Outlining the Roles of Membrane-Foulant and Foulant-Foulant Interactions in Organic Fouling During Microfiltration and Ultrafiltration: A Mini-Review.

Kang Xiao,Chunhai Wei,Xianghua Wen,Xiaomao Wang,Xia Huang,Shuai Liang,Hao Xu

doi:10.3389/fchem.2020.00417

Abstract

Membrane fouling remains a notorious problem in microfiltration (MF) and ultrafiltration (UF), and a systematic understanding of the fouling mechanisms is fundamental for solving this problem. Given a wide assortment of fouling studies in the literature, it is essential that the numerous pieces of information on this topic could be clearly compiled. In this review, we outline the roles of membrane-foulant and foulant-foulant intermolecular interactions in MF/UF organic fouling. The membrane-foulant interactions govern the initial pore blocking and adsorption stage, whereas the foulant-foulant interactions prevail in the subsequent build-up of a surface foulant layer (e.g., a gel layer). We classify the interactions into non-covalent interactions (e.g., hydrophobic and electrostatic interactions), covalent interactions (e.g., metal-organic complexation), and spatial effects (related to pore structure, surface morphology, and foulants size for instance). They have either short- or long-range influences on the transportation and immobilization of the foulant toward the membrane. Specifically, we profile the individual impacts and interplay between the different interactions along the fouling stages. Finally, anti-fouling strategies are discussed for a targeted control of the membrane-foulant and foulant-foulant interactions.

Highlights

Microfiltration (MF) and ultrafiltration (UF) membrane separation technologies are playing an increasingly important role in water purification, wastewater treatment, and resource recovery (Baker, 2012; Tong et al, 2019; Xiao et al, 2019b)
In an organic-inorganic composite foulant layer, the non-covalent adsorption or covalent bridging between the inorganic particles and organic polymer backbones will increase the compactness of the foulant layer (You et al, 2005; Meng et al, 2007; Chen et al, 2018)
Further fundamental research is required on experimental quantification and theoretical simulation of the interactions in order to identify the key factors and their influences on the fouling process

Summary

INTRODUCTION

Microfiltration (MF) and ultrafiltration (UF) membrane separation technologies are playing an increasingly important role in water purification, wastewater treatment, and resource recovery (Baker, 2012; Tong et al, 2019; Xiao et al, 2019b). In MF/UF water treatment systems, the hydrophobicity and surface charge (potential) of the membrane and foulant are two important factors for the membrane-foulant non-covalent interaction, corresponding to hydrophobic adsorption and electrostatic attraction/repulsion, respectively (Weis et al, 2005; van Oss, 2006; Maximous et al, 2009; Meng et al, 2009; Xiao et al, 2014b). Xiao et al (2011) derived a semi-empirical multiple regression model based on the XDLVO theory, describing the combined effect of the hydrophobic and electrostatic properties (represented by water contact angle and zeta potential, respectively) of the membrane and foulant on the adsorption equilibrium constant. The membrane-foulant complexation is beneficial to the accumulation of foulant on the membrane surface, composing a premise layer to promote subsequent growth of the gel layer (Mo et al, 2012; Chen et al, 2018)

Summary

CONCLUDING REMARKS