This paper presents results from a technique that provides visualization and imaging of ink particles in flows around bubbles to characterize ink adsorption at bubble surfaces. The goal is to develop further understanding of dissolved air flotation and flotation deinking processes important to paper recycling. High-resolution and high-speed video and images show ink attachment and interaction at bubble surfaces. The study looked at the interaction of single bubbles ranging in diameter from 0.2 to 2 mm with ink in model solutions and dispersions in two flow facilities. Those included a bubble suspending facility where bubbles are suspended in a down flow of water in an observation pipe and a stationary bubble facility where bubbles are held at the tip of a needle in an observation tank. The study used an image processing method to determine th esizes and number of adsorbed ink particles. The adsorption of oil-based offset ink was observed for several solutions and flows. Water-dispersible flexographic ink did not exhibit adsorption in solutions based on fatty acid chemistry.
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