A pH responsive nanogel composed of magnetite, silica and poly(4-vinylpyridine) for extraction of Cd(II), Cu(II), Ni(II) and Pb(II)

A pH responsive nanogel composed of magnetite (Fe3O4), silica and poly(4-vinylpyridine) was designed and utilized as an adsorbent for the simultaneous separation of ultra-trace amounts of cadmium, lead, copper and nickel ions. This solid phase extraction system was characterized by Fourier transform infrared spectrometry, transmission electron microscopy and X-ray diffraction analysis. The sorbent can be separated from the sample solution by applying an external magnetic field, and the analytes eluted with 1 M hydrochloric acid. The extracted ions were quantified by flame atomic absorption spectrophotometry. Effects of pH value, adsorption and desorption time, type, concentration and volume of the eluent, breakthrough volume, and effect of potentially interfering ions were studied. Under optimized conditions, the extraction efficiency is > 98 %, the limits of detection are 0.03, 0.2, 0.6 and 0.9 ng mL(-1) for Cd(II), Cu(II), Ni(II) and Pb(II), respectively, and the adsorption capacities for these ions are 52, 61, 75 and 65 mg g(-1). The sorbent has a high affinity for the above target ions. Eventually, the pH responsive system was used for rapid, efficient, fairly selective and highly sensitive extraction of these ions from various water samples.