Kinetic models for alkali and detergent cleaning of ceramic tubular membrane fouled with whey proteins

Abstract

This work investigates fouling of ceramic membrane (200 nm) with whey proteins, followed by the full cycle of cleaning, i.e., pre-rinsing (with water), cleaning (with the solutions of cleaning agents) and final rinsing (with water). As cleaning agents, four solutions were used: two solutions of NaOH (0.2%w/w and 1%w/w) and two detergents solutions (0.8%w/w P3-ultrasil 69 + 0.5%w/w P3-ultrasil 67 and 1.2%w/w P3-ultrasil 69 + 0.75%w/w P3-ultrasil 67). The flux recovery during cleaning and the efficiency of cleaning were determined by measuring the flux of water and that of the cleaning solutions. After statistical processing of the acquired data, kinetic models for cleaning were proposed. These models enable to predict how the total resistance due to the attachment of the fouling material decreases with time, as well how the various other resistances (the resistance of membrane, the hydraulic resistance of fouling at the membrane surface and the resistance due to material accumulation into the pore volumes) decrease with time. Further, the models also allow an estimation of the effective pore diameter changes occurring during cleaning and the thickness of the attached in-pore material during cleaning and at the end of cleaning. The results from kinetic models provide important insights into the mechanisms underpinning alkali and detergent cleaning.