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PubMed2003

Investigation of the complexation of metal-ions by strong ligands in fresh and marine water.

SCOPE: The detection and investigation of metal ions bound in strong complexes in natural waters is a difficult task, due to low concentration of the metal ions themselves, and also of the strong ligands, which, moreover, are often not of a well-defined composition. Here, a method is proposed for the investigation of the speciation of metal ions in natural waters. OBJECTIVE AND METHOD: It is based on the sorption of metal ions on strongly sorbing ion exchange resins, i.e. complexing resins. For this reason the method is called Resin Titration. It has been shown in previous investigations that the concentration of metal ion totally sorbed by a particular resin, and its reaction coefficient in the solution phase in the presence of the resin, can be determined from the sorption data using a simple relationship. Here, a data treatment (the Ruzic linearization method) is proposed for also determining the concentration of the ligands responsible for the complex in equilibrium with the resin. RESULTS: The method was applied to data obtained by Resin Titration of a freshwater and a seawater. Copper(II) and aluminium(III) were considered, using Chelex 100 as a titrant, due to its strong sorbing properties towards these metal ions. The results were: the total metal concentration in equilibrium with the resin, the side reaction coefficients, and the concentration of ligands. In all these cases the ligands forming very strong complexes were found to be at concentration lower than that of the metals. CONCLUSION: The Ruzic linearization method allows the determination of the concentration of the ligands forming very strong complexes in equilibrium with Chelex 100. The reaction coefficient was better determined by the calculation method previously proposed for RT. The ligands responsible for the strong complexes were found to be at low concentration, often lower than that of the metal ions considered. The metal in the original sample is partly bound to these ligands, since the complexes are very strong. Only a part of the metal is linked to weaker ligands, or free.

Chelating Agents↗
PubMed2004

Remineralization potential of a new toothpaste formulation: an in vitro study.

The aim of the present study was to determine the ability of a dentifrice containing a mixture of ion-exchange resins (named NMTD), which supplies calcium, fluoride, phosphate, and zinc ions, to promote remineralization and/or inhibit demineralization of dental human enamel in a pH cycling model in vitro. A fluoride toothpaste was used as the control. The enamel specimens were tested for microhardness before and after 10 days and 16 days of the demineralizing and remineralizing treatments. The results of this study showed both dentifrices were effective in limiting in vitro enamel demineralization although the effects were not significantly different from each other. Inclusion of calcium and phosphate ion-exchange resins in the dentifrice containing a fluoride ion-exchange resin maintained a similar net outcome of the conventional dentifrice in the demineralization/remineralization process under the experimental conditions employed.

Analysis of Variance↗
PubMed1985

[Therapeutic effect of dried ion exchange resin-treated human immunoglobulin (SM-4300) against severe bacterial and/or fungal infections in surgery].

A newly developed human immunoglobulin for intravenous use, SM-4300, purified by cold ethanol precipitation and ion exchange resin, has been studied in the surgery. SM-4300 has been evaluated clinically against inpatients with severe bacterial and/or fungal infections in the combined use with the antibiotics which were resistant to antibiotic therapy. Total number of 13 patients affected with various severe infections were treated with SM-4300. Clinical effects of SM-4300 were excellent in 2 cases, good in 6, fair in 3 and poor in 2. The efficacy rate was summarized as 61.5%. No subjective and objective clinical side effects and abnormal laboratory findings were observed. In conclusion, combination therapy with SM-4300 and antibiotics was considered to be safe and effective against severe bacterial and/or fungal infections in the surgery.

Adolescent↗
PubMed2004

Sorption and binary exchange of nitrate, sulfate, and uranium on an anion-exchange resin.

Competitive ion-exchange reactions were studied on a strong-base anion-exchange resin to remove NO3- and uranium from a contaminated groundwater containing high levels of NO3- (approximately 140 mM), SO4(2-) (approximately 10 mM), and U(VI) (approximately 0.2 mM). Results indicate that although SO4(2-) carries divalent negative charges, it showed the least selectivity for sorption by the Purolite A-520E resin, which is functionalized with triethylamine exchange sites. Nitrate was the most strongly sorbed. Sorption selectivity followed the order of NO3- > Cl- > SO4(2-) under the experimental conditions. Nitrate competitively sorbed and displaced previously sorbed SO4(2-) in a column flow-through experiment and resulted in a high elution front of SO4(2-) in the effluent. Although the concentration of uranium in groundwater is orders of magnitude lower than that of NO3- or SO4(2-), it was found to be strongly sorbed by the anion-exchange resin. Because the most stable uranium species in oxic and suboxic environments is the UO2(2+) cation, its strong sorption by anion-exchange resins is hypothesized to be the result of the co-ion effect of NO3- by forming anionic UO2(NO3)3- complexes in the resin matrix. These observations point out a potential alternative remediation strategy that uses strong-base anion-exchange resins to remove uranium from this site-specific groundwater, which has a low pH and a relatively high NO3- concentration.

Adsorption↗
PubMed2005

A new configuration of membrane stack for retrieval of nickel absorbed in resins.

A new configuration integrated ion exchange effect system with both electro-migration and electrochemical reaction in a single cell was developed to effectively retrieve metal ions from simulated wastewater using ion exchange resins without additive chemicals. By simply assembling cation exchange resins and anion exchange resins separated by homogeneous membranes, we found that the system will always be acidic in the concentrate compartment so that ion exchange resins could be in-situ regenerated without hydroxide precipitation. Such a realizable design will be really suitable for wastewater purification.

Absorption↗
PubMed1953

[Ion exchangers].

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Ion Exchange↗