Presence Of Heavy Metal Cations Research Articles

The C2-Symmetry Colorimetric Dye Based on a Thiosemicarbazone Derivative and its Cadmium Complex for Detecting Heavy Metal Cations (Ni2+, Co2+, Cd2+, and Cu2+) Collectively, in DMF.

The field of chemosensing has been experiencing an exponential expansion in recent times, due to increased demands for simpler and user-friendly analytical techniques, in order to combat and confront the challenges of industrial pollutions in the twenty-first century. Metal complex-based chemosensors have received little attention while exhibiting excellent sensing properties, comparing to their organic counterparts. Thus, a thiosemicarbazone-based (H) and its cadmium complex (P) were synthesized, characterized and their photophysical and chemosensing properties were investigated in DMF solvent. The addition of molar equivalents of selected cations (of nitrates or chloride salts) to H and P, produced visually detectable colour changes as well as remarkable spectral shifts. Explicitly, the two probes (H and P) were able to collectively discriminate heavy metal cations such as Cd2+, Co2+, Zn2+, Cu2+, Ni2+, and Ag+, both in DMF, among all other heavy metal cations tested. None of the anions could be detected by H or P, even when the tetrabutylammonium salts (TBAs) were used, the action presumably ascribed to the solvent effect. Thus, H and P can be used to selectively and sensitively detect the presence of heavy metal cations, via naked-eye detectable colour changes in an aqueous soluble solvent such as DMF.

Sol-Gel Derived Adsorbents with Enzymatic and Complexonate Functions for Complex Water Remediation.

Sol-gel technology is a versatile tool for preparation of complex silica-based materials with targeting functions for use as adsorbents in water purification. Most efficient removal of organic pollutants is achieved by using enzymatic reagents grafted on nano-carriers. However, enzymes are easily deactivated in the presence of heavy metal cations. In this work, we avoided inactivation of immobilized urease by Cu (II) and Cd (II) ions using magnetic nanoparticles provided with additional complexonate (diethylene triamine pentaacetic acid or DTPA) functions. Obtained nanomaterials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). According to TGA, the obtained Fe3O4/SiO2-NH2-DTPA nanoadsorbents contained up to 0.401 mmol/g of DTPA groups. In the concentration range Ceq = 0–50 mmol/L, maximum adsorption capacities towards Cu (II) and Cd (II) ions were 1.1 mmol/g and 1.7 mmol/g, respectively. Langmuir adsorption model fits experimental data in concentration range Ceq = 0–10 mmol/L. The adsorption mechanisms have been evaluated for both of cations. Crosslinking of 5 wt % of immobilized urease with glutaraldehyde prevented the loss of the enzyme in repeated use of the adsorbent and improved the stability of the enzymatic function leading to unchanged activity in at least 18 cycles. Crosslinking of 10 wt % urease on the surface of the particles allowed a decrease in urea concentration in 20 mmol/L model solutions to 2 mmol/L in up to 10 consequent decomposition cycles. Due to the presence of DTPA groups, Cu2+ ions in concentration 1 µmol/L did not significantly affect the urease activity. Obtained magnetic Fe3O4/SiO2-NH2-DTPA-Urease nanocomposite sorbents revealed a high potential for urease decomposition, even in presence of heavy metal ions.

Temperature–heavy metal- and temperature–anion/molecule-responsive systems based on PEG acrylate copolymers containing dipyridyl ligands

Thermoresponsive copolymers carrying di(2-pyridyl)methyl ligands are shown to respond sensitively and selectively to the presence of heavy metal cations, while their metal complexes respond in a likewise selective and sensitive manner to the presence of anions or molecules with higher metal affinity. A set of well-defined copolymers of poly(ethylene glycol) methyl/phenyl ether acrylate, and N-di(2-pyridyl)methylacrylamide was prepared through a combination of RAFT radical polymerization and postpolymerization modification of activated esters. Products were characterised by 1H and 19F NMR spectroscopy, size exclusion chromatography, FT-IR spectroscopy, and turbidity measurements. Ligand–metal complexation, as observed by UV–vis spectroscopy, was found to increase lower critical solution temperature (LCST) transitions in water drastically (e.g. up to 22°C) for addition of small amounts (e.g. 0.4mM) of Cu(II), Co(II), Fe(II) and Ag(I) salts, attributed to a tethering of charge to the polymer. Conversely, salts of Mn(II) and Gd(III) did not affect copolymer solubility. Observed LCST transitions of polymer–metal complexes decreased with the addition of anions or molecules which formed more stable complexes, poorly soluble compounds, or underwent redox reactions with the metal cation. Selectivity toward specific anion or molecule analytes could be tuned though the choice of metal. An isothermal phase separation of a polymer–Cu(II) solution (5g/L) in response to the addition of as little as 0.4mM sodium cyanide is demonstrated while the addition of an equal amount of sodium azide did not cause any response, signifying the potential of the proposed concept for sensing applications.

