Salt cleaning of ultrafiltration membranes fouled by whey model solutions

• Cleaning efficiency of NaCl on UF membranes fouled with BSA + CaCl2 was tested.
• NaCl solutions were able to clean the 5, 15 and 30 kDa membranes tested.
• An increase in temperature and crossflow velocity increased cleaning efficiency.
• Cleaning efficiency first increased and afterward decreased with NaCl concentration.
• Optimal cleaning conditions were selected from RSM and pattern-search analysis.

In this work, three ultrafiltration (UF) membranes were fouled with whey model solutions that contained BSA (1% w/w) and CaCl2 (0.06% w/w). These membranes were cleaned with NaCl solutions. Temperature, crossflow velocity and concentration were varied. The membranes considered were a polyethersulfone (PES) membrane, a ceramic ZrO2–TiO2 membrane and a permanently hydrophilic polyethersulfone (PESH) membrane. Their molecular weight cut-offs (MWCOs) are 5, 15 and 30 kDa, respectively. The cleaning efficiency was related to the MWCO, membrane material and operating conditions. The results obtained demonstrated that NaCl solutions were able to clean the membranes tested. In addition, the higher the temperature and the crossflow velocity of the cleaning solution, the higher the cleaning efficiency was. However, there was an optimum value of NaCl concentration to clean the membranes effectively. When concentration was higher than the optimum, the cleaning efficiency decreased. The relationship between the cleaning efficiency and the operating conditions was obtained with statistical and optimization analysis.