"green" ZnO-Interlinked