Presence Of Lead Ions Research Articles

Electrochemical Behavior of the Oxidative Dissolution of Gold Catalyzed by Lead Ion in Thiourea Solution

ABSTRACT Thiourea is a low-toxicity gold lixiviant that has promise to substitute highly toxic cyanide for gold extraction. The electrochemical behavior of lead ion in the dissolution of gold in thiourea solution was investigated by electrochemical and analytical technique. Electrochemical results suggest that the addition of lead ion (10 mg/L and 20 mg/L) to thiourea solution increased the open circuit potential from 0.31 V to 0.32 V and 0.34 V, respectively, due to the significant increase of cathodic current density. The presence of lead ion could significantly improve the oxidative dissolution of gold and thus resulted in higher gold dissolution in thiourea solution, particularly at higher anodic potentials. The scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS) and X-ray photoelectrode spectroscopy (XPS) analyses indicate the improvement of gold dissolution is attributed to the formation of gold-lead (AuPb2) layer on gold surface, which acts as a cathode to promote galvanic corrosion of gold. The possible mechanism is proposed that gold dissolution in thiourea solution with lead ion follows a two-step process: (1) the formation of AuPb2 layer on gold surface and (2) the dissolution of AuPb2 layer under the applied anodic potential.

An electrochemical aptasensor based on silver-thiolated graphene for highly sensitive detection of Pb2.

The presence of lead ions (Pb2+) in the environment not only leads to environmental contamination but also poses a significant risk to public health through their migration into food and drinking water. Therefore, the development of rapid and effective techniques for detection of trace amounts of Pb2+ is crucial for safeguarding both the environment and biosafety. In this study, an aptamer-based electrochemical sensor was developed for specific detection of Pb2+ by modifying a polylysine (PLL) coated silver-thiolated graphene (Ag-SH-G) nanocomposite (PLL/Ag-SH-G) on the surface of a glassy carbon electrode, which was further modified with gold nanoparticles (AuNPs) for attachment of aptamers (Apt) that specifically recognized Pb2+. The Ag-SH-G particles were synthesized using a one-step in situ method, resulting in significantly enhanced electrochemical properties upon incorporating Ag nanoparticles into the PLL/Ag-SH-G composite. Coating of the covalently or no-covalently bonded Ag-SH-G particles with PLL provides an excellent supporting matrix, facilitating the assembly of AuNPs and a thiol-modified aptamer for Pb2+. Under optimized conditions, Apt/AuNPs/PLL/Ag-SH-G/GCE exhibited excellent sensing performance for Pb2+ with a wide linear response range (10-1000 nM), a low detection limit (0.047 nM) and extraordinary selectivity. The sensor was employed and satisfactory results were obtained in river water, soil and vegetable samples for the detection of Pb2+.

The capability of Bacillus pseudomycoides from soil to remove Cu(II) in water and prevent it from entering plants.

Copper ion is widespread in wastewater and threatens the condition and human health. Micro-organisms have unique advantages to remove heavy-metal ions from water, but are rarely reported in the removal of copper ion. This aims to develop micro-organisms that can remove copper ion in water, characterize their properties and analyse their potential application in practice. Sewage sludge was used as the source to isolate wild bacteria that can remove copper ion in water. The most efficient strain was screened out from 23 obtained isolates, identified as Bacillus pseudomycoides and coded as C6. The properties of C6 in the removal of copper ion in water were investigated in the aspects of reaction conditions, reaction groups, reaction dynamic and the application in oat planting. The reaction at pH 7 within 10min yielded the highest removal rate of copper ion, 83%. The presence of lead ion in the reaction system could promote the removal rate of copper ion. Carboxyl groups and amidogen of C6 biomass were mainly involved in the removal of copper ion. The removal of copper ion was in accord with single-layer adsorption and Langmuir adsorption isotherm model. In application, C6 biomass reduced the copper content in the oat seedlings grown in copper ion containing water by more than seven times. B. pseudomycoides C6 can efficiently remove copper ion in water and inhibit it from entering plants. This is the first time to report the capability of B. pseudomycoides to remove copper ion in water, which is also more efficient than the currently reported chemical and biological methods.

