Molecules 2019 , 24 , 1800
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Table1. Morphology of recycled old newspaper.
Item
Units
Recycled ONP Recycled OCC
Fibers Length weighted in length
( μ m) ( μ m)
861 21.4
1054 22.2 0.159
Average width
Coarseness Microfibrils
(mg / m)
0.141
(%) (%)
1.72 37.2
1.35 34.1
Broken ends Average angle Kinked fibers Average curl Pulps Kappa index
(º)
130.3 13.70
133.5 13.54
(%) (%)
5.89
5.64
40
72
(number × 10 6 / g) (number / g)
15.82
11.80
Fibers
Aggregates
98,837 118,646
92,667 92,322
Fines
(number / g)
The yield of nanofibrillation increased with the degree of oxidation, reaching values close to 80% and 100% when 15 mmol of NaClO per gram of dry pulp was used to produce CNF from recycled ONP and recycled OCC, respectively (Figure 3a). As expected, catalytic oxidation with TEMPO and NaClO had an important impact on the transmittance and on the cationic demand of the CNF suspensions, obtaining higher values when the degree of oxidation applied to the recycled pulp increased (Figure 3b,c). The production of CNF from recycled OCC pulps with a degree of oxidation of 2.5 mmol of NaClO per gram of pulp was not possible due to the obstruction of the homogenizer, requiring a minimum degree of oxidation (5 mmol of NaClO per gram of pulp) to carry out the mechanical treatment.
Figure3. Characterization of CNF from recycled ONP and recycled OCC pulps oxidized by NaClO in the presence of TEMPO. ( a ) Yield of nanofibrillation, ( b ) transmittance at 800 nm, and ( c ) cationic demand.
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