Target Metal Ions Research Articles

Indigoidine biosynthesis triggered by the heavy metal-responsive transcription regulator: a visual whole-cell biosensor.

During the last few decades, whole-cell biosensors have attracted increasing attention for their enormous potential in monitoring bioavailable heavy metal contaminations in the ecosystem. Visual and measurable output signals by employing natural pigments have been demonstrated to offer another potential choice to indicate the existence of bioavailable heavy metals in recent years. The biosynthesis of the blue pigment indigoidine has been achieved in E. coli following heterologous expression of both BpsA (a single-module non-ribosomal peptide synthetase) and PcpS (a PPTase to activate apo-BpsA). Moreover, we demonstrated herein the development of the indigoidine-based whole-cell biosensors to detect bioavailable Hg(II) and Pb(II) in water samples by employing metal-responsive transcriptional regulator MerR and PbrR as the sensory elements, and the indigoidine biosynthesis gene cluster as a reporter element. The resulting indigoidine-based biosensors presented a good selectivity and high sensitivity to target metal ions. High concentration of target metal exposure could be clearly recognized by the naked eye due to the color change by the secretion of indigoidine, and quantified by measuring the absorbance of the culture supernatants at 600 nm. Dose-response relationships existed between the exposure concentrations of target heavy metals and the production of indigoidine. Although fairly good linear relationships were obtained in a relatively limited concentration range of the concentrations of heavy metal ions, these findings suggest that genetically controlled indigoidine biosynthesis triggered by the MerR family transcriptional regulator can enable a sensitive, visual, and qualitative whole-cell biosensor for bioindicating the presence of bioaccessible heavy metal in environmental water samples. KEY POINTS: • Biosynthesis pathway of indigoidine reconstructed in a high copy number plasmid in E. coli. • Visual and colorimetric detection of Hg(II) and Pb(II) by manipulation of indigoidine biosynthesis through MerR family metalloregulator. •Enhanced detection sensitivity toward Hg(II) and Pb(II) achieved using novel pigment-based whole-cell biosensors.

Synthesis and Characterization of Poly(pyrrole-1-carboxylic acid) for Preconcentration and Determination of Rare Earth Elements and Heavy Metals in Water Matrices.

Pyrrole was N-functionalized with solid carbon dioxide followed by chemical polymerization to create a new air-stable, granular, and water-insoluble sorbent, poly(pyrrole-1-carboxylic acid) (PPy-CO2). PPy-CO2 exhibited enhanced affinity for the sorption of metal ions compared to unfunctionalized PPy due to the incorporation of carboxylate functional groups directly onto the polymer backbone. As a freestanding sorbent material, immobilization to an additional solid support is not needed. Sorption, and therefore preconcentration, occurs simultaneously to achieve efficient removal and recovery of metal ions by a pH-dependent sorption-desorption mechanism. PPy-CO2 was evaluated on the analytical scale for the solid-phase extraction of a range of metal ions and found to efficiently preconcentrate rare earth elements (REEs), Th, and heavy metals (Cr, Fe, Cd, and Pb), which allowed quantitation by inductively coupled plasma mass spectrometry (ICP-MS). The impact of sorption parameters, such as solution pH, amount of sorbent, and sorption time, and the effect of desorption flow rate for recovery were investigated and optimized using ultrasound-assisted dispersive solid-phase extraction (UAD-SPE) with ICP-MS analysis. Maximum efficiency for sorption and recovery of most metal ions was achieved at a solution pH of 6.0, 10 mg of sorbent, a sorption time of 5 min, and desorption conditions of 1 mL of 2 M nitric acid applied at a flow rate of 0.25 mL min-1. Detection limits for REEs and Th ranged from 0.2-3.4 ng L-1 for REEs and Th and 0.9-5.7 ng L-1 for heavy metals. Linear ranges from 0.1-1000 μg L-1 for REEs and 0.1-500 μg L-1 for heavy metals and Th were also observed. PPy-CO2 successfully preconcentrated and facilitated the determination of the targeted metal ions in water matrices of varying complexity, including tap water, well water, river water, and produced water samples. These results indicate the potential application of PPy-CO2 for larger-scale recovery and removal of valuable or hazardous metal ions.

