Alexandru Cecal

The sorption of some radiocations on microporous titanosilicate ETS-10

The microporous titanosilicate ETS-10 synthesized from gel with following molar composition: 1.0 Na2O: 1.49 SiO2 : 0.2 TiO2 : 0.6 KF : 1.28 HCl : 39.5 H2O was subjected to sorption of radioactive cations 115Cd2+, 204Hg2+, 60Co2+ and 137Cs+ (M) from aqueous solution, in the absence of ionic competition. The uptake of these cations on the ETS-10 was compared by means of the distribution coefficient (Kd) versus contact time and sorption capacity (R) at equilibrium. The FT-IR spectra of M-ETS-10 sorption products exhibit a modification of the absorption band, principally at 381 cm-1.

Uptake of uranyl ions from uranium ores and sludges by means of Spirulina platensis, Porphyridium cruentum and Nostok linckia alga.

In this paper was studied the uranyl ions biosorption on three types of alga: Nostok linckia, Porphyridium cruentum and Spirulina platensis. These ions were supplied either from a pure solution of uranyl nitrate, or after leaching process of uranium ore, or from the sludge resulting in the output of pure UO(2) technology. It was investigated the retention degree versus contact time and afterwards the Langmuir and Freundlich biosorption isotherms of uranyl ions on the three alga types. The retention of UO(2)(2+) ions on alga was proved through FTIR spectra plotted before and after biosorption processes. From the experimental data it was found that regardless of origin of uranyl ions, the retention degree on alga decreased in the series. Spirulina platensis > Porphyridium cruentum ≥ Nostok linckia.

Effect of radioactive and non-radioactive mercury on wheat germination and the anti-toxic role of glutathione

Studies to test the noxious effect of mercury ions on wheat germination and seedling growth showed that germination rate, shoot length, and fresh weights varied as a function of their concentration in the treatment solutions. At the same concentration, the radioactive mercury proved to be more harmful to the living seeds and seedlings. The detoxification action of glutathione for both radioactive and non-radioactive mercury was also followed. After a seven-day period of germination in the presence of the investigated compounds, the wheat plantlets were cut from the seeds, and their height, weight, and residual radioactivity were measured. The shoot length decreased from 8.1 (blank) to 4.6 cm (non-radioactive mercury) or even to 2.5 cm (203Hg), while glutathione had both an anti-toxic and an anti-radiotoxic effect (6.4 and 6.0 cm, respectively). The root weight of the lot decreased from 1.7 to 0.7 g and 0.4 g, respectively, while glutathione showed a healing action (1.5 and 1.7 g). The radioactive ions accumulated especially in roots (35.5 %), and less in shoots (11.2 %). Results were statistically validated.

Laboratory analyses of 60Co2+, 65Zn2+ and 55+59Fe3+ radiocations uptake by Lemna minor

The living Lemna minor vascular plant and two different sorbents obtained by chemical treatment of this plant were tested to study the removal process of 60Co2+, 65Zn2+ and 55+59Fe3+ from low radioactive wastewaters. The most effective sorbent was the protonated biomass, indicating the decisive contribution of the complexation process in the assembly of the uptake mechanisms. The uptake performance of the biosorbent obtained from the L. minor can be increased with ∼20% by treatment with 0.1 N HNO3. Concerning the metabolically active mechanism, it can be notice the slow elimination of 65Zn2+ and the continuously increase of 55+59Fe3+ uptake degree. The Na2CO3 generated in situ in systems participates to a double exchange reaction with the metallic cations during the uptake. 60Co2+, 65Zn2+ and 55+59Fe3+ radiocations prefer for coordination N-donor ligands at the expense O-donors ones.

Bioleaching of UO22+ Ions from Poor Uranium Ores by Means of Cyanobacteria

The present paper deals with the study on uranium (VI) leaching, as uranyl ions, from ores with a poor content in util minerals, using some algae as: Porphyridium cruentum (Smith and Soerly) Nägeli, Spirulina platensis CNM-CB-02 and Nostoc linkia (Roth) Born and Flah. The basic composition of these ores allowed the self-maintenance and self-development of these microorganisms, which have facilitated then the leaching of the uranium (VI) as UO22+ ions. The microbial leaching degree was comprised between 40–90%, depending on the used alga and experimental conditions.

