Treatment of UF membranes with simple and formulated cleaning agents

Both hydrophilic (C 30F) and hydrophobic (PA 50H and PES 50H) ultrafiltration membranes were fouled with (i) a 3.5 wt% whey protein solution or (ii) ground wood mill circulation water from an integrated pulp and paper mill. The membranes were subsequently treated with different cleaning agents (NaOH, HNO3, Ultrasil 11 and Libranone 960). For whey protein fouled membranes, the effectiveness of the cleaning protocol was a strong function of the sodium hydroxide concentration used. After treatment with Libranone 960, membranes fouled with ground wood mill water displayed a substantial increase in water permeability. The less hydrophilic the membrane surface, the greater the observed flux increase following cleaning. After a short period of cleaning with Libranone 960, the pure water permeability decreased as the surfactant desorbed from the membrane surface. No such trend was seen when cleaning with Ultrasil 11. FTIR, SEM and AFM techniques were used to investigate the nature of the membrane surface before and after fouling and cleaning. These techniques confirmed the efficacy of the Libranone 960 cleaning protocol.