Improve Deinking Flotation from the Fundamental Research

ABSTRACT
In the early 1980s, froth flotation was introduced to the paper industry to remove ink particles during the
paper recycling process. While the deinking flotation process is widely used, it also suffers from inherent
inefficiencies, primarily due to the poor liberation, weak hydrophobicity, and small size of the ink particles. In the
present work, we took several approaches to address these problems by investigating the fundamental surface
interactions between ink particles, paper fibers, and air bubbles. First, we evaluated the role of dispersants and
polyelectrolytes in liberation of ink from fiber, which can be considered a prerequisite to separation. After identifying
the optimal conditions for liberation, we developed new hydrophobicity enhancing agents to improve the separation
of oil-based inks from fibers. These new reagents were initially studied by measuring the surface forces during the
bubble-ink interactions using the force apparatus for deformable surfaces (FADS), and later tested in batch deinking
flotation tests. We observed that the hydrophobic force between air bubble and modeled oil-based ink surface
increased significantly with the addition of hydrophobicity enhancing agents, which in turn led to an improvement of
deinking flotation efficiency. The rejection of oil-based inks from the recycled paper fibers was improved by 20%
over the current methods attained in industrial paper mills. The findings obtained in the present work will be useful
for increasing fiber yields, which can in turn lead to reduced embodied energy and CO2 emissions for paper feedstocks.
Future work will extend these efforts to address the unique challenges associated with removal of water-based inks. 

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