Role Of Chelating Agents Research Articles

Role of chelating agents on the sol-gel synthesis of bismuth ferrite nanoparticles

Role of chelating agents on the sol-gel synthesis of bismuth ferrite nanoparticles

The role of chelating agent in the self-assembly of amphoteric surfactants

Hypothesis: Limited research has been conducted on the influence of chelating agents on the self-assembly process in surfactant solutions. The traditional approach assumes the chelating agent only interferes as a salting-out ion, therefore promoting surfactant separation. However, the opposite behavior has been observed for iminodipropionate based surfactants, in which the presence of chelating agents of the aminopolycarboxylate type increases solubility of nonionic ethoxylated surfactants in mixed micellar systems. Specific interaction between chelating agents-surfactants can be an important parameter in the self-assembly processes.Experiments: Physicochemical properties of solutions containing amphoteric surfactant and tetrasodium glutamatediacetate have been investigated. Macroscopic properties, such as viscosity and cloud point, were evaluated in the presence of a non-water-soluble alkyl ethoxylated surfactant. Interactions between amphoteric surfactant and chelating agent were monitored by NMR spectroscopy, including 13C chemical shift and lineshape analysis as well as 1H diffusometry.Findings: The study reveals that there is an interaction between the head group of the surfactant and the chelating agent forming oligomeric surfactant analogues with larger hydrophilic moieties, which results in smaller, more spherical micelles. The combined interactions provide possibilities for tuning the aggregation behavior of systems containing surfactants and chelating agents, and with that, the macroscopic properties of the system.

The role of chelating agent on the structure and up-conversion property of NaLuF4:Yb,Tm as security ink phosphor

Purpose This study aims to investigate the effect of trisodium nitrilotriacetic acid (NTA) on the physical and luminescence emission properties of NaLuF4:Yb, Tm Upconversion (UC) particles and compared with trisodium citrate (CA). Upconversion materials have been remarkably considered in many applications in the past decades. However, the morphology of the UC particles affects their emission properties, depending on the synthesis situation. Design/methodology/approach The UC particles were synthesized by the hydrothermal method. Properties such as crystal phase, particle morphology, particle size, smoothness and uniformity of particle surface and their emission intensity in the UV–Vis region were studied. Findings Observations showed that pH is an essential factor in determining the crystalline phase. In addition, quality factors affect the morphology, particle size and surface smoothness of crystalline facets. It was also found that the UC particles synthesized in the presence of trisodium NTA have a much higher emission intensity than those synthesized in the presence of CA. The use of UC particles in security inks to maintain the brand was also investigated. Originality/value To the best of the authors’ knowledge, for the first time, the effect of trisodium NTA as a chelating agent was investigated on morphology and UC intensity of NaLuF4:Yb,Tm phosphor.

