Recent developments in chemical techniques for foulant removal from NF membranes

Abstract

Nanofiltration (NF) membranes find extensive use in many fields such as food processing, water treatment, and resource recovery due to their exceptional capacity to selectively separate small solutes and exhibit high permeability to water. Nonetheless, the occurrence of membrane fouling is an unavoidable consequence over extended periods of operation, hence imposing constraints on the widespread use of NF technology at a larger scale. Chemical cleaning is widely acknowledged as the most efficient method for mitigating fouling, subsequently restoring membrane permeability. The repeated use of chemical cleaning methods may induce both reversible and permanent alterations in the chemical and physical characteristics of NF membranes. These changes can lead to membrane degradation and a decline in separation efficiency. Additionally, the NF membrane, characterized by its high selectivity and relatively low degree of crosslinking, exhibits greater sensitivity to chemical cleaning procedures. Despite the extensive work reported for chemical cleaning of NF membrane, a systematic discussion and analyses of these approaches have not been performed. This review offers an overview of NF selectivity and separation fundamentals, exploring various factors affecting fouling in NF membranes. It provides a thorough examination of multiple aspects pertaining to the chemical cleansing of membranes. The examination encompasses the comprehension of the goals that direct this cleaning procedure, the calculated methods utilized, the complex mechanisms in operation, and the methodical processes that are fundamental to the overarching methodology. An in-depth exploration of these facets is intended to yield a nuanced comprehension of membrane chemical cleansing. In addition to the comprehensive discussion on elements that influence the efficacy of chemical cleaning, such as suitable cleaning agents, cleaning duration, concentration of cleaning agents, pressure, pH levels, and cleaning temperature, they were thoroughly investigated. The purpose of this review is to enhance comprehension of the membrane cleaning procedure to optimize the efficiency of membrane separation processes.