Poly (N-isopropylacrylamide) (PNIPAM) as a flotation collector: Effect of temperature and molecular weight

Poly (N-isopropylacrylamide) (PNIPAM), a temperature responsive polymer, was tested for its potential use as a collector in a quartz flotation system. The effect of PNIPAM on the surface characteristics of quartz particles were studied using induction time, contact angle and zeta potential measurement and analysed in terms of the probability of bubble/particle attachment and the probability of formation of stable bubble/particle aggregates. It was found that probability of bubble/particle attachment of quartz significantly increases in the presence of PNIPAM, particularly at temperatures above the lower critical solution temperature (LCST) of 32 °C. Furthermore, the probability of bubble/particle attachment increases with increasing PNIPAM molecular weight. This was attributed to the increased hydrophobicity of the quartz surface as well as the decrease in the double layer repulsion between bubbles and particles. This leads to the conclusion that PNIPAM could act as an effective collector in a flotation system.