STUDY OF THE SELECTIVITY CHARACTERISTICS INCORPORATED INTO PHYSICALLY ADSORBED ALUMINA PHASES. II. MERCAPTONICOTINIC ACID AND POTENTIAL APPLICATIONS AS SELECTIVE STATIONARY PHASES FOR SEPARATION, EXTRACTION, AND PRECONCENTRATION OF LEAD(II) AND COPPER(II)

Abstract

ABSTRACT A method is described for the immobilization of 2-mercaptonicotinic acid on the surface of three different alumina phases. The selected alumina phases are characterized by different acidity properties, acidic phase (I), neutral phase (II), and basic phase (III). Evidences for the physical adsorption of the organic modifier on the surface of the newly synthesized alumina phases (IV–VI) were evaluated on the basis of infrared spectrophotometric analysis, as well as the surface coverage values and pH values of all alumina phases (I–VI). The determined mmol g−1 values for the modified alumina were found to be 0.886, 1.012, and 0.958 for the modified acidic phase (IV), neutral phase (V), and basic phase (VI), respectively. These alumina phases (I–VI) were extensively investigated to identify the possible selectivity characters incorporated into the modified alumina phases and compared with the unmodified ones. This study was accomplished by the determination of the distribution coefficient value (Kd), as well as the separation factor (α) for a series of mono-, di-, and trivalent metal ions. The results of this study were found to confirm the strong affinity and selectivity of the modified alumina phases (IV–VI) for Pb(II) and Cu(II), due to the noticeably high increase in their separation factors versus other interfering metal ions. The advantage of the selectivity character in the modified phases (IV–VI) was also confirmed by the application of a micro-column for selective separation of Cu(II) and Pb(II) from other interfering metal ions, such as Ca(II), Cr(III), Co(II), and Cd(II). Finally, a micro-column was also used and applied for the selective separation, extraction, and preconcentration of Cu(II) and Pb(II) from sea water samples, and the results indicated good recovery values for the spiked 1.0 ng mL−1 of these two metal ions. The percentage recovery values of Cu(II) and Pb(II) were found to be in the range of 95.2– 98.7±2.0 – 4.0% by the three physically adsorbed alumina phases with 2-mercaptonicotinic acid (IV–VI), with a preconcentration factor of 500.