Cavitation Fibrillation of Cellulose Fiber

Abstract

Cellulose fibrils are the structural backbone of plants and, if carefully liberated from biomass, a promising building block for a bio-based society. The mechanism of the mechanical release—fibrillation—is not yet understood, which hinders efficient production with the required reliable quality. One promising process for fine fibrillation and total fibrillation of cellulose is cavitation. In this study, we investigate the cavitation treatment of dissolving, enzymatically pretreated, and derivatized (TEMPO oxidized and carboxymethylated) cellulose fiber pulp by hydrodynamic and acoustic (i.e., sonication) cavitation. The derivatized fibers exhibited significant damage from the cavitation treatment, and sonication efficiently fibrillated the fibers into nanocellulose with an elementary fibril thickness. The breakage of cellulose fibers and fibrils depends on the number of cavitation treatment events. In assessing the damage to the fiber, we presume that microstreaming in the vicinity of imploding cavities breaks the fiber into fibrils, most likely by bending. A simple model showed the correlation between the fibrillation of the carboxymethylated cellulose (CMCe) fibers, the sonication power and time, and the relative size of the active zone below the sonication horn.

Computational analysis of flow conditions in hydrodynamic cavitation generator for water treatment processes

“…Recent experimental and numerical studies on the interaction between bubbles on one side and a solid object, liposome, or bacterium on the other side point to the high shear as the dominant mechanism of contaminant destruction. [ 30,33–36 ] The shear is most simply shown by the strain rate magnitude field. The strain rate tensor definition is written as: where strain rate magnitude is defined as: Figure 8 shows the strain rate magnitude distribution across the entire computational domain and, in detail, in the rotor‐stator pin interaction area.…”

“…And it indirectly confirms our previous experimental and numerical observations that cavitation‐triggered high strain rate causes the destruction of contaminants. [ 30 , 33 , 34 , 35 , 36 ]…”

“…Recent experimental and numerical studies on the interaction between bubbles on one side and a solid object, liposome, or bacterium on the other side point to the high shear as the dominant mechanism of contaminant destruction. [30,[33][34][35][36] The shear is most simply shown by the strain rate magnitude field. The strain rate tensor definition is written as:…”

“…And it indirectly confirms our previous experimental and numerical observations that cavitation-triggered high strain rate causes the destruction of contaminants. [30,[33][34][35][36] Based on the results interpretation, the optimization should proceed in the direction of shortening the rotorstator gap and not increasing the rotor pin number or shortening the distance between to consequent rotor elements. The cases with 8/12 pins and the shortest rotorstator gap exhibit more cavitation events, namely, vapour cloud onset, growth, and collapse, indicated by larger overall vapour fraction in the cases.…”

Glass-like transparent and heat-sealable films of cellulose nanoworms via ethanol triggered swelling of esterified cellulose

“…Thus, the energy from the collapse of cavities causes ber disintegration. [53][54][55] TEM analysis was performed to reveal more closely the inuence of ultrasonication on the structural alteration of esteried bers, and to determine whether the cellulose was mainly dissolved or formed nanoscale particles (Fig. 2e).…”