Oxidized multiwalled carbon nanotubes modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole for solid phase extraction and preconcentration of some metal ions

In this work, a new procedure for the enrichment of the trace amount of Cu²⁺, Ni²⁺, Co²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions based on the utilization of multiwalled carbon nanotubes (MWCNT) modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole as chelating agent prior to their determination by flame atomic absorption spectrometry has been described. The influence of effective parameters including pH, amount of ligand and MWCNT, composition of eluent, and coexisting ions on recoveries of understudy metal ions was examined. At the optimum pH of 5.0, all metal ions were quantitatively sorbed onto the proposed solid phase and completely desorbed with 8?mL of 5.0?mol?L^?1 HNO₃. The detection limit of Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions was 1.7, 2.4, 2.3, 2.9, 2.8, and 1.4?µg?L^?1, while the preconcentration factor was 63 for Cu²⁺ and 94 for the other metal ions and relative standard deviations between 1.8 less than 3.0%. The proposed procedure was applied for the analysis of various samples.     

Effects of cadmium on intracellular cation homoeostasis in the yeast Saccharomyces cerevisiae

Previous studies have demonstrated that cadmium can induce biochemical and physiological changes in yeast Saccharomyces cerevisiae. However, studies on the influence of cadmium on the ion balance in the cell and the interaction between cadmium and other ions are still relatively few in number. By using inductively coupled plasma-atomic emission spectrometry, the contents of some cations, including Zn²⁺, Ca²⁺, Fe³⁺, Cu²⁺, Mg²⁺, K⁺, and Na⁺ were measured. The data showed that the levels of Zn²⁺ and Fe³⁺ were increased, while those of Cu²⁺, K⁺, and Na⁺ were decreased after cadmium treatment. Afterwards, using the drop test assay, the interactions between cadmium and the selected ions were investigated. The results suggested that the cytotoxicity of cadmium could be attributable to the interference of cadmium with the intracellular cation homoeostasis. Calcium channel transporter Cch1 participates in the intracellular uptake of cadmium. Additionally, Zn²⁺, Ca²⁺, Fe³⁺, Mg²⁺, and K⁺ can rescue the toxic effect of cadmium in yeast.     

Preconcentration of some trace metal ions on coated alumina modified by 1-((6-(-(2-hydroxynaphthalen-1-yl)methyleneamino) hexylimino) methyl) naphthalen-2-ol

A sensitive and efficient method for preconcentration of trace amounts of some metal ions such as Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Cr³⁺, and Fe³⁺ ions based on modification of sodium-dodecyl-sulphate (SDS) coated alumina with 1-(6-(-(2-hydroxynaphthalen-1-yl) methyleneamino) hexylimino) methyl) naphthalen-2-ol (HNMAHN) is reported. The method is based on the uptake of these ions following their chelation with HNMAHN and their recovery using a suitable eluent. The influence of parameters such as pH, concentration of ligand and amount of coated alumina, SDS concentration, eluent (type and concentrations), and elution volume on metal ion recoveries are investigated. The preconcentration factor is 150 (10?mL elution volume) for a 1500?mL sample volume. The method has been successfully applied for extraction and determination of these ions content in some real samples. Extraction efficiency is generally >95% with low relative standard deviations between 1.8% and 2.4 %.     

Synthesis and characterization of an ion exchanger based on tamarind kernel powder and its application for removal of some metal ions from industrial effluents

A resin synthesized from tamarind kernel powder possesses high selectivity for metal ions. Distribution coefficients for some metal ions has been determined by the batch method. The influence of pH on ion exchange capacity and K _d value of metal ions were studied. The resin has been characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, chemical composition and ion exchange capacity (IEC). The selectivity order is Pb²⁺?>?Cu²⁺?>?Fe²⁺?>?Zn²⁺?>?Ni²⁺. Removal of metal ions from the aqueous solution and from effluents of a steel mill has been studied.     

