Beata Szczepanik

Protolytic dissociation of cyanophenols in ground and excited states in alcohol and water solutions.

The effect of cyano substituents on acidity in ground and excited states of mono- and dicyanophenols was investigated. The equilibrium dissociation constants of 3,4-dicyanophenol in ground and lowest excited states in water solution and the change of these constants in the excited state during the transfer to the ground state for o-, m-, p-cyanophenol and 3,4-dicyanophenol in alcohol and water solutions were determined. It was shown that the cyano substitution increases the acidity of ortho-, meta- and dicyano-derivative in ground state in comparison to the phenol, which makes the anions of these derivatives appear in solutions from methanol to 1-butanol. In the excited state the acidity of investigated compounds changes significantly in comparison to the ground state. 3,4-Dicyanophenol is the strongest acid in the lowest excited singlet state, while p-cyanophenol is the weakest one in both alcohol and water solutions. The distribution of the electronic charge and dipole moments of all investigated cyanophenols in ground and excited states were determined on the basis of ab initio calculations using the GAMESS program.

EFFECT OF TEMPERATURE ON HALLOYSITE ACID TREATMENT FOR EFFICIENT CHLOROANILINE REMOVAL FROM AQUEOUS SOLUTIONS

Monochloroanilines and dichloroanilines are important reagents or chemical intermediates in the production of dyes, pharmaceuticals, and agricultural chemicals. These toxic compounds have a large tendency to accumulate in the environment and a low natural biodegradability, so improved methods to remove or sequester them are needed. Halloysite is used as an efficient adsorbent to remove toxic compounds, such as aniline, from aqueous solutions. The purpose of this study was to evaluate whether acid-activated halloysites from the “Dunino” (Poland) strip mine could be effective in the removal of not just aniline but also of its chloro-substituted forms from aqueous solutions. The composition, structure, and morphology of activated halloysites were characterized using the following methods: wavelength dispersive X-ray fluorescence analysis (WDXRF), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and N2 adsorption-desorption analysis. The acidactivated halloysites had an increased ability to remove aniline and chloroanilines from aqueous solutions as the acid activation temperature was increased. This suggests that the acid activation temperature is an important factor that influences the ability of acid activated halloysites to adsorb aromatic amines (anilines) from water. The efficiency of aniline and chloroaniline removal by halloysite activated at 80°C reached maximum levels, especially for the removal of aniline and 4-chloroaniline. The adsorption isotherm data were best described by the Langmuir adsorption model. The values of the Langmuir adsorption constants were calculated using the inverse liquid chromatography method.

Determination of Adsorption Equations for Chloro Derivatives of Aniline on Halloysite Adsorbents Using Inverse Liquid Chromatography

Chloro derivatives of aniline are commonly used in the production of dyes, pharmaceuticals, and agricultural agents. They are toxic compounds with a large accumulation ability and low natural biodegradability. Halloysite is known as an efficient adsorbent of toxic compounds, such as phenols or herbicides, from wastewater. Inverse LC was applied to measure the adsorption of aniline and 2-chloroaniline (2-CA), 3-chloroaniline (3-CA), and 4-chloroaniline (4-CA) on halloysite adsorbents. A peak division (PD) method was used to determine a Langmuir equation in accordance with the adsorption measurement results. The values of adsorption equilibrium constants and enthalpy were determined and compared by breakthrough curve and PD methods. The physical sense of the calculated adsorption enthalpy values was checked by applying Boudarts entropy criteria. Of note, adsorption enthalpy values for halloysite adsorbents decreased in the following order: aniline > 4-CA > 2-CA > 3-CA.