Presence Of Heavy Metal Ions Research Articles

Influence of Cd 2+, Hg 2+ and Pb 2+ on (+)-catechin binding to bovine serum albumin studied by fluorescence spectroscopic methods

The effect of heavy metal ions, Cd 2+, Hg 2+ and Pb 2+ on (+)-catechin binding to bovine serum albumin (BSA) has been investigated by spectroscopic methods. The results indicated that the presence of heavy metal ions significantly affected the binding modes and binding affinities of (+)-catechin to BSA, and the effects depend on the types of heavy metal ion. One binding mode was found for (+)-catechin with and without Cd 2+, while two binding modes – a weaker one at low concentration and a stronger one at high concentration were found for (+)-catechin in the presence of Hg 2+ and Pb 2+. The presence of Cd 2+ decreased the binding affinities of (+)-catechin for BSA by 20.5%. The presence of Hg 2+ and Pb 2+ decreased the binding affinity of (+)-catechin for BSA by 8.9% and 26.7% in lower concentration, respectively, and increased the binding affinity of (+)-catechin for BSA by 5.2% and 9.2% in higher concentration, respectively. The changed binding affinity and binding distance of (+)-catechin for BSA in the presence of Cd 2+, Hg 2+ and Pb 2+ were mainly because of the conformational change of BSA induced by heavy metal ions. However, the quenching mechanism for (+)-catechin to BSA was based on static quenching combined with non-radiative energy transfer irrespective of the absence or presence of heavy metal ions.

Surface-Enhanced Raman Detection of Melamine on Silver-Nanoparticle-Decorated Silver/Carbon Nanospheres: Effect of Metal Ions

Silver/carbon (Ag/C) core-shell nanospheres synthesized by a hydrothermal method were used as templates for fabricating silver nanoparticle-decorated Ag/C (Ag/C/AgNps) nanospheres. The particle size of Ag nanoparticles can be tuned by varying the concentration of Ag precursor. Detection of melamine molecules at concentrations as low as 5.0×10(-8) M shows that the Ag/C/AgNps nanosphere is a good SERS-active substrate. The effect of heavy metal ions on the detection of melamine is also investigated. It was found that the SERS spectrum profile of melamine is very sensitive to the presence of heavy metal ions: the peak positions of the SERS bands exhibit some apparent change with the kind of metal ion, showing a blue or red shift compared with those in the SERS spectrum of melamine; the SERS signal intensity decrease with increasing the concentration of metal ion.

Synthesis and Characterization of Colorimetric Metal Sensing Properties Based on Azo Chromophore Moiety

In this work, we have designed and synthesized a particular colorimetric dye sensor for the detection of heavy metal ions. Dye sensor, namely 4-hydroxy-3-(fluoro-phenyl-thiourea-N'-nitrilo-methylidynyl)-azobenzene was synthesized using 5-phenyldiazenyl salicylaldehyde and 4-phenylthiosemi carbazide. The dye sensor has promising properties which are applicable to detect and recognize the presence of heavy metal ions with colorimetric changing functions. Electron rich part in dye sensor structure, which can be utilized as metal binding unit, such as NH, N, S and OH (atom/group) provides the functions to coordinate metal ions. This metal ion detection property was determined by using UV-Vis absorption, 1H-NMR peak shift and computational calculation method analysis. Furthermore, we estimated the electrochemical properties of dye sensor by using cyclicvoltammetry. In addition, the formation type of metal binding complex was determined by Job's plot measurements.

The effects of the composition of growth medium and fermentation conditions on the production of lipase by R. delemar

Lipases (triacylglycerol hydrolases) are hydrolytic enzymes that can catalyze the hydrolysis of the ester bond of long-chain acylglycerols at the oil-water interface. The present study investigated the effects of inducers, surface-active materials, activators, and inhibitors in the fermentation medium on lipase activity in Rhizopus delemar. In the presence of certain commercial oils and tributyrin as an inducer, lipase activity decreased in the order of sunflower oil > soybean oil > hazelnut oil > corn oil > tributyrin > olive oil. In addition, the effects of the stirring and aeration rates on lipase activity were investigated. To investigate the effect of surface-active materials on lipase activity 2 different surface-active materials, Tween-80 and rhamnolipid (biosurfactant), were used as comparatives with tributyrin. Maximum lipase activity was observed in the fermentation medium containing Tween-80 as both an inducer and surface-active material. The combined effects of molasses and sucrose on lipase production by R. delemar were also investigated. Lipase activity in the presence of activators decreased in the order of NaCl > KCl > CaCl_2 > MgCl_2 > gum arabic > EDTA, and maximum lipase activity of 964.55 U/L was obtained. The presence of heavy metal ions in the fermentation media severely inhibited lipase activity. Lipase activity in the presence of heavy metal ions decreased in the order of Fe^{2+} > Mn^{2+}> Co^{2+}> Ni^{2+}.

