No description available.

No description available.

No description available.

Solution- and solid-state Nuclear Magnetic Resonance Spectroscopy (NMR) have been used to investigate a series of substituted, triazinylamino azo dyes. Proton, (^13)C and (^15)N solution-state spectra have been assigned using a variety of techniques and the chemical shifts are discussed. Site-exchange effects have been observed in (^1)H and (^13)C spectra for many of the dyes studied but most prominently for compound 13.The exchange effects were investigated at different temperatures below ambient, for a CD(_3)OD solution of compound 13. The bandshapes were fitted for three-site exchange and the relevant rate constants extracted. The exchange has been attributed to internal rotation of the substituents about the triazine ring. Activation parameters have been calculated: for exchange between one pair of sites H(^#) = 76 ± 8 kJ mol(^-1) and ɅS(^#) = 52 ± 27 J mol(^-1) K-(^-1) and for a second pair, H(^#) = 76 ± 4 kJ mol(^-1), S(^#) = 55 + 15 J mol(^-1) K(^-1). Direct exchange between the remaining pair of sites is negligible. Exchange involving a fourth site affects the spectra at somewhat lower temperatures, which assists in a partial assignment of the observed peaks to the rotamers. The rotations that are causing the effects observable in the NMR spectra are identified, with the help of molecular modelling investigations. Three out of the four possible energy barriers are found to be a combination of rotation and nitrogen inversion. Exploration of the energy surface shows that nitrogen inversion with rotation actually reduces the rotational energy barrier, compared to the planar rotation. The relative barrier heights can be rationalised, although their exact values are not consistent with those measured using NMR. Solid-state (^13)C spectra have also been recorded but are broad, making detailed assignment difficult. The broadness is found to be mainly due to the amorphous nature of the samples. The resolution is not vastly improved on increasing the spectrometer field and the powder X-ray diffraction exhibits only broad reflections.

An elegant synthesis of hitherto inaccessible naphthopyrans bearing one or more strongly electron withdrawing sulfone functions was accomplished. Key to the success of this approach was the development of the deactivating sulfone unit through the oxidation of a thioether moiety post to the Claisen propargyl ether rearrangement to form the naphthopyran.

The dyeing of cotton can be problematic to the dyeing industry when dyeing with different dye classes because a significant amount of dyes find their way into effluents. Cotton dyed with different class of dyes suffers from washing-off, wash-fastness, light-fastness, rubfastness and ring-dyeing problems. A method to increase the substantivity for the cotton fiber is to create a positive charge on the fiber. For this purpose the cotton fiber was pretreated with cationising agents Servon XRK and NMM derivative. Servon XRK and NMM derivative were used as part of EU Frame Work V. Servon XRK (3-chloro-2-hydroxy-N, N, N-trimethyl-l-propanaminium chloride) and NMM derivative [4-(3-chloro-2- hydroxypropyl)-4-methylmorpholin-4-ium chloride)] were applied to cotton by pad-batch method. In this research vat dyes, acid dyes, azoic colourants and reactive dyes have been used. The dyeings from vat dyes gave improved colour yield values when applied to the Servon XRK and NMM modified cotton fabrics as compared to the unmodified cotton fabrics. The dyeings from anthraquinone vat dyes (Cl Vat Violet 1, Cl Vat Red 13 and Cl Vat Green 1) on modified (Servon XRK and NMM) cotton fabric absolutely did not lose any colour in wash-off liquor as the dyeings from anthraquinone vat dyes (Cl Vat Violet 1, Cl Vat Red 13 and Cl Vat Green 1) on the unmodified cotton fabric gave a significant amount of colour in wash-off liquor. Vat dyes on the modified cotton fabric gave overall better dyeing results than on the unmodified cotton fabric. Disulphonated acid dyes Cl Acid Red 13 and Cl Acid Red 17 gave better wash-fastness results than monosulphonated (Cl Acid Red 88) and trisulphonated (Cl Acid Red 18 and Cl Acid Red 27). The light-fastness results were better for the dyeings from trisulphonated acid dyes than the monosulphonated and disulphonated acid dyes. The dyeings from Cl Acid Blue 193 gave good dyeing results than the dyeings from Cl Acid Violet 92. The overall dyeing results are better for the dyeings obtained by the application o f Naphthol AS to the Servon XRK modified cotton fabric by pad-dry and pad-batch-dry methods followed by coupling than the corresponding dyeings on the unmodified cotton fabric. Sumifix Supra Blue BRF and Sumifix Supra Red 3BF applied on the Servon XRK modified cotton fabric gave improved dyeing results than applying on unmodified cotton fabric. Reactive dyes co-applied with NMM have given overall better results than when applied without NMM.

No description available.

MENVSC / Department of Ecology and Resource Management / In this study, the efficacy of bentonite clay, pre-treated magnesite and their nanocomposite on the removal of Congo red dye from aqueous solution was explored. Batch experimental approach was a technique used to fulfil the goals of this study. A number of operational parameters were optimised, and they include effects of shaking time, adsorbent dosage, initial CR dye concentration, initial solution pH and temperature. Findings of the study revealed that the optimum conditions that are suitable for the removal of CR dye are 20 minutes, 0.5 g of dosage, 120 mg/L, 250 rpm, and pH = 7. This has achieved > 99% removal efficacy of CR dye for the nanocomposite and reduced it to below the South African National Standard (SANS) 241 water quality specifications. Furthermore, kinetic studies revealed that bentonite clay, pre-treated magnesite, and their nanocomposite fitted very well to pseudo-second-order kinetics than pseudo-first-order kinetics. The regression analysis was observed to be 1, 0.9, and 0.9 for bentonite clay, pre-treated magnesite, and their nanocomposite respectively. Adsorption isotherms indicated that CR removal by bentonite clay, pre-treated magnesite, and their nanocomposite fitted well to Langmuir adsorption isotherm than the Freundlich adsorption isotherm hence indicating mono-layer adsorption. Thermodynamic values for CR removal were observed to be: ΔH0 (kJ mol-1) = 43.86, 30.67, and 24.88 for bentonite clay, pre-treated magnesite, and their nanocomposite respectively. This indicates that the reaction is endothermic. The positive ΔS0 (kJ mol-1 K-1) values for bentonite clay and 25 °C for pre-treated magnesite confirms that there is an increase in the degree of randomness at solid/solution interface during the removal of CR ions from aqueous solution. The negative values of ΔG0 (kJ mol-1) for 40 – 70 °C on bentonite and the entire range for the nanocomposite suggest the spontaneity and feasibility of CR adsorption whereas the positive ΔG0 (kJ mol-1) for bentonite clay suggest a non-spontaneous nature of adsorption. As such, pre-treated magnesite/bentonite clay nanocomposite demonstrated superior adsorption capacity in relation to individual materials and other materials reported in literature. / NRF