Flotation recovery of toner containing iron oxide from water suspension

Abstract

Flotation of fine solids is important as the particles are not only contain valuable metals, which it is essential to recover, but negatively affect the environment. Fine particles often cause difficulties in flotation both surface chemistry and flotation kinetics. In this paper, flotation of toner particles was studied. The results show that toner particles, containing magnetite disseminated in organic matter, are fine in size (5–25 μm), and exhibit magnetic properties. The studies of contact angle revealed a high degree of hydrophobicity of toner surface, which resulted in high rates of particles attachment to air bubbles under stirring conditions of toner suspension. A multilayer coverage of the bubble surface with toner particles was observed, proved high bubble-particle and particle-particle interactions. Flocculation of toner as a result of either self-flocculation due to magnetic and hydrophobic properties of toner particles, or induced by collector was observed. Flotation kinetics tests were carried out to investigate the natural floatability of toner and the effect of kerosene on recovery and flotation kinetics of toner particles. Froth flotation can be used to recover toner from water suspension with no addition of collector. It indicates a reduction in chemicals consumption and environmentally friendly approach. Flotation kinetics of toner was described by second order flotation model. The findings revealed the effect of collector dosage to the rate of toner flotation. A significant recovery of toner 95.5% was observed at 2 min flotation time and it was higher compared to natural floatation of toner. High efficiency of flotation was achieved with small dosage of kerosene, which increased recovery and flotation rate of toner particles. Effect of concentration of solids in water suspension on flotation recovery was studied. Increasing the concentration of solids in the suspension from 1 g/l to 20 g/l resulted in the growth of flotation recovery from 78.13% to 96.72%. Despite this, the flotation rate constant for various concentrations of solids in the suspension was of the same order.