Adsorption and magnetic solid-phase extraction of cadmium and lead using magnetite modified with schiff bases

In this work, three Schiff bases were prepared and characterized: E-2-methoxy-4-(((3-(triethoxysilyl)propyl) imino)-methyl)phenol (VSB), E-4-(((3-(triethoxysilyl)propyl)imino)-methyl)phenol (4-HSB) and E-2-(((3-(triethoxysilyl)propyl)imino)methyl)phenol (2-HSB)). These were used to modify magnetite (Mag) to produce the corresponding modified magnetite sorbents (VSB-Mag, 4-HSB-Mag and 2-HSB-Mag). Magnetite was also modified by loading with ((3-aminopropyl)triethoxysilane (Sil) to produce the sorbent Sil-Mag. The sorbents were tested for adsorption and magnetic solid phase extraction (MSPE) of cadmium (Cd(II)) and lead (Pb(II)). The sorbents were characterized by infrared spectroscopy, x-ray diffraction and scanning electron microscopy. The adsorption capacity and intensity were in the order: VSB-Mag > 4-HSB-Mag > Sil-Mag > Mag. Complexation of VSB-Mag with Pb(II) and Cd(II) was confirmed by infrared spectroscopy. A MSPE method of Cd (II) and Pb(II) was optimized where the highest recoveries were obtained at pH 9 using 0.075 g of (VSB-Mag) adsorbent for 60 min shaking time and then elution with 10 mL of 0.1 M HNO3. Figures of merit for the proposed method were estimated (for Cd(II) and Pb(II), respectively) as follows: limit of detection ([0.0015 and 0.017] mg L-1; sensitivity [0.8188 and 0.0851] L mg(-1); dynamic range: [0.0048 to 0.3] and [0.058 to 0.3] mgL(-1); %RSD range [1.9-9.3] and [1.9-7.7] %; %bias range [-15.3 to1.5] and [-25.1-4.9] %; enrichment factor [8.4-10.1] and [7.3-11.4]. Application of the method on real water samples gave the following spiked recovery ranges for Cd(II) and Pb(II), respectively: tap water 72.2 and 58.1%; well water 60.0 and 63.3%.