Radiochemical study of the kinetics of crystal growth in gels

Abstract A kinetic study was performed on nucleation and growth of crystals containing radioactive ions in gelatin and agar gels. The investigated crystals were: 60CoHPO4, 60CoS, 60Co(OH)2, 60Co(SCN)2, 204Tl(OH)3, and 204Tl[(C2H5)2NCS2]3. The study shows that the crystal growth rate depends on the cation size and charge, the nature of anion as well as on the colloidal medium. The crystallisation process in the gel has two distinctive steps: diffusion of reactant ions in the gel followed by a chemical reaction which leads to nucleation of the crystal. Both steps are described quantitatively.

Comparison of various sensitive and selective spectrophotometric assays of environmental cyanide

A review is presented to show the advantages involved in the use of some new spectrophotometric cyanide (CN) assays, which are highly sensitive and selective, quick and affordable. Among these, the ninhydrin-based assay, the method based on CN reaction with resorcinol, as well as the Berthelot reaction were found to be highly selective. The old Aldridge 1 method, based on the formation of cyanogen bromide and its subsequent reaction with pyridine and benzidine to form a highly-colored polymethine chromophore is still in use, although recent assays using isonicotinic acid–sodium barbiturate are safe, selective, and sensitive (with a detection limit of 0.005–0.01 mg L−1 CN). Ninhydrin-based procedures are suitable to detect low trace amounts of CN with a molar absorptivity below 2.2 × 105 L M− 1 cm−1 and detection limit of less than 1 ng cm−1 CN. The sensitivity, specificity, and reliability of the investigated methods were compared and the most appropriate protocol for a given analytical problem described.

Bioaccumulation of 65Zn2+ Ions by Some Hydrophytic Plants

Abstract This paper deals with a study on the retention of radioactive ions 65Zn2+ from diluted waste solutions by the hydrophytic plants Lemna minor, Elodea canadensis, Pistia stratiotes and Riccia fluitans. The bioaccumulation degree decreases in the following order: Riccia fluitans ≈ Pistia stratiotes ≥ Lemna minor > Elodea canadensis The possibility to improve the bioaccumulation degree varying the temperature and the solution pH, in the absence of other cations, has been studied. The thin layer radiochromatography method has been used and it proved that the saccharides and lipids are the biochemical fractions responsible for the 65Zn2+ retention.

Removal of uranyl ions from UO2(NO3)2 solution by means of Chlorella vulgaris and Dunaliella salina algae

AbstractThis paper deals with a study of the biosorption of UO22+ ions on two green algae: Chlorella vulgaris and Dunaliella salina. By investigating the retention degree versus contact time from Langmuir and Freundlich biosorption isotherms, kinetic investigations and FTIR spectra it was found that the biosorption process was greater for Chlorella vulgaris than for Dunaliella salina. A new kinetics method is proposed to establish the reaction order concerning the biosorption process of uranyl ions on these biomasses.

BIOAKKUMULATION VON UO2+2- UND TH4+-IONEN AUS ABWASSERN

Abstract Using different algea types the bioaccumulation of UO2 2+ and Th4+ ions from experimental residual wastes of nuclear facilities was investivated. The retaining degree of these ions on microbiological sorbents decreases as: Scenedesmus quadricauda > Porphyridium cruentum > Spirulina platensis > Calothrix sp.2 > Calothrix sp.1 for UO2 2+ and Porphyridium cruentum > Spirulina platensis > Scenedesmus quadricauda for Th 4+. For the same algae it was observed that the retaining degree is much higher for UO2 2+ than for Th4+, probably due to the different linking degrees of hydrolysed species of these ions on the macromolecular compounds of the living cells through the chemical functional groups.