Post-Treatment of CO₂ Emissions With Microalgae: Magnetic Field-Induced Improvements in an AirLift Photoreactor

Abstract

Atmospheric pollution from volatile organic compounds (VOCs) and rising global temperatures due to greenhouse gases (GHGs) emissions, such as carbon dioxide (CO₂) pose significant threats to air quality and public health. Coupled biological systems can mitigate VOC emissions, generating CO₂, which is then assimilated by microalgae. Static magnetic field (SMF) stimulation has been shown to enhance microalgal growth and CO₂ fixation. This study evaluated the impact of SMF on CO₂ fixation in an airlift photoreactor (ARL) following VOCs treatment in a semi-continuous stirred tank reactor (S-CSTR) processing toluene vapors. The ARL was exposed to SMF at 45 mT for 6, 4, and 2 h d⁻¹. Results demonstrated a 96% increase in CO₂ capture after 4 h of exposure, while removing 45% of the remanent toluene. The highest biomass increase (12%) occurred after 6 h of exposure, whereas total chlorophyll content peaked at 18.4 mg L⁻¹ under 4 h of SMF, compared with 6.8 mg L⁻¹ in the control. Therefore, 4 h exposure at 45 mT was identified as the optimal condition, balancing VOCs reduction, CO₂ mitigation, and high pigment production. Microalgal cultures under SMF present a promising and versatile approach for air pollution control and carbon valorization, offering potential economic benefits through biomass applications and supporting circular economy initiatives.