The use of new class α-amino nitrile modified magnetic adsorbents for removal of Cd(II) from aqueous medium: Sorbent modification vs. α-amino nitrile addition to the adsorption medium

Abstract

In the present work, some novel α-amino nitriles were prepared: amino-2- (anthracen-9-yl) acetonitrile (AAN), and 2-(naphthalen-1-yl) -2- ((triethoxysilyl) propyl) amino) acetonitrile (Si-AN). With the aid of other organic compounds (3-aminopropyl triethoxysilane “APTES” and tetraethyl orthosilicate “TEOS”), the following carbon nanotubes “CNT” and magnetite “Mag” based adsorbents were prepared: CNT-AAN, Mag-SiO2, Mag-SiO2-APTES, Mag-SiO2-Si-AN. The FT-IR, 1H and 13C NMR spectroscopy proved the formation of (C ≡ N) and (NH-) bonds which indicated successful amino nitrile modification of the adsorbents. The ability of the above-mentioned adsorbents to remove cadmium “Cd(II)” from water was studied at various pH values. CNT modification with AAN reduced Cd(II) uptake, while all Mag modifications increased Cd uptake. The addition of AAN to the extraction medium with CNT sorbent reduced Cd(II) uptake. The addition of TEOS and Si-AN to the extraction medium for Cd(II) removal using Mag was studied where a positive impact was observed. Based on the above experiments, it was decided to use Mag as adsorbent with the addition of Si-AN to the extraction medium. Method optimization recommended pH 8 and Cd:Si-AN molar ratio of 1:1. The maximum adsorption capacity towards Cd(II) achieved in this study was 65 mg g−1. The method selectivity, re-usability and applicability on well water and tap water samples gave appropriate results. The adsorption of Cd(II) on Mag in the presence of Si-AN was fast, endothermic, spontaneous, favored and physi-sorption was predominant.

Keywords

• Amino nitriles
• Magnetite
• Carbon nanotubes
• Cadmium uptake