New Insights into the Dissolution of Iron Sulfide Using Chelating Agents

SummaryIron sulfide (FeS) scales create well deliverability and integrity problems such as decreased production rates and damage to well tubulars. The application of chelating agents for production enhancement has been successful because of its high-temperature stability and its clean characteristic nature without the need for expensive additives. However, chelating agents have not been studied adequately for FeS dissolution. This paper investigates ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacteic acid (DTPA), and N-(2-hydroxyethyl) ethylenediamine-N,N′,N′-triacetic acid (HEDTA) for their FeS dissolution capacities and kinetics at 150°F and 300°F.Chelating agents are expensive chemicals and must be investigated carefully to determine the optimum concentration, pH, treatment time, and dissolver/scale ratio. FeS (0.1 g) composed of mainly troilite was used as the scale. EDTA, DTPA, and HEDTA solutions (10 cm3) were prepared at different concentrations ranging from 0.05 to 0.4 mol/L using deionized water with a resistivity of 18.2 MΩ-cm. The pH of the dissolvers was dependent on the concentration and the degree of neutralization. The ligands were deprotonated at higher pH using sodium hydroxide or potassium hydroxide. A comparative study of the chelating agents with a low pH (3 to 5), moderate pH (5 to 9), and high pH (10 to 14) determined the optimum pH for the scale treatment. The sampling time of the dissolution process set at 1, 2, 4, 8, 20, 30, and 72 hours determined the kinetics of the scale-dissolution process and helped optimize the treatment time. A dissolver/scale ratio of 100:1, 50:1, and 20:1 cm3/g were tested. The iron concentration in the dissolver was quantified using inductively coupled plasma-optical emission spectroscopy (ICP-OES).Two calculated parameters, dissolution capacity and dissolver consumption, determined the effectiveness of the chelating agent in dissolving FeS sulfide. From the bottle tests at 150°F, lower pH solutions were more effective. One hundred percent of the iron from FeS was complexed by 0.3 mol/L dipotassium DTPA (K2-DTPA) after 20 hours of soaking; 0.2 mol/L disodium EDTA (Na2-EDTA) and 0.3 mol/L potassium HEDTA (K-HEDTA) were able to remove, respectively, 69 and 96% of the initial iron present in 0.1 g FeS. The mechanism of dissolution at pH < 5 was determined to be hydrogen ion (H+) attack with surface complexation. At alkaline conditions (pH > 10), the dissolution of the scale was negligible and was a result of solution complexation after FeS dissociation. The order of the chelating agents in terms of dissolution capacity was DTPA > HEDTA > EDTA at all pH conditions. The kinetics study showed that the optimum treatment depended on the pH of the chelating agent. For pH < 5 dissolvers, 16 to 20 hours was sufficient to obtain the maximum dissolution capacity. For dissolvers with a pH greater than 10, the dissolution continued for more than 72 hours and was minimal. Increasing the concentration of the chelating agent aided the solubility of the scale only at pH < 5. At 300°F and pH > 5, there was an improvement in the effectiveness of the ligands because of the increase in the system energy and increased activity of the chelating agent. A scanning electron microscopy (SEM) study showed the changes in the morphology of the FeS particles after dissolution with low- and high-pH solutions of the chelating agent.The role of chelating agents in FeS dissolution has not been thoroughly investigated. No study reports the optimum treatment time and dissolver/scale ratio. The role of the pH of the dissolver also needs more attention. This paper fills these gaps in the literature and provides the optimum dissolver composition and treatment time for field operations.

Effect of calcination temperature on magnetic, structural, thermal and optical properties of BFO-T nanoparticles

BFO-T (BiFeO3) nanoparticles have been prepared via auto-combustion technique using tartaric acid as a chelating agent. Role of chelating agent and effect of different calcination temperatures on the structural, morphological, optical, thermal and magnetic behaviour were demonstrated. The properties related to phase structure, surface morphology, thermal stability were investigated by XRD, TEM and TGA respectively. Fourier Transformed Infrared spectra of BFO-T nanoparticles calcinated at different temperatures showed various types of bond formations in the samples. The average particle size of BFO-T nanoparticles were found to be in the range 6-30 nm at different calcinated temperature. The optical band gaps of pure BFO-T nanoparticles were estimated using the Tauc’s equation which was found to be 2.20 eV. Magnetic measurement of pure BFO-T nanoparticles indicated ferromagnetic behavior with saturation magnetization of 0.36 emu/g.

The influence of organic and inorganic chelators on the toxicity of bulk and nanoparticles of zinc oxide during germination and seedling growth of Nicotiana tabacum L.

