Evaluation of Maghemite-Rich Iron Oxide Composite Prepared from Magnetite as Adsorbent for Gold from Chloride Solution

Abstract

The capacity and effectiveness of a composite magnetic iron oxide, consisting mainly of maghemite $$ (\gamma {\text{Fe}}_{2} {\text{O}}_{3} ) $$, prepared by oxidation of synthetic magnetite at 350°C have been evaluated. X-ray diffraction analysis of the synthesized product indicated an iron oxide with 44%, 33%, and 23% of maghemite, hematite (Fe2O3), and magnetite (Fe3O4), respectively. The produced composite material was used in this study as adsorbent to recover gold from chloride solution. The effects of different process parameters, such as solution pH, contact time, chloride ion concentration, and initial Au concentration, on the recovery of Au were studied. Almost all Au in solution (99.78%) was recovered at pH of about 6.5 after 24 h of contact time. The maximum Au uptake of about 11.5 µmol/g was obtained at initial Au concentration of 3.5 × 10−4 mol/L. No significant difference in Au uptake was observed upon increasing the contact time to 48 h. High chloride concentration was found to be detrimental to Au recovery. These results indicate that the prepared maghemite-rich iron oxide composite is more effective than synthetic magnetite reported in previous studies for recovery of Au from chloride solution.