A solid-phase extraction method using acid-modified Transcarpathian clinoptilolite for preconcentration of trace amounts of lead in water samples

Abstract

The sorption properties of acid-modified Ukrainian Transcarpathian clinoptilolite towards lead aqueous solutions under dynamic conditions have been investigated. The obtained results show that this nanomaterial most effectively sorbs cationic aqua hydroxo complexes of Pb(II) ions. The optimal conditions for the sorption of Pb(II) on the acid-modified Transcarpathian clinoptilolite are as follows: temperature of H-clinoptilolite thermal pre-treatment—600 °C; sorbent grains diameter—0.20–0.31 mm; pH—8.5; flow rate of Pb(II) solution with the concentration of 0.5 µg mL−1 through the sorbent—5 mL min−1. The maximal sorption capacity value of the acid-modified Transcarpathian clinoptilolite towards Pb(II) is equal to 48.79 mg g−1, that is 4.5 times higher than the respective sorption capacity value of the natural form of this zeolite. The best desorbent of Pb(II) from acid-modified clinoptilolite is 1 M KCl (acidified with hydrochloric acid to pH 4.0). This desorbent removes 97% of sorbed Pb(II). The preconcentration method of Pb(II) nanogram amounts in the solid-phase extraction mode during the atomic absorption analysis of natural waters has been proposed. The linearity of the proposed method was evaluated in the range of 0.08–16 ng mL−1 with the detection limit of 0.025 ng mL−1. Due to acceptable recoveries (≥ 96%) and relative standard deviation (RSD) values (1.6–6.6%) from a spiked tap water.