Deinking of Mixed Office Waste (MOW) Paper Using Enzymes

*G. Ramiro Escudero, González P. Jeovani and Perez S. Rosa Elena*

## **Abstract**

Deinking of Mixed Office Waste [MOW] paper was carried out by using a flotation device and adding enzymes as defibrillators. Employing the computational simulation of the molecular coupling between the cellulase enzyme obtained from *Trichoderma* sp. and cellulose, the enzyme-cellulose molecular complex and the main amino acids endo-β-1,4-D-glucanase of this molecule, responsible for the hydrolysis of cellulose, were obtained. Three of these amino acids were used for deinking. The deinked cellulose fibers were evaluated according to the standards of the paper industry (ISO whiteness [brightness], factor of reflectance, opacity, and tonality) to determine the efficiency of deinking. The experimental results show that the best optical characteristics of the sheets of deinked paper with amino acids are those where a mixture of aspartate, glutamate, and asparagine was applied, instead of their individual dosage. In addition to the aforesaid, the use of enzymes instead of the traditionally used reagent, such as sodium hydroxide, avoids the contamination of wastewater; additionally, the operation of the column is carried out easily, taking into consideration that the pH of the system goes from alkaline to neutral.

**Keywords:** paper deinking, flotation column, cellulose, aspartate, glutamate, asparagine

## **1. Introduction**

The recycling of paper is a necessary option for the care of the environment and to comply with the environmental regulations established by governments toward the pulp and paper industry, and specifically, the industry that processes recycled paper fibers to obtain pulp free of ink and that includes in its process the passivation of colloidal particles [1]. Traditional deinking paper (e.g., office paper) is industrially "cleaned" by adding sodium hydroxide (defibrillator) and adding chemical reagents to improve the quality of recycled paper, such as whiteness and mechanical strength [2, 3]. This traditional process undoubtedly damages the environment and specifically urban water reservoirs due to the additional chemical agents contained in the recycled pulps [4–6].

The deinking process exposes the deinking equipment to highly alkaline conditions (pH greater than 10) because the addition of chemical reagents, so ideal conditions in conditions close to neutral pH are preferred, regardless of the chemical

reagents used to defribillate the cellulose, capture ink particles, and improve optical and mechanical properties of the recycled paper [5–9].

The conditioning of the cellulose pulp is essential to ensure the detachment and capture of the ink particles. The conditioning of the pulp by adding enzymes will promote the disintegration of the paper and the detachment of the ink, as the enzyme is introduced into the cellulose-ink interface. The catalytic action of the enzymes reduces the activation energy of the reactions that occur in the system, even at low concentrations of the reagent, which implies a low contamination of the conditioning medium. Like any chemical reagent, enzymes function within specific pH ranges [10–12]; for example, enzymes called cellulases hydrolyze cellulose fibers and enhance the detachment of ink particles [13–15], which will be available for capture, for example, through the use of devices that generate air dispersions, such as the case of flotation devices [6, 16].

This research work presents the results of the conditioning of recycled office paper pulp (Mixed Office Waste [MOW] type) using enzymes and capturing the ink particles through a flotation column, equipment that is commonly used for mineral processing. The variables that were quantified in the deinked paper to establish the feasibility of the use of enzymes are whiteness, reflectance, opacity, and tonality.