A versatile user-friendly electrochemical cell with three 3D-pen-printed electrodes in a tiny micropipette tip

This work describes a practical, portable and versatile electrochemical cell containing three-electrode integrated in a small disposable micropipette tip. The electrodes were manufactured using 3D pen and a commercial carbon black-polylactic acid filament and the tip-based cell was fabricated using alternative materials. The cell requires low sample volumes (10 μL) and may be operated with several commercial micropipettes (manual and electronic) that performs the aspiration of solution before or simultaneously to the electrochemical measurement, resulting in electroanalysis under static or flowing conditions, respectively. As proof-of-concept, measurements of catechol were performed in stationary and hydrodynamic mode, in which the sensitivity of the hydrodynamic was around five-fold greater when compared to the stationary method (47 vs 9 nA μmol−1 L), due to the faster mass transport of the analyte. Moreover, the proposed cell exhibited analytical parameters for catechol comparable with a commercial screen-printed electrode. The versatility of the cell was also demonstrated for square wave anodic stripping voltammetry in the presence of lead ions, in which the deposition (pre-concentration) step was performed during the solution aspiration controlled by an electronic pipette. The obtained LOD was 6-fold better than a conventional system for ASV (0.010 vs 0.059 μmol L-1). The analytical feasibility of the cell was demonstrated through the determination of catechol and lead in tap and ground water, being obtained recoveries close to 100%. The proposed cell and is cheaper (< US$ 0.10), smaller and more versatile than other tip-based and 3D-printed cells, being promising for on-site analyses and education purposes.

Photoelectrochemical biosensor for lead ion determination based on complementary strand aptamers

AbstractLead ion causes heavy metal pollution, which can cause serious damage to the ecological environment and human health. In this paper, a simple and sensitive photoelectrochemical method was designed for lead ion detection by using ZnO nanorods as the photoactive substrate and complementary strand aptamers as target recognition element. ZnO nanorods with favorable stability and photoelectric activity can provide a biocompatible microenvironment for aptamer loading. In the presence of lead ion, it would combine with the recognition aptamer S2 by competing with the aptamer S1, which led to changes in surface structure and charge density before and after the recognition of target, causing regular response of photocurrent. The developed method under optimized experimental conditions presented high sensitivity and good selectivity for lead ion detection with low detection limit as 3.5 × 10−11 mol/L. In addition, the proposed strategy was also further applied to the detection of lake water sample, which provided reliable experimental support and basis for further exploration and establishment of complex aptamer recognition and detection system.

Study on the flotation behavior and interaction mechanism of ilmenite with mixed BHA/NaOL collector

The mixed BHA/NaOL collector was studied to improve the floatability of ilmenite in the presence of lead ions. The mechanism was discussed through surface tension measurements, zeta potential measurements, adsorption amount measurements, and XPS analysis. Microflotation results show that the mixed BHA/NaOL collector exhibited a better performance on the floatability of ilmenite than single BHA and NaOL collector. The recovery of ilmenite was 92.9% when the molar ratio of BHA/NaOL was set to 7:3. The adsorption amount of mixed collectors on the ilmenite surface was greater than that of equivalent single BHA and NaOL. The results of surface tension suggest that there was synergism between BHA and NaOL in aqueous solution. Zeta potential results indicate that mixed BHA/NaOL adsorbed onto ilmenite surface and had a more negative shift than single BHA. XPS results further confirm that BHA and NaOL adsorbed onto the ilmenite surface through chemisorption and hydrogen bonds.

The Synthesis of PbS NPs and Biosorption of Pb(II) by Shinella Zoogloeoides PQ7 in Aqueous Conditions

Increasing heavy metal pollution in water continues to endanger human health. The genus Shinella has potential for heavy metal bioremediation but has rarely been studied. In this study, we report that Shinella zoogloeoides PQ7 turns black in the presence of lead ions. Transmission electron microscopy (TEM), Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) indicated that PbS nanoparticles (NPs) were synthesized by PQ7. Moreover, PQ7 was used as a biosorbent to remove Pb(II) from aqueous solutions. Biosorption performance was evaluated in terms of contact time, pH, biomass dosage and initial Pb(II) concentration. The equilibrium and kinetic data were consistent with the Freundlich isotherm model (R2 = 0.986) and pseudo-second-order model (R2 = 0.977), respectively. The maximum (qmax) Pb(II) adsorption reached 222.22 mg/g, which was higher than that of other bacteria reported in previous literature. SEM–EDS, XRD and Fourier transform infrared (FTIR) analyses also confirmed the adsorption of Pb(II) by the PQ7 cells. In conclusion, PQ7 is a promising strain in removing and recovering Pb(II) from wastewater.

