Polymers 2022 , 14 , 3309
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The remaining samples (GT0.02_F, GT0.04_F, GT0.16_F and GT0.36_FP) that were obtained after the HPH treatment clearly show the effect of the mechanical treatment. Samples GT0.02_F and GT0.04_F reveal that the cellulose fibers broke down into smaller fiber fragments, along with the liberation of micro/nanofibrils into the medium (which are shorter than those present in sample CH0.13_F). Similarly to sample GT1.06_P, for samples GT0.16_F and GT0.36_FP, only residual small fiber fragments can be seen, with all the cellulose fibers being converted to micro/nanofibrils and then partially or totally solubilized. The samples treated in the HPH were also characterized in terms of YF and SF to quantify the deconstruction level suffered by the cellulose fibers. Sample CH0.13_F presents a YF of 29% and shows no solubilization of cellulose fibers (SF of 0%) (Table 2). All the samples that were cationized with GT have solubilized cellulose, ranging from 6.1% for GT0.02_F to 99.6% for GT0.36_FP. As for the YF, it increases from 6.4% (sample GT0.02_F) to 100% (sample GT0.36_FP). For the Mw of the cationic cellulose polyelectrolytes (GT0.36_FP and GT1.06_P) and for the soluble fraction of sample GT0.16_F, a bimodal distribution was obtained (Table 2), with samples GT0.36_FP and GT0.16_F presenting peaks near 1000 and 500 Da and sample GT1.06_P presenting peaks at 2150 and 972 Da. 3.3. Performance in the Flocculation Tests The evolution of the d 50 of the PCC flocs formed by the contact of the PCC with the retention agent (CPAM or CCs) as a function of the dosage of the retention agent, monitored by LDS, is plotted in Figure 5.
Figure 5. The median floc size as a function of flocculant dosage (the x -axis corresponds to both the flocculant dosage and the time of flocculation). When no retention agent was added to the PCC suspension (black line), the d 50 of PCC suffered a small increase from the initial 4.8 μ mto 5.8 μ m after 15 min, indicating
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