Extraction of Th, Zr and Sc from rock matrix using silica modified with arsenazo-III and their determination by inductively coupled plasma atomic emission spectrometery

Abstract

A simple, selective and rapid determination procedure for Th, Zr and Sc in rock samples using adsorbent silica modified with arsenazo-III is described. Silica modified with arsenazo-III (SAR-III) was synthesised by a single step process in presence of cationic surfactant cetyltrimethylammonium bromide. Effect of pH, amount of adsorbent, contact time for adsorption and the optimum eluent for the quantitative recovery of Th, Zr and Sc were investigated. Optimum conditions selected for the selective extraction of these elements by SAR III are pH-3, 0.2 g adsorbent, contact time 30 minutes and 10 mL of 5 % ammonium oxalate as eluent. Adsorption capacities of SAR III for Th, Zr and Sc are 5.68, 23.9 and 4.42 mg g−1, respectively. Effect of major elements present in the rock on the pre-concentration of these elements was investigated. Interference of iron was eliminated by reducing ferric iron with hydroxylamine hydrochloride. The method was validated by applying the procedure to synthetic rock sample solutions and certified geological reference materials SY-2 (CCRMP, Canada), BCR-1 (USGS), GSN (ANRT, France) and AGV-1(USGS). Detection limits obtained for Th and Zr by this method are 1 µg g−1 and that of Sc is 0.1 µg g−1. The relative standard deviation of the method at 1 µg g−1 was in the range of 1.0–2.5%. Synthesis of silica modified arsenazo-III and its application for the determination of Zr, Th and Sc in rock samples by ICP- AES is described. The result of this study indicates silica modified with arsenazo-III as very selective and sensitive solid phase extractant for Zr, Sc and Th in presence of all the other major elements of rock.