Molecular dynamics of stability and structures in phytochelatin complexes with Zn,Cu, Fe,Mg, and Ca: Implications for metal detoxification

Phytochelatins, or (γ-glutamyl-cysteine) _n -glycine, are specialized peptides produced by plants and algae to mitigate toxic metal exposure, for instance in response to high levels of metals such as Cu, Cd, and Zn. Stability constants and structural characterization of metal–phytochelatin complexes are lacking. This information is required to gain mechanistic insights on the metal selectivity of phytochelatins. Here, we studied structural coordination and thermodynamic stability by performing molecular dynamics simulations of a fully hydrated phytochelatin molecule complexed with Ca²⁺, Mg²⁺, Fe²⁺, Zn²⁺, and Cu²⁺. Our results predict the following decreasing order for the thermodynamic stability of the phytochelatin complexes: Zn²⁺ ≥ Cu²⁺ ≥ Fe²⁺ > Mg²⁺ > Ca²⁺. The favorable binding energies with Zn²⁺ and Cu²⁺ over the other metal cations can be explained by shorter binding distances and greater coordination from carboxylate and keto O atoms. Conformational rearrangement of phytochelatin following metal chelation was captured by monitoring changes in the solvent-accessible volume. Accessibility of solvent molecules to the phytochelatin structure was inversely proportional to the distance between the coordinated ligands and the chelated metal. These new findings demonstrate the influence of the metal–phytochelatin structure on the metal-binding thermodynamics and the phytochelatin conformation, both of which are important to evaluate the intracellular role of phytochelatin in mediating algal response to toxic heavy metal exposure.     

Attenuation of metal species in acidic solutions using bentonite clay: implications for acid mine drainage remediation

A laboratory batch experimental study has been carried out to evaluate the adsorption capacity of selected metal species in acid mine drainage (AMD) by bentonite clay. Bentonite clay was mixed with simulated AMD at specific solid–liquid (S/L) ratios and agitated in a reciprocating shaker and adsorption of selected toxic metals assessed over time. Cation exchange capacity varied from 1140 to 1290 meq kg^?1. Contact of AMD with bentonite leads to increase in pH and a possible reduction in electrical conductivity and total dissolved solids. At constant agitation time of 60 min, the pH increased with dosage of bentonite. Removal of Mn²⁺, Al ³⁺, and Fe³⁺ was observed to be greatest at 60 min of agitation. Bentonite clay exhibits high adsorption for Al³⁺ and Fe³⁺ at concentration less than 300 mg L^?1, while the capacity for Mn²⁺ was observed to be lower. Adsorption capacity for SO₄^2? was low with a great percentage of the SO₄^2? remaining in solution. Adsorption capacity of bentonite with more complex formulated AMD and gold tailing leachates was low for Fe³⁺, Al³⁺, and Mn²⁺. This indicates that optimum adsorption of bentonite clay is dependent on the chemistry of the AMD and its application might be site specific.     

Removal of metal ions from aqueous solution by chelating polymeric hydrogel

Polysaccharide natural seed coat from the tree Magonia pubescens, in the form of hydrogel was used to remove metals in aqueous solution. Swelling tests indicate that seed coat presents hydrogel behavior, with maximum water absorption of 292 g water/g. Adsorption experiments performed using Na⁺, Mg²⁺, K⁺, Ca²⁺, Cr³⁺, Fe³⁺ and Zn²⁺ demonstrated that the polysaccharide structure has a high capacity to extract these ions from the aqueous solution. Scanning electron microscopy revealed significant morphological changes of the material before and after water contact. Differential scanning calorimetry measurements indicate a signal shift of the water evaporation temperature in the material with adsorbed zinc. X-ray photoelectron spectroscopy analysis combined with theoretical studies by the density functional theory and on Hartree–Fock (HF) level evidence that the metallic ions were adsorbed through coordination with hydroxyl groups of polysaccharide. In the case of Zn²⁺ the lowest HF energy was observed for the tetracoordination mode, where Zn²⁺ is coordinated by two hydroxyl groups and two water molecules.     

