Inkjet inks have been widely used due to higher printing speed, competitive cost and healthy non-organic solvent. However, since the hydrophilic property and sub-micron size, the inkjet inks are considered as non-deinkable. The residual ink in pulp is detrimental to the pulp quality. Furthermore, the high ink concentration in filtrate makes the phenomenon even worse because most paper mills are closure in water. Currently there are several optimizations in pulping stage to prevent the redeposition and improve deinking efficiency, including enzyme deinking, neutral pulping, and adsorption deinking. Electric treatment was utilized in this study to improve the flotation efficiency. Electric treatment was shown to be able to increase the ink sizes through electrocoagulation. Furthermore, fine bubbles generated by electroflotation could also improve the collision probability between bubbles and ink particles. A new cationic mediator could also attach to the anionic inks and render a hydrophobic ink. All of the three effects could improve the flotation efficiency. The ERIC value decreased with the assisted flotation and filtrate darkening effect was alleviated at the same time. Since most paper mills also has a low level of inkjet ink compared with offset ink, the optimized flotation technique could produce high quality pulp.
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