In Situ Healing of Compromised Membranes via Polyethylenimine-Functionalized Silica Microparticles.

Microscale damages to membranes used in large-scale filtration processes for water treatment can result in severe degradation of product water quality. One promising technology to address this issue is in situ healing of compromised membranes via healing agents that are added to the feed side of a membrane system and seal the defect site because of increased hydraulic drag through damage site during filtration. We herein introduce an improved in situ membrane healing method using amine-functionalized silica microparticles that is effective under varying operating conditions, overcoming limitations faced by previous healing agents such as chitosan agglomerates. The silica microparticles are functionalized with branched polyethylenimine (PEI) molecules for efficient interparticle cross-linking with glutaraldehyde. The PEI-decorated silica microparticles (SiO2@PEI MPs) were characterized using scanning electron microscopy, dynamic light scattering, and zeta potential analysis. This study investigates the selective deposition of the SiO2@PEI MPs on the damage area using confocal laser scanning microscopy under variable cross-flow rate (0.5-2.0 L/min) and flushing time (10 to 30 min) conditions. The in situ healing technique recovered the particle rejection of compromised membranes to 99.1% of the original membrane's performance without any flux decline. The results of this study show that the use of SiO2@PEI MPs is a promising and practical approach to ensure membrane process integrity.