Fluorescence enhanced microfluidic sensor with CsPbI3 probe for lubricant copper ions on-site rapid detection based on SiO2 inverse opal photonic crystals

Cu2+ content in diesel engine lubricating oil refers to a vital parameter suggesting the quality of oil and judging mechanical wear. Accordingly, the on-site rapid copper ions content determination in lubricant is of great significance to safe operation of diesel engines. However, most of the current researches on detection are carried out in laboratory, requiring the use of large-scale equipment such as spectrometer, which are not suitable for rapid on-site detection. Quantum dot-based optical microfluidic chip provides the possibility for heavy metal ions on-site detection, but it is subject to the defect of weak fluorescence intensity, thereby the increase in sensitivity is limited. In the present study, a microfluidic sensor using SiO2 inverse opal photonic crystals (IOPCs) to heighten CsPbI3 perovskite quantum dots (PQDs) photoluminescence (PL) intensity is proposed, which can realize rapid Cu2+ content detection in lubricant. Firstly, the selective detection characteristic of CsPbI3 on Cu2+ was studied. Experimental results showed that the photoluminescence of CsPbI3 was significantly quenched by Cu2+ because electrons were effectively transferred from CsPbI3 to Cu2+. Subsequently, to enhance the fluorescence intensity of CsPbI3 probe, the SiO2 IOPCs structure was formed in chip detection well. The effective PL intensity of CsPbI3 PQDs was enhanced by the photonic stopband effect formed by the periodically arranged micro-nano structure of photonic crystals. This enhancement effect was attributed to the coupling effect between stopband with excitation and emission light. As the stopband of SiO2 IOPCs was coupled with the excitation light wavelength and emission light wavelength of CsPbI3, the enhancement factors could reach 17-fold and 22-fold, respectively. The mentioned strategy could effectively improve the detection sensitivity of the microfluidic sensor and reduce the detection limit to 0.34 nM. Moreover, the formed microfluidic sensor system can be used for determination of Cu2+ content in lubricating oil on site. Meanwhile, the sturdy porous structure of SiO2 IOPCs also facilitated target metal ions to be captured and enriched.

Ferrocene-functionalized Ni(II)-based metal-organic framework as electrochemical sensing interface for ratiometric analysis of Cu2+, Pb2+ and Cd2+

• Ferrocene-functionalized NH 2 -Ni-MOF was fabricated by post-synthesis modification. • NH 2 -Ni-MOF nanoplates promote the adsorption and pre-concentration of target metal ions. • The bonded Fc moiety improves the conductivity of MOF and acts as an reference reporter. • Improved reproducibility is obtained via the ratiometric strategy. • Simultaneous electrochemical detection of multiple toxic heavy metal ions is realized. The development of selective electrochemical response materials and new detection strategies are the research focus in the field of heavy metal ion (HMI) electroanalysis. Herein, a Ni(II)-based metal-organic framework (NH 2 -Ni-MOF) was synthesized and functionalized by electrochemically active molecule of ferrocene (Fc) via post-synthesis modification. Based on the Fc-functionalized NH 2 -Ni-MOF (Fc-NH 2 -Ni-MOF), a novel electrochemical ratiometric sensing platform was developed and applied for the simultaneous determination of various HMIs. The prepared NH 2 -Ni-MOF exhibits nanoplate structure, which is conducive to increase accessible electrode area and expose more active sites, thus promoting the adsorption and pre-concentration of HMIs. The modification of Fc on MOF not only enhances the electrical conductivity of the MOF material, but also provides an internal reference signal for the ratiometric analysis. Due to the excellent characteristics of the Fc-NH 2 -Ni-MOF, the as-prepared ratiometric electrochemical sensing platform exhibits wide linear ranges (0.001 μM to 2.0 μM for lead ions (Pb 2+ ), and 0.01 μM to 2.0 μM for copper ions (Cu 2+ ) as well as cadmium ions (Cd 2+ )) and high sensitivity (the detection limit toward Cu 2+ , Pb 2+ and Cd 2+ is 6.3 nM, 0.2 nM and 7.1 nM, respectively). In addition, compared with the non-ratiometric strategy, the reproducibility of ratiometric analysis is significantly improved. The developed electrochemical method with high sensitivity, selectivity and reliability exhibits bright application prospects in the detection of real samples. Moreover, the electrochemical application of MOF materials has been effectively expanded.