Захисний вплив тіакалікс[4]арен-тетрасульфонату на інгібування АТР -гідролазної активності субфрагмента-1 міозину міометрія катіонами важких металів

Heavy metals have a negative effect on the contractility of uterine smooth muscles (myometrium), these effects can lead to various pathologies of a women reproductive system. To overcome these effects the methods for correcting the myometrium contractile activity are to be developed. Catalyzed by myosin ATPase ATP hydrolysis is the most important reaction in the molecular mechanism of myometrium contraction. We have found an inhibitory effect of 0.03-0.3 mM Ni2+, Pb2+ and Cd2+ on enzymatic hydrolysis of ATP by myosin subfragment-1 obtained from swine uterine smooth muscles. We have demonstrated that 100 μM thiacalix[4]arene-tetrasulphonate (C-798) recovered to the control level of ATPase activity of myosin subfragment-1 in the presence of heavy metal cations. One of the most probable mechanisms of C-798 corrective activity is based on its ability to chelate heavy metals, thus cations Pb, Cd and Ni can be removed from the incubation medium. Computer simulation has demonstrated that the protective effect of C-798 may also be the result of weakening the interaction of heavy metal ions with amino acid residues of the myosin molecule near the active site of ATP hydrolase. The obtained results can be used for further research aimed at assessing the prospects of thiacalix[4]arene-tetrasulfonate as pharmacological compounds.

Cytoplasmic inorganic polyphosphate participates in the heavy metal tolerance of Cryptococcus humicola

The basidiomycetous yeast Cryptococcus humicola was shown to be tolerant to manganese, cobalt, nickel, zinc, lanthanum, and cadmium cations at a concentration of 2.5 mmol/L, which is toxic for many yeasts. The basidiomycetous yeast Cryptococcus terreus was sensitive to all these ions and did not grow at the above concentration. In the presence of heavy metal cations, С. humicola, as opposed to C. terreus, was characterized by the higher content of acid-soluble inorganic polyphosphates. In vivo 4',6'-diamino-2-phenylindole dihydrochloride staining revealed polyphosphate accumulation in the cell wall and cytoplasmic inclusions of С. humicola in the presence of heavy metals. In C. terreus, polyphosphates in the presence of heavy metals accumulate mainly in vacuoles, which results in morphological changes in these organelles and, probably, disturbance of their function. The role of polyphosphate accumulation and cellular localization as factors of heavy metal tolerance of Cryptococcus humicola is discussed.

Identification of coexisting pentose, hexose, and disaccharides with preliminary separation through hydrophilic interaction on silica HPTLC plate using aqueous sodium deoxycholate-acetonitrile mobile phase system

Aqueous micellar bile salt, sodium deoxycholate (NaDC) solution as additive in acetonitrile (ACN) in the ratio (1:5 ν/ν) was identified as the most favorable mobile phase for on-plate identification and resolution of three series of common sugars (disaccharide, pentose and hexose) on commercially available high performance silica gel plates. Effect of mobile phase composition and the presence of heavy metal cations as impurities in the analyte sample have been investigated to optimize experimental conditions for the separation. The lowest possible amount of all sugar on high-performance thin-layer chromatography (HPTLC) plate has been determined at nanogram level. This method was successfully applied for identification and separation of sugars in pharmaceutical formulations [cough syrup (Honitus), multivitamin syrup (Becozinc)] and biological matrix (human blood).

Hexavalent Chromium Reduction by Bacillus sp. Strain FM1 Isolated from Heavy-Metal Contaminated Soil

A Cr(VI) reducing bacterial strain FM1 was isolated from heavy metal contaminated agricultural soil irrigated with tannery effluents of Jajmau, Kanpur (India), and was identified as Bacillus sp. on the basis of biochemical methods and 16S rDNA gene sequence analysis. FM1 strain was found to be resistant to some toxic heavy metals (Cr(VI), Cr(III), Cu²+, Co²+, Cd²+, Ni²+ and Zn²+) up to several fold concentrations to the normal levels occurring in highly polluted region. FM1 was resistant to very high concentration of Cr(VI) (1,000 mg/L) and completely reduced 100 mg/L Cr(VI) within 48 h. Factors (pH, temperature, initial Cr(VI) concentration) affecting Cr(VI) reduction under culture condition were also evaluated. Reduction was optimum at 37 °C and pH 8. Cr(VI) reduction was enhanced by addition of glucose. The presence of heavy metal cations, such as Cu²+, Co²+, Cd²+, Ni²+ and Zn²+ showed differential effect on reduction. Since strain FM1 could grow in the presence of significant concentrations of metals and due to high Cr(VI) reduction ability, this bacterium may be potentially applicable in Cr(VI) detoxification.

