Deinking, up to now, is generally carried out under alkaline conditions and requires the use of chemical reagents such as sodium hydroxide, hydrogen peroxide, sodium silicate, etc., to be more efficient in the process and obtain a product with specific optical properties. Sodium hydroxide (NaOH) is traditionally used to hydrolyze cellulose fibers, and to set the pH of the medium to values greater than 10, during deinking of MOW (Mixed Office Waste) type paper; 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, using a laboratory column
flotation. The cellulase enzyme Trichoderma
sp. was used.
The efficiency of deinking office paper using enzymes, and the
traditional procedure using sodium hydroxide is compared. 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 by 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. For each deinking procedure samples were collected
from the tailings stream (deinked fiber), with standard laboratory sheets,
conforming to the standard TAPPI T-205-OM-81, to which the optical properties
were determined: ISO whiteness (Brightness), Factor of Reflectance, Opacity and
Tonality.
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%.
From the paper deinking experiments using the conventional method
with NaOH and enzymatic deinking with the help of the commercial enzyme
Cellulase Trichoderma sp., it is
concluded that the optical and physical properties in the fiber deinked by the
conventional method are slightly better than those obtained in the fiber
deinked with the enzyme cellulase; however, the weight ratio between the enzyme
and the MOW paper should be varied to establish the possibility of improving
the optical characteristics of the deinked fibers with this enzyme, until
reaching optical properties greater than the deinked with NaOH.
Author (s) Details
Jeovani González P.
Institute of Research in Metallurgy and Materials, Universidad
Michoacana de San Nicolás de Hidalgo, Santiago Tapia 403, C.P. 58000, Morelia,
Michoacán, México.
Ramiro Escudero G.
Institute of Research in Metallurgy and Materials, Universidad
Michoacana de San Nicolás de Hidalgo, Santiago
Tapia 403, C.P. 58000, Morelia, Michoacán, México.
Please see the book here:- https://doi.org/10.9734/bpi/cmsdi/v7/3063
