Evaluation of the performance of different chemicals for cleaning capillary membranes

Often the evaluation of the best chemical agent to be used in ultrafiltration (UF) and microfiltration (MF) membrane processes is a trial and error process usually derived from pilot plant experiments in half technical scale. This is expensive and time-consuming as the membranes have to be fouled again after the cleaning step. To overcome this problem, a single membrane capillary test unit for testing out-in capillaries was used. The major benefit is the possibility of investigating the performance of different cleaning agents at several capillaries, which were fouled comparably as they were taken out of the same module. Within this study 16 capillaries were cleaned with different cleaning agents of the categories oxidants, bases and acids, alone or in combination with each other at two different temperatures. After each cleaning step the cleaning solution was gathered and analysed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) on inorganic and Liquid Chromatography-Organic Carbon Detection (LC-OCD) on organic eluted foulants to evaluate how the foulants are affected by the different cleaning agents. Additionally, the permeability before and after each elution experiment was measured in order to determine the cleaning efficiency. Based on the results proposals for the use of specific cleaning agents for specific fouling substances are derived.