Solid phase preconcentration and determination of mercury and uranyl ions using an itaconic acid functionalized adsorptive membrane

Abstract

A potential sorbent for preconcentration and quantification of mercury and uranyl ions was developed by grafting cross-linked micro-gel in pores of the host polyethersulfone membrane. The micro-gel was formed by in situ photo-polymerization of itaconic acid (ICA) along with co-monomer acrylamide (AM) and crosslinker pentaerythritoltetraacrylate (PETA) in pores of the host membrane. The photo-polymerization was initiated by α,α′-dimethoxy-α′-phenyl acetophenone (DMPA) dissolved in polymerizing solution along with ICA, AM and PETA. Fourier Transform Infrared Spectroscopy and Gravimetry were used to confirm the anchoring of micro-gel in pores of the host membrane. The comparison of scanning electron microscopic images of blank and grafted membranes indicated that pores of membrane were completely blocked after grafting micro-gel in the membrane. The radiotracers and Energy Dispersive X-ray Fluorescence (EDXRF) were used to study the metal ion uptake efficiency of membrane as a function of pH of the aqueous samples. It was observed that only U(VI) and Hg(II) sorbed with high efficiency (>80%) in the grafted membrane in the presence of other competing cations like Th(IV), V(IV), Eu(III), Fe(III), Cu(II), Pb(II) and Cd(II). It was also observed that desorption of Hg(II) and U(VI) from the membrane sample is possible by 0.01 mol L⁻¹ EDTA disodium salt and 0.5 mol L⁻¹Na₂CO₃, respectively. To explore analytical applications of the membrane, the concentrations of Hg²⁺ ions in the mining soil samples were determined by first preconcentrating mercury ions in the grafted membrane samples and then subjecting these membrane samples to cold vapour atomic absorption spectrophotometry (CV-AAS). The studies carried out in the present work demonstrated that the membrane developed in the present work could be used for removal of Hg²⁺ and UO₂²⁺ ions from waste streams as well as for their quanitative determinations in complex aqueous samples.