Multidentate polyzwitterion attachment to polydopamine modified ultrafiltration membranes for dairy processing: characterization, performance and durability

Filtration membrane technologies are used extensively in dairy processing and due to the high quantities of both organic and inorganic foulant, membrane fouling is a significant problem in the industry. To address this issue, a polyzwitterionic antifouling coating was applied to polyethersulfone ultrafiltration membranes for reduction of biofouling in skim milk filtration. The novel polyzwitterion was synthesised from a branched polyethyleneimine-based macroinitiator to allow multidentate binding to polydopamine coated membranes. Attachment of polyzwitterion to the polydopamine was confirmed using FTIR-ATR and XPS and the coating proved effective in increasing the wettability and smoothness of the membrane surface as well as reducing its charge. The reduced strength of binding between proteins and the membrane of the coated membrane compared to the control was demonstrated with its positive influence on fouling coefficient and recovery of the membranes while retaining skim milk flux and the rejection characteristics of the control membrane. The improved filtration characteristics of the coated membranes were generally retained through multiple cleaning cycles, though there was evidence of oxidative degradation after sanitation.