Utilization of carbon dioxide to synthesize large scorodite particles under ultrasound irradiation

Abstract

This study aims to synthesize large scorodite particles at 70 °C for 3 h via the oxidation of a precursor containing Fe(II) under flowing O2 gas by adding CO2 during ultrasound agglomeration process. First, the size of the precursor was increased with flowing O2 gas and stirring until the particle size was large enough to allow aggregation by 200 kHz ultrasound (1.1–2.9 µm). Next, the reaction solution was ultrasonically irradiated for 10 min under the flow of a mixed gas (O2 + CO2). Finally, the agglomerated precursor was oxidized under flowing O2 gas and stirring without ultrasound irradiation. The addition of a mixed gas containing 80 vol % O2 and 20 vol % CO2 and a short period (10 min) of ultrasound irradiation mitigated cavitation-related dispersion while preserving oxidation by O2 and oxidant radicals. Thus, the average size of synthesized particles was >10 µm from the laser diffraction particle size analysis.