Chromium (VI) Sorption with Different Heavy Metals in Inceptisols

Chromium (Cr) (VI) sorption in soils having high pH (pH > 7.0) is negligible because of the soil's negative surface charge, which aggravates the negative sorption of Cr (VI) by negative leaching phenomenon. However, the sorption of Cr (VI) is influenced by the presence of different heavy metal cations in these soils. For a better understanding of mechanisms responsible for differential sorption of Cr (VI) in soil, laboratory experiments were conducted. This study evaluated the effect of different heavy metals, viz. Pb, Cd, Ni and Zn, on Cr (VI) sorption in Inceptisols. Kinetic study revealed that cation sorption was more rapid and took place during the first hour, whereas sorption of Cr (VI) was slower. The presence of heavy metal cations in the solution matrix increased the sorption of Cr (VI) by the Inceptisols, but Cr (VI) sorption was negligible, in the range of 0—0.03 mM, in the absence of heavy metal cations. In the presence of cations, sorption of Cr (VI) was first observed at an equilibrium concentration of 0.008 mM for the Delhi (Delhi, Typic Ustochrept) soil and 0.02 mM for the Hisar (Hisar, Typic Ustochrept) soil. Based on the calculated distribution coefficient (Kd) for those metals, Pb generally exhibited the highest affinity for soil sorption. An investigation was also conducted to determine the individual effect of heavy metals on Cr (VI) sorption, and it was found that amongst the studied heavy metal cations Pb strongly influenced the sorption of Cr (VI) in soil.

Semifluorinated thiols in Langmuir monolayers

A series of semifluorinated thiols of the general formula CF 3(CF 2) m −1(CH 2) n SH (abbreviated to FmHnSH) have been synthesized and the Langmuir monolayers thoroughly characterized using surface pressure ( π) and electric surface potential (Δ V) measurements. These data have been complemented with Brewster angle microscopy (BAM) visualization of the monolayers structure and IR spectroscopy (PM-IRRAS) analysis of the alkyl chain conformation. The investigated thiols (namely F4H10SH, F8H6SH, F6H10SH, F10H6SH, F6H11SH, F8H10SH and F10H10SH) differ in the length of the hydrophobic chain as well as in the degree of fluorination. Although the –SH group cannot form strong hydrogen bonds with the water subphase, thereby causing only weak anchoring, it has been found that all the investigated thiols, except for F4H10SH, are capable of stable Langmuir monolayer formation. The investigated thiols can be divided into two categories – thiols with longer alkyl chain (F10H10SH, F10H6SH, F8H10SH) and compounds with shorter hydrophobic part (F6H10SH, F6H11SH, F8H6SH). The monolayers of the latter thiols have their equilibrium surface pressure (ESP) comparable with the collapse pressure ( π C) of their monolayers; thus these films are stable within the whole range of compression. On the contrary, thiols with longer perfluorinated fragments have considerably lower ESP than the π C of their monolayers; therefore, both stable and metastable regions can be distinguished in their π– A isotherms. Interestingly, for F8H6SH, a smectic ordering of molecules can be observed in monolayers as visualized with BAM. By comparing film-forming properties of the studied semifluorinated thiols with previously studied semifluorinated alkanes it has been found that the presence of –SH group facilitates spreading at the free water surface. Semifluorinated thiols have been found to maintain their monomolecular ordering in the presence of heavy metal cations in the aqueous subphase, contrary to their hydrogenated analogues, which have been reported to crystallize under the same conditions.

The structural origin and biological function of pH-sensitivity in firefly luciferases

Firefly luciferases are called pH-sensitive because their bioluminescence spectra display a typical red-shift at acidic pH, higher temperatures, and in the presence of heavy metal cations, whereas other beetle luciferases (click beetles and railroadworms) do not, and for this reason they are called pH-insensitive. Despite many studies on firefly luciferases, the origin of pH-sensitivity is far from being understood. This subject is revised in view of recent results. Some substitutions of amino-acid residues influencing pH-sensitivity in firefly luciferases have been identified. Sequence comparison, site-directed mutagenesis and modeling studies have shown a set of residues differing between pH-sensitive and pH-insensitive luciferases which affect bioluminescence colors. Some substitutions dramatically affecting bioluminescence colors in both groups of luciferases are clustered in the loop between residues 223-235 (Photinus pyralis sequence). A network of hydrogen bonds and salt bridges involving the residues N229-S284-E311-R337 was found to be important for affecting bioluminescence colors. It is suggested that these structural elements may affect the benzothiazolyl side of the luciferin-binding site affecting bioluminescence colors. Experimental evidence suggest that the residual red light emission in pH-sensitive luciferases could be a vestige that may have biological importance in some firefly species. Furthermore, the potential utility of pH-sensitivity for intracellular biosensing applications is considered.

