Styrene vapor mass transfer in a biotrickling filter: Effects of silicone oil volume fraction, gas-to-liquid flow ratio, and operating temperature

• Effects of oil, flow ratio, and temperature on mass transfer in a BTF were studied.
• Full-factorial experimental design was used to study the interactions.
• Oil fraction and flow ratio were significant factors affecting mass transfer.
• Addition of more than 10% oil had just a slight effect on the mass transfer.
• Mesophilic/thermophilic conditions did not have main effect on mass transfer in BTF.

The addition of silicone oil as a non-aqueous phase (NAP) to the trickling liquid enhances the mass transfer of hydrophobic compounds from gas to liquid phase in biotrickling filters (BTFs). The present study investigated the effect of NAP volume fraction (ϕ; 0–20%), gas-to-liquid flow ratio (7.5, 16 and 32), and operating temperature (30 and 50 °C) on styrene mass transfer in a BTF under abiotic conditions using a full-factorial experimental design. The BTF was packed with a mixture of pumice and steel pall rings. The inlet styrene concentration was 0.5–1.2 g m−3 and EBRTs were set at 1 and 2 min. The results were incorporated into a model to calculate the maximum fraction of styrene transferable from the gas to the aqueous phase (βS∗). The βS∗ was determined to be 0.208–1, depending on the operating conditions. Flow ratio and ϕ were the most significant factors affecting styrene mass transfer (p-value = 0.0348 and p-value = 0.0230, respectively). Temperature had no significant effect on the model (p-value = 0.9322) at a 95% confidence interval. Styrene mass transfer was very sensitive to ϕ when ϕ < 10%; at ϕ > 10% the addition of silicone oil had a slight effect on βS∗.