aqueous solution with high adsorptive capacity and sensitive fluorescent response

Mercury pollution in aqueous solutions is a severe problem in environmental protection and the contaminated water may cause serious risks to human health. Based on the constant development of adsorptive materials, adsorption technique is widely applied as an efficient and convenient approach to eliminate mercury species from waters. In this work, we report a one-pot procedure to prepare a bis-Schiff base cellulosic adsorbent to integrate the advantages of large adsorptive capacity and excellent fluorescent recognition towards mercury ions. The adsorption experiments demonstrate that sulfydryl-contained cellulosic nanocrystals exhibit specific affinity with mercury species and the adsorption capacity reaches as high as 624.8 mg/g at room temperature. Besides, the introduction of rhodamine moiety endows the material a 19 times enhancement of selective “off-on” fluorescent sensing while exposed to mercury. Additionally, the bifunctional adsorbent material shows high sensitivity towards mercury ions in aqueous solution with detection limits of as low as 8.29 × 10−8 M for fluorescence and 5.9 × 10−9 M for UV–vis spectrum, respectively. The fitting results of the adsorption models indicate a monolayer adsorption during the uptake of mercury ions and the removal process follows the pseudo-second order kinetics. Moreover, density functional theory studies are employed to further understand the adsorptive and responsive mechanisms.

A highly selective and sensitive fluorescent light-up probe for rapid detection of mercury ions in aqueous solution

Due to its complex biological toxicity, mercury ions can cause various neurological diseases and even death. Therefore, developing a rapid and efficient mercury ions analysis method is of great significance. In this study, we designed a new water-soluble fluorescent chemical sensor, Hg535, which can sensitively detect mercury ions in an aqueous solution. Based on the specific mercury-mediated desulfurization reaction, the probe exhibits high selectivity for mercury ions, excellent sensitivity, significant Stokes shift (108 nm), and fast kinetics (within 15 s), with a low detection limit (1.66 ppb). Finally, agar gels based on the probe Hg535 were fabricated, which could act as a solid optical sensor to conveniently and efficiently detect Hg2+.

Graphitic sulfur functionalized carbon sheets as an efficient “turn-off” absorption probe for the optical sensing of mercury ions in aqueous solutions

The sulfur - rich activated carbon (g-SFCSs) derived from coconut husk is used for detection of Hg2+ ions. The presence of sulfur groups results in remarkable absorbance quenching of g-SFCSs on the addition of different concentrations of Hg2+ ions.

Selective and sensitive colorimetric detection of mercury ions in aqueous solutions using silver nanoparticles synthesized in innovative biomaterial matrix

Selective and sensitive colorimetric detection of mercury ions in aqueous solutions using silver nanoparticles synthesized in innovative biomaterial matrix

New derivatives of urea-grafted alginate for improving the sorption of mercury ions in aqueous solutions

Chemically-modified alginate (obtained by grafting urea on alginate, with different ratios; alginate-urea (1:1) and its new derivatives alginate-urea (1:2) with an exceed of the percent of amino group by 7%) was successfully tested for mercury sorption in aqueous solutions. The influence of pH on metal sorption was first investigated: optimum pH was close to 5.5. Sorption isotherms were modeled using the Langmuir and the Sips equations, and sorption capacity slightly increased with the increased of the % of–NH2 in the sorbent and the maximum sorption capacity exceeded 200 mg Hg l−1 (1.07 mmol Hg g−1; for alginate-urea (1:2)), this means two times the sorption capacity of reference material (i.e., non-modified alginate), and also has a capacity improved compared to alginate-urea (1:1). Under selected experimental conditions the equilibrium was reached with 6–8 h of contact and the kinetic profiles were modeled using the pseudo-first order equation (PFORE), the pseudo-second-order rate equation (PSORE) and the resistance to intraparticle diffusion (RIDE). Surface functional groups, notably; –NH2, –OH and –COOH, were involved in mercury sorption by alginate-urea, suggesting the ion exchange, complexation and/or electrostatic interaction of Hg(II) on the alginate-urea surface. The use of this material, environmentally friendly and simply obtained from a renewable resource, reveals promising for the treatment of low-metal concentration effluents: sorption capacities are comparable to alternative academic and commercials sorbents.

The fluorescence of a mercury probe based on osthol.

The ability of osthol (OST) to recognize mercury ions in aqueous solution was studied using fluorescence, UV–vis spectrophotometry, mass spectrometry, and 1H NMR spectroscopy, and the recognition mechanism is discussed. The results showed that OST and Hg2+ can form a complex with a stoichiometric ratio of 1:1. The binding constant was 1.552 × 105 L∙mol−1, having a highly efficient and specific selectivity for Hg2+. The fluorescence intensity of OST showed a good linear correlation with the Hg2+ concentration (6.0 × 10−5 to 24.0 × 10−5 mol∙L−1, R2 = 0.9954), and the detection limit of the probe was 5.04 × 10−8 mol∙L−1, which can be used for the determination of Hg2+ traces.