The influence of some heavy metals cations on the FTIR spectra of zeolites

In the present work we show results of FTIR studies of clinoptilolite with introduced Pb2+, Cd2+, or Cr2+ cations. We compared both hydrogen and sodium forms of zeolites after the process of heavy metal cation introduction. In the MIR spectra the presence of heavy metal cations causes changes in the intensity of the pseudo-lattice bands. These bands are the result of SiO4 and AlO4 ring vibrations and are located at 673 as well as 693cm−1. The FIR spectra do not show essential changes after introduction of cations (in comparison with the initial clinoptilolite spectrum). Therefore investigations using additional methods, i.e. EDX and X-ray diffraction were also carried out.

Zur adsorptiven Eliminierung ausgewählter Pestizide aus wäßrigen Lösungen. Teil 1. Adsorption von 2,4‐Dichlorphenol und verwandten Verbindungen

The adsorption behaviour of 2,4‐dichlorophenol and 2,4‐dichlorophenoxyacetic acid from aqueous solutions onto synthetic porous copolymers has been investigated by equilibrium and kinetic measurements. Model equations considering pH dependent equilibrium loadings as well as film and surface diffusion parameters were used to describe the pH influence on the adsorption phenomena and the breakthrough curves determined experimentally. The adsorption capacity of the polymer for the 2,4‐D acid increased substantially in the presence of heavy metal cations due to salt formation in the liquid phase.

Influence of hydrostatic pressure on the effects of the heavy metal cations of manganese, copper, cobalt, and nickel on the growth of three deep-sea bacterial isolates.

Increases hydrostatic pressure varied the 72-h growth yield of three bacterial isolates from the deep sea in the presence of heavy metal cations of Mn, Cu, Co, and Ni, depending on the bacterial isolate, the metal cation and its concentration, and the level of hydrostatic pressure. Above atmospheric, hydrostatic pressure was found to have one of the following four effects on the response of culture growth to a heavy metal cation. (i) It could be without effect; (ii) it could enhance inhibition by a metal cation; (iii) it could increase the 72-h growth yield by a metal cation; or (iv) it could protect against a growth inhibitory effect noted at a lower pressure. Possible reasons for these varied responses are discussed.

8-quinolinol-5-sulphonic acid as both indicator and masking agent—I: The zinc-ferrocyanide titration

A method has been suggested by which μg amounts of Zn(II) in 10 −5-10 −6 M solution can be titrated with K 4Fe(CN) 6 in the presence of heavy metal cations, by using 8-quinolinol-5-sulphonic acid at pH 4 as a combined indicator and masking agent. Cd(II) interferes.

Stability of hectorite in weakly acidic solutions. III. Adsorption of heavy metal cations and hectorite solubility

AbstractThe heavy metal cations studied were adsorbed by hectorite suspended in 0.05 M calcium chloride as a pH-dependent reaction in the order, Cu > Zn > (Co, Mn) > Ni. The adsorption of heavy metal cations was accompanied by the removal from solution of silicic acid released by clay dissolution. It is proposed that the reaction takes place on edge surfaces such that the clay lattice is effectively extended. This result complements other work in which it has been shown that the adsorption of silicic acid by other silicate clays results in an increased adsorption of zinc, cobalt and nickel. The present study did not provide evidence of the exchange of zinc and other cations for lattice magnesium.The solubility of hectorite was decreased in the presence of heavy metal cations in the same order that favoured their adsorption. It is proposed that they limit the dissolution of hectorite in weakly acidic solutions by adsorption on or near the sites most prone to proton attack, that is, the magnesium ions of the octahedral layer exposed at edges and defects.

Die säulenchromatographische aminosäure-analyse in gegenwart von schwermetall-kationen

Amino acids were analyzed by ion-exchange chromatography in the presence of heavy metal cations. The positions of Fe 3+, Cu 2+ and Ni 2+ were determined under conditions used for the separation of amino acids on Amberlite CG 120. The Fe 3+-peak is eluted together with cystein acid. Valine and methionine overlap with Cu 2+, while the position of Ni 2+ coincides with that of methionine, isoleucine, and leucine. Iron significantly increases the extinction values of the reaction products of the amino acids cystein acid, cystine, leucine and histidine with ninhydrin-hydrindantin. It has been shown that iron may cause erroneous results in the column chromatographic determination of cystein acid.