The Effect Of Pre-oxidant Potassium Permanganate On The Structure And Properties Of Hollow Fiber Membranes

The structure and performance of membrane materials are crucial to the safety and stability of membrane filtration system.This study investigates the effect of potassium permanganate(KMnO4)on membrane structure and performance of polyvinylidene fluoride(PVDF)and polyethersulfone(PES)membranes.The membrane surface morphology,hydrophobicity,mechanical strength,zeta potential,pure water flux,rejection performance and the anti-pollution performance were investigated to reflect the effects of pre-oxidant KMnO4 under different concentrations(10,100 and 1000 mg/L)on both two membranes.The effects of different pH(5,6,7,8 and 9)on PVDF membrane structure and performance was discussed when exposed to KMnO4 of 3 mg/L.The results indicated that the membrane pore size and porosity enlarged due to the degradation and dislodgment of PVP when PVDF and PES membranes exposed to 10,100 and 1000 mg/L KMnO4 for 6 d.Therefore,the pure water flux and the membrane surface hydrophilicity increased.However,the membrane pore size and porosity reduced due to the oxidation reaction between membrane materials and KMnO4 when exposed for 12 d,and the pure water flux and the membrane surface hydrophilicity decreased.The formation of sulfonic group for PES membranes increased the negative charge on membrane surface.In addition,the membranes showed a more serious fouling when exposed to KMnO4,especially for irreversible fouling,which can due to the loss of PVP and change of membrane pore diameter.The effects of KMnO4 on the structure and performance of PVDF membrane is the greatest under the acidic condition,the alkaline condition is second,and the neutral effect is the smallest when PVDF membranes exposed to KMnO4 solution of 3 mg/L under different pH(5-9)for 10 and 20 d.Oxidation and degradation of membrane additive PVP resulted in the enhancement of the membrane surface hydrophobicity.With the increase of contact time,the membrane surface pore size and porosity reduced for the reactions of chain scission and cross-lingking on membrane surface.On the one hand,the pure water flux decreased and mechanical property weakened,but on the other,the membrane rejection rate increased and the effluent quality improved.This study could provide some data references for the structure and performance of membrane materials under different concentration and pH of KMnO4 solution in pre-oxidation membrane filtration process.