Green route of silver nanoparticles synthesis using watermelon (Citrullus lanatus) fruit extract for mercury ions detection

In this paper, we report the green synthesis of silver nanoparticles using a reductant of fruit extract of watermelon (Citrullus lanatus), and its application for mercury ions detection. Silver nanoparticles were made from small amount of silver nitrate, assisted with sunlight irradiation. After 30 minutes of irradiation, the yellowish-brown silver nanoparticles were formed with peak absorbance at 420 nm wavelength. The formed silver nanoparticles were then tested to various alkaline, alkaline earth and transition metals. Most of the metals has no effect to the silver nanoparticles except for mercury ions that change the color of silver nanoparticles to colorless. Therefore, silver nanoparticles are selective to detect mercury ions in aqueous solution. Compared to the reference method, the developed colorimetry method for mercury ions detection was accurate up to 99.38%.

Tuning of hydrogen peroxide etching during the synthesis of silver nanoparticles. An application of triangular nanoplates as plasmon sensors for Hg2+ in aqueous solution

Abstract A simple method to prepare silver nanoparticles (AgNPs) with different shapes and dimensions was optimized by using a one-step reduction method with NaBH4, TSC and PVP, with H2O2 acting as an oxidation agent, to etch the nanoparticles and produce different morphologies. A series of AgNPs were obtained with different colours, including yellow to green and passing through orange, red, violet and blue, that exhibited different localized surface plasmon resonance (LSPR) as analysed by UV–visible spectroscopy. The dimensions and morphologies of the nanostructures were characterized in detail by scanning electron microscopy (SEM) and dynamic light scattering (DLS) techniques. The characterizations showed different trends in the morphologies, starting from spherical to not well-defined structures, triangular nanoplates, hexagonal nanoplates and ultimately once again showing quasi-spherical shapes. The triangular nanoplates were tested as plasmon sensors for mercury ions in aqueous solution, and they showed an LSPR-blueshift with a change in colour from blue to violet. When a calibration curve was measured in the concentration range from 0.14 to 0.5 mg l−1, the nanoparticles showed good linearity between the Hg2+ concentration in the solutions and the LSPR blueshift, with a correlation factor R2 of 0.9978 and an LOD of 0.013 mg l−1 (64.9 nM).

Effective Removal of Mercury Ions in Aqueous Solutions: A Review

Background: Due to its high toxicity and bioaccumulation, the existence of mercury in the environment is always a big threat to human beings. In order to control mercury pollution, scientists have put great efforts in the past decades. Methods: Precipitation, adsorption, membrane separation, biological treatment and ion exchange are reviewed as a remover for mercury removal. For each material type, we not only reported on the removal mechanism, but also discussed the best areas for it. The correlation method and step-to-step focusing method have been used for references. Conclusion: With the exploration and application of research, people have mastered a variety of mature technologies for the treatment of mercury-containing wastewater. Using inexpensive adsorbents is a cost-effective method for treating low concentrations of heavy metal wastewater. Ion exchange with a fast removal rate has been widely used in the field of heavy metal removal from wastewater. The biological treatment method can effectively treat low-concentration mercurycontaining wastewater. However, there is still a need to develop novel mercury removers with high capacity, fast removal rate, and low removal limit. Nanomaterials with a high specific surface area on substrate with synergistic effects, such as high adsorption and ion exchange, are the future research points.

Detection of Mercury Ions in Aqueous Solution by Fluorescence Spectrometry

This paper proposes a simpler and operable method to replace the traditional detection method and detect the mercury ion in water samples quickly and easily. Firstly, the rhodamine derivatives are synthetised, then a rhodamine derivative fluorescent molecular probe is constructed and adopted to detect mercury ions in water samples. In order to detect mercury ions in aqueous solutions, the fluorescence spectroscopy was adopted in this experiment, and rhodamine derivatives were used as fluorescent molecular probes. The rhodamine and its corresponding derivatives were used to detect mercury ions in aqueous solutions. Different metal ions and different chlorides were added to the solution of the compound. Only the one with the addition of mercury ion shows a peak at 555 nm. Therefore, it is concluded that the mercury ion derivative has a better response to metal mercury ion.

Electrochemical sensing of mercury ions in electrolyte solutions by nitrogen-doped graphene quantum dot electrodes at ultralow concentrations

Electrochemical detection of mercury ions in aqueous solution was investigated at indium tin oxide (ITO) conducting glass electrode modified by nitrogen-doped graphene quantum dots (N-doped GQDs). The N-doped GQDs with an average particle size of 4.5 nm were synthesized through an infrared-assisted pyrolysis of citric acid and urea at 250 °C. The GQD sample contains high oxidation and amidation level, i.e., O/C and N/C atomic ratios: 37.6% and 30.7%, respectively. The electrochemical sensing toward Hg2+ ions was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Based on the CV and EIS analyses, both the reductive and oxidative peak currents as well as the equivalent series resistance demonstrate a decreasing trend with increased Hg2+ concentration. The detection limit of N-doped GQD/ITO electrodes toward Hg2+ ions reached 10 ppb with the accumulation time of 32 s. The GQD/ITO electrodes also exhibit superior selectivity toward the target contaminant (i.e. Hg2+ ion). Accordingly, the functionalized GQDs pave the way for engineering the electrochemical sensors capable of detecting toxic Hg2+ ions with superb sensitivity and selectivity.