Nano and bulk-forms of zinc oxide (ZnO) are used extensively in industry and consequently may accumulate in the environment. However, there is little information available on the comparative effects of these forms during the critical early stages of plant life. Furthermore, the role of chelating agents, which affect the bioavailability of metals, in ameliorating plant stress due to exposure to nano and bulk-forms of ZnO is not well characterised. In this study, the effects of different concentrations (0.5, 2.5, 5, 10, 50 and 100 ppm) of nano ZnO (22 nm) and bulk ZnO (natural form, 1000 nm) with and without organic (citrate) and inorganic (EDTA) chelators on germination and seedling growth, and oxidative stress markers of Nicotiana tabacum L. were compared. Chelators (without ZnO) enhanced root growth, whilst ZnO negatively affected seedling growth. ZnO toxicity was often mitigated by adding chelators, especially citrate, although at the highest levels (50 and 100 ppm) of ZnO, toxicity was more pronounced when chelated with EDTA, but was decreased with citrate. Collectively, our findings provide important information regarding the different morpho-physiological and biochemical effects of bulk and nano ZnO and organic and inorganic chelators (citrate and EDTA), which are all prevalent in the environment.

The role of chelating agents and amino acids in preventing free radical formation in bleaching systems

The control of bleaching reaction is important in hair bleaching and laundry detergents to ensure quality of the final product. A better understanding of the reaction mechanisms is needed to minimize product failures. 31P NMR-spectroscopy-based spin trap technique was employed to detect and quantify the free radical species that were generated in different bleaching solutions. These solutions contained the key actives in an alkaline hair colorant/bleaching product, an ammonium salt and hydrogen peroxide at pH = 10. Generally, the main radical species detected in hair oxidative coloring or bleaching processes, were hydroperoxyl/superoxide radicals HO2·/O2.-, amino radicals ·NH2 and hydroxyl radicals ·OH. Their amounts showed a variation based on the chemical composition of the bleaching systems and the metal ion content. The generation of free radicals from reactions between transition metal ions, such as copper, and hydrogen peroxide at pH = 10 was evaluated. In the absence of chelating agents, the copper ions generated a significant level of hydroxyl radicals in a Fenton-like reaction with hydrogen peroxide at pH = 10. Besides that, an increase in copper ion content led to an increase of amino radical ·NH2, whereas the concentration of superoxide radical O2·- decreased which was not yet well reported in the previous literature.The effect of chelating agents like ethylenediaminetetraacetic acid (EDTA), tetrasodium-iminodisuccinate (IDS), a mixture of basic amino acids and dicarboxylic acid on free radical formation was investigated in the presence of binary Cu2+-Ca2+ bleaching systems. As expected, in the binary Cu2+-Ca2+ ion system EDTA did not suppress hydroxyl radical formation effectively, but the mixture containing sodium succinate, lysine and arginine reduced hydroxyl radical formation, whereas IDS (nearly) completely inhibited hydroxyl radical formation. The results indicated that each bleaching solution has its characteristic performance and damage profile. Whereas the reactivity can be controlled by the usage of chelating agents.

Electrochemical Action of FA/O II Chelating Agent and H2O2 on Copper Film in the Polishing Process

The role of chelating agents and H2O2 in chemical mechanical planarization was investigated by electrochemical measurements. First, the open circuit potential, polarization curves and cyclic voltammetry curves of the slurry were tested when it contained FA/O II chelating agent by concentrations of 0%, 0.5%, 1%, 3% and 5%, respectively, and at the H2O2 concentration of 0%, 0.5% and 2% in the slurry, respectively. The results showed that when the concentration of FA/O II chelating agent was 0.5% and the concentration of H2O2 was 0.5%, the open circuit potential moved towards the negative, and the electrochemical anodic reaction was enhanced. At this point, the polarization curve showed that the oxidation was obviously strengthened. The cyclic voltammetry curves showed that when the concentration of H2O2 was 0.5%, with the increase of the concentration of chelating agent, the anodic peak current increased, the electrochemical anodic reaction enhanced. The open circuit potential and polarization curves obtained consistent results. Therefore, when the concentration of FA/O II chelating agent was 0.5% and the concentration of H2O2 was 0.5%, the excessive corrosion could be avoided, and the selectivity of removal rate of copper surface would be improved, and the planarization efficiency could be improved.

