Essential oil-incorporated carbon nanotubes filters for bacterial removal and inactivation.

Xiuli Dong,Liju Yang,Ambrose E Bond,Amitava Mukherjee

doi:10.1371/journal.pone.0227220

Abstract

In this study, essential oils (EO)-incorporated multi-walled carbon nanotubes (MWCNTs) filters were developed for achieving dual functions in effective removing bacteria from aqueous solutions and inactivating bacteria cells captured on the filters. Tea tree essential oil (TTO), lemon essential oil (LEO), and TTO-LEO-mixture were coated on MWCNTs filters with different MWCNTs loadings ranging from 3 mg to 6 mg. MWCNTs filters with 6.0 mg MWCNTs showed complete removal (100%) of E. coli cells from PBS buffer with 6.35 log10 decrease of cell numbers. TTO, LEO, and TTO/LEO Mix (1:1) coatings at the volume of 50 μL on MWCNTs filters achieved bacterial removal rates of >98%, and highly effective inactivation efficiency. TTO coatings had the highest antimicrobial efficacies than LEO and Mix coatings, MWCNTs filters with 50 μL TTO coating showed 100% inhibitory rate of the captured bacteria on the filter surfaces. Those captured but survived cells on filters with less TTO coating (20μL) significantly reduced their salt tolerances to 30 and 40 g/L NaCl in LB agar, and became less salt tolerance with longer incubation time on the filters. The developed TTO-MWCNTs filters had much higher antimicrobial efficacies than the filters with dual functions developed previously.

Highlights

Waterborne diseases caused by pathogens account for 3.4 million deaths each year [1]
The loading of multi-walled carbon nanotubes (MWCNTs) was obviously proportional to the coverage and density of MWCNTs on the membrane, which attributed to the reduced pore sizes on the resulting membranes
Vecitis et al found that anodic MWCNTs microfilters in the absence of electrolysis showed a complete removal of bacteria by sieving and multilog removal of MS2 viruses by depth-filtration [22]

Summary

Introduction

Waterborne diseases caused by pathogens account for 3.4 million deaths each year [1]. The occurrence of pathogenic microorganisms in contaminated water is a serious issue for almost all types of ambient water bodies. The United Nations identified improvement of water quality as one of the eight Millennium Development Goals (MDGs) in 2000. It aimed to reduce the number of people without the access to safe water by 50% by 2015 and this goal was achieved. To protect public health in the United States, the U.S Environmental Protection Agency (EPA) has established the National Primary Drinking Water Regulations which set the standards of maximum contaminant level (MCL) of pathogens and require routine sampling of drinking water for testing total coliforms and E. coli [1, 3]

Objectives

Methods

Results

Conclusion