New switch on fluorescent probe with AIE characteristics for selective and reversible detection of mercury ion in aqueous solution

A new tetraphenylethylene derivative based fluorescenct probe (probe 2) was synthesized in a simple two-step process for selectively switch on and reversible detection of Hg2+ in aqueous solution based on aggregation-induced emission phenomenon. Probe 2 exhibited weak emission in aqueous solution due to the fast non-radiative decay of the excited singlet state facilitated by the free rotation of four phenyl rotors. While after coordination with Hg2+, the Hg2+-promoted aggregation formation will occur and restrict the intramolecular rotation, which blocks the non-radiative pathways and opens up the emission channel, resulting in the switch on response of probe 2 toward Hg2+. Probe 2 exhibited high sensitivity and good selectivity toward Hg2+ with a detection limit of 45.4 nM. Moreover, the detection can be reversible by subsequent addition of S2- into the detection system, which may be applied in the removal of toxic Hg2+ from water. Elsevier B.V. All rights reserved.

A light controlled, sensitive, selective and portable spiropyran based receptor for mercury ions in aqueous solution

A substituted benzothiazolinic spiropyran was synthesized through a reaction between 2-hydroxy-3-methoxy-5-nitrobenzaldehyde and 2-ethyl-3-methylbenzo[d]thiazol-3-ium-4-toluenesulfonate in the presence of piperidine. The spiropyran derivative was characterized using IR, NMR, mass and SCXRD analysis. Owing to the presence of a methoxy group ortho to the phenolic oxygen atom, the affinity of the synthesized spiropyran derivative towards toxic metal ions was investigated in CH3CN: water (1:1). A hypsochromic shift in the absorption and fluorescence spectra was observed in response to the presence of Hg2+ ions. The formation of complex was also observed through a visible change in color from dark yellow to colorless. UV–vis, fluorescence spectroscopy and digital image analysis were used to obtain good limit of detection value (5.5 μM, 78.5 nM and 0.62 μM, respectively) for the receptor towards Hg2+ ions. The 1H-NMR spectroscopy indicated the interaction of the phenolic oxygen atom and Hg2+ ions. The density functional theory was further used to investigate the stabilities of the different stereoisomers of the spiropyran derivative and their complex. The DFT studies also supported the interaction between the phenolic oxygen atom and the Hg2+ ions. TD-DFT studies were also performed to analyze the observed changes in the UV-Visible spectra upon addition of the Hg2+ ions, which indicates an increase in the HOMO-LUMO gap.

A Highly Selective and Ultrasensitive Fluorescent Probe for Monitoring Hg2+ and Its Applications in Real Water Samples.

Mercury ions as high toxic pollutants have received wide-spread attention because of their poisonousness, persistence and enrichment. To better understand the distribution of mercury species and supplement more detailed toxicological research, it is necessary to develop some methods for monitoring mercury ions with high sensitivity and selectivity. Therefore, a simple rhodol-based highly selective fluorescent probe, RH-Hg, has been developed for monitoring Hg2+ with thiocarbamate as the recognition receptor. The probe RH-Hg can quantificationally detect mercury ions in aqueous solution assisted by hydrogen peroxide (H2O2), and it can discriminate Hg2+ through "naked-eye" observation of the color changes from light orange to dark pink. Finally, the practical applications of the probe RH-Hg in the river water further demonstrated that it will be an effective and economical tool for monitoring the distribution of Hg2+ in the environment.

Optimization of Plasmonic U-Shaped Optical Fiber Sensor for Mercury Ions Detection Using Glucose Capped Silver Nanoparticles

Heavy metal contamination of water bodies has an adverse effect on human health and the environment even at very low concentrations. In this paper, we report U-shaped fiber optic probe coated with glucose capped silver nanoparticles (AgNPs) for label-free detection of mercury ions in aqueous solution. The reaction between glucose capped AgNPs and mercury ions resulted in a reduction in the plasmonic absorbance. The developed sensor probe was able to detect mercury ions concentration as low as 2 ppb, which is less than the World Health Organization acceptable limit for mercury ions in drinking water. The sensor probes displayed excellent selectivity towards mercury ions over other metal ions. Furthermore, the developed sensor probe was able to detect mercury ions down to 5 ppb in domestic tap water, i.e., selective detection of mercury even in real matrix having high concentration mixtures of various essential ions. The response of AgNPs coated sensor probe was found to be better than glucose capped gold nanoparticles and hollow gold-silver nanostructures coated fiber-optic probes.