Role of chelating agent in chemical and fluorescent properties of SnO2 nanoparticles

A modified Polyacrylamide gel route is applied to synthesize SnO2 nanoparticles. High-quality SnO2 nanoparticles with a uniform size are prepared using different chelating agents. The average particle size of the samples is found to depend on the choice of the chelating agent. The photoluminescence spectrum detected at λex = 230 nm shows a new peak located at 740 nm due to the surface defect level distributed at the nanoparticle boundaries.

Role of chelating agents on release kinetics of metals and their uptake by maize from chromated copper arsenate-contaminated soil

Kinetic aspects of metal release were investigated to understand the effects of synthetic chelating agents (EDTA, EDDS and NTA) and low molecular weight (LMW) organic acids (oxalic and citric acids) on the release kinetics of Cr, Cu and As in chromated copper arsenate (CCA)-contaminated soil, as well as their uptake by maize (Zea mays L.). The results showed that the release of metals from soil was better described by parabolic diffusion, power function or simple Elovich model than by the first- and second-order models, indicating a heterogeneous diffusion of metals. Synthetic chelating agents afforded a higher release of Cu than that of LMW organic acids, whereas citric acid was the most effective chelating agent for Cr and As release. The most effective treatments for stimulating metal uptake in plant shoots were EDDS for Cu, EDTA for Cr, and citric acid for As, as indicated by the removal efficiencies of 0.046%, 0.036%, and 0.004%, respectively. However, Zea mays is not an attractive species for chelate-enhanced phytoremediation of CCA-contaminated soils due to its low phytoextraction rate, even in the presence of chelating agents and ligands.

Olivine-type cathode for rechargeable batteries: Role of chelating agents

Olivine (LiCo1/3Mn1/3Ni1/3PO4) powders were synthesized at 550–600°C for 6h in air by a sol–gel method using multiple chelating agents and used as a cathode material for rechargeable batteries. Range of chelating agents like a weak organic acid (citric acid – CA), emulsifier (triethanolamine – TEA) and non-ionic surfactant (polyvinylpyrrolidone – PVP) in sol–gel wet chemical synthesis were used. The dependence of the physicochemical properties of the olivine powders such as particle size, morphology, structural bonding and crystallinity on the chelating agent was extensively investigated. Among the chelating agents used, unique cycling behavior (75mAh/g after 25 cycles) is observed for the PVP assisted olivine. This is due to volumetric change in trapped organic layer for first few cycles. The trapped organic species in the electrode–electrolyte interface enhances the rate of lithium ion diffusion with better capacity retention. In contrast, CA and TEA showed a gradual capacity fade of 30 and 38mAh/g respectively after multiple cycles. The combination of all the three mixed chelating agents showed an excellent electrochemical behavior of 100mAh/g after multiple cycles and the synergistic effect of these agents are discussed.

Article Commentary: Chelation Therapy for Mercury Poisoning

Chelation therapy has been the major treatment for heavy metal poisoning. Various chelating agents have been developed and tested for treatment of heavy metal intoxications, including mercury poisoning. It has been clearly shown that chelating agents could rescue the toxicity caused by heavy metal intoxication, but the potential preventive role of chelating agents against heavy metal poisoning has not been explored much. Recent paper by Siddiqi and colleagues has suggested a protective role of chelating agents against mercury poisoning, which provides a promising research direction for broader application of chelation therapy in prevention and treatment of mercury poisoning.

The role of chelating agents on the corrosion mechanisms of aluminium in alkaline aqueous solutions

The influence of 1,2-diaminoethane (DAE) on the mechanism of aluminium corrosion in KOH solutions at pH 13 was investigated by combining time-resolved inductively coupled plasma optical emission spectrocopy, open-circuit potential measurements and X-ray photoelectron spectroscopy. In pure KOH solutions, a very slow corrosion rate is initially observed, corresponding to the dissolution of the native oxide layer. Following this incubation stage, the corrosion rate is increasing due to the formation and oxidation of Al hydride, until a steady state is reached. DAE behaves as a strong initial corrosion accelerator, due to synergistic effects with hydroxyl ions and a dissolution mechanism in three successive steps has been proposed: (i) a rapid initial dissolution induced by the formation and detachment from the surface of bidentate (chelate) Al–DAE metal bound surface complexes; (ii) a slower step ascribed to the formation and release of monodentate Al–DAE metal bound surface complexes and (iii) a final step dominated by direct oxidation of surface aluminium hydride by hydroxyl species as in pure KOH.

