Polyvinylidene fluoride (PVDF) hollow fibre membranes for ammonia removal from water

Polyvinylidene fluoride (PVDF) hollow fibre membranes with asymmetric structures and good hydrophobicity have been prepared by a phase-inversion method and have been applied to removal of ammonia from water. Aqueous solution containing sulfuric acid was used as stripping solution to accelerate the removal of ammonia. A mathematical model was presented to simulate the ammonia removal in PVDF hollow fibre modules. Experimental results indicate that the post-treatment with ethanol is useful to improve both the hydrophobility and the effective surface porosity of the resulting PVDF hollow fibre membranes, and thus favors the ammonia removal. Increasing the pH value of water is capable of promoting the removal of ammonia. The initial concentration of ammonia and the feed velocity of the acid stripping solution have negligible effects on the ammonia removal. The ammonia stripping rate increases as the feed velocity is increased up to 0.59 m/s or Re > 0.32, after which the feed velocity shows no effect. All the experimental data are in excellent agreement with the modeling results.