Development and Characterization of Membranes with PVA Containing Silver Particles: A Study of the Addition and Stability

Audie K Thompson,Tony L Grady,Quincy C Moore,Silver Enyinnia,Felecia M Nave,Cannon Hackett

doi:10.3390/polym12091937

Audie K Thompson, Tony L Grady + Show 4 more

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https://doi.org/10.3390/polym12091937

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Abstract

Developing technologies for the reduction of biofouling and enhancement of membrane functionality and durability are challenging but critical for the advancement of water purification processes. Silver (Ag) is often used in the process of purification due to its anti-fouling properties; however, the leaching of this metal from a filtration membrane significantly reduces its effectiveness. Our study was designed to integrate the positive characteristics of poly vinyl alcohol (PVA) with the controlled incorporation of nano-scale silver ions across the membrane. This approach was designed with three goals in mind: (1) to improve antifouling activity; (2) to prevent leaching of the metal; and (3) to extend the durability of the functionalized membrane. The fabrication method we used was a modified version of manual coating in combination with sufficient pressure to ensure impregnation and proper blending of PVA with cellulose acetate. We then used the spin coater to enhance the cross-linking reaction, which improved membrane durability. Our results indicate that PVA acts as a reducing agent of Ag+ to Ag0 using X-ray photoelectron spectroscopy analysis and demonstrate that the metal retention was increased by more than 90% using PVA in combination with ultraviolet-photo-irradiated Ag+ reduced to Ag0. The Ag+ ions have sp hybrid orbitals, which accept lone pairs of electrons from a hydroxyl oxygen atom, and the covalent binding of silver to the hydroxyl groups of PVA enhanced retention. In fact, membranes with reduced Ag displayed a more effective attachment of Ag and a more efficient eradication of E. coli growth. Compared to pristine membranes, bovine serum albumin (BSA) flux increased by 8% after the initial addition of Ag and by 17% following ultraviolet irradiation and reduction of Ag, whereas BSA rejection increased by 10% and 11%, respectively. The implementation of this hybrid method for modifying commercial membranes could lead to significant savings due to increased metal retention and membrane effectiveness. These enhancements would ultimately increase the membrane’s longevity and reduce the cost/benefit ratio.

Highlights

The search for more rapid and effective water filtration membranes remains a vital area for research.Biofouling, especially microbial accumulation, is detrimental to water filtration processes and decreases the durability of membranes
Membranes were analyzed on both both sides for desired functional groups and observations of membrane impregnation: Top
We evaluated the membrane performance and biofouling characteristics of membranes fabricated using the hybrid method in combination with silver nanoparticle technology

Summary

Introduction

Biofouling, especially microbial accumulation, is detrimental to water filtration processes and decreases the durability of membranes. Both organic and biofouling are attributed to polysaccharides [1]. Copper has been used to prevent microorganism accumulation [2], and magnesium affects polysaccharide fouling [1,3]. It is well known that hydrophilic surface modification can be an effective method for reducing membrane fouling since the hydrophilic surface can repel foulant adsorption via the repulsive hydration force [5]. Besides enhancing the membrane’s antimicrobial properties, silver is known to affect a membrane’s hydrophilicity as well. Preventing Ag+ from leaching into the permeate and causing loss of antimicrobial properties [13] is critical to silver’s effectiveness

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