Measurement of interaction forces between talc and toner particles

The interactions between talc and toner particles, crucial for the improved ink removal by talc-assisted deinking process, are measured using an atomi c force microscope (AFM). The cleaved talc showed a molecularly smooth surf ace. The advancing contact angles were determined to be approximately 80 de grees for the talc and 100 degrees for the fused toner particles, insensiti ve to the presence of calcium ions in the probing electrolyte solutions. Th e energy barriers measured between the toner and talc surfaces increased wi th increasing solution pH. The repulsive forces decayed exponentially with separation between the toner and the talc surfaces. The addition of calcium up to 0.5 mmol/L decreased the energy barrier significantly, particularly around pH 10. The adhesion force between the talc and toner decreased with increasing pH. The presence of calcium ions increased the adhesion force. T he comparison of measured force profiles with those calculated using the cl assical DLVO theory indicated the presence of hydrophobic attractive forces .