Improved froth zone and collection zone recoveries of fine mineral particles in a flotation column with oscillatory air supply

Froth flotation has been widely used for the separation and concentration of minerals and other particulate materials by exploiting the difference in their affinity to air bubbles in aquoues medium. One of the key challenges in flotation separation is to improve the recovery of valuable fine particles. This paper reports the column flotation of fine silica particles with oscillatory air supply generated using a fast-switching solenoid valve. The flotation tests were carried out at continuous mode using a specially designed 50 mm diameter column with the recoveries of silica in the froth zone and the collection zone being measured directly. A comparative study with oscillatory air supply and conventional steady air supply was conducted by varying valve switching frequency, valve on/off time ratio, superficial gas velocity, air pressure, and reagent dosage. It was found that use of oscillatory air supply with a proper frequency and valve on/off time ratio to replace steady air supply would increase not only the collection zone recovery but also the froth zone recovery. A strong correlation between the measured froth zone recovery and collection zone recovery was observed.