Ammonium persulphate as novel additive for filtration performance improvement of PVDF microporous membrane

• Ammonium persulphate was used as additive for PVDF membrane modification.
• The membrane micro-structure was changed by adding ammonium persulphate as additive.
• The flux recovery of modified membrane was increased in short term filtration.
• Extension of long term filtration time was shown in 0.7% APS modified membrane.

Ammonium persulphate (APS) was used as a novel additive for blending modification of Polyvinylidene Fluoride (PVDF) membrane in this study. The addition of APS changed the macroscopic and micro-structure of membrane, as the small scaly aggregates appeared and hydrophilicity increased slightly. Comparing with blank membrane, the specific surface area of PVDF membrane was reduced from 19.98 m2/g to 7.95 m2/g, and the total adsorption average pore size of membrane was increased from 89.82 nm to 253.58 nm when 0.7% of APS was added. During the short term filtration, the pure water flux of blank membrane was reduced by 61% and 81% after the first and second testing cycle, respectively. As a comparison, it was only reduced by 39% and 60% for 0.7% APS modified membrane. The effluent turbidity values of those modified membranes were all lower than that of blank membrane. During the long term operation in MBR, the filtration time of 0.7% APS modified membrane lasted for 21 days including 2 operational cycles. Comparing with modified membrane, the filtration time of blank membrane only lasted for 19 days, which included 3 times of membrane cleaning.

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