Recovery of Zinc from Municipal Solid Waste Incineration Fly Ash

In recent years, over one million tons of Municipal Solid Waste (MSW) incineration fly ash has been generated annually Taiwan. Only a small percentage of the ash was used as raw material for other utilities besides landfill. Fly ash contains many harmful heavy metals, such as Cd and Cr, among others; however, fly ash also contains many valuable metals, including as Zn, Pb, and Ga.To recover Zn from fly ash, in this work, an experiment was first designed to determine the physical and chemical properties of the fly ash. Then, treatment processes, including water leaching, acid leaching, and ion exchange were conducted.Test samples were subjected to scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), and atomic absorption spectroscopy (AAS) to determine their physical and chemical properties. Then, water leaching was conducted under optimal experimental conditions. Thereafter, acid leaching was performed using two different acids (hydrochloric and sulfuric) to extract the target metal ions, and finally the ion exchange process was deployed to concentrate and recover the target metal ions.Ultimately, an optimal process to recover zinc from MSW incineration fly ash was developed in this work. An aqueous solution containing approximately 1 wt% zinc was obtained by leaching with sulfuric acid. Zn was then concentrated using a chelating resin IRC-747 in column mode.

Research progress of solid phase extraction materials in the application of metal ion pretreatment

为避免摄入过量重金属、危害人类健康,应提高对金属离子的检测能力。常用的金属检测技术如电感耦合等离子体质谱、电热原子吸收光谱、火焰原子吸收光谱等可以有效识别痕量重金属,并且具有多组分分析能力以及检出限低、产量高等优点。但复杂样品本身浓度较低且基质干扰大,因此检测前需进行前处理以消除基质干扰,满足低浓度和小体积样品的检测需求。固相萃取是富集样品中金属离子常用的方法之一,开发能够进行高效、快速富集分离的固相萃取新材料及前处理技术是金属离子检测的关键。限制接触碳纳米管、纳米吸附剂、纳米粒子载体、磁性纳米粒子等纳米材料可提供大的比表面积和可调的官能团,以促进金属离子吸收,其优越的光学性能则可用于荧光和比色检测;高分子聚合物具有卓越的机械性能和化学稳定性,可用于微量金属粒子的前富集、分离和检测;离子印迹聚合物对目标离子具有选择性识别能力的空间结构,可以吸附待分离体系中的金属离子;双功能材料可同时进行多种金属离子的萃取和快速定量检测,新型的光敏络合物则可以将结合态的金属离子转变为游离态,使其被多种生物传感器快速检测,也可以研究生物体内金属离子的信号传递过程。该文综述了纳米材料、聚合物、功能材料等新型固相萃取材料的特点及在复杂样品前处理中的应用和研究进展,并对其未来发展方向进行了展望。

Bismuth Film-Coated Gold Ultramicroelectrode Array for Simultaneous Quantification of Pb(II) and Cd(II) by Square Wave Anodic Stripping Voltammetry