Selective Transport of Cu2+ Ions through Bulk Liquid Membrane System Mediated by Erythromycin Ethyl Succinate

The carrier mediated transport of Cu2+ ions from an aqueous medium has been examined. The ability of Erythromycin Ethyl Succinate (EES) as a carrier to form a complex with Cu2+ ions and transport them to the receiving phase is reported. The fundamental parameters influencing the transport of Cu2+ ions such as the pH in the source and receiving phases and concentration of the stripping agent in the receiving phase have been optimized and accordingly, the amount of Cu2+ transported across the liquid membrane after 5 h was 94.3 ± 1.8% in the presence of L-histidine as a suitable stripping agent. Moreover, the selectivity and efficiency of Cu2+ ions transport from aqueous solution over other cations in ternary and quaternary mixtures have been investigated. The results indicate that our fabricated membrane is very sensitive toward Cu+2 ions in the presence of heavy metal ions.

Characterization of graphite–polyurethane composite electrodes modified with organofunctionalized SBA-15 nanostructured silica in the presence of heavy metal ions. Application to anodic stripping voltammetry

A graphite–polyurethane composite electrode with Santa Barbara Amorphous 15, SBA-15, mesoporous silica organofunctionalized with 2-benzothiazolethiol (BTSBA) as bulk modifier has been characterized electrochemically by voltammetry and electrochemical impedance spectroscopy (EIS) in the presence of cadmium ions, as an example of a toxic trace heavy metal, as well as by solid-state 13C-NMR and by scanning electron microscopy. EIS measurements performed on the modified composite electrodes to investigate the influence of BTSBA on the deposition of cadmium during square wave anodic stripping voltammetry showed that organofunctionalization of the SBA-15 bulk modifier in the composite electrode facilitates heavy metal deposition. Experiments were also carried out with a mixture of submicromolar cadmium, lead, copper and mercury ions and led to similar conclusions.

Change of microstructure of clays due to the presence of heavy metal ions in pore water

The compressibility of engineered barrier clays is, to a large extent, controlled by microstructure change due to the presence of chemical ions in clay-water system. This paper aims to investigate the change of microstructure of clays due to the presence of heavy metal ions in pore water. We use two pure clays (kaolinite and bentonite) in the study. One-dimensional consolidation tests were performed on reconstituted samples, which are prepared with distilled water and three types of heavy metal solutions (Pb(NO3)2, Cu(NO3)2, Zn(NO3)2,). In order to better understand the impact of chemical pore fluid on microstructure of the two clays, following the consolidation test, scanning electron microscope (SEM) observations and mercury intrusion pore size distribution measurements (MIP) were conducted. Due to the measurement range of MIP, which is only allowed to measure the minimal pore size 20 Å, BET method by gas sorption, whose measurement pore size range is from 3.5 Å to 500 Å, is used to measure the micropore size distribution. By this method, specific surface area of the soils can be also determined. It can be employed to demonstrate the difference of creep performance between the soils. Furthermore, a series of batch equilibrium tests were conducted to better understand the physical-chemical interactions between the particles of soils and the heavy metal ions. With the further consideration of the interparticle electrical attractive and repulsive force, an attempt has been made to predict the creep behaviour by using the modified Gouy-Chapman double layer theory. The results of calculation were compared with that of tests. The comparison shows that the prediction of compressibility of the clays according to the modified double diffuse layer theory can be reasonably agreement with the experimental data.

BOD Exertion and OD600 Measurements in Presence of Heavy Metal Ions Using Microbes from Dairy Wastewater as a Seed

BOD measurements in presence of cobalt, nickel, copper, zinc, silver and cadmium are reported using wastewater from dairy industry as a seed. Extent of inhibition in BOD is studied for variables like, concen-tration of metal ions (0.2 mM to 1.4 mM), pH (3 to 8) and temperature of incubation (15℃, 20℃, 25℃, 30℃ and 35℃). Results of BOD inhibition are supported by absorbance measurement (OD600) studies of microbial matter preserved in Luriya broth medium. OD measurement results are used to derive minimum inhibitory concentration, i.e., threshold concentration of each metal showing toxicity towards microbes. Sil-ver is found to be the most toxic element.

