Separation and determination of trace level of gold from hydrochloric acid solutions using ultrasound-assisted cold-induced aggregation microextraction

Abstract

A new methodology ultrasound assisted cold-induced aggregation microextraction (USA-CIAME) was developed for the determination and extraction of ultra trace levels of Au³⁺ from aqueous hydrochloric acid solutions by pure ionic liquid (IL), in the absence of chelating agents. The extraction behaviour of metal ions by [Hmim]PF₆ was particularly studied. Moreover, the stripping of metal ions from the IL phase was investigated. Au³⁺ in IL phase can be quantitatively recovered by NaPF₆. Recycle testing indicated that IL loss can be avoided by the additon of [Hmim]⁺ to the initial AuCl₄⁻ solutions before extraction and/or using PF₆⁻ solutions for stripping. The main factors affecting Au³⁺ extraction, the amount of IL, the pH of the sample solutions, and the chloride ion concentration on extraction efficiencies were carefully studied. A linear calibration was obtained for 1.5 to 200 μg L⁻¹ of Au³⁺ and the limit of detection was 0.59 μg L⁻¹. The validation of this method was done by recovery and determination of trace amount of gold in river, sea water and geological samples with satisfactory results.