Kinetic Study of Air Bubbles-Cetyltrimethylammonium Bromide (CTAB) Surfactant for Recovering Microalgae Biomass in a Foam Flotation Column

Abstract

Owing to their efficient photosynthesis, microalgae tend to possess superior growth rates and high lipid production, hence their significance to the biofuel sector. The bulk harvesting of microalgae from cultures is a substantial stage in advancing the production of biomass-based fuels. However, a reliable and cost-effective harvesting technology is not yet available. Foam flotation, which is a subcategory of the adsorptive bubble separation process, shows considerable promise for the harvesting and enrichment of microalgae biomass. The available literature indicates that virtually no data has been reported on the flotation kinetics of microalgae. Therefore, to better describe the recovery of microalgae by the flotation process, this work studied the flotation kinetics of the freshwater microalgae Chlorella vulgaris. The recovery of microalgae cells in a batch foam flotation column over time at different operating conditions was fitted to nine flotation kinetic models, including first, fractional, and second order kinetic models; a first order kinetic model with rectangular, exponential, gamma, and sinusoidal distributions of floatabilities; a second order kinetic model with rectangular distribution of floatabilities; a fully mixed reactor; and modified Kelsall flotation kinetic models. Evaluation of the kinetic models showed that the discrete rate constant model (i.e. modified Kelsall kinetic model) fitted the experimental data best. The modified Kelsall model shows the highest values of adjusted R2 (>0.995) and the lowest values of mean squared error (<2.63). Apart from the modified Kelsall model, which has discrete rate constants, no single kinetic model, with or without a continuous distribution, was sufficient to represent the flotation data, and the optimal model may vary under different conditions. More work is recommended using different freshwater and marine microalgae species.

Keywords

• biofuel
• chlorella vulgaris
• foam flotation
• kinetic rate constant
• ultimate recovery