Polymer-Coated Quartz Crystal Microbalance Chemical Sensor for Heavy Cations in Water

A flow type quartz crystal microbalance (QCM) (bio)chemical sensor was developed for the real time determination of heavy metal ions that is suitable for environmental monitoring. A new process has been developed which enables to obtain surface-modified gold electrodes with high heavy metal ions complexing ability. The sensing performances of the piezoelectric sensor used in a flow-through setup were investigated by monitoring the frequency variation induced by the presence of heavy metal ions, such as copper and lead, as model ions, in aqueous media. X-Ray Reflectivity (XRR) and Atomic Force Microscopy (AFM) were carried out to characterize the unmodified and modified gold surfaces.

Ultrasensitive SERS Nanoprobes for Hazardous Metal Ions Based on Trimercaptotriazine-Modified Gold Nanoparticles

Trimercaptotriazine-modified gold nanoparticles exhibit strong SERS effects, yielding vibrational profiles very sensitive to the presence of heavy metal ions. Because of the contrasting response observed for selected vibrational bands in the SERS profiles, they provide useful nanoprobes for Hg2+ and Cd2+ ions, allowing direct quantitative assays by employing relative peak intensity ratios instead of using internal standards.

Evaluation of iron oxidation rate of Acidithiobacillus ferrooxidans in presence of heavy metal ions

The present study deals with the determination of the iron oxidation rate (IOR) of Acidithiobacillus ferrooxidans in the presence of various heavy metal ions. Initially, the IOR of this particular strain was enhanced to 718 mg L–1 h–1 by several sets of subculturing of the whole biomass in fresh medium. In the process, the bacterial regeneration time was determined to be 3˙7 h. The effect of various heavy metal ions (Hg, Ag and Pb) on IOR of this active strain was studied and the reaction kinetics in the presence of various concentrations of heavy metal ions in the solution has been determined. The tolerance index of the active culture to various heavy metals has also been established. The tolerance index in the presence of 700 mg L–1 Pb, 50 mg L–1 Ag and 0˙1 mg L–1 Hg was 5˙1, 5˙1 and 11˙9 respectively. Therefore, it was concluded that Hg ion rendered maximum toxicity to the bacterial strains followed by Ag and Pb. By statistical interpretation of the observed data, it was possible to formulate a very significant correlation between all the sets of experiments that were conducted in the presence and absence of metal ions.

Influence of heavy metal contaminants at variable pH regimes on rheological behaviour of bentonite

Long-term competent performances of clays as barrier and liner systems for waste landfills are dependent on both the physico-mechanical properties and attenuation characteristics of the clay soils. The presence of heavy metal ions in the pore water will alter the physico-chemical characteristics of the clay–water system, resulting in changes in the short- and long-term mechanical and chemical behaviour of the clay soil barrier materials. This study investigates bentonite–contaminant interaction at different pH levels and heavy metal ion concentrations, and their resultant effect on the mechanical behaviour of bentonite soil. A set of physico-chemical experiments including Atterberg limits, precipitation testing, pH measurement and consolidation were performed to investigate the fundamental mechanism of soil–contaminant interaction from a rheological point of view. Consolidation tests were performed to study volume change behaviour with respect to the control exercised by mechanical and osmotic stresses. The impact of multiple aspects of heavy metal ion interaction on the osmotic compressibility and consolidation of bentonite is investigated. It is shown that while the selectivity phenomenon governs the adsorption characteristics of contaminated bentonite, the microstructural change due to the lower pH level and the high concentration of HMs, the different onset of precipitation for Zn and Pb, and the osmotic phenomenon control the rheological performance of compacted bentonite. The theoretical aspect of the experimental investigation is addressed and the restrictions of classical double layer theory for heavy metal/clay soils interaction are illustrated.

Kinetic study of ferrous sulphate oxidation of Acidithiobacillus ferrooxidans in the presence of heavy metal ions

Acidophilic microorganisms such as Acidithiobacillus ferrooxidans have the capability to carry out processes of bioleaching, biosorption and bioprecipitation of heavy metal ions, which have important environmental applications. At. ferrooxidans derives the energy for their metabolism from ferrous iron oxidation, process, which can be affected by the presence of heavy metals in the medium. Moreover, organic matter produces an inhibitory effect over the ferrous iron oxidation of At. ferrooxidans. In this work, heterotrophic bacterium Acidiphilium sp. was added when the medium is supplemented with organic matter to reduce this negative effect. The purpose of this work is the kinetic study of ferrous sulphate oxidation by At. ferrooxidans in the presence of different concentrations of several heavy metal ions (Cr(III), Cu(II), Cd(II), Zn(II) and Ni(II)) and compare this kinetic behaviour with a mixed culture with Acidiphilium sp. The obtained results show a non-competitive inhibition of heavy metals over bacterial oxidation of ferrous sulphate. In accordance with this kind of inhibition, a kinetic equation has been proposed to predict the behaviour of At. ferrooxidans in the presence of heavy metals in the range of concentrations studied.

