Selection of the most effective chemical cleaning procedure in the membrane clarification of pomegranate juice

Abstract

Membrane fouling is an important drawback of membrane-based separation processes. After clarification of pomegranate juice by 0.22 µm polyvinylidene fluoride membrane, analysis of the FTIR spectra of formed-cake showed that polyphenols are the main components of blocking materials. Various solutions including water (with 0.5, 1, and 1.5% NaOH or 0.1% hydrochloric acid), ethanol (with 77% and 96% purity), and mixture of ethanol (77%) with acetic acid (96%) with 99:01 ratio were used to clean membranes with different washing time of 10–30 min. The permeate flux recovery was calculated to determine the efficiency of cleaning protocols. The results showed that the cake layer was dominant because the blocking index was between 0 and 0.5. Overall, the ethanol 77% had the best performance among different solutions for cleaning (mainly due to its positive effects on membrane hydrophilicity) and the initial permeate fluxes of pomegranate juice and pure water did not change significantly after using this protocol. Practical applications Membrane technology is widely used in industrial juice clarification processes. The main problem with this process is the formation of fouling on the membrane surface, which minimizes its use in the fruit juice industry. This affects the lifetime of the membrane, the number of times the membrane is cleaned, the size of the membrane required, and ultimately the operation costs. In fact, cleaning costs make up 5%–20% of operating budgets, so more research is needed. The main method in regenerating a fouled membrane is its chemical cleaning, and the first step in this method is to find the best chemical detergent, which is determined according to the type of food, the type of membrane, and the nature of the deposition.