Metal Ions In Solution Research Articles

Development of a new generation of ion beams

Ion beams have many applications. Junior Associate Professor Masahi Nojima, Research Institute of Science and Technology at the Tokyo University of Science, Japan, is working to create a new generation of ion beams. Already, he has successfully developed new techniques for producing focused ion beams (FIB). In his most recent work, Nojima has developed a metallic solution ion source that will be used to construct unknown functional materials by using ion beams made up of specific elements. The metallic solution ion source can generate a copy of an original structure using elementally selected materials. With support from the Japan Society for the Promotion of Science (JSPS), KAKENHI, the academic incentive system of the KIOXIA Corporation 2021 and the Toshiba Electric Devices & Storage Corporation 2021, Nojima is seeking to open up new materials for use as ion sources utilising electrospray ionisation (ESI) methods. By harnessing the elements of FIBs primarily created from liquid metal ion source (LMIS) by field ionisation processes, Nojima hopes to create new generations of ion beams. To date, he and the team have displayed the result of mass separating metallic ion solution ion beams on random conditions and, looking ahead, intend to estimate the stopping range of mass selected ion beams in solid materials.

Extraction of some heavy metal ions from aquatic solution by banana peel-based biosorbents

In this work, economic, natural, and eco-friendly biosorbent want to be advised instead of traditional methods. For that reason, banana peel-based biosorbents were been done to remove Cu2+, Ni2+, and Co2+ ions from the solution by batch method. Moreover, how their natural assets like density, water intake, solubility, and heavy metal extraction performance were affected by their starch and oil contents had been determined. Flame atomic absorption spectroscopy (FAAS) having been using for the analysis of biosorbents uprooting performance. The density of the biosorbents had worked according to ASTM D 792 standards. As a result, the untreated banana peel-based biosorbents had transported 4.87 mg of Co2+ ions, 4.73 mg of Ni2+ ions, and 4.29 mg of Cu2+ ions from 25 ml 7 ppm of each heavy metal ions solution with 175 rpm agitation speed at 24 °C during half-hour.

Copper-Hydrazide Coordinated Multifunctional Hyaluronan Hydrogels for Infected Wound Healing.

Bacterial infection and delayed healing are two major obstacles in cutaneous wound management, and developing multifunctional hydrogels with antibacterial and prohealing capabilities presents a promising strategy to dress wounds. However, the simple and facile fabrication of such hydrogel dressings remains challenging. Herein, we report the first observation on hydrazide-metal coordination crosslinking that is utilized to successfully construct a series of hyaluronan (HA)-metal hydrogels by mixing hydrazided HA and metal ion solutions. Considering the antibacterial, prohealing, and proangiogenic properties of HA and Cu(II), as a proof of principle, a HA-Cu hydrogel was systematically investigated as a wound dressing. Surprisingly, the hydrazide-Cu(II) coordination was dynamic in nature and imparted the HA-Cu hydrogel with physicochemical multifunctions, including spontaneous self-healing, shear-thinning injectability, reversible pH/redox/ion pair triple responsiveness, etc. Moreover, the HA-Cu hydrogel exhibited a robust broad-spectrum antibacterial activity and could significantly accelerate infectious wound healing. Impressively, glutathione-triggered hydroxyl radical generation further potentiated wound healing, providing a paradigm for on-demand antibacterial activity enhancement. Hence, the HA-Cu hydrogel is a clinically applicable "smart" dressing for multi-scenario wound healing. We envision that the simple and versatile coordination approach opens up a new avenue to develop multifunctional hydrogels and shows great potential in frontier fields, such as biomedicine, wearable devices, and soft robots.