Adsorption mechanism of cadmium on microplastics and their desorption behavior in sediment and gut environments: The roles of water pH, lead ions, natural organic matter and phenanthrene

Microplastics (MPs) in aquatic systems can act as a vector for various toxic contaminants, such as metal ions. Although some studies have investigated the adsorption characteristics of metal ions on MPs, the desorption behaviors of metal ions from MPs in different environments are largely unknown. Here, the adsorption of cadmium (Cd(II)) onto five different types of MPs were compared to examine the relationship between the surface characteristics and the adsorption properties of MPs. Our results showed that polyamide had the highest Cd(II) adsorption capability with a value of 1.70 ± 0.04 mg/g, followed by polyvinyl chloride (1.04 ± 0.03 mg/g), polystyrene (0.76 ± 0.02 mg/g), acrylonitrile butadiene styrene (0.65 ± 0.02 mg/g) and polyethylene terephthalate (0.25 ± 0.01 mg/g). The specific surface area and total pore volume were closely correlated with the adsorption capacity of the MPs, and the π–π interaction, electrostatic interaction and oxygen-containing functional groups played crucial roles in the adsorption of Cd(II) onto the MPs. The sorption capabilities of Cd(II) onto the MPs first increased and then decreased with increasing solution pH from 2.0 to 9.0. In addition, the adsorption capacities were suppressed with the presence of lead ions (20–80 mg/L), while the coexistence of phenanthrene had a minor impact. Interestingly, the presence of humic acid promoted the desorption of Cd(II) from the MPs both in the synthetic earthworm gut and in the sediment system. A higher desorption rate was observed in the simulated gut environment, suggesting that metal-contaminated MPs would pose higher ecological risks to macroinvertebrates. Overall, our findings provide a better understanding of the sorption mechanism of Cd(II) onto MPs and the desorption behavior under different environmental conditions in aquatic ecosystems.

Fluorescent cellulose nanocrystals for the detection of lead ions in complete aqueous solution

A fluorescent probe for the detection of lead ions in complete aqueous solution was synthesized by covalently combining a fluorescent 1,8-naphthalimide dye with cellulose nanocrystals (CNCs). The dye-labelled CNCs have lots of carboxyl and hydroxyl groups on the surface, which make them disperse well in water. There is little fluorescence discrimination for 1,8-naphthalimide dye in the presence of different metal ions, while the fluorescent CNCs exhibit selective and sensitive response to Pb(II) with remarkably enhanced emission intensity. The limit of detection of the fluorescent CNCs is as low as 1.5 × 10−7 mol/L, and there is good linear relationship between the fluorescence maxima and the Pb(II) concentration in a wide range of 2.5 × 10−7–5.0 × 10−5 mol/L. The sensing ability of the dye-labeled CNCs to Pb(II) is ascribed to the synergistic complexation of Pb(II) with both the grafted dye groups and the adjacent carboxyl groups on the surface of the CNCs. The combination ratio of Pb(II) to the fluorophore on CNCs is determined to be 1.2:1 via Job’s plot experiment, which is basically consistent with the theoretical value of 1:1. The offered fluorescent CNCs can be employed as a nanosensor for the detection of metal ions and can be further promoted for many applications in chemical, environmental, and biological systems. Water-dispersible fluorescent probe via covalent immobilization of 1,8-naphthalimide on cellulose nanocrystals (CNCs) exhibits selective and sensitive detection of lead ions in complete aqueous solution. The inhibited intramolecular charge transfer process (ICT) of the fluorophores loaded on CNCs contributes to the remarkably enhanced fluorescence emission in the presence of lead ions.

Activation effect of lead ions on scheelite flotation: Adsorption mechanism, AFM imaging and adsorption model

This paper systematically studied the effect of lead ions on floatability of scheelite under sodium oleate (NaOL) system, and the deep adsorption mechanism was revealed by a series of mechanism experiments and the adsorption morphology of NaOL was observed by atomic force microscope (AFM). Micro-flotation test indicated that the floatability of scheelite increased sharply from 47.25% to 80.12% in the presence of lead ions at pH 7. Zeta potential results revealed the positively charged lead ions species (Pb2+ and PbOH+) positively changed the zeta potential of scheelite, which favored the adsorption of negatively charged NaOL species (RCOO−, RCOOH·RCOO− etc.). XPS and FTIR analysis confirmed that NaOL was chemisorbed on scheelite surface and the adsorption was more severe in the presence of lead ions. Lead ions were chemisorbed on scheelite surface in the form of W-O-Pb2+, which facilitated the further adsorption of NaOL. This increased the active sites on scheelite surface for NaOL adsorption. AFM images intuitively showed the presence of lead ions increased the adsorption coverage of NaOL but did not affect the thickness of the adsorption layer. The adsorption thickness was still 6 nm–7 nm and the adsorption was multilayer adsorption. Based on these studies, an adsorption model was finally obtained.

