Investigation of fouling mechanism in membrane distillation using in-situ optical coherence tomography with green regeneration of fouled membrane

Membrane distillation (MD) has the potential to expand its application from desalination to wastewater treatment by developing a in-situ membrane fouling and wetting detection system. In this study, advanced in-situ 3D optical coherence tomography (OCT), coupled with model simulation, was used to reveal the fouling mechanisms in real-time during MD treatment of industrial textile wastewater. Additionally, an ultrasonic cleaning operation was conducted to control fouling and regenerate the fouled membrane. Two commercial membranes, polyvinylidene fluoride (C-PVDF) and polytetrafluoroethylene (C-PTFE), were applied in dye wastewater treatment by MD, where the C-PTFE membrane achieved 99.9% dye removal. 3D-OCT images indicated that the foulant attachment on the C-PTFE membrane was much looser than on the C-PVDF membrane, owing to its pattern shaped surface morphology and higher hydrophobicity as explained through mathematic modeling. Average water flux was maintained above 31.38 +/- 0.19 LMH for 24 h MD operation with the C-PTFE membrane and a water recovery rate of 73.2 +/- 0.26% was attained by using the in-line ultrasonic operation.

Automated summary

This study used advanced in-situ 3D optical coherence tomography (OCT) and model simulation to reveal fouling mechanisms during industrial textile wastewater treatment with membrane distillation (MD). The study also demonstrated the effectiveness of ultrasonic cleaning to control fouling and regenerate the membrane. The C-PTFE membrane showed 99.9% dye removal in dye wastewater treatment by MD, with its looser foulant attachment attributed to its surface morphology and higher hydrophobicity explained through mathematic modeling.