Green synthesis and characterization of metal ions-mixed titania for application in dye-sensitized solar cells

Abstract

The objective of the present study is to synthesize various metal ions mixed TiO₂ nanoparticles using a continuous hydrothermal synthesis pilot reactor for dye-sensitized solar cells (DSCs). In the pilot plant, aqueous solutions of the metal salts are mixed with a flow of supercritical water (450?°C and 24.1?MPa) in a confined jet mixer for continuous synthesis of metal ions-mixed nano-titania. Characterization of the particles was made using Brunauer–Emmett–Teller technique for specific surface area, powder X-ray diffraction analysis and transmission electron microscopy for identification and crystallite size, X-ray photoelectron spectroscopy for surface analysis and infrared spectroscopy for distinct group identification. Following the already existing procedures and using the titanates synthesized, dye-sensitized cells of 1?cm² area were assembled and their photovoltaic parameters were evaluated under standard test conditions. The power conversion efficiencies (η %) for 40?mol % Zn²⁺, 5?mol % Zr⁴⁺ and 10?mol % Zn⁴⁺ titania were obtained to be 4.8, 4.95 and 4.9, respectively. The promising efficiency results from a greener and large-scale production of nano-titania is a step forward towards commercializing DSC technology.     

Effect of transition metal ions on photocatalytic activity of ZnO in bleaching of some dyes

The photocatalytic bleaching of some dyes (erythrosin-B, fast green FCF and eosin Y) was carried in the presence of semiconducting zinc oxide and was observed spectrophotometrically. The effects of various operating variables like pH, concentration of dyes, amount of semiconductor and light intensity on the efficiency of the reaction were also observed. Attempts have been made to study the effect of the addition of other metal ions (Fe²⁺, Ni²⁺, Ag⁺, Cu²⁺, Co²⁺, V²⁺ and Mn²⁺). All the added metal ions increase the reaction rate to some extent. It was also observed that Fe²⁺ is most effective in photobleaching of erythrosin-B, whereas V²⁺ is more effective in the cases of fast green FCF and eosin Y. A tentative mechanism has been proposed.     

Removal of heavy metals from aqueous solutions using activated carbon prepared from Cicer arietinum

Removal of Cu²⁺, Cd²⁺, Pb²⁺, and Zn²⁺ from aqueous solutions by activated carbon prepared from stems and seed hulls of Cicer arietinum, an agricultural solid waste, has been studied. The influence of various parameters, such as pH, contact time, adsorbent dose, and initial concentration of metal ions on removal was evaluated. The activated carbon was characterized by FT-IR spectroscopy, X-ray diffraction, and elemental analysis. Sorption isotherms were studied using Langmuir and Freundlich isotherm models. All experimental sorption data were fitted to the sorption models using nonlinear least-squares regression. The maximum adsorption capacity values for activated carbon prepared from Cicer arietinum waste for metal ions were 18 mg g^?1 (Cu²⁺), 18 mg g^?1 (Cd²⁺), 20 mg g^?1 (Pb²⁺), and 20 mg g^?1 (Zn²⁺), respectively. The Freundlich isotherm model fit was best, followed by the pseudo-second-order kinetic model. Desorption studies were carried out with dilute hydrochloric acid for quantitative recovery of the metal ions and for regeneration of the adsorbent.     

In vitro toxic effects of heavy metals on fungal growth and phosphate-solubilising abilities of isolates obtained from Phragmites australis rhizosphere