Electrokinetic and flotation behavior of rutile in the presence of lead ions and aluminium ions

Electrokinetic and flotation behavior of rutile in the presence of lead ions and aluminium ions

Chemoresponsive Nanofluidic Pump That Turns Off in the Presence of Lead Ion.

There are many applications that require the integration of a pump and a chemical sensor so that the solution being pumped can be analyzed in real time for a specific chemical species and the flow adjusted according to the measured concentration of that species. We describe here an alternative strategy: a chemoresponsive pump where a single device acts as both the sensor and pump simultaneously. We demonstrate this concept with a nanofluidic Pb2+-responsive pump that uses electroosmotic flow as the pumping technology, and a Pb2+-binding ionophore that allows the device to selectively respond to Pb2+. The pump yields high flow rates at low Pb2+ concentrations (<1 μM), but flow rate decreases with concentrations above this threshold and ultimately goes to zero at concentrations above 100 μM.

Microfluidic bead trap as a visual bar for quantitative detection of oligonucleotides.

We demonstrate a microfluidic bead trap capable of forming a dipstick-type bar visible to the naked eye for simple and quantitative detection of oligonucleotides. We use magnetic microparticles (MMPs) and polystyrene microparticles (PMPs) that are connected and form MMPs-targets-PMPs when target oligonucleotides are present, leaving free PMPs with a number inversely proportional to the amount of targets. Using a capillary flow-driven microfluidic circuitry consisting of a magnetic separator to remove the MMPs-targets-PMPs, the free PMPs can be trapped at the narrowing nozzle downstream, forming a visual bar quantifiable based on the length of PMP accumulation. Such a power-free and instrument-free platform enables a limit of detection at 13 fmol (0.65 nM in 20 μl, S/N = 3) of oligonucleotides and is compatible with single-nucleotide polymorphisms and operation in a complex bio-fluid. Moreover, using DNAzyme as the target oligonucleotide that catalyzes a specific hydrolytic cleavage in the presence of lead ions, we demonstrate a model application that detects lead ions with a limit of detection of 12.2 nM (2.5 μg l-1), providing quantitative and visual detection of lead contamination at resource-limited sites.

Curcumin Protects β-Lactoglobulin Fibril Formation and Fibril-Induced Neurotoxicity in PC12 Cells.

In this study the β-lactoglobulin fibrillation, in the presence or absence of lead ions, aflatoxin M1 and curcumin, was evaluated using ThT fluorescence, Circular dichroism spectroscopy and atomic force microscopy. To investigate the toxicity of the different form of β-Lg fibrils, in the presence or absence of above toxins and curcumin, we monitored changes in the level of reactive oxygen species and morphology of the differentiated neuron-like PC12 cells. The cell viability, cell body area, average neurite length, neurite width, number of primary neurites, percent of bipolar cells and node/primary neurite ratios were used to assess the growth and complexity of PC12 cells exposed to different form of β-Lg fibrils. Incubation of β-Lg with curcumin resulted in a significant decrease in ROS levels even in the presence of lead ions and aflatoxin M1. The β-Lg fibrils formed in the presence of lead ions and aflatoxin M1 attenuated the growth and complexity of PC12 cells compared with other form of β-Lg fibrils. However, the adverse effects of these toxins and protein fibrils were negated in the presence of curcumin. Furthermore, the antioxidant and inhibitory effects of curcumin protected PC12 cells against fibril neurotoxicity and enhanced their survival. Thus, curcumin may provide a protective effect toward β-Lg, and perhaps other protein, fibrils mediated neurotoxicity.

Detection of Lead Ions in Water Based on the Surface Energy Transfer between Gold Nanoparticles and Fluorescent Dyes

Abstract In this paper, a sensitive method for the detection of lead ions in aqueous solution based on the surface energy transfer between gold nanoparticles and fluorescent dyes was established. The fluorescein-modified thrombin aptamer (5′-FAM-GGTTGGTGTGGTTGG-3′) could be selectively transformed to G-quadruplex structure in the presence of lead ions. The conformational change of the aptamer could alter the distance between the energy donor of fluorescent dyes and the energy receptor of gold nanoparticles, resulting in an enhanced fluorescence intensity. The fluorescence recovery efficiency ( F / F 0 ) was proportional to the concentration of lead ions in the range of 12.5−100 nM. The linear regression equation was y = 0.910 + 0.007 c ( R 2 = 0.997) with the limit of detection (3σ) of 10 nM. The proposed method was applied to the determination of lead ions in tap water with satisfactory results.

