Precipitation of indium using sodium tripolyphosphate

The main purpose of this study was to precipitate indium and extract indium from pressure oxidative leaching liquor using sodium tripolyphosphate. Various influential factors were evaluated in the paper, such as pH value, temperature, reaction time, molar ratio of Na5P3O10/indium and metal ions including Fe3+, Fe2+, Cu2+, Cd2+, Zn2+, etc. Over 95% of the indium was precipitated under the conditions employed, e.g. at a pH of 2.6, with a Na5P3O10 to indium molar ratio of 0.91, and 1.5 h reaction time. The chemical and X-ray diffraction analyses showed that the main component of the precipitates was NaIn3 (P3O10)2·12H2O. The resulting precipitate was dissolved by using NaOH solution and hot sulfuric acid solution respectively, and then the solution was subjected to solvent extraction and cementation using zinc powder for the recovery of indium.