Test of elimination of cadmium and lead ions from water using polyurethane loaded with Cymbopogon citratus activated carbon

The elimination of heavy metals from industrial and agricultural wastewater became a challenging environmental topic due to their health hazards. Adsorption is one of the physicochemical techniques that proved its effectiveness in removing inorganic pollutants at low concentrations. Polymer-based composites using inorganic fillers have received increased attention due to their adsorptive properties. In addition, loaded/modified polyurethane foams have been effectively tested in removing heavy metals from polluted water. In this work, activated carbon derived from valorized Cymbopogon citratus (lemongrass) was synthesized by simple pyrolysis and activation with hydrogen peroxide and used as a filler in the polyurethane foam. The characteristics and properties of the prepared activated carbon were assessed using several methods and techniques. The cost-effective activated carbon-loaded polyurethane was synthesized in a straightforward step in the shape of pellets and used to eliminate lead (II) and cadmium (II) ions from water. It demonstrated a significant adsorption capacity even after one filtration. Furthermore, the effects of the adsorbate concentration and the number of filtrations were investigated. Highlights Cymbopogon citratus plant was valorized. Cost-effective C. citratus activated carbon-Loaded polyurethane foams were prepared to remove Cd2+ and Pb2+ from water. High removal efficiency was obtained using 150 mg/L metal ion solutions after one filtration.

The incorporation of upper vs lower rim substituted thia- and calix[4]arene ligands into polydiacethylene polymeric bilayers for rational design of sensors to heavy metal ions

1,3-Diketone calix [4]arene (CA) and thiacalix [4]arene (TCA), with the hydrophobic substituents introduced onto lower or upper rims respectively, form mixed aggregates with 10,12-pentacosadiynoic acid (PCDA) through the thin film hydration technique. Computer simulations, showing the arrangement of TCA and CA molecules in supramolecular clusters with PCDA molecules, suggest that PCDA assemblies with both cyclophanes are a convinient basis for the coordination of metal ions. However, photopolymerization of mixed aggregates reveals more disruption of the vesicular nanostructure of polydiacetylene (PDA) when CA molecules are included compared to TCA. The incorporation of the TCA and CA ligands influences the ability of the mixed PDA-bilayers to conformational and spectral changes and provides tight coordination of Tb3+ ions and efficient sensitizing of the Tb3+-centered luminescence. The PDA-bilayers incorporated by terbium TCA complex provide more sensitive response on the series of heavy metal ions vs their CA-based analogues. The surface exposed TCA rims and carboxylate moieties of PDA provide two different binding sites for Tb3+ and heavy metal ions. Both distribution of Tb3+ and heavy metal ions between these sites and heterometallic complex formation are revealed as the factors affecting the luminescence response of PDA-TCA terbium complex in the solutions of heavy metal ions. The interplay between these factors is the reason for the different luminescence response of PDA-TCA terbium complex on Cd2+, Hg2+ and Pb2+ ions. The PDA-vesicles incorporated by terbium TCA complex exhibit easier phase separation vs the PDA vesicles themselves, which favors the extraction of Pb2+ ions.

Selective Adsorption of Au(Ⅲ) by Activated Carbon Supported Polythioamides and Adsorption Mechanism

By using in-situ synthesis of polythioamide (PTA) on activated carbon (AC), a polythioamide-modified activated carbon-based adsorbent (AC-PTA) was successfully prepared and used to study the selective adsorption effect and mechanism of Au(Ⅲ) in wastewater. The results showed that AC-PTA exhibited excellent selective adsorption to Au(Ⅲ) in the coexisting solution of multiple metal ions in a wide pH range (<5.0). The adsorption effect for Au(Ⅲ) was the best at a pH of 2 and 3; the concentration of residue Au(Ⅲ) was less than 0.1 mg·L-1, whereas other metals were barely adsorbed. The selective adsorption process for Au(Ⅲ) conformed to the pseudo-second kinetic model (R2=0.9853), the thermodynamic process conformed to the Langmuir isotherm process (R2=0.9936), and adsorption capacity was up to 2018 mg·g-1. Such advantages were mainly attributed to the coordination interaction between the -C([FY=,1]S)NH- functional groups on the AC-PTA surface and Au(Ⅲ), the electrostatic adsorption between the positive AC-PTA and negative Au(Ⅲ) complex anions, and the direct reduction of Au(Ⅲ) by AC. The successful recovery of gold was finally realized by burning the adsorbed AC-PTA at 1000℃ for 4 hours under air conditions, and solid gold with a mass fraction higher than 90.0% was obtained. This study provided the possibility for selective adsorption and recovery of low concentration Au(Ⅲ) from actual wastewater.

