Ceramic membrane defouling (cleaning) by air Nano Bubbles

Ceramic membranes are among the most promising technologies for membrane applications, owing to their excellent resistance to mechanical, chemical, and thermal stresses. However, membrane fouling is still an issue that hampers the applications at large scales. Air Nano Bubbles (NBs), due to high mass transfer efficiency, could potentially prevent fouling of ceramic membrane filtration processes. In this study, bench and pilot scale ceramic membrane filtration was performed with air NBs to resist fouling. To simulate fouling, humic acid, as an organic foulant, was applied to the membrane flat sheet surface. Complete membrane clogging was achieved in less than 6 h. Membrane defouling (cleaning) was performed by directly feeding of air NBs to the membrane cells. The surface of the ceramic membrane was superbly cleaned by air NBs, as revealed by atomic force microscope (AFM) images before and after the treatment. The permeate flux recovered to its initial level (e.g., 26.7 × 10−9 m3/m2/s at applied pressure of 275.8 kPa), which indicated that NBs successfully unclogged the pores of the membrane. The integrated ceramic membrane and air NBs system holds potential as an innovative sustainable technology. •The membrane fouled surface was cleaned by feeding air NBs into the membrane holder.•It was predicted that OH• radicals make a bond with organic foulants like humic acids and break down the organic matter.•NBs dramatically cleaned the membrane with minimum observed adverse effects.•The Cubic method showed the most accurate prediction of the permeate flux at any of the applied pressures and times.•The economic benefit of air NBs application is minimizing the usage of chemicals.