The widespread presence of heavy metals in drinking water sources arises as a major health concern, particularly in developing countries. The development of low-cost and reliable detection techniques is identified as a societal need to provide affordable water quality control. Herein, a bismuth film-coated gold ultramicroelectrode array (BF-UMEA) was used for the detection of Pb(II) and Cd(II) in water samples via square wave anodic stripping voltammetry (SWASV). Experimental parameters such as deposition time, Bi(III) concentration, acetate buffer concentration, pH, square wave frequency, amplitude, and step potential were all varied to determine their effects on the current peak intensities of the target metal ions. Ten-fold excess in the concentration of interferences was found to cause a decrease in the stripping peak areas of Cd(II) and Pb(II) in the following order of magnitude: benzene < NaCl < Ni(II) < Cu(II). Using Box–Behnken design, the optimum SWASV parameters that provided maximum current peak areas were 14.76 Hz (frequency), 50.10 mV (amplitude), and 8.76 mV (step potential). The limits of detection of the as-prepared BF-UMEA were 5 and 7 µg L−1 for Pb(II) and Cd(II), respectively. These results demonstrate the potential use of a BF-UMEA in SWASV for the trace quantification of Pb(II) and Cd(II) in water samples.

The impact of an Amberlite XAD-16-based chelating resin for the removal of aqueous Cd(II) and Pb(II)ions

The main objective of this study is to investigate the influence of the Amberlite XAD-16-based chelating resin, 1,8-(3,6-dithiaoctyl)-4-polyvinylbenzenesulphonate (dpvbs), for the removal of the highly lethal Pb(II) and Cd(II) from aqueous solutions. The extractor`s behavior is examined, as adsorbent as well as coordinating agent showing structural changes upon the interaction with the targeted metal ions. Elemental analyses, FTIR, electronic spectra, EDS and XPS were used to provide a close image of the composition, structural and morphological changes upon the interaction with Pb(II) and Cd(II). Thermal behavior of the sorption products, compared with the coordinating resin, were also, studied and the estimated thermodynamic parameters indicated an endothermic spontaneous sorption mechanism. The BET surface area, BJH desorption volume and the pore diameters increased upon chelation with Cd(II) and Pb(II), indicating the destruction of the cross-linking of the free resin. SEM and AFM studies confirmed the surface morphological change of dpvbs, after sorption processes. The sorption effectiveness was examined utilizing batch and column methods, showing high removal efficiency with an average sorption of 99.9%. dpvbs was tested for the removal of metal ions from tap watershowing a metal uptake of almost the same after 3 cycles, with an efficiency of 98–99%.

Novel nanoscale Yb-MOF used as highly efficient electrode for simultaneous detection of heavy metal ions

It is essential to develop new nanomaterials able to improve sensing performance of electrochemical sensors for determination of heavy metal pollutants. In this work, a novel nanoscale metal–organic-framework material (Yb-MOF) with Ytterbium (Yb) rare-earth metal core and benzenetricarboxylic (BTC) ligands was prepared in aqueous conditions using hydrothermal approach. The results have revealed highly porous structure of the as-synthesized material with specific active area up to 1166 m2 g−1. A sensing platform was then constructed by drop-casting Yb-MOF onto glassy carbon electrode for detection of two most commonly found heavy metal ion pollutants (Cd2+ and Pb2+) in water sources. The nanoporous structure of Yb-MOF is very profitable to the selective preconcentration of targeted metal ions. The detection limits were estimated to be 3.0 ppb, 1.6 ppb for Cd2+ and Pb2+ species, respectively. This work provides a new electrochemical sensing platform for fast and sensitive in-situ detection of water contaminants.

Studies on a glutathione coated hollow ZnO modified glassy carbon electrode; a novel Pb(ii) selective electrochemical sensor.