Plasmonic Semiconductor Nanocrystals as Chemical Sensors: Pb2+ Quantitation via Aggregation-Induced Plasmon Resonance Shift

We demonstrate, for the first time, the use of plasmonic semiconductor nanocrystals for the analysis of heavy metal ions in water. This highly sensitive localized surface plasmon resonance (LSPR)-based platform is built on glutathione (GSH) capped Cu2−xS nanocrystals, which exhibit LSPR at near infrared (NIR) wavelengths. Aggregation of GSH-capped Cu2−x S occurs specifically in the presence of lead ions, Pb2+, producing a shift in the LSPR absorbance peak. Under optimal assay conditions, the detection limit was as low as 0.25 μM (52.5 ppb) of Pb2+. This provides a new plasmonic semiconductor nanocrystal-based assay for the detection of environmentally hazardous materials. The assay employs non-toxic and earth-abundant elements and could potentially be produced at much lower cost than similar gold nanoparticle-based assays.

Use of ground crawfish shells for the removal of chromium in solution

Crawfish shells are an abundant waste product that has the potential to remediate contaminated bodies of water. This study demonstrates that ground crawfish shell could be used as an effective biosorbent material for the treatment of chromium in contaminated aqueous solutions. Phase I experiments determined that the adsorption was completed within 2h. For the time periods examined it could be concluded that the maximum chromium adsorption occurs within the first 2h. Phase II experiments demonstrated that chromium adsorption increased with sample volume and concentration, however the efficiency decreased with increasing sample volume for the relative high concentrations of chromium. Phase III experiments showed that chitin is a major constituent for biosorption of chromium and likely other metals in crustacean species including crawfish. Salinity experiments showed that salt (sodium chloride) at the 30ppt (parts per thousand) concentrations does not affect the crawfish shell ability to adsorb chromium. The pH was the most important factor for chromium adsorption by the crawfish powder. Chromium adsorption increased with increasing pH. The presence of lead ions did not significantly interfere with the adsorption of chromium ions onto the crawfish shell powder for the relatively high concentrations examined. However, for relatively low concentrations the chromium adsorption was somewhat suppressed by the lead ions.

A Dual Colorimetric and Fluorometric Sensor for Lead Ion Based on Conjugated Polydiacetylenes

A PDA based sensor, derived from a di-(2-picolyl) amine (DPA) substituted diacetylene monomer, displayed a selective colorimetric change and a large fluorescence enhancement in the presence of lead ions. The lead selective PDA-based chemosensor enabled easy detection of the presence of lead in 100% aqueous solution by the naked-eye.

Gold nanorods-based FRET assay for sensitive detection of Pb2+ using 8-17DNAzyme

In this paper, we have reported a sensitive assay for fluorescence "turn-on" detection of Pb(2+) in aqueous solutions based on FRET between gold nanorods (GNRs) and the FAM-labeled substrate strand of 8-17DNAzyme. The fluorescence of the FAM-labeled substrate strand is quenched when 8-17DNAzyme is adsorbed on GNRs surface through electrostatic interaction. In the presence of lead ions, the fluorescence is restored due to the decrease of FRET efficiency caused by the specific cleavage of the FAM-labeled substrate strand by the enzyme, which weakens the electrostatic interaction between the GNRs and short FAM-labeled DNA fragment. The interference of eleven common metal ions has been tested, indicating that Pb(2+) can be selectively detected. This method exhibits a high sensitivity for Pb(2+) with a detection limit of 61.8 pM and a linear range from 0.1 nM to 100 nM. It is a simple, sensitive, and selective method for Pb(2+) detection. Moreover, this sensing system obtained satisfying results for Pb(2+) detection in tap water samples.

Gold Nanoparticle‐Based Optical Probe for Quick Colorimetric Visualization of Cysteine

AbstractIn this work, a highly sensitive and selective optical probe for cysteine was developed using unmodified gold nanoparticles. Quick visual detection depended on the distance‐dependent optical properties of gold nanoparticles, the self‐assembly of cysteine on the surface of gold nanoparticles, and the chelation in the presence of lead ions. The form of complex could rapidly induced the aggregation of gold nanoparticles, thereby resulting in red‐to‐blue (or purple) color change. The concentration of cysteine was determined with a limit of detection (LOD) lower than 1 × 10−7 M by the naked eye and could further be monitored by a UV‐vis spectrometer easily. The highest selectivity was proved in comparison with other seventeen amino acids and the relative mechanism was detailedly investigated by the addition of ethylenediaminetetraacetate (EDTA).