Oral:

In this study, hydrolyses of 3 g of cotton fiber with 65% sulfuric acid (m/v), biomass to acid ratio 1:20 (g/mL), temperature 50°C, and times 50 and 70 min were performed to obtain cellulose nanocrystals suspensions. The objective of this work was to evaluate the suspension stage of the nanocrystals in the centrifuge by means of the supernatant pH and turbidity of each centrifugation cycle. With this, achieve a more efficient washing, with reduction of materials loss and much diluted suspensions. The nanocrystals characterization of each cycle was performed through hydrodynamic diameter and the surface charge measurements of the nanoparticles by dynamic light scattering and zeta potential, respectively. For 70 min of hydrolysis time, the results showed that the cellulose nanocrystals began to suspend at pH values around 1.0 reaching the maximum at pH 2.0, according to the turbidity results, 10 NTU and 300 NTU, respectively. After 300 NTU, the pH and turbidity of the suspensions behaved inversely. Similar results were found for 50 min of hydrolysis time. There was no significant variation in the zeta potential results between the third (-50 mV) and the fifth cycle (-55 mV) for the 70 min, and between the third (-51 mV) and the fourth cycle (-54 mV) for the 50 min time. The centrifugation control for cellulose nanocrystals suspension with pH-meter and turbidimeter was efficient. In addition, these equipments are characterized by being easy to operate and having a low cost.