Herein, we report the electrochemical detection of heavy metal ions such as Pb(ii), Cd(ii) and Hg(ii) ions while using glutathione coated hollow ZnO modified glassy carbon electrode (Glu-h-ZnO/GCE). An excellent voltammetric response of the modified electrode towards these metal ions was observed by different voltammetric techniques. Among the different target metal ions, a selective electrochemical response (sensitivity = 4.57 μA μM−1) for the detection of Pb(ii) ions was obtained with differential pulse voltammetric (DPV) measurements. Besides, under optimal experimental conditions and in the linear concentration range of 2–18 μM, a very low detection limit of 0.42 μM was obtained for Pb(ii) ion. The observed electrochemical behaviour of Glu-h-ZnO/GCE towards these metal ions is in conformity with the band gap of the composite in the presence of various test metal ions. The band gap studies of the composite and various “Composite-Metal Ion” systems were obtained by reflectance as well as by computational methods where results are in close agreement, justifying the observed electrochemical behaviour of the systems. The lowest band gap value of the “Composite-Pb” system may be the reason for the excellent electrochemical response of the Glu-h-ZnO modified GCE towards the detection of Pb(ii) ion.

Attaining record-high magnetic exchange, magnetic anisotropy and blocking barriers in dilanthanofullerenes.

While the blocking barrier (Ueff) and blocking temperature (TB) for “Dysprocenium” SIMs have been increased beyond liquid N2 temperature, device fabrication of these molecules remains a challenge as low-coordinate Ln3+ complexes are very unstable. Encapsulating the lanthanide ion inside a cage such as a fullerene (called endohedral metallofullerene or EMF) opens up a new avenue leading to several Ln@EMF SMMs. The ab initio CASSCF calculations play a pivotal role in identifying target metal ions and suitable cages in this area. Encouraged by our earlier prediction on Ln2@C79N, which was verified by experiments, here we have undertaken a search to enhance the exchange coupling in this class of molecules beyond the highest reported value. Using DFT and ab initio calculations, we have studied a series of Gd2@C2n (30 ≤ 2n ≤ 80), where an antiferromagnetic JGd⋯Gd of −43 cm−1 was found for a stable Gd2@C38-D3h cage. This extremely large and exceptionally rare 4f⋯4f interaction results from a direct overlap of 4f orbitals due to the confinement effect. In larger cages such as Gd2@C60 and Gd2@C80, the formation of two centre-one-electron (2c-1e−) Gd–Gd bonds is perceived. This results in a radical formation in the fullerene cage leading to its instability. To avoid this, we have studied heterofullerenes where one of the carbon atoms is replaced by a nitrogen atom. Specifically, we have studied Ln2@C59N and Ln2@C79N, where strong delocalisation of the electron yields a mixed valence-like behaviour. This suggests a double-exchange (B) is operational, and CASSCF calculations yield a B value of 434.8 cm−1 and resultant JGd–rad of 869.5 cm−1 for the Gd2@C59N complex. These parameters are found to be two times larger than the world-record J reported for Gd2@C79N. Further ab initio calculations reveal an unprecedented Ucal of 1183 and 1501 cm−1 for Dy2@C59N and Tb2@C59N, respectively. Thus, this study offers strong exchange coupling as criteria for new generation SMMs as the existing idea of enhancing the blocking barrier via crystal field modulation has reached its saturation point.

Valorisation of Pine Cone as an Efficient Biosorbent for the Removal of Pb(II), Cd(II), Cu(II), and Cr(VI)

