Computational and experimental study of chromium (VI) removal in direct contact membrane distillation

•PTFE/PET performed better than PTFE/PP terms of normalized flux for Cr (VI) removal.•Flowrate, concentration, inlet temperature significant effects on flux and rejection.•Modified coupled Knudsen–Poiseuille flow models validated experimental results.•A 2D mathematical model was built up based on mass, momentum and energy balances.

Computational and experimental study of a countercurrent direct contact membrane distillation (DCMD) module equipped with commercially available flat sheet hydrophobic polytetrafluoroethylene (PTFE) microporous membrane with polyethylene terephthalate (PET) and polypropylene (PP) support was investigated to remove toxic chromium (VI) from simulated water. PTFE/PET membrane exhibited better performance in terms of normalized flux. Liquid entry pressure (LEP) was used to characterize the thin film membrane. The effects of flowrate, chromium concentration, feed and permeate inlet temperature were studied with significant results on the flux and complete rejection. A two dimensional mathematical model was built up based on mass, momentum and energy balances to explore the effects of operating parameters on flux, flow conduit temperature distributions across entire domain and membrane surface temperatures across module length. The predictions exhibited good agreement with the experimental results using a modified coupled Knudsen and Poiseuille flow models.