Naked-eye detection of some metal ions using amberlite XAD-7 coated with 1-(2-phridylazo)-2-naphthol

Abstract

Amberlite XAD-7 coated with 1-(2-pyridylazo)-2-naphthol (PAN) was used as a naked-eye solid sensor for Cu(II), Co(II), Ni(II) and Zn(II). Parameters for coating PAN onto Amberlite XAD-7 such as the amount of Amberlite XAD-7, the concentration of PAN and the stirring time were studied. Amberlite-PAN was characterized by DR-UV-vis spectrophotometry. The color change of Amberlite XAD-7 coated with PAN was observed from yellow to purple, green, pink and orange for Cu(II), Co(II), Ni(II) and Zn(II), respectively. In batch system, the proper pH was found to be 5 with the response time of 1 min for Cu(II), 5 min for Co(II), 20 min for Ni(II) and 45 min for Zn(II). The optimum concentration of PAN for coating PAN onto Amberlite XAD-7 was 0.5 mM which was suitable to detect the lowest concentration of Cu(II), Co(II), Ni(II) and Zn(II). The naked-eye detection limit of Cu(II), Co(II) and Ni(II) was found to be 0.2 mg/L while the detection limit of Zn(II) was found to be 4.0 mg/L. The concentration ranges for color calibrations were 1x10⁻⁶-1x10⁻² M for Cu(II), 1x10⁻⁶-1x10⁻⁴ M for Co(II) and Ni(II) and 1x10⁻⁶-1x10⁻² M for Zn(II). Thiourea was used as a masking agent for Cu(II) and potassium chloride was used as a masking agent for Ni(II). Moreover, the Amberlite-PAN was used as a naked-eye solid sensor for Cu(II), Co(II), Ni(II) and Zn(II) at least 10 weeks and can be reused by 1 M nitric acid regeneration at least 4 times. The determination of Cu(II), Co(II), Ni(II) and Zn(II) in real water samples by naked-eye detection using Amberlite-PAN under the optimum conditions was achieved. The naked-eye determination of Co(II), Ni(II) and Zn(II) in the presence of Cu(II) and the naked-eye determination of Zn(II) in the presence of Ni(II) in real water sample by using Amberlite-PAN with masking agent under the optimum conditions were accomplished.