Valorisation of pine cone as an efficient, low-cost, and eco-friendly biosorbent for the removal of heavy metals from aqueous solutions is evaluated. The morphology and surface chemistry of the biosorbent are characterized by scanning electron microscopy, energy-dispersive elemental analysis, and Fourier transform infrared spectroscopy, revealing the presence of carboxylic and alcoholic functional groups that interact with metal ions. The effect of the contact time, pH, amount of adsorbent, and initial metal concentration in the adsorption is studied, resulting in removal percentages for Cd(II), Cu(II), Pb(II), and Cr(VI) (metal concentration of 5 mg L-1) of 82.24%, 93.71%, 94.67%, and 88.8%, respectively ([Formula: see text], 2 g L-1 of adsorbent), except for Cr(VI) ([Formula: see text], 10 g L-1). The equilibrium data of Pb(II) and Cd(II) were found to follow the Langmuir-Freundlich model, with maximum adsorption capacities of 100.01 and 78.73 mg g-1, respectively, whereas Cu(II) followed the Langmuir model with 33.55 mg g-1. Cr(VI) adsorption data also fitted the Langmuir model, and the maximum adsorption capacity was 57.36 mg g-1. Adsorption data was obtained at pH 5.4 for divalent metal ions and at pH 2 for Cr(VI) and in a range of metal concentrations ranging from 1 to 500 mg L-1 at 298.2 K. The presence of the three metal ions in the solution does not affect the percentage of the target metal ion adsorbed, proving the absence of competition between them and showing the pine cone to be an efficient adsorbent to treat multimetal effluents allowing water reuse.

Controlling assembly-induced single layer RGO to achieve highly sensitive electrochemical detection of Pb(II) via synergistic enhancement

In this work, the preparation of a single-layer nanocomposite electrode material with good electron transfer through controlled assembly was studied, and it was used for high-sensitivity electrochemical detection of Pb2+. Mechanism studies have found that single-layer graphene nanostructures bring significant advantages to electron transfer along RhB/RGO nanocomposite electrode material. This solving the main obstacle of low electron transfer caused by aggregation in electroanalysis. Moreover, since RhB has good metal ion adsorption capacity, it helps to enhance the interfacial adhesion between graphene and target metal ions. Through the synergistic enhancement of RhB and RGO, RhB/RGO shows high sensitivity in Pb2+ trace analysis. The detection limit is 10 nM, and the linear correlation coefficient is 0.9999. RhB/RGO/GCE sensors have been used to detect Pb2+ in environmental water. In addition, the competitive relationship between the active binding site and the electron transfer resistance (Rct) in the detection of Pb2+ was studied. This provides a reference for the design of electrode materials in the future.

A highly selective and sensitive thiophene substituted 1,3,4-oxadiazole based turn-off fluorescence chemosensor for Fe2+and turn on fluorescence chemosensor for Ni2+ and Cu2+ detection

In the present work, a newly synthesized thiophene substituted 1,3,4-oxadiazole derivative namely 2-(-4-(thiophene-3-yl)phenyl)-5-(5-(thiophene-3-yl)thiophene-2-yl)-1,3,4-oxadiazole [TTO] is characterized as chemosensor for detecting Fe2+, Ni2+ and Cu2+ metal ions through absorption and fluorescence studies. We found that, on changing media chemosensor shows different behavior with Fe2+, Ni2+ and Cu2+ metal ions. In ethanol-water (1/1,v/v, pH 7.2) medium on varying concentration of Fe2+, chemosensor shows turn off fluorescence, whereas Ni2+ and Cu2+ metal ions induced a strong turn on fluorescence respectively in methanol-water (1/1,v/v, pH 7.2) and acetonitrile-water (1/1,v/v, pH 7.2) media. The competitive metal ion experimental results revealed that chemosensor is highly selective for recognizing Fe2+, Ni2+ and Cu2+ ions without the interference of other metal ions (Pb2+, Ca2+, Mg2+, Co2+, Zn2+, Na+, and Mn2+). The detection limit of chemosensor for all targeted metal ions is in the range of 0.5–3 μM. The detection capacity for targeted metal ion studies shows less than 6.5 min indicating highly sensitive nature of the TTO. Job's plot indicates that, the binding stoichiometry between chemosensor TTO and targeted metal ions is 1:1 for Fe2+, Ni2+ and Cu2+ metal ions respectively. Further, linear variation in the fluorescence intensity of the chemosensor with different concentrations of the metal ions suggests the possibility of quantitative measurement of the targeted metal ions. Hence, our experimental findings very strongly suggest that, TTO can be used as chemosensor for detecting Fe2+, Ni2+ and Cu2+ metal ions in future.

