A selective sensor for nanolevel detection of lead (II) in hazardous wastes using ionic-liquid/Schiff base/MWCNTs/nanosilica as a highly sensitive composite

An effective potentiometric sensor had been fabricated for the rapid determination of Pb2+ based on carbon paste electrode consisting of room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), multiwalled carbon nanotubes (MWCNTs), nanosilica, synthesized Schiff base, as an ionophore, and graphite powder. The constructed nanocomposite electrode showed better sensitivity, selectivity, response time, response stability, and lifetime in comparison with typical Pb2+ carbon paste electrode for the successfully determination of Pb2+ ions in water and in waste water samples. The best response for nanocomposite electrode was obtained with electrode composition of 18% ionophore, 20% BMIM-PF6, 49% graphite powder, 10% MWCNT, and 3% nanosilica. The new electrode exhibited a Nernstian response (29.76 +/- 0.10 mV decade(-1)) toward Pb2+ ions in the range of 5 x 10(-9)-1.0 x 10(-1) mol L-1 with a detection limit of 2.51 x 10(-9) mol L-1. The potentiometric response of prepared sensor is independent of the pH of test solution in the pH range of 4.5-8.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition, and heavy metal ions.