Piezoelectric sensor functionalised by a self-assembled bipyridinium derivative: characterisation and preliminary applications in the detection of heavy metal ions

The synthesis of a molecule, 1-(11-dodecylsulfanyl-undecyl)-[4,4′]bipyridinium bromide ( 1), suitable at the same time to form a covalent bond with gold electrodes of a piezoelectric quartz crystal and to interact with heavy metal ions in aqueous solutions, has been successfully accomplished. A commercial quartz crystal microbalance instrument has been modified in order to perform a Flow-Injection Analysis. The behaviour of the system follows the Kanazawa–Gordon equation as demonstrated by measurements with glucose solutions. The self-assembled layer of 1 onto a gold electrode has been characterised by Atomic Force Microscopy before and after the sensing tests. The sensing performances of the modified gold electrode were investigated by monitoring the frequency variation induced by the presence of heavy metal ions, such as lead, cadmium and mercury, in aqueous media. The explored concentrations ranged between 10 −4 and 10 −2 M and the corresponding frequency variations ranged between 10 and 50 Hz. All responses observed were fast, reproducible and reversible. In particular, the response to mercury appears significantly higher in comparison with the other analytes. To the best of our knowledge, this contribution represents the first example of sensing layer based on bipyridinium receptor showing reversible and, at some extent, differentiated response towards heavy metal ions.

Allosteric manipulation of photoexcited state relaxation in (bpy)2RuII(binicotinic acid).

The emission spectrum and luminescent lifetime of (bpy)2RuII(binicotinic acid) is affected by the presence of heavy metal ions in solution. As little as 1 microM Pb2+ causes a red shift in emission, an increase in the emission quantum yield, and an increase in the room-temperature lifetime. A smaller red shift is observed in the 4,4'-dicarboxy analogue in the presence of large quantities of lead; however, the emission lifetime and intensity are diminished. An X-ray determination of the ground-state geometry shows that the bipyridine rings of the binicotinic acid are twisted along the 2,2' bond by 19.3 degrees. The interaction between lead and the binicotinic acid complex was modeled by molecular mechanics and extended Hückel calculations. The calculations show that interaction with lead flattens the bridged ring system of the binicotinic acid ligand, which affects the pi* energy levels of the ligand, the d-orbital energies of the Ru(II), and the vibrational modes available to the substituted bipyridine ligand. The inverse energy gap law behavior observed in the binicotinic acid complex is explained in terms of an allosteric interaction between lead and the binicotinic acid complex.

Interaction between thallium(III) bromide and dicyclohexano-18-crown-6 immobilized on silica

The adsorption of cis-syn-cis-dicyclohexano-18-crown-6 on silica gel from organic solvents was studied. In the adsorption from chloroform solutions, the immobilization of the reagent molecules at the surface was coplanar. Hydrogen bonds between surface silanol groups and oxygen atoms of the polyether ring of the crown ether play an important role in the immobilization of the reagent. The reaction between thallium(III) bromide and the immobilized reagent was studied. The composition of complex compounds formed at the surface of the modified adsorbent was found. A procedure was proposed for the sorption-spectrophotometric determination of thallium(III) (≥0.05 mg/L) in the presence of heavy metal ions.

Radiation Chemical Effects in the Near Field of a Final Disposal Site–I: Radiolytic Products Formed in Concentrated NaCl Solutions

The yields of the different radiolytic products formed by gamma radiolysis from NaCl brines at ambient temperature and dose rates between 0.1 and 1 kGy/h were determined. At a chloride concentration of 5.3 mol/l, H2, O2, and ClO3- were formed proportional to the dose and independent from the dose rate with G values of 0.6, 0.16, and 0.074, respectively. At a concentration of 2 mol/l, the chlorate yield dropped to a value close to zero, and the gas composition became stoichiometric. At pH 12 and in the presence of heavy metal ions, the yield of oxygen increased at the expense of chlorate. The concentrations of hypochlorite and chlorite were usually in the micromole per litre range. In pressurized solutions of 5.3 mol/l Cl- where all radiolytic gases were kept dissolved, equilibrium concentrations of radiolytic products were almost reached at a dose of ~1 MGy. The partial pressure of radiolytic gases was ~35 bars, and the chlorate concentration was ~170 μmol/l.