Role of chelating agent on the oxidic state of hydrotreating catalysts

Chelating agents enhance the catalytic properties of HDT catalysts. It was evidenced that the presence of this organic compounds delays sulfidation. In the present study, we focused on the interaction of the chelating agent with industrial CoMo on alumina HDT catalysts after impregnation with a diammonium salt of ethylenediaminetetraacetate (diA-EDTA), drying or drying and calcination. X-ray diffraction (XRD) and Raman spectroscopy characterization demonstrate the strong interaction of the chelating agent with CoMoO 4. After sulfidation, enhanced catalytic activities are obtained for the treated catalysts. Interaction of model CoMoO 4 and CoAl 2O 4 solids with a solution of diA-EDTA demonstrates that the chelating agent is able to solubilize Co 2+ cations from the molybdate but not from the spinel structure.

Surface structure and Fischer–Tropsch synthesis activity of highly active Co/SiO2 catalysts prepared from the impregnating solution modified with some chelating agents

The present study investigated the surface structure and Fischer–Tropsch synthesis (FTS) activity of highly active Co/SiO2 catalyst prepared from the aqueous Co nitrate solution modified with chelating agents, i.e. nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and/or trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CyDTA), in order to make clear the origin of their promoting effects reported previously. The catalyst was prepared by impregnating SiO2 support with the aqueous solution containing Co nitrate and the chelating agent followed by drying and calcination. Characterization results of the calcined catalysts by XRD, XPS and TPR showed that modification of the impregnating solution with different chelating agents results in the formation of Co species with different structures after the calcination. On one hand, dispersed Co oxide species was formed on the calcined catalyst modified with NTA, which was in more dispersed state compared with Co3O4-like species on the calcined catalyst without chelating agents. On the other hand, highly dispersed α-Co2SiO4-like species was mainly formed after the calcination when modified with EDTA and/or CyDTA. After H2 reduction, about 90% of Co oxide species over NTA-modified catalyst was reduced to create more metallic Co sites compared with the catalyst without chelating agents, which yielded C10–20 hydrocarbons from syngas at 503 K and 1.1 MPa ca. three times greater than the catalyst without chelating agents. The catalysts modified with EDTA and/or CyDTA showed relatively lower activities after the reduction because the reduction degree of highly dispersed α-Co2SiO4-like species was much lower than that of Co3O4-like species. Therefore, modification of the impregnating solution with chelating agents increases the number of surface metallic Co sites through modification of the structure of Co species after the calcination, leading to the higher FTS activity. The role of chelating agents during the preparation of the catalyst was also discussed here.

Role of chelating agents, monovalent anion and cation in the dissociation of Autographa californica nuclear polyhedrosis virus occlusion body

The degree of dissolution brought about by individual constituents of dilute alkaline saline (DAS) was examined using radioactively labeled Autographa californica nuclear polyhedrosis virus occlusion bodies (AcNPV OB). DAS consists of 50 m m Na 2CO 3, 50 m m NaCl, and 2 m m Na 4-EDTA and is often used for the in vitro release of virions from OBs. Both monovalent cation (Na +) and anion (Cl −), as well as CO 3 2− , in a Tris-NH 4OH solution, pH 11.0, individually induced dissolution of the OB matrix. Each of the DAS constituents induced dissolution to different degrees and at different ionic concentrations. In addition, the kinetics of matrix solubilization effected by Na +, Cl −, and CO 3 2− were dissimilar indicating unique mechanisms of actions in the dissociation process. Our results indicate that electrostatic interactions are important for OB stability in addition to hydrophobic contributions as previously demonstrated.