Selective capture of Hg(II) and Ag(I) from water by sulfur-functionalized polyamidoamine dendrimer/magnetic Fe3O4 hybrid materials

Heavy metal ions pollution in water system has been imposing serious damage to aquatic ecosystem and public health. Efficient and selective capture of targeted metal ion from water is a great challenge and the focus of extensive research. Herein, sulfur-functionalized polyamidoamine (PAMAM) dendrimer/magnetic Fe3O4 hybrid materials were constructed for capturing Hg(II) and Ag(I) from water solution. The as-prepared adsorbents were fully characterized and the factors that influence the adsorption performance were investigated. The maximum adsorption of Fe3O4@SiO2-M2 were 0.8 and 1.29 mmol∙g−1 for Hg(II) and Ag(I). The hybrid materials display good adsorption selectivity and 100% selective adsorb Hg(II) with the presence of Ni(II), Mn(II), and Zn(II). Adsorption mechanism suggests sulfur groups play the predominant role during the capture of Hg(II). These hybrid materials exhibit excellent regeneration property and can be reused with practical application value.

Facile and green fabrication of electrochemical sensor based on poly(glutamic acid) and carboxylated carbon nanosheets for the sensitive simultaneous detection of Cd(II) and Pb(II)

This work describes the development of a simple, effective, and sensitive electrochemical sensor based on a glassy carbon electrode (GCE) modified with carboxylated carbon nanosheets (cCNSs) and poly(glutamic acid) (PGA) for the simultaneous detection of trace amount of Cd(II) and Pb(II) by differential pulse anodic stripping voltammetry (DPASV). The cCNSs were introduced to increase the effective surface area and electron transport efficiency of the sensor, while PGA acting as a capturer could capture target metal ions and eventually enhance the selectivity and sensitivity in the detection of Cd(II) and Pb(II). The designed sensor showed a linear range of 1.0–100.0 μg/L for both metal ions, with detection limits (S/N = 3) of 0.13 μg/L for Cd(II) and 0.15 μg/L for Pb(II), respectively. The sensor was applied to the simultaneous detection of Cd(II) and Pb(II) in the water and rice samples, and the results were in good agreement with those obtained by graphite furnace atomic absorption spectrometry (GFAAS). It also gave excellent performance with regard to its selectivity, recovery, stability, and reproducibility.

Sensitive and selective detection of Cu2+ and Pb2+ ions using Field Effect Transistor (FET) based on L-Cysteine anchored PEDOT:PSS/rGO composite

Herein, Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/reduced graphene oxide (rGO) (PEDOT:PSS/rGO) composite was prepared and further functionalized with L-Cysteine (LC) to manifest sensitive and selective detection of copper (Cu2+) and lead (Pb2+) ions using Field Effect Transistor (FET) in the concentration range of 1–60 µg/L. The sensor (PEDOT:PSS/rGO/L-Cysteine) exhibits low-voltage operations, highly sensitive and selective towards target metal ions (Cu2+ and Pb2+). The lower detection limits for Cu2+ and Pb2+ were found to be 0.33 µg/L and 2.36 µg/L, which is well below the World Health Organization WHO recommendations (2 mg/L (2 ppm) for Cu2+ ions and 10 µg/L (10 ppb) for Pb2+ ions.

