pH-Controlled Mixed Micelle Cloud Point Extraction for Selective Removal of Trace Levels of Iron from Titanium Concentrates

Abstract Removal of trace iron contaminations from valuable concentrates such as titanium is necessary to obtain highly-pure metals. In this regard, a new green mixed-micelle cloud point extraction is proposed to preferentially remove trace concentrations of iron from various geological samples. The developed procedure is based on the formation of a ternary complex of Fe(III) with eriochrome cyanine R (ECR) and cetyltrimethylammonium bromide (CTAB) that is simply extracted by Triton X-114 in the existence of KNO3 at 35 °C. The concentration of Fe(III) in the surfactant-rich phase was detected by ICP-OES. The main parameters influencing the extraction efficiency of Fe(III) were investigated systematically. The presence of KNO3 and CTAB is crucial to induce the clouding phenomena, consequently, achieving high extraction efficiency. At the optimum conditions, the extraction efficiency of Fe(III) was higher than 98.50% in the concentration range of 0.03-80 mg L-1, accompanied by an enrichment factor of 100. Interestingly, Fe(III) can be selectively extracted from complex matrices by a simple modulation of the aqueous phase pH. Fe(III) is completely extracted in the micellar phase at pH 1.0, where no separation of Ti(IV) is observable. These findings reflect the validity of the developed method for preferential removal of trace concentrations of iron from different metal concentrates.