Enhanced Oxygen Mass Transfer in Mixing Bioreactor Using Silica Microparticles

Abstract

This work aimed to improve the oxygen transfer mass coefficient (kLa) in mixing reactors, first evaluating the effect of agitation and aeration and then evaluating the influence of the size and concentration of silica microparticles. Silicon dioxide synthesized via the sol-gel technique, commercial sand, and beach sand were characterized by particle size distribution, scanning electron microscopy, XRD, EDS, FTIR, TG/DTA, and BET. The particles presented average values of approximately 9.2, 76.9, 165.1, and 364.4 µm, with irregular surfaces and different roughness. Silica sol-gel is amorphous while beach and commercial sand have a crystalline structure consisting of silicon, oxygen, and carbon residues. Silica sol-gel presents a higher loss of mass and surface area than other silica microparticles, with a shallow mass loss and a smaller surface. Increasing aeration and agitation improves the kLa, as well as adding silica microparticles. The best kLa was found using silica microparticles with approximately 75 µm concentrations of 1.0 g L−1 (silica sol-gel) and 2.0 g L−1 (commercial and treated beach sand). All silica microparticles used in this work improve mass transfer performance in mixing bioreactors.