Exploitation of polypyrrole nanostructured thin films for detecting poisonous lead metal ions using surface plasmon resonance technique

Optical refractive index sensor based on highly sensitive and reliable technique i.e. Surface Plasmon Resonance (SPR) uses the principle of refractive index change at the interface of metal and dielectric for sensitive detection of analyte. In SPR configuration, Surface Plasmon (SP) mode is excited at the interface. Polymer film of polypyrrole nanostructured thin film was prepared using chemical route and spin coating method. Lead metal ions solution was prepared of different concentration. The resonance parameters of the prepared sensor structure showed a systematic variation with continuous rise in the concentration of lead ions. The prepared sensor structure i.e. prism/Au/PPy is found to be highly sensitive towards detecting lead ions at room temperature. The sensor was tested for a concentration range varying from 0.5 to 50 ppm and found to exhibit fast response and recovery time. Sensitivity ∼ 0.767 °/ppm was achieved for the presently prepared sensor for detecting low concentration of 0.5 to 10 ppm.

Heat-based procedure for detectability enhancement of colorimetric paper-based spot tests

Colorimetry is an analytical procedure in which a colored compound is formed or degraded from a selective reaction between the analyte and a chromophore followed by color intensity measurement for quantification purposes. The employment of paper-based analytical devices as a solid substrate to perform chemical reactions enabled the miniaturization of the analytical system, thus requiring a minimum volume of sample (e.g., µL) and resulting in low cost, disposability, and ease of use. On the other hand, the detectability of such devices is usually not suitable for a variety of practical applications where the analyte concentration is present in either low parts-per-million or high parts-per-billion concentration range. In this study, we describe a simple procedure for analyte preconcentration (i.e., enrichment) based on a multiple and automated sample delivery of 15 µL per time on a heated paper surface. In this procedure, an aliquot of the sample solution diffuses through the center of the paper to form a circular spot, followed by quick solvent vaporization prior to the next volume injection. After the enrichment procedure,15 µL of the reagent is added to perform the colorimetric reaction. The applicability of the proposed procedure was demonstrated for the determination of nickel (II) in natural waters and iron (III) in ethanol fuel using dimethylglyoxime and 1,10 phenanthroline as colorimetric reagents, respectively. By relating the color intensity of the products formed to the concentration, the limits of detection were as low as 0.1 mg L−1 for nickel (II) and iron (III) using 20 and 10 aliquots of 15 µL of each metal ion solution. Under these conditions, the enrichment factors were 180- and 20-fold higher for Ni2+ and Fe3+, respectively, with a total time of analysis inferior to 10 min. We anticipate that the proposed procedure can be tailored for a wide range of analytical problems using colorimetric determinations in spot tests with low concentration detectability and ease of operation.

Synthesis of bifunctional groups-integrated mesoporous silica hybrid adsorbent for simultaneous removal of Hg2+ and Cu2+ ions from aqueous solution

A mesoporous organosilica hybrid integrated with disulfide and amine groups was synthesized in a sol-gel co-condensation method using Pluronic P123 as structural directing surfactant. In the initial silane mixture, the organic functional groups content of disulfide and amine groups along with tetraethyl orthosilicate incorporated into the pore walls of mesoporous silica is approximately 30 mol/g (BDSTES: AAPTES is 15:15 mol/g). The surface area, pore volume and pore size of the prepared disulfide bridged and amine groups integrated mesoporous silica hybrid adsorbent (MSHA@SS-NH2) materials are approximately 462 m2/g, 0.58 cm3/g, and 2.6 nm, respectively. The MSHA@SS-NH2 adsorbent materials demonstrated that adsorption equilibrium could be achieved in 30 min and the adsorbed amount of Hg2+ and Cu2+ ions calculated to be about 166 mg/g and 153 mg/g, respectively, with the ∼ 90% of Hg2+ ions and ∼ 84% of Cu2+ ions removal capacity from the mixture of initial metal ions solutions (100 mg/L). By washing with 0.1 M HCl solution and regenerating with aqueous ammonia (3%) solution, the MSHA@SS-NH2 adsorbent demonstrated recyclable and reusable ability up to 5 times. As a result, the MSHA@SS-NH2 material developed could be used as an effective adsorbent for the simultaneous removal of Hg2+ and Cu2+ ions from wastewater.

