Spectrochimica Acta Part A 78 (2011) 1342–1348 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s a a Synthesis, physical studies and uptake behavior of: Copper(II) and lead(II) by Schiﬀ base chelating resins Mohammed K. Othman, Fatima A. Al-Qadri ∗ , Fatima A. Al-Yusufy Department of Chemistry, University of Sana’a, Aldaree Street, Sana’a, Yemen a r t i c l e i n f o Article history: Received 9 August 2009 Received in revised form 11 March 2010 Accepted 25 December 2010 Keywords: Chelating resins Metal ion uptake Thermal stability Adsorption isotherms Metal ion selectivity a b s t r a c t Two new chelating resins possessing multiple functional groups capable of coordinating with sev- eral metal ions are reported. The resins were synthesized by condensing Schiﬀ bases derived from 2-aminophenol, 2-hydroxy-5-chloroaniline and terephthaldehyde with formaldehyde in an alkaline medium. The eﬀects of pH and contact time of the Cu 2+ and Pb 2+ in aqueous solutions on the uptake behavior of the resins were studied. The metal ion uptake behavior of the resins was investigated by the batch method. Both the uptake and the selectivity of the resins towards the investigated metal ions were related to the structure of the resins, type of the metal ion and the uptake conditions. The resins showed maximum uptake capacity for Cu 2+ and Pb 2+ at pH 10. Cu 2+ was seen to undergo preferential adsorption in separate and mixture solutions of Cu 2+ and Pb 2+ . Kinetic studies for the resins using Langmiur equation were also performed.The Schiﬀ base monomers and their formaldehyde resins were characterized by elemental analyses, FTIR and 1 H NMR spectroscopy. The thermal stability of the resins was studied using TGA/DTG analysis. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Since metal ions are non-biodegradable in nature and their intake at a certain level is toxic, detoxiﬁcation of the metal ions from the environmental samples is a challenging task [1]. Con- sidering all the separating techniques for pre-concentration and separation of analytes from diﬀerent matrices, chelating resins can be recommended due to their triple function of ion exchange, chelate formation and physical adsorption [2,3].Chelate-forming polymeric ligands with diﬀerent functional groups containing O, N, S and P in the polymer matrix 2 capable of coordinating to diﬀer- ent metal ions have been extensively studied [4,5]. Polymeric Schiﬀ bases constitute an important class of chelating resins. Schiﬀ bases possessing multidentate coordination sites are known to form com- plexes with transition metal ions readily [6–8]. Schiﬀ base chelating polymers with nitrogen, oxygen donor atoms are found to possess very good selectivity for transition metal ions and show negligible aﬃnity for alkali and alkaline earth metals [9,10]. This makes the resins useful for removal of trace concentrations of metal ions from natural samples. Many reports have been published investigating the chelating properties of Schiﬀ bases resins towards diﬀerent metal ions. The eﬀect of pH, contact time, chemical structure of the resin, concen- ∗ Corresponding author. Tel.: +967 734185160; fax: +967 1464724. E-mail addresses: falkadri@gmail.com, f Alkadri@yahoo.com (F.A. Al-Qadri). tration of the metal ions were investigated to ﬁnd out their metal uptake characteristics [11–15]. Recently, phenol–formaldehyde type resins containing Schiﬀ base moiety have been prepared and their metal ion uptake behavior was studied [11,13]. Phenolic Schiﬀ base monomers were found to undergo condensation polymer- ization readily with formaldehyde and furfuraldehyde. Samal and coworkers, [5,9,16] reported the synthesis of phenolic Schiﬀ base resins which were used for the pre-concentration and separation of Cu(II) and Ni(II) ions from dilute aqueous solutions. In the present work, we report on the syntheses, characterization, physical stud- ies, and the uptake behavior of Cu(II) and Pb(II) ions from dilute aqueous solutions by phenol–Schiﬀ bases of 2-aminophenol, 2- hydroxy-5-chloroaniline and terephthaldehyde, condensed with formaldehyde.The eﬀects of the chemical structure of the resins and the pH on the metal ion uptake in batch technique were studied. 2. Experimental 2.1. Chemicals 2-Aminophenol, terephaldehyde, and 2-hydroxy-5- chloroaniline (Aldrich) were recrystallized from ethanol, 9:1 water/methanol solvent and ethanol, respectively. Copper acetate and lead acetate (BDH) were used as sources of Cu 2+ and Pb 2+ , respectively. Absolute ethanol (Fluka), methanol (Analar, BDH) and formaldehyde (Fluka, 37–40%) were used as received. The buﬀers 1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2010.12.073