BOD measurement in the presence of heavy metal ions using a thermally-killed- Bacillus subtilis biosensor

The measurement of the biochemical oxygen demand (BOD) of an aqueous solution using a thermally-killed Bacillus subtilis BOD biosensor was unaffected by the presence of 5 mM of Al 3+, Cd 2+, Co 2+, Cr 3+, Fe 2+, Fe 3+, Ni 2+ and Pb 2+ in the sample. In the presence of 5 mM of Zn 2+, Mn 2+ and Sn 2+, the sensor over-estimated the BOD 5 of the test samples by 12–68% compared with 13% under-estimation at the same concentration of Cu 2+. The sensor completely and irreversibly lost its BOD sensing ability in the presence of 0.5 mM of Ag + or Hg 2+. Similar effect was observed with a living B. subtilis BOD biosensor. The interference of copper, manganese, stannous and zinc ions was effectively eliminated by dosing the substrate with 6.2 mM of ethylene diamine tetra-acetate (EDTA) or 5.8 mM of sodium diethyl dithiocarbamate (DDTC). The total concentration of mercury of the solution at which the sensor completely and irreversibly lost its BOD sensing characteristics was raised from 0.5 to 4.7 mM when the solution was dosed with 31.8 mM of NH 4Cl; to 6 mM with 6.2 mM EDTA and to 3 mM with 5.8 mM DDTC. The total concentration of silver which would incapacitate the sensor was correspondingly raised to 9.7, 5 and 5.5 mM for the respective dosages and complexing agents. The sensor showed no response towards NH 4Cl up to about 0.5 M and up to about 50 mM of EDTA and DDTC.

Phytochelatin synthase genes from Arabidopsis and the yeast Schizosaccharomyces pombe.

Phytochelatins (PCs), a family of heavy metal-inducible peptides important in the detoxification of heavy metals, have been identified in plants and some microorganisms, including Schizosaccharomyces pombe, but not in animals. PCs are synthesized enzymatically from glutathione (GSH) by PC synthase in the presence of heavy metal ions. In Arabidopsis, the CAD1 gene, identified by using Cd-sensitive, PC-deficient cad1 mutants, has been proposed to encode PC synthase. Using a positional cloning strategy, we have isolated the CAD1 gene. Database searches identified a homologous gene in S. pombe, and a mutant with a targeted deletion of this gene was also Cd sensitive and PC deficient. Extracts of Escherichia coli cells expressing a CAD1 cDNA or the S. pombe gene catalyzing GSH-dependent, heavy metal-activated synthesis of PCs in vitro demonstrated that both genes encode PC synthase activity. Both enzymes were activated by a range of metal ions. In contrast, reverse transcription-polymerase chain reaction experiments showed that expression of the CAD1 mRNA is not influenced by the presence of Cd. A comparison of the two predicted amino acid sequences revealed a highly conserved N-terminal region, which is presumed to be the catalytic domain, and a variable C-terminal region containing multiple Cys residues, which is proposed to be involved in activation of the enzyme by metal ions. Interestingly, a similar gene was identified in the nematode, Caenorhabditis elegans, suggesting that PCs may also be expressed in some animal species.

Biochemical oxygen demand sensor using Serratia marcescens LSY 4

A microbial biochemical oxygen demand (BOD) sensor consisting of Serratia marcescens LSY 4 and an oxygen electrode was prepared for estimation of the biochemical oxygen demand. The response of the BOD sensor was insensitive to pH in the range of pH 6.0∼8.0, and the baseline drift of the signal was nearly absent even in unbuffered aqueous solution. Because heavy metal ions were precipitated from the phosphate buffer solution, unbuffered solution was used to investigate the effect of the concentration of heavy metal ions on the sensor response. Contrary to previous studies, not only Cu 2+ and Ag + but also Cd 2+ and Zn 2+ significantly decreased the response of the BOD sensor in unbuffered solution. Graft polymerization of sodium styrene sulfonate on the surface of the porous teflon membrane was carried out to absorb the heavy metal ions permeating through the membrane. Tolerance against Zn 2+ was induced for S. marcescens LSY 4 to make the cells less sensitive to the presence of heavy metal ions. The membrane modification and the Zn 2+ tolerance induction showed some positive effects in such a way that they reduced the inhibitory effects of Zn 2+ and Cd 2+ on the sensitivity of the BOD sensor. However, they had no effect on the protection of the cells against the interference of Cu 2+ and Ag + on the performance of the sensor.