Deinking flotation is an important part of the recycling process for used fibers, in which liberation is a key step in preparing the ink particles to be separated from fibers. The pigments of oil-based inks are hydrophobic and, therefore, can be readily separated from hydrophilic fibers by flotation, which is designed to selectively collect hydrophobic particles on the surface of air bubbles. On the other hand, the pigments in water-based inks are hydrophilic; therefore, they cannot be separated from fibers by flotation. Furthermore, the pigments in water-based inks are much smaller than those in oil-based inks and readily redeposit onto the fiber surfaces after they are liberated during the pulping process. Team members and I developed a novel method of measuring the degree of liberation of oil-based ink by ζ-potential measurement. The same method has been used to determine the degree of liberation of water-based ink. It has been found that adding a polyelectrolyte during the pulping stage greatly increases the liberation by increasing the disjoining pressure in the thin liquid film (TLF) of water confined between the pigment and fiber while at the same time preventing re-deposition. After the liberation, the pigments are then hydrophobized by adsorbing a surfactant on the surface to greatly improve flotation deinking. Finally, different types of flotation equipment were tested to identify the optimal flotation system to use in the deinking process. / Department of Energy grant DE-EE0007897, awarded to the REMADE Institute. / Master of Science / Paper recycling is a key way to participate in the circular economy. Part of the process of recycling paper is to remove any ink on the surface of the paper so that a clean white sheet of paper can be produced for additional uses. There are two types of ink commonly used for printing, oil-based and water-based. The latter seeing more and more adoption as climate goals continue to be a focus of society. One of the processes that is used in this process is deinking flotation, where the ink is separated from the fiber, attached to a bubble, floated to the surface, and separated from the fiber. The current work focuses on improving the ability to separate the ink from the fiber, improving the ability of the ink particle to attach to the bubble, and improving the equipment that is used for the separation. The work found that using common dispersants used in the mineral industry, novel reagents, and alternate equipment greatly increased the efficiency of the deinking process.