Shear-Thinning Effect of the Spinning Disc Mixer on Starch Nanoparticle Precipitation

Abstract

Spinning disc technology is capable of achieving intensified micromixing within thin liquid films created through large shear rates, typically of the order of 103 s−1, generated by means of fast disc surface rotation. In this study the effect of the high shear on solvent–antisolvent mixing and starch nanoparticle precipitation is reported. Rheological studies of starch solutions at 2% w/v and 4% w/v have demonstrated their shear-thinning behaviour at the large shear rates experienced on the spinning disc surface. The effect of such high shear rate on starch nanoparticle precipitation is investigated alongside solute concentration and several other operating parameters such as flow rate, disc rotational speed, and solvent/antisolvent ratio. A reduction in nanoparticle size has been observed with an increase in starch concentration, although agglomeration was found to be more prevalent amongst these smaller particles particularly at larger flow rates and disc rotational speeds. Micromixing time, estimated on the basis of an engulfment mechanism, has been correlated against shear rate. With fast micromixing of the order of 1 ms observed at higher shear rates, and which are practically unaffected by the starch concentrations used, micromixing is not thought to be influential in determining the particle characteristics highlighted in this work.

Purification of hemicellulose hydrolysates by antisolvent precipitation in a spinning disc reactor

“…The thin film and high shear environment in the SDR generates rapid micro-mixing, leading to high mass transfer rates 14 and producing uniformity in local supersaturation almost immediately upon contact between the solvent and the antisolvent streams. [15][16][17][18] With near ideal plug flow conditions, the residence time distribution is tightly controlled with the molecules experiencing close identical processing conditions with minimal processing time. 19 This creates homogenous products, with consistent yields and narrow particle-size distributions.…”

“…Spinning disc reactors (SDRs) have been identified as a promising technology to intensify antisolvent precipitation processes, which require high‐intensity mixing for rapid and uniform incorporation of the antisolvent stream into the solute‐containing solvent. The thin film and high shear environment in the SDR generates rapid micro‐mixing, leading to high mass transfer rates 14 and producing uniformity in local supersaturation almost immediately upon contact between the solvent and the antisolvent streams 15–18 . With near ideal plug flow conditions, the residence time distribution is tightly controlled with the molecules experiencing close identical processing conditions with minimal processing time 19 .…”

Process Intensification in Chemical Reaction Engineering

“…Such equipment demonstrated the allowance of a superior gas dissolution compared with conventional technologies (Figure 4A). Sana et al investigated the effect of the spinning disc mixer on starch nanoparticle precipitation [7]. By using high shear rate on starch nanoparticle precipitation, a reduction in nanoparticle size was observed with an increase in starch concentration, although agglomeration, thus leading to good performances (Figure 4B).…”