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Complexation of [2.2]paracyclophane with β- and γ-cyclodextrins studied by HPLC and NMR

100%

Dodziuk H., Bielejewska A., Schilf W., Ueda H.

Open Chemistry

2011

vol. 9

issue 6

1056-1061

The NMR spectra of [2.2]paracyclophane with β- or γ-cyclodextrin in DMF-d7 at room temperature do not show significant complexation, while HPLC of the complexes in mixed H2O:alcohol solvents demonstrate complexation with different stoichiometries. At 243 K in DMF solution the H3 and H5 NMR signals of γ-cyclodextrin (but not β) exhibit complexation-induced chemical shifts denoting complex formation. According to HPLC, at room temperature the [2.2]paracyclophane complex with β-cyclodextrin in 20% H2O:EtOH exhibits 1:2 stoichiometry with K 1 = 1×102 ± 2, K 2 = 9.0×104 ± 2×103 (K = 9×106) while that with γ-cyclodextrin in 50% H2O:MeOH exhibits 1:1 stoichiometry with K 1 = 4×103 ± 150 M−1. Thermodynamic parameters for both complexes have been estimated from the retention time temperature dependence. For the β-cyclodextrin complexation at 25°C ΔG 0CD is −39.7 kJ mol−1 while ΔH 0CD and ΔS 0CD are −88.2 kJ mol−1 and −0.16 kJ mol−1 K−1. For γ-cyclodextrin, the corresponding values are ΔG 0CD = −20.5 kJ mol−1, ΔH 0CD = −33.5 kJ mol−1 and ΔS 0CD = −0.04 kJ mol−1 K−1. [...]

Removal of reactive dye brilliant red HE-3B from aqueous solutions by hydrolyzed polyacrylonitrile fibres: equilibrium and kinetics modelling

88%

Bilba D., Suteu D., Malutan T.

Open Chemistry

2008

vol. 6

issue 2

258-266

A cheap and efficient fibrous hydrolyzed polyacrylonitrile (HPAN) sorbent was obtained by alkaline hydrolysis of Romanian polyacrylonitrile fibres. Scanning electronic microscopy and infrared spectroscopy were used to characterize the hydrolyzed product and to confirm its functionalization. The adsorptive potential of the proposed sorbent for reactive dye Brilliant Red HE-3B removal from aqueous solutions of pH=2 was examined by the batch technique as a function of dye concentration, temperature solution and contact time. The Freundlich, Langmuir and Dubinin-Radushkevich adsorption models were applied to describe equilibrium sorption data and to determine the corresponding isotherm constants. The thermodynamic parameters ΔG, ΔH and ΔS were also determined; the values obtained show that sorption of reactive dye on HPAN fibres is a spontaneous, endothermic and entropy-driven process. The kinetics of sorption of the reactive dye were analyzed using pseudo-first order and pseudo-second order kinetic models. The kinetic data fitted well to pseudo-second order kinetics, indicating the chemisorption of reactive dye onto the fibrous sorbent. The sorption mechanism of the dye onto hydrolyzed fibres was confirmed by FTIR spectroscopy. The dye-loaded HPAN sorbent can be regenerated by treatment with 0.1M NaOH and the regenerated sorbent may be reused in several adsorption-desorption cycles. The results of this study provided evidence that the HPAN fibres are effective for removing reactive dye Brilliant Red HE-3B from aqueous effluents. [...]

Batch adsorption of malachite green dye from aqueous solution using sawdust of Swietenia macrophylla (mahogany wood)

75%

Opia C. F., Obinna N. V., Chizoruo I. F., Obinna I. B.

World News of Natural Sciences

2023

vol. 50

222-246

Sawdust of Swietenia macrophylla waste was used as a bio-sorbent for the removal malachite green from aqueous solutions in this study. Various parameters’ effect such as contact time, pH, initial dye concentration, temperature and adsorbent dosage were studied on the bio-sorbent. Spectrophotometric technique was implemented for the measurement of dye concentration before and after adsorption. The study indicated that the quantity of dye adsorbed increased steadily with increase in the dye’s initial concentration and contact time because as the concentration increases the dye molecules available for adsorption also increases. There was a sharp rise in the quantity of dye adsorbed as the pH increases from pH 2 to pH 7, equilibrium was obtained at pH 10 after which the quantity of dye adsorbed decreased with an increased to pH 12. As the temperature increases the quantity of dye adsorbed decreased, this can be attributed to an increase in solubility as the temperature increases. The experimental data were fitted to the Langmuir and Freundlich adsorption isotherms with Langmuir isotherm showing a better fit than Freundlich isotherm model, this shows that the adsorption follows a homogenous coverage signifying saturated monolayer coverage of the solute molecules on the adsorbent surface. The adsorption kinetics data were fitted to pseudo-first and pseudo-second order kinetic model with pseudo-second order kinetic model showing a better fit than pseudo-first order kinetic model, indicating that more than one process affects the adsorption of malachite green dye onto Swietenia macrophylla. In terms of thermodynamic parameters, negative values were obtained for Gibbs free energy ∆G o, indicating a spontaneous adsorption process; also the enthalpy change ∆H° was negative signifying the adsorption is exothermic in nature. Similarly, entropy ∆S° values were negative indicating that the degree of disorderliness of malachite green reduced as it got adsorbed onto the surface of the adsorbent.

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2 Open Chemistry

1 World News of Natural Sciences

1 2023

1 2011

1 2008

1 Bielejewska A.

1 Bilba D.

1 Chizoruo I. F.

1 Dodziuk H.

1 Malutan T.

1 Obinna I. B.

1 Obinna N. V.

1 Opia C. F.

1 Schilf W.

1 Suteu D.

1 Ueda H.

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Complexation of [2.2]paracyclophane with β- and γ-cyclodextrins studied by HPLC and NMR

Removal of reactive dye brilliant red HE-3B from aqueous solutions by hydrolyzed polyacrylonitrile fibres: equilibrium and kinetics modelling

Batch adsorption of malachite green dye from aqueous solution using sawdust of Swietenia macrophylla (mahogany wood)