Efficient removal of aluminium(III) from aqueous solutions via ion-flotation technique using aluminon as a chelating agent and oleic acid as a surfactant

Abstract

ABSTRACT In the current work, a green, simple and rapid method was developed and used for the separation and preconcentration of aluminium(III) from aqueous solutions via the ion-flotation technique. Aluminon has been used as an organic chelating agent and combined with aluminium(III) forming a reddish complex. The oleic acid (HOL) was used as a surfactant to float the formed complex to the scum layer. The concentration of aluminium(III) was determined spectrometrically using the ICP-OES instrument at 396.153 nm. 1.0 mol/L HCl was used as a suitable eluting agent for the scum layer before introduction to the ICP-OES instrument. The dissimilar factors influencing the ion-flotation procedure as pH, the concentration of (Al(III), aluminon, and HOL), surfactant type, sample volume, temperature, shaking time, and ionic strength were studied and adjusted. About 100% of aluminium(III) was floated and separated at 25°C and pH 4 after 5 min of shaking time in the presence of 1 × 10−3 mol/L of HOL surfactant. The stoichiometric ratio of the formed complex was investigated through the molar ratio method and found to be 1:3 (Al(III):aluminon). Also, the formation constant (Kf) was calculated and found to be 2.34 × 104. The analytical characteristics of the procedure (limit of detection, limit of quantification, and range of linearity) were evaluated and found to be (0.67 μg/L, 2.20 μg/L, and 1–20 μg/L), respectively. The tolerance limits of different interfering ions (individually or in combination) were also examined and the interferences resulted from some foreign ions were avoided by adding excess aluminon. The method was successfully applied to recover aluminium(III) spiked into some real water samples. Al(III) was preconcentrated successfully from different aqueous volumes with a preconcentration factor of 200. Additionally, a flotation-separation mechanism is suggested based on some physical and chemical studies for the formed complex and found to occur via physical interaction.