In this research, we evaluated the toxic effect of metal ions on mycelial growth and phosphate-solubilising activity of soil-borne micromycetes isolated from the Phragmites australis rhizosphere using Pikovskaya-agar plates supplemented with four metal concentrations. The diameter growth rate (DGR) decreased as the metal concentration rise for all tested fungi. Trichoderma atroviride had the fastest growth rate (1.48?cm²?day^?1) and was the least susceptible to Al³⁺, Cd²⁺, Cr³⁺, Cu²⁺ and Pb²⁺ with a median effective concentration (MEC₅₀) of 12.19, 0.48, 4.51, 11.44 and 50.05?mM, respectively. Aspergillus japonicus was the most tolerant to Co²⁺, Ni²⁺ and Zn²⁺, with MEC₅₀ values of 3.36, 1.095 and 2.34?mM, respectively. Penicillium italicum was the most tolerant to Cr6⁺ (MEC₅₀?=?0.677?mM). The ability to solubilise phosphate remained, despite the decrease in the DGR, and P. italicum and Penicillium dipodomyicola had the highest Phosphate Solubilisation Indexes (PSIs) at 1.97 and 2.12, respectively. In particular, P. italicum recorded the highest PSI of all the studied isolates at 0.62?mM Cr³⁺ (PSI?=?4.74). A. japonicus and T. atroviride were the most tolerant isolates to all tested metals, which suggests that these isolates are promising candidates for further study with regard to mycoremediation and biofertilisation of metal-polluted soils.     

Utilization of fly ash in adsorption of heavy metals from wastewater

The aim of this study was to assess the toxicity reduction of wastewaster after treatment with fly ash. Fly ash is a waste material which is formed as a result of coal burning in power plants, but has the potential to adsorb heavy metal ions. The present study examined the adsorption capacity of fly ash to adsorb Pb²⁺, Cu²⁺, and Zn²⁺ from waste water under different conditions of contact time, pH, and temperature. Uptake of metal ions by fly ash generally rose with increasing pH. At lower temperatures the uptake of heavy metal adsorption were enhanced. Significant reduction in Pb²⁺ (79%), Cu²⁺ (53%), and Zn²⁺ (80%) content was found after treatment with fly ash of waste water treatment. Using the microtox test toxicity of the effluent was reduced by 75% due to removal of Pb²⁺ ion by the fly ash. Data indicated that fly ash generated by power plants may be used beneficially to remove metals from waste water.     

Toxic effects of dietary of Al3+ ions in tilapias (Oreochromis niloticus) and protective effect of Zn2+ ion

The lethal effects of aluminum ion (Al³⁺) in tilapia (Oreochromis niloticus) raised in concrete tanks were investigated. Tilapias were fed daily with commercial feed enriched with known concentrations of Al³⁺ and analyzed by differential pulse anodic stripping voltammetry (DPASV). The concentrations of Al³⁺ in feces, water, muscle tissue, viscera, and heads were determined every 3 months for a period of 365 days. The Tilapia head was the most affected tissue by Al³⁺. In general, Al³⁺ bioaccumulation reached the lethal dose (LD₅₀) after 335 days of experiment as follows: 34.9?mg?kg^?1 (muscle tissue), 88.2?mg?kg^?1 (viscera), and 126.9?mg?kg^?1 (head without gills). After determining Cu²⁺, Zn²⁺, and Ca²⁺ by absorption spectrometry, a decrease in the Ca²⁺ concentration was noted in the head during the experimental period. These observations were associated with the occurrence of a decalcification in the bone tissue in the presence of Al³⁺. In contrast, it was found that Zn²⁺ ions may act as a protective agent against Al³⁺-induced contamination.     

Solid phase extraction of trace metals from environmental samples using Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone and determination by inductively coupled plasma–atomic emission spectrometry

A method for the solid phase extraction of trace metals, namely Co, Cu, Pb, Ni and Zn, from environmental and biological samples using column Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone (HPPPTSC) and determination by inductively coupled spectrometry (ICP–AES) has been developed. The reagent has the capacity to form chelate complexes with the metals because of three binding sites in the reagent molecule. The optimum experimental conditions for the quantitative sorption of five metals, pH, effect of flow rate, concentration of eluent, sorption capacity and the effect of diverse ions on the preconcentration of analytes have been investigated. The sorption capacity of the resin has 83, 127, 35, 88 and 85?µmol?g^?1 for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺, respectively. The preconcentration factors for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺ were 100, 110, 120, 140 and 150, respectively. The accuracy of the proposed procedure was evaluated by standard reference materials. The achieved results were in good agreement with certified values. The proposed method was applied for the determination of trace metals in river water and plant leaves.     

