Georgeta Maria Simu

The Hydractinia echinata test-system. III: Structure-toxicity relationship study of some azo-, azo-anilide, and diazonium salt derivatives.

Structure-toxicity relationships for a series of 75 azo and azo-anilide dyes and five diazonium salts were developed using Hydractinia echinata (H. echinata) as model species. In addition, based on these relationships, predictions for 58 other azo-dyes were made. The experimental results showed that the measured effectiveness Mlog(1/MRC50) does not depend on the number of azo groups or the ones corresponding to metobolites, but it is influenced by the number of anilide groups, as well as by the substituents’ positions within molecules. The conformational analysis pointed out the intramolecular hydrogen bonds, especially the simple tautomerization of quinoidic (STOH) or aminoidic (STNH2) type. The effectiveness is strongly influenced by the “push-pull” electronic effect, specific to two hydroxy or amino groups separated by an azo moiety (double alternate tautomery, (DAT), to the –COOH or –SO3H groups which are located in ortho or para position with respect to the azo group. The levels of the lipophylic/hydrophilic, electronic and steric equilibriums, pointed out by the Mlog(1/MRC50) values, enabled the calculation of their average values Clog(1/MRC50) (“Köln model”), characteristic to one derivative class (class isotoxicity). The azo group reduction and the hydrolysis of the amido/peptidic group are two concurrent enzymatic reactions, which occur with different reaction rates and mechanisms. The products of the partial biodegradation are aromatic amines. No additive or synergic effects are noticed among them.

Synthesis, characterization and colour determination using CIELAB colour space of stilbene dyes

The synthesis of six new symmetrical disazo direct dyes containing 4,4′-diaminostilbene-2,2′-disulphonic acid as middle component and N-(2-chlorophenyl)-2-hydroxybenzamide, N-(3-chlorophenyl)-2-hydroxybenzamide, N-(4-chlorophenyl)-2-hydroxybenzamide, N-(2-bromophenyl)-2-hydroxybenzamide, N-(3-bromophenyl)-2-hydroxybenzamide, N-(4-bromophenyl)-2-hydroxybenzamide as coupling components is presented. The synthesized dyes were analyzed by thin layer chromatography, electronic spectra and HPLC technique. Their structures were elucidated by FT/IR and 13C-NMR spectroscopy. The CIELAB (1976) colour space was used in all the colour measurements for the six disazo stilbene dyes under the CIE recommended illuminants: D65 (natural day light), A (tungsten light), F2 (fluorescent light) and the standard 10° observer, respectively. The colour differences: ΔEab* and ΔECMC were calculated against one standard. The results reveal a good colouring power of the new azo-stilbene dyes.

Azo Direct Dye Immobilized onto Copolymer (Styrene DVB Functionalized with Quaternary Phosphonium Groups) for Removal of Heavy Metal Ions

In this study we investigated a new sorbent system, Azoic Direct Dye-attached poly(S-DVB functionalized)microbeads, for removal of heavy metal ions from aqueous solutions. Quaternary phosphonium salts grafted on a“gel-type”styrene-7%divinylbenzen copolymer were prepared by polymer-analogues direct quaternization reaction, and characterized by IR spectroscopy. A symmetric disazoic direct dye, containing 4, 4′-diaminobenzanilide as middle component and naphthionic acid as coupling component, was then attached to these microbeads. Microbeads carrying 1.33 mmol Azo Direct Dye/g polymer were used in adsorption/desorption studies. Adsorption rate and capacity of the microbeads for selected metal ions, i.e., Cu(II)and Zn(II), were investigated in aqueous media containing different amounts of these ions(6–200 ppm)at different pH values(2–7). Very high adsorption rates were observed at the beginning, and adsorption equilibria were then gradually achieved in about 5–80 minutes. The maximum adsorptions of metal ions onto the azo direct dye attached microbeads were 2.9 mg/g for Cu(II)ions, and 53.8 mg/g for Zn(II)ions. Desorption of metal ions was studied by using 0.1 M HNO3solution(pH 1.0). High desorption ratios(more than 85%)were achieved in all cases. Adsorption/desorption cycles showed the feasibility of repeated use of this novel sorbent system.

Experimental And Theoretical Study Of The Adsorption Of A Trisazo Direct Dye Derived From 4,4'-Diaminobenzanilide On A Cellulose Substrate

An experimental and theoretical study of the adsorption of a trisazo direct dye on mercerized cotton fibre was performed at three different temperatures: 60°, 86°and 96°C and one salt concentration. The experimental data obtained from the dyeing process was fitted by linear regression analysis to the standard Nernst isotherm and by non-linear regression analysis to the Freundlich and Langmuir isotherms. In order to find out the best sorption model, the multimodal sorption model performed by non-linear regression analysis was considered too. Better statistical results were obtained in the case of the dual mode sorption model.