**2. Materials and methods**

#### **2.1 Enzymatic deinking**

Mixed Office Waste (MOW)-type paper was used. The sheets were cut and disintegrated in an industrial blender without chemical reagents. The amino acids such as aspartate, glutamate, and asparagine (Sigma-Aldrich) were added (individually and mixed of all three), as hydrolytic reagents to promote ink detachment.

Once the cellulose pulp had been conditioned for 30 minutes by adding the corresponding chemical reagents, it was fed to a laboratory flotation column made of transparent acrylic tubes. The device (gas disperser) responsible for the generation of bubbles was installed at the external base of the column (venturi-type disperser). The consistency of the pulp fed to the column was set at 4.0%. The experimental conditions are shown in **Table 1**.

In all experiments, pine oil was added as a surfactant to fix and maintain the surface tension at 0.63 N/m. **Figure 1** shows the experimental setup for paper deinking.


*ASP, aspartate; GLU, glutamate; ASN, asparagine. The % is calculated based on the dry paper mass.*

#### **Table 1.**

*Experimental conditions for deinking with amino acids.*

*Deinking of Mixed Office Waste (MOW) Paper Using Enzymes DOI: http://dx.doi.org/10.5772/intechopen.99373*

**Figure 1.** *Experimental setup for deinking of recycled paper. PT = pressure transducer devices.*

The gas holdup in the column was estimated through the pressure drop values from pressure transducers installed in two points along the column. The mean bubble diameter of a swarm was calculated by solving the Drift Flux Analysis model [17].
