Mechanisms of MOW paper deinking in flotation columns, by enzymatic catalysis using Trichoderma sp.
In traditional paper pulp deinking, sodium hydroxide (NaOH) is used as a hydrolysing agent for fibers in concentrations that set the pH of the medium to values greater than 10; however, substantial amounts of solid and liquid waste are created, and their management is problematic and dangerous.
Recently, the implementation of biological treatments, for example, enzymatic deinking, is presented as an option to deink mixed office prints at neutral pH; that is, with the minimum use of chemical reagents and, therefore, better waste management and less environmental impact.
The main objective of this research work is to study the mechanism of hydrolysis, detachment and ink capture in the bubble-enzyme-ink particle system, during the deinking of office paper type MOW (Mixed Office Waste), using a laboratory column flotation. The cellulase enzyme Trichoderma sp. was used.
To compare the deinking efficiency of office paper using enzymes, deinking experiments were performed according to the traditional procedure using sodium hydroxide. The quality of the deinked fibers by measuring their optical properties (whiteness, reflectance, opacity, black spots and tonality) was performed in the Laboratory of the Paper Industry Bio Papel Scribe SA de CV, located in the city of Morelia, Michoacán, México.
The operational variables of the flotation column were established through experiments in the water-air system and adding 100 ppm of pine oil as a surfactant (surface tension of the liquid in 56.6 dynes / cm). The superficial air flowrate was set at 1.27 cm / s (6 LPM), whereas the pulp feed flow rate was 0.88 cm / s.
The experimental results show the feasibility of recycling MOW-type office paper by using the enzyme cellulase Endo-β-1,4-D-glucanase and the amino acids Aspartate, Glutamate and Asparagine; the latter, individually and mixed. The optical properties of the sheets of paper formed with the cellulose deinked by this procedure, were better than those evaluated to sheets of paper formed with fibers of recycled and deinked paper by the traditional procedure.
In the case of the combined use of the three amino acids, the ISO whiteness is 90.8%, 303.4 ppm of black spots, reflectance of 47.1% and 89.5 of opacity. By the traditional procedure, the reported whiteness is 80.2%, the reflectance is 57.4%, and the opacity is 99.6%.