Analysis of the structure and properties of dextran produced by Weissella confusa

An EPS produced by Weissella confusa H2 was purified through Sephadex G-100, and the preliminary structure characteristics and biological activities of H2 EPS were analyzed. Molecular mass of purified H2 EPS was 2.705 × 106 Da as measured with gel permeation chromatography (GPC). Composition of monosaccharides, nuclear magnetic resonance (NMR) spectroscopy spectroscopy and fourier transform infrared (FT-IR) showed that the EPS was a linear homopolysaccharide, mainly constituted of glucose and it is suggested that the EPS was dextran with α-(1 → 6) glycosidic bonds and a few α-(1 → 3) branches. Atomic force micrograph (AFM) and scanning electron microscopy (SEM) analysis of dextran further revealed sheets branched microstructure anchored with many irregular protuberances in aqueous solution. The XRD pattern reflected non-crystalline amorphous nature. In addition, the solubility, water-holding capacity, thermal property, rheological property and heavy metal chelating activity of the purified H2 dextran were determined. The dissolution percentage and water holding capacity of the dextran were 98.78 ± 1.37% and 426.03 ± 7.26%, respectively. The dextran exhibited good hydrophilicity, thermal stability and heavy metal chelating activity. Rheological studies exhibited rotational speed, pH, temperature, metal ions solutions dependent semiviscous nature. These results support its use as an additive in the food and environmental protection fields.

Triazine-Based Functionalized Activated Carbon Prepared from Water Hyacinth for the Removal of Hg2+, Pb2+, and Cd2+ Ions from Water.

A novel chelating adsorbent, based on the functionalization of activated carbon (AC) derived from water hyacinth (WH) with melamine thiourea (MT) to form melamine thiourea-modified activated carbon (MT-MAC), is used for the effective removal of Hg2+, Pb2+, and Cd2+ from aqueous solution. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) theory confirm the successful functionalization of AC with the melamine thiourea chelating ligand through the amidation reaction between the carboxyl groups of oxidized activated carbon (OAC) and the amino groups of melamine thiourea (MT) in the presence of dicyclohexylcarbodiimide (DCC) as a coupling agent. The prepared MT-MAC exhibited extensive potential for the adsorption of the toxic metal ions Hg2+, Pb2+, and Cd2+ from wastewater. The MT-MAC showed high capacities for the adsorption of Hg2+ (292.6 mg·g–1), Pb2+ (237.4 mg·g–1), and Cd2+ (97.9 mg·g–1) from aqueous solution. Additionally, 100% removal efficiency of Hg2+ at pH 5.5 was observed at very low initial concentrations (25–1000 ppb).The experimental sorption data could be fitted well with the Langmuir isotherm model, suggesting a monolayer adsorption behavior. The kinetic data of the chemisorption mechanism realized by the melamine thiourea groups grafted onto the activated carbon surface have a perfect match with the pseudo-second-order (PSO) kinetic model. In a mixed solution of metal ions containing 50 ppm of each ion, MT-MAC showed a removal of 97.0% Hg2+, 68% Pb2+, 45.0% Cd2+, 17.0% Cu2+, 7.0% Ni2+, and 5.0% Zn2+. Consequently, MT-MAC has exceptional selectivity for Hg2+ ions from the mixed metal ion solutions. The MT-MAC adsorbent showed high stability even after three adsorption–desorption cycles. According to the results obtained, the use of the MT-MAC adsorbent for the adsorption of Pb2+, Hg2+, and Cd2+ metal ions from polluted water is promising.

Transporter drives the biosorption of heavy metals by Stenotrophomonas rhizophila JC1.

