Ultrasonic-aided dispersive solid-phase microextraction employing magnetic halloysite nano clay for simultaneous preconcentration of lead (II) and cadmium (II)

Abstract

Heavy metal poisoning of water by lead Pb(II) and cadmium Cd(II) is a severe environmental issue. A magnetic halloysite nano clay (Fe₃O₄@HNT) was synthesised for the simultaneous preconcentration of Cd(II) and Pb(II) using an ultrasound-assisted dispersive micro-solid phase extraction technique (US-DMSPE). Various characterisation techniques were employed to characterise the nanocomposite, confirming the nanostructure and chemical composition of Fe₃O₄@HNT. The transmission electron microscope (TEM) showed that the inner cavity of the tube was approximately 10–21 nm (with an average of 13.4 ± 3.4 nm), and the lengths are variable. In addition, the open-ended and inner cavity characteristics provided a passage and additional active sorption sites for the target analytes.

Brunauer–Emmett–Teller (BET) confirmed the mesoporosity of the adsorbent, which corresponds with the inner diameter as confirmed by TEM. The preconcentration parameters were optimised using fractional factorial design (FrFD) and central composite design (CCD). Under the optimised experimental conditions, the detection limits were 0.037 and 0.054 µg/L, and the dynamic range was 0.1–400 µg/L for cadmium and lead, respectively. The method had good precision with RSD (<4.5 %) and R² (0.9987 for cadmium and 0.9975 for lead). This technique successfully determined lead and cadmium in water samples with excellent relative recovery in the 98.8 to 106 % range.