Immobilization of some metals in contaminated sludge by zeolite prepared from local materials

In this study, zeolite was prepared from cheap local Egyptian clay (kaolin) and characterized by X-ray diffraction, X-ray fluorescence spectroscopy, SEM. The prepared zeolite was used as a binder for immobilization of the metals Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ in contaminated sewage sludge. Different leaching tests were conducted to determine the efficiency of the prepared zeolite for metal stabilization. The leaching of the metals from stabilized sludge decreased as the zeolite amount increased. It was found that 10% of zeolite is sufficient for the stabilization of all metal ions under investigation. It was suggested that the metal uptake mechanism by zeolite was by an ion-exchange mechanism. Examination of the solidified sample for its compressive strength after curing for 28 days yielded a value of 0.83?MPa, which indicates that the treated sludge was well solidified and safe to be used in a wide variety of applications, for instance as a raw material for pavement blocks.     

Removal of Eu3+, Ce3+, Sr2+, and Cs+ ions from radioactive waste solutions by modified activated carbon prepared from coconut shells

As a biomass agricultural waste material, coconut shells were used for the preparation of high-quality modified activated carbon. Chemical modification of the surface of the prepared activated carbon is done by oxidation using H₂O₂ and HNO₃, respectively. The surface area and pore volume of the coconut shells activated carbon are increased by the chemical modification, and followingly the removal of the metals is improved. The structural morphology and composition of the modified activated carbon coconut shells (MACCS) were evaluated by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis–differential thermal analysis (TGA-DTA), scanning electron microscope (SEM), X-ray diffraction (XRD), surface area analysis (SAA), X-ray fluorescence (XRF), and carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis. The prepared MACCS has reasonably good chemical stability. The influence of solution pH, contact time, adsorbent dosage, adsorption temperature, initial metal concentrations, and interfering ions on the adsorption performance of the investigated ions onto the prepared sorbent was examined by a batch method. The selectivity sequence for sorption of Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions on MACCS was found to be Eu^3+?>?Ce^3+?>?Sr^2+?>?Cs⁺. The saturation capacities of MACCS for the studied metal ions were found to be 136.84, 85.55, 69.85, and 60.00?mg?g^?1 for Eu³⁺, Ce³⁺, Sr²⁺, and Cs⁺ ions, respectively. The thermodynamic parameters, ΔH°, ΔS°, and ΔG° were also evaluated.     

Catalytic determination of ultratrace chromium based on gallocyanine‐hydrogen peroxide indicator reaction

A highly sensitive catalytic procedure for the determination of ultratrace chromium(VI) was developed based on its catalytic effect on the oxidation of gallocyanine by hydrogen peroxide in hexamine‐hydrochloric acid buffer solution. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance at 620 nm. The apparent active energy of the catalytic reaction is 6.84 kJ . mol^‐1. The calibration graph is linear for 0–150 ng.ml^‐1, and the detection limit is 0.8 ng.ml^‐1. Most foreign ions have no interfering effect on the determination of chromium(VI) except for Al³⁺, Cu²⁺, Fe³⁺and Fe²⁺. The interference of Al³⁺ is eliminated by masking with F^‐, and those of Cu²⁺, Fe³⁺ and Fe²⁺ are eliminated by adding appropriate amount of EDTA. The present procedure had been used for the determination of trace chromium(VI) in lake water, mine water and electroplating wastewater, and the results were satisfactory.     

Removal of Zn2+ from aqueous solution by biomass of Agaricus bisporus

Biosorption of Zn²⁺ from aqueous solutions by biomass of Agaricus bisporus was investigated. The removal rates of Zn²⁺ by A. bisporus under different parameters (e.g., solution pH, bio-sorbent dosage and initial Zn²⁺ concentration) were studied. The inhibition of A. bisporus’s biosorption by anionic ligands EDTA (Ethylene Diamine Tetraacetic Acid), acetate and citrate) implied that EDTA and citrate might be used as eluting reagents. Regular and simultaneous solution pH change and light metal ions release after biosorption indicated that an ion exchange mechanism was involved. From FT-IR (Fourier Transform Infrared) spectroscopy, the main functional groups participated in biosorption were found. Biosorption of Zn²⁺ by A. bisporus could be well described by the Freundlich and Langmuir models. In conclusion, the biomass of A. bisporus showed high potential for the treatment of wastewater containing Zn²⁺.     