To better understand the function of transporter in heavy metal detoxification of bacteria, the transporters associated with heavy metal detoxification in S. rhizophila JC1 were analyzed, among which four members were verified by RT-qPCR. In addition, the removal rates of four single metal ions (Cr6+, Cu2+, Zn2+, Pb2+) and polymetallic ions by strain JC1 were studied, respectively. We also researched the physiological response of strain JC1 to different metal stress via morphological observation, elemental composition, functional group and membrane permeability analysis. The results showed that in the single metal ion solution, removal capacities of Cu2+ (120 mg/L) and Cr6+ (80 mg/L) of S. rhizophila JC1 reached to 79.9% and 89.3%, respectively, while in polymetallic ions solution, the removal capacity of each metal ion all decreased, and in detail, the adsorption capacity was determined Cr6+>Cu2+>Zn2+>Pb2+ under the same condition. The physiological response analyses results showed that extracellular adsorption phenomena occurred, and the change of membrane permeability hindered the uptake of metal ions by bacteria. The analysis of transporters in strain JC1 genome illustrated that a total of 323 transporters were predicted. Among them, two, six and five proteins of the cation diffusion facilitator, resistance-nodulation-division efflux and P-type ATPase families were, respectively, predicted. The expression of corresponding genes showed that the synergistic action of correlative transporters played important roles in the process of adsorption. The comparative genomics analysis revealed that S. rhizophila JC1 has long-distance evolutionary relationships with other strains, but the efflux system of S. rhizophila JC1 contained the same types of metal transporters as other metal-resistant bacteria.

Identification and determination of multiple heavy metal ions using a miniaturized paper-based optical device

A simple colorimetric paper-based sensor array (optical tongue), which can quickly and accurately identify and discriminate twenty-five kinds of heavy metal ions, is developed. It functions by immobilizing six metal indicators on the paper substrate using polyvinyl chloride. Exposing the device to the aqueous solution of metal ions produces a unique colorimetric signature for each ion, enabling discrimination of the ions by visual inspection. Further analysis of the colorimetric patterns by chemometrics data analysis methods leads to a clustering map for accurate classifying of the metal ions at different concentrations (10.0, 5.0, 2.5, and 1.0 mg L−1). In addition, the device was applied to analyze binary and ternary mixtures of metal ions as well. An interesting feature of this tasting device is speciation analysis of an element of different oxidation states and their mixtures. Beside to qualitative analysis, it represented quantitative analysis ability, e.g., for Zn2+ and Co2+, in the concentration ranges of 0.10–10.00 mg L−1 (R2 = 0.99) and 0.25–12.50 mg L−1 (R2 = 0.99) and detection limits of 0.03 and 0.08 mg L−1, respectively. This optoelectronic tongue shows promising results to be used potentially of on-site analysis of water for its quality.

Modified magnetic-metal organic framework as a green and efficient adsorbent for removal of heavy metals

A novel adsorbent was prepared for fast and selective removal of heavy metal ions Hg(II), Cd(II) and Pb(II). The adsorbent was simply prepared by immobilizing tripeptide glutathione on the surface of a magnetic metal-organic framework (Fe3O4-ZrMOF). The microcrystalline structure of ZrMOF provided a high surface area in an ordered structure for deposition of large amounts of glutathione. All measurements were performed by electrothermal atomic absorption spectroscopy (EAAS). Adsorbent structure was studied by using X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier-transform infrared (FT-IR) spectroscopic methods, transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM), Zeta potential measurement, and BET analysis. Computational modeling was used to obtain optimized structures for the adsorbent before and after binding to the heavy metals, which showed the most stable adduct for Hg attached to Fe3O4-ZrMOF@GSH (ΔGº = −1068.45 kJmol−1L−1). In removal procedure, the effective factors were discussed and optimized, such as the dosage of adsorbent, initial pH of solution, contact time, and initial concentration of metal ions. The maximum adsorption capacity (Qm) for Hg, Cd, and Pb was calculated to be 431, 393, and 397 (mg g−1), respectively. The proposed adsorbent was able to remove 95–99% of these ions from the solution, under optimum conditions in 20 min. Adsorption isotherm and kinetics for Hg(II), Cd(II), and Pb(II) on Fe3O4-ZrMOF@GSH were well described by Langmuir model and pseudo-second-order kinetics, respectively.

Effect of Mono- and Divalent Metal Ions on Current-Voltage Features of a λ-DNA Solution Electrically Driven in a Microfluidic Capillary.

