Antibacterial studies of Ag@HPEI@GO nanocomposites and their effects on fouling and dye rejection in PES UF membranes

Christopher N Chukwuati; Richard M Moutloali

doi:10.1016/j.heliyon.2022.e11825

Antibacterial studies of Ag@HPEI@GO nanocomposites and their effects on fouling and dye rejection in PES UF membranes

Heliyon. 2022 Nov 21;8(11):e11825. doi: 10.1016/j.heliyon.2022.e11825. eCollection 2022 Nov.

Authors

Christopher N Chukwuati^{1

2}, Richard M Moutloali^{2

3}

Affiliations

¹ Department of Chemical Sciences, Faculty of Science, University of Johannesburg, P. O. Box 17011, Doornfontein 2028, Johannesburg, South Africa.
² DSI/MINTEK Nanotechnology Innovation Centre - Water Research Node, University of Johannesburg, P. O. Box 17011, Doornfontein 2028, Johannesburg, South Africa.
³ Institute for Nanotechnology and Water Sustainability, College of Science, Engineering and Technology, University of South Africa, Florida, 1790, Johannesburg, South Africa.

Abstract

A series of polyethersulfone membranes containing Ag@HPEI@GO composite was fabricated using non-solvent induced phase separations (NIPS) to mitigate against biofilm causing bacteria and modulate solute rejection. All materials produced and used were fully characterised using a combination of appropriate physicochemical techniques including FTIR, XRD, BET, SEM, AFM. The GO-based fillers exhibited bactericidal activities. The bactericidal activities of GO, HPEI@GO against Escherichia Coli (E. coli) were observed at 8 mg mL^-1 whilst Ag@HPEI@GO composites exhibit bactericidal activities against E. coli at 4 mg mL^-1. Against Klebsiella pneumonia (K. pneumonia), GO bactericidal activities were observed at 8 mg mL^-1, whilst HPEI@GO and Ag@HPEI@GO bactericidal activities on K. pneumonia were observed at 4 mg mL^-1. Against Staphylococcus aureus (S. aureus), GO exhibit bactericidal activities at 8 mg mL^-1, HPEI@GO and Ag@HPEI@GO composites exhibit bactericidal activities on S. aureus at 4 mg mL^-1. The aforementioned microorganisms are among the microorganism that causes biofilm formation on surfaces. The membrane performance was assessed by measuring pure water flux, solute rejections and fouling propensity with three different organic dye molecules and bovine serum albumin (BSA). All composite membranes (GO/PES, HPEI@GO/PES, and Ag@HPEI@GO/PES) exhibited increased hydrophilicity and higher pure water flux compared to the baseline PES membranes with concomitant increase in fouling resistance, The observed flux recovery ratios (FRR) were 80% (GO/PES), 70% (HPEI@GO/PES) and 69% (Ag@HPEI@GO/PES) respectively compared to the 45% FRR observed for the baseline PES membrane after BSA fouling. Congo red (CR) used as an indicator for molecular cut-off of UF membranes was rejected above 95% by all nanocomposite membranes. Furthermore, the nanocomposite membranes-maintained rejection for the positively charged methylene blue (MB) of above 90% whilst rejection observed for amaranth (AR) dye decreased from 80 to 58% with increasing filler content in the PES matrix. The results demonstrate the positive influence of GO, HPEI@GO and Ag/HPEI@GO nanofillers on flux, fouling and solute rejection performance of resultant PES nanocomposite membranes.

Keywords: Antibacterial; Antifouling; Graphene oxide; Hyperbranched polyethyleneimine; Nanocomposite; Ultrafiltration.