الملخص الإنجليزي
Ionic liquids (ILs) indicate a modern class of ionic solvents of bulky cations and
anions, with the feasibility of tuning their thermal and physical properties for various
applications. In the current work new choline salicylate derivatives based ILs such as
Choline Salicylate, [Ch][SA]; Choline para-Methyl Salicylic Acid, [Ch][p-MSA];
Choline para-Amino Salicylic Acid, [Ch][p-ASA]; Choline para-Nitro Salicylic Acid,
[Ch][p-NSA]; Choline para-Chloro Salicylic Acid, [Ch][p-Clsa]; Choline para Hydroxy Salicylic Acid, [Ch][P-HSA]; Di-Choline Salicylic Acid, [Ch]2[SA]; Di Choline p-Methyl Salicylic Acid, [Ch]2[MSA]; Tri-Choline Hydroxy Salicylic Acid,
[Ch]3[HSA] and Choline Acetyl Salicylic Acid, [Ch][AcSA] were synthesized and
characterized using various techniques like NMR, IR, TGA and HPLC-MS. These ILs
are used to study their effect as additives on the properties of aqueous anionic surfactant
sodium dodecyl sulfate (SDS) solutions and the ability of the studied ILs to form
aqueous biphasic systems (ABS) for application in extraction.
Understanding the effect of (ILs) as additives on the properties of aqueous SDS
surfactant solutions is intensely important because of the various applications of
surfactant-based in the industry. Aggregation behavior of SDS were investigated in the
absence and presence of 5 mM ILs in aqueous solutions. The critical micelle
concentration (CMC) values have been estimated for different IL+ surfactant systems
at three different temperatures 288.15, 298.15 and 308.15 K using different techniques
like electrical conductivity and surface tension. The results indicate that the addition of
all employed ILs to SDS surfactant leads to a decrease in the CMC in this order: [Ch][p ClSA]> [Ch][p-NSA] > [Ch][p-ASA] > [Ch][p-HSA] > [Ch][SA] > water. The
obtained CMC values are employed to determine the thermodynamic parameters of
micellization such as standard free energy (∆𝐺𝑚
°
), standard enthalpy (∆𝐻𝑚
°
), and
standard entropy (∆𝑆𝑚
°
). The values of these parameters indicate that adding ILs adjust
the micellization properties of SDS solution. Parameters such as maximum surface
excess concentration (Г𝑚𝑎𝑥), minimum area per molecule (𝐴𝑚𝑖𝑛 ), surface pressure at
CMC (𝜋𝐶𝑀𝐶), the efficiency of adsorption (𝑝𝐶20) and packing parameters (𝑃) were
calculated and analyzed in this study to predict the interfacial behavior of SDS
surfactant for a better understanding of the rule of ILs' anions in upgrading their
efficiencies in comparison with the aqueous system. The values of the standard Gibbs
free energy of micellization (∆𝐺𝑚
) are negative for all systems indicating that the
micellization is a spontaneous process
Recently, choline-based biphasic systems (ABS) have a great interest because
of their "green" separation processes for the extraction of value-added compounds. We
study the effects of the anion of the IL in forming the ABS with tri-potassium phosphate
salt (K3PO4). Seven ILs were able to form ABS. The used ABS system "IL+ salt +
water" was determined at 298.15 K & atmospheric pressure and the respective
solubility curves, tie-lines, and tie-line lengths are reported. The trend in capability of
forming ABS was observed in the following order: [Ch]3[p-HSA] > [Ch]2[p-MSA]
> [Ch]2[SA] >[Ch][AcetylSA] > [Ch][p-ASA] > [Ch][p-MSA] > [Ch][SA]. The
solubility curve was fitted to the Merchuk equation and tie lines were calculated from
mass phase fractions based on the lever arm rule that are described using the Othmer Tobias and Bancroft equations. Also, the ABS is evaluated through its extraction
capability for caffeine using partition coefficient which found to be greater than one in
all studied systems indicating an efficient extraction.