Preparation of Highly Selective Sorbents Composed of Peptides and Silica Using Novel Molecular Imprinting Technology for Target Metal Ions

A novel molecular imprinting technology was developed to prepare highly selective sorbents, composed of adhesive peptides and microporous silica particles, for the adsorption of target metal ions from aqueous environments. Using solid-phase peptide-synthesis, tyrosine-, lysine-, and histidine-containing peptides were tailored to contain tyrosine-, lysine- and histidine-rich regions. The tyrosine residues of the peptide were converted to 3,4-dihydroxy-L-phenylalanine (DOPA) residues to give the peptides adhesive properties mimicking the adhesion of mussel-foot proteins to wet surfaces. The resulting DOPA-peptides were incubated with target metal ions Ni(II), Cu(II), Co(II), or Zn(II), and subsequently with microporous silica particles, at pH 8.0 and 25°C. Almost all the DOPA-peptides, with the metal ions, strongly attached to the particles within 24 h and were not detached from them upon washing with an aqueous solution of pH 1–12. However, the metal ions were easily released from the particles at a pH below 7.0, implying that imprinted cavities from the target metal ions, created on the peptide-immobilized silica particles, remained after the removal of the template metal ions. The metal adsorption characteristics of the resulting particles, which were termed metal-imprinted peptide–silica particles (metal-iPSPs), were investigated. The target metal ions were adsorbed to metal-iPSPs at a pH of 8.0. The adsorption kinetics fit a pseudo-second-order model well. The adsorption isotherm was well approximated using the Langmuir model, indicating that the metal-iPSP surface was homogeneous, adsorption sites were equivalent, and the coverage formed a monolayer. The metal-iPSPs exhibited a significant and high selectivity for the imprinted target metal ions in the presence of an equimolar quantity of competitive metal ions.

Recovery of pure molybdenum and vanadium compounds from spent petroleum catalysts by treatment with ionic liquid solution in the presence of oxidizing agent

Nonaqueous solutions were employed to investigate the selective recovery of vanadium and molybdenum from the spent petroleum catalysts. In this work, commercial extractants such as D2EHPA, Alamine336 and Aliquat336, and an ionic liquid synthesized from Aliquat336 and D2EHPA, ALi-D2, were employed as a lixiviant and extractant for the target metal ions in the presence of oxidizing agent, H2O2. Among the 4 nonaqueous systems, ALi-D2 showed the best performance for the selective and effective leaching of vanadium and molybdenum over alumina, nickel and iron. The effect of several parameters on the leaching efficiency was also studied. Under the optimum conditions, the leaching percentage of vanadium and molybdenum was 74.6 and 89.6% in the first stage and 26.0 and 66.9% in the second stage by ALi-D2 system. Vanadium and molybdenum from the ALi-D2 loaded phase can be sequentially precipitated by NH4Cl and BaCl2 solutions in alkaline media. Precipitation percentage of vanadium were 94.2% and its purity was 99.5%, whereas that of molybdenum was 99.4% with 84.1% purity. A process was proposed for recovery of vanadium and molybdenum from the spent petroleum catalysts. Pure vanadium and molybdenum compounds can be recovered by this process with less burden to the environment.

Coral-inspired “nanotentaclization” porous composite gel for efficient removal of Lead(II) from aqueous solution

Specific surface area and active groups are major concerns in the design and synthesis of metal ion adsorbent. Inspired by coral's high efficiency in preying on tiny plankton in the ocean, we pioneered a simple method for the in situ construction of “nano-tentacles” based on the original porous material skeleton. The introduction of “nano-tentacles” can further redesign and remolding of the existing interconnected pores to increase the specific surface areas and specific chelating sites for target metal ions. Herein, a proof-of-concept design is illustrated by in situ growing (3-aminopropyl)trimethoxysilane (APS) on the inner wall of the porous structure of chitosan/graphene oxide composite gel (CGG). The resulting material (NT-CGG) has a distribution coefficient (Kd) of 1.25 × 108 mL g−1, which exhibits ultrahigh affinity for lead ions, and the uptake capacity can reach 470 mg g−1. More significantly, the NT-CGG can effectively remove lead from 10 ppm to undetectable levels (≤0.02 ppb) with remove efficiency ≥99.9998% in the breakthrough experiment. The method proposed in this paper may be widely applicable to the redesign and remolding of most existing porous materials.