Membrane Distillation for Methylene Blue Dye Removal from Wastewater: Investigating Process Optimization and Membrane Wettability

Membrane distillation (MD) is a promising technology for desalination of different water streams. However, treating wastewater with complex compositions remains a challenge. In this study, we adopted the MD process to treat complex and harmful methylene blue (MB) dye-containing textile wastewater. The effect of relevant operating parameters on the MD process performance was investigated. Additionally, the membrane wettability during the MD process was evaluated. The results showed that increasing the temperature difference and feed flow velocity led to an increase in permeate flux (Jp) and a decrease in specific energy consumption (SEC). The Jp and SEC models exhibited good agreement between predicted and experimental values, with an R2 of 98.50% and 86.18%, respectively. During the 22 h of operation, the MD process applied for the treatment of dye wastewater demonstrated a decline of Jp by 71.8% and a slight decrease in dye rejection to attain 95.9%. The decline of the surface contact angle and the liquid entry pressure values and an increase in the permeate water conductivity detected the membrane wettability. The obtained results suggest that the MD process could present an efficient solution for the treatment of MB-dye wastewater. However, upscaling the MD technology requires further improvements on real wastewater treatment for a longer run time.