Effective separation of methylene blue dye from aqueous solutions by integration of micellar enhanced ultrafiltration with vacuum membrane distillation

Abstract

Micellar enhanced ultrafiltration is widely used for separation of dyes and other dissolved organics from aqueous solutions. However, generation of reject water that contains highly concentrated dyes, surfactants and electrolytes is a major concern in this process. In this study, micellar enhanced ultrafiltration (MEUF) was integrated with vacuum membrane distillation (VMD) for effective removal of methylene blue dye from aqueous solutions with enhanced water recovery. Activated carbon loaded polyethersulfone (PES) ultrafiltration membrane was used in the process with sodium dodecyl sulphate as an anionic surfactant for micelle formation. The reject of MEUF was further processed via VMD for additional water recovery using a tetraethyl orthosilicate crosslinked polystyrene (PSt) membrane. Effect of feed dye concentration, surfactant concentration and feed pressure on MEUF process performance was evaluated. The effect of feed dye concentration, degree of vacuum and membrane thickness on VMD was also studied. A theoretical model based on modified resistance in series model was used to predict MEUF process flux. Also, an interesting model based on computational fluid dynamics was developed to predict the liquid entry pressure for dye solution which is an important parameter in VMD. The final concentrated dye in VMD retentate could directly be used as an emulsion in paint or textile industry, with simultaneous generation of utility water.