The interactions of DNA molecules and metal ions lead to changes in their configuration and conformation, which in turn influence the current characteristics of the solution as DNA molecules are translocated through a micro/nanofluidic channel and ultimately cause serious impacts on the practical applications of DNA/gene chips for precisely manipulating and studying the molecular properties of single DNA molecules. In this study, the current characteristics of λ-DNA solutions without or with metal ions (i.e., K+, Na+, Mg2+, and Ca2+) were experimentally investigated when they were transported through a 5 μm microcapillary under an external electric field with asymmetric electrodes. Experimental data indicated some meaningful results. First, the current-voltage relations of the metal ion solutions were all linear, while those of λ-DNA solutions without or with metal ions were all nonlinear and followed power functions, of which the indices were related to the type, valence, and mobility of ions. Furthermore, as the concentrations of metal ions increased, the power indices of the λ-DNA solutions with monovalent metal ions increased, while those of the λ-DNA solutions with divalent ions decreased. Finally, the main reasons for the current characteristics were theoretically attributed to two possible mechanisms: the polarizations on the asymmetric electrodes and the interactions between λ-DNA and metal ions. These findings are helpful for the design of new biomedical micro/nanofluidic sensors and labs on a chip for accurately manipulating single DNA molecules.

Development of highly sensitive metal-ion chemosensor and key-lock anticounterfeiting technology based on oxazolidine

Optical chemosensors and ionochromic cellulosic papers based on oxazolidine chromophores were developed for selective photosensing of metal ions and information encryption as security tags, respectively. The oxazolidine molecules have been displayed highly intense fluorescent emission and coloration characteristics that are usable in sensing and anticounterfeiting applications. Obtained results indicated that oxazolidine molecules can be used for selective detection of pb2+ (0.01 M), and photosensing of Fe3+, Co2+ and Ag+ metal ion solutions by colorimetric and fluorometric mechanisms with higher intensity and sensitivity. Also, oxazolidine derivatives were coated on cellulosic papers via layer-by-layer method to prepare ionochromic papers. Prepared ionochromic papers were used for printing and handwriting of optical security tags by using of metal ion solutions as a new class of anticounterfeiting inks with dual-mode fluorometric and colorimetric securities. The ionochromic cellulosic papers can be used for photodetection of metal ions in a fast and facile manner that presence of metal ions is detectable by naked eyes. Also, key-lock anticounterfeiting technology based on ionochromic papers and metal ion solution as ink is the most significant strategy for encryption of information to optical tags with higher security.

Spontaneous Carbon-Support-Induced Metal Deposition.

Recent investigations have demonstrated the possibility for spontaneous deposition of noble metal nanoparticles from corresponding metal ion solutions on carbon supports, in the absence of additional reductants in the experimental systems. This process is a result of a direct redox reaction between the solute metal species and the carbon materials and differs from the typical electroless plating, the latter requiring additional reducing agents or catalysts to drive the reduction reaction. Due to the diversity of the used carbon materials including both dispersed nanostructured carbons and supported electrode-like carbon materials and the different approaches to follow the process and characterize the products, these studies are scattered in the scientific literature. The aim of the present review is to put these diverse investigations in a common context and focus on the existing experimental findings, the ways to monitor and control the process, and the general concept. Some aspects that need to be further corroborated are outlined in view of the involvement of the spontaneous redox process as a practical tool for the development of new catalysts.

Biosynthesis of Silver Nanoparticles from Rhododendron arboreum for Metal Sensing, Antibacterial Assessment, and Photocatalytic Degradation

The nanomaterial industry has focused on green synthetic methods to avoid unpleasant compounds produced during manufacturing, offering eco‐friendly, sustainable, and nature‐derived alternative methods. In this study, silver nanoparticles (Ag NPs) have been synthesized from an aqueous extract of the leaves of Rhododendron arboreum, where the pH of the reaction mixture is found to be crucial. The reaction progress monitored using the UV‐Vis spectrophotometer displayed a strong absorption band at 425 nm at pH 9, suggesting an optimum pH for the synthesis. The Ag NPs thus synthesized were characterized using instrumental techniques. The attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy showed the presence of phytoconstituents in the aqueous extract, which are believed to be responsible for reducing Ag+ ions to Ag NPs and capping agents on its surface for stability. X‐ray diffraction (XRD) showed a highly crystalline nature, and energy‐dispersive X‐ray (EDX) demonstrated the presence of metallic silver. The scanning and transmission electron microscopy (SEM and TEM, respectively) revealed crystalline morphology and monodisperse Ag NPs of sizes ranging from 23 to 41 nm. Furthermore, the metal‐sensing activity of biosynthesized Ag NPs was evaluated using various metal ions; they were utilized for highly selective and sensitive colorimetric detection of Hg2+ in an aqueous medium among various metal ion solutions tested with the detection limit of 0.5 mM using the UV‐Vis spectrophotometer. Similarly, they were also shown to be effective for the nanocatalytic activity for degradation of methylene blue dye up to 81%. These studies demonstrated Ag NPs as potential candidates for selective detection of mercury in water resources, a tool for sensing the heavy metals and degradation of synthetic dye from industrial effluents in wastewater treatment. Having the high surface‐to‐volume ratio and size‐dependent functionality of Ag NPs, further optimization studies at micromolar and nanomolar detection limits will avail its better industrial utilization. Moreover, biologically mediated Ag NPs can also exhibit good antimicrobial activity against Staphylococcus aureus and Escherichia coli.

