Improvement of iron removal from silica sand using ultrasound-assisted oxalic acid

This paper deals with the removal of iron from silica sand in aqueous oxalic acid, in the absence and presence of ultrasound. The parameters investigated were the reaction temperature, stirring speed, ultrasound power, acid concentration and reaction time. The optimum conditions for the maximum removal of 75.4% of iron with ultrasound were determined as follows: reaction temperature, 95 °C; stirring speed, 500 rpm; ultrasound power, 150 W; acid concentration, 4 g/l; reaction time 30 min. The method induces a remarkable acceleration for the iron leaching process, the leach acid concentration reducing dramatically and the removal efficiency increasing considerably, compared to conventional stirring method. The advantages of ultrasound-assisted leaching were also confirmed by characterizing the silica sand and the leached solid samples using particle size, SEM and color measurement analysis.