Purification and some properties of β-N-acetyl-D-glucosaminidase from prawn (<Emphasis Type="Italic">Penaeus vannamei</Emphasis>)

The -N-acetyl-D-glucosaminidase (NAGase, EC 3.2.1.52) from prawn (Penaeus vannamei) was purified by extraction with 30% ethanol solution and ammonium sulfate fractionation, then chromatographed on Sephadex G-100 followed by DEAE-cellulose (DE-32) columns. The purified enzyme determined to be homogeneous by polyacrylamide gel electrophoresis (PAGE) and SDS-PAGE. The specific activity of the purified enzyme was 1,560 U mg^–1. Enzyme molecular weight was determined to be 105,000 Da; it contained two subunits of the same mass (45,000 Da). The pI value was calculated to be 4.8 by isoelectric focusing. The optimum pH and optimum temperature of the enzyme for the hydrolysis of pNP--D-GlcNAc (enzyme substrate) were determined to be pH 5.2 and 45°C, respectively. The behavior of the enzyme during hydrolysis of pNP--D-GlcNAc followed Michaelis–Menten kinetics, with K_m=0.254 mM and V_m=9.438 M min^–1, at pH 5.2 and 37°C. The stability of the enzyme was investigated, and the results showed that the enzyme was stable in a pH range from 4.2 to 10.0 and at temperatures <40°C. The effects of metal ions on the enzyme were also studied. Li⁺, Na⁺ and K⁺ had no influence on enzyme activity. Mg²⁺, Ca²⁺ and Mn²⁺ activated the enzyme, while Ba²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Pb²⁺ Cu²⁺, Fe³⁺ and Al³⁺ showed various degrees of inhibitory effects on the enzyme.Communicated by O. Kinne, Oldendorf/Luhe     

The chelation of metal ions by the acylpolyamine toxins from the web-spider Nephilengys cruentata: effects in the intoxication/detoxification of preys

Summary. Orb-web-spiders present a series of different strategies for prey capture, involving the use of different types of silk for web building, the use of adhesive traps in the webs, the secretion of toxic compounds to the spider’s preys in the adhesive coating of the capture web and the biosynthesis of a wide range of structurally related acylpolyamine toxins in their venoms. The polyamine toxins usually block neuromuscular junctions and/or the central nervous system (CNS) of Arthropods, targeting specially the ionotropic glutamate receptors; this way these toxins are used are as chemical weapons to kill / paralyze the spider’s prey. Polyamine toxins contain many azamethylene groups involved with the chelation of metal ions, which in turn can interact with the glutamate receptors, affecting the toxicity of these toxins. It was demonstrated that the chelation of Ni⁺², Fe⁺², Pb⁺², Ca⁺² and Mg⁺² ions by the desalted crude venom of Nephilengys cruentata and by the synthetic toxin JSTX-3, did not cause any significant change in the toxicity of the acylpolyamine toxins to the model-prey insect (honeybees). However, it was also reported that the chelation of Zn⁺² ions by the acylpolyamines potentiated the lethal / paralytic action of these toxins to the honeybees, while the chelation of Cu⁺² ions caused the inverse effect. Atomic absorption spectrometry and Plasma-ICP analysis both of N. cruentata venom and honeybee’s hemolymph revealed that the spider’s venom concentrates Zn⁺² ions, while the honeybee’s hemolymph concentrates Cu⁺² ions. These results are suggesting that the natural accumulation of Zn⁺² ions in N. cruentata venom favors the prey catching and/or its maintenance in the web, while the natural accumulation of Cu⁺² ions in prey’s hemolymph minimizes the efficiency of the acylpolyamine toxins as killing/paralyzing tool.