Green synthesis, characterisation of Au and Ag nanoparticles by various bioextracts and their usability at graphite electrode modification.

In this study, the biosynthesis of Au and Ag nanoparticles (AuNp and AgNp) with a green chemistry approach was performed by using bioextracts of various fruits and vegetables (Lycopersicon esculentum (LE), Cucumis sativus (CS), Malus domestica (MD), Cucurbita pepo (CP), Apiumgraveolens var. rapaceum (AVR), Prunus cerasifera (PC), Oleraceae var. botrytis (OVB)). In the determination of optimum experimental conditions, the parameters such as the type and concentration of bioextract, concentration of metal ion solutions, the ratio of metal ion solution to bioextract, pH, reaction time and temperature were found to be significant. The characterisation of AuNp and AgNp synthesized by providing the most appropriate experimental conditions was performed by UV-Vis., SEM, EDX, XPS and FTIR techniques. The characterisation study showed that, AuNp and AgNp were successfully synthesized and detailed information was obtained about their stabilities, sizes, homogeneities etc. In the final step, the usability of the green synthesized nanoparticles in the modification of pencil graphite electrodes (PGE) was investigated. Electrochemical characterisation of AuNp/GE and AgNp/GE electrodes was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The obtained results and calculated electrochemical parameters showed that these modified electrodes have better conductivity, electron transfer rate and electrocatalytic activity.

Study of simultaneous adsorption efficiency of metals using modified organic and synthetic adsorbents

Water contamination by heavy metals represents a high risk of environmental pollution and a precursor of several human diseases. The presence of these metals at high levels in wastewater treatment plants and industrial effluents motivated the search for remediating these pollutants. Among remediation methods, adsorption is extensively used to decontaminate waters containing these metals. Thus, this study prepared, characterized, optimized, and applied two types of adsorbents to a prepared metal ion solution (PMS): a bioadsorbent based on banana peel flour (BPF) and a synthetic adsorbent based on magnetite encapsulated by chitosan (MEC). A systematic study was performed with PMS containing Al (III), Ba (II), Pb (II), Cu (II), Cr (III), Fe (II), Mn (II), and Zn (II) to determine the best conditions for simultaneous metal ion adsorption Adsorption studies evaluated the experimental adsorption isotherms according to the variation in pH values, the mass of adsorbents, and contact time, and the kinetic study applied pseudo-first- and pseudo-second-order models. The best parameters were the pH of 6, a mass of adsorbents of 25 mg, and fast saturation time of around 10 minutes. The kinetic model that best fitted the process was the pseudo-second-order for all metals in both adsorbents. The PMS adsorption capacity achieved by MEC was higher than BPF. The removal by MEC was Al=Fe=Pb=Cu=Cr> Zn>Mn>Ba, in the percentages of 100, 100, 100, 100, 100, 98, 88, and 76%, respectively. The BPF showed Pb>Fe>Cr>Cu>Al>Zn>Ba>Mn, in the percentages of 97, 67, 63, 50, 46, 45, 44, and 5%, respectively. The results suggest that the affinity between adsorbents with certain metal ions is due to the characteristics of the adsorbent surface and the number of chemical species available in the solution, which may interfere with the adsorptive process. Above all, the percentage of simultaneous removal of metal ions by both adsorbents was relevant, making them promising for remediating heavy metal ions in sanitary sewage after conventional treatment and industrial effluents containing mixed metal ions.