Role of chelating agents in metal toxicity

Role of chelating agents in metal toxicity

Mobilization of some metals in water and animal tissue by NTA, EDTA and TPP

Parallel experiments were conducted under stagnant and flowing conditions to determine whether sodium tripolyphosphate (TPP), the conventional detergent builder, or two potential replacements, nitrilotriacetic acid (NTA) and ethylene—diaminetetraacetic acid (EDTA) significantly influenced the mobilization of major cations (Ca, Mg, Na, K) and some heavy metals (Fe, Mn, Zn, Cu, Pb, Cr). Water sediments and tissue of chironomid adults ( Chironomus tentans Fabricius), crayfish ( Orconectes virilis Hagen) and rainbow trout ( Salmo gairdnerii Richardson) were examined. The results showed that the chelating agents applied in concentrations of 0.2–5.0 mg 1 −1 often increased the concentration of iron, manganese, lead and zinc in water above contaminated lake sediments. Other heavy metals were not affected significantly. EDTA was the most active mobilizing agent while NTA and TPP both had a less significant effect. The chelating agents generally had little effect on the rate of uptake of most metals by chironomids in aquaria. The role of chelating agents in flowing systems was even less pronounced. Zinc concentrations in water were significantly elevated by the treatment with 1 mg 1 −1 EDTA and manganese concentrations were significantly higher in trout from the pond treated with an intermediate level (1 mg 1 −1) of NTA. All other treatments yielded levels of major ions and heavy metals that were not significantly different from those in the control ponds.

Growth and flowering of Lemna paucicostata I. General aspects and role of chelating agents in flowering1

Lemna paucicostata HEGELM. is normally a short-day plant and flowers only in the presence of a chelating agent (EDTA or EDDHA) in the medium. The plant can be induced to flower even by a single long night treatment; the flowering percentage, however, increases with further inductive cycles. The length of the critical dark period depends upon the chelating agent employed in the medium. It is between 10 and 12 hr in the medium containing EDTA and about 8 hr in the EDDHA-supplemented medium. Red light interruption in the middle of the dark period-even for a minute-is inhibitory for flowering. Attempts to identify the metal ion(s) chelated reveal that the chelating agents affect flowering by facilitating iron uptake. This is also supported by the fact that the requirement of a chelating agent for flowering can be overcome with an excess of iron in the medium. Interestingly, provision of EDDHA and excess of ferric citrate, together, can bring about flowering even under long days.

Acute iron poisoning in children: role of chelating agents.

With the development of the fran-chelating agents, desferriox amine and diethylenetriamine penta-acetic acid (D.T.P.A.), it was appreciated that these substances were potentially valuable in the treatment of acute iron poisoning (Rubin and Princiotto, 1960; Bannerman et.al., 1962 ; Moeschlin and Schnider, 1963; Brit. med. 7., 1963; Lancet, 1964). In the past four years a number of reports have been pub lished on the usefulness of these drugs in clinical practice (Henderson et al., 1963; Gokulanathan at al., 1963; Santos and Pisciotta, 1964; Dugdale and Powell, 1964; Shapiro and Barbezat, 1964; McEnery and Mack, 1964; Whitten et al., 1965; Jacobs et al., 1965; McEnery and Greengard, 1966). Several authors have stressed the need for further experience in this form of treatment, particularly in determining the optimal dosage schedule for desferrioxamine, and present regimens have been considered to be tentative (Ciba, 1965; Brit. med. 7., 1965; Whitten et al., 1965). This paper presents an account of experience with 16 child 'ren suffering from iron intoxication of varying degrees. An attempt is made to achieve a critical appraisal of the chelating drugs by considering their biochemical effectiveness, the inci dence of side-effects, and their influence on mortality and morbidity.