Application of biosurfactant rhamnolipid for cleaning of UF membranes

• Rhamnolipid manifested excellent cleaning activity on fouled membrane.
• Rhamnolipid showed superior properties over typically cleaners on cleaning.
• Rhamnolipid cleaning would not affect the membrane performance.
• Rhamnolipid presented great potential on industrial membrane cleaning.

Membrane fouling was inevitable in the ultrafiltration process in dairy industry, causing harsh reduction of the membrane performance. The current cleaning agents like acid/base and chemical surfactants would be limitedly used in future due to their detrimental effect on membrane or/and environment/health. In this study, the environmental-friendly biosurfactant rhamnolipid was for the first time applied to clean the ultrafiltration membrane fouled by protein. The cleaning by rhamnolipid under pH 9 could largely remove the foulant from the PSU, PAN and PEG-g-PSU membranes and restore the water flux to about 94% of the initial level, performing much better than the flux recovery of 50–70% for Tween 20 and SDS, the most extensively used surfactants in membrane cleaning. Moreover, rhamnolipid exhibited superior properties over the commonly used cleaner of sodium hydrate (NaOH) and even the commercial membrane cleaner in view of cleaning efficiency and operation mildness. Finally, rhamnolipid was demonstrated to be effective in cleaning the long-term fouling membrane. Taken together, rhamnolipid as an economical product of lowly costive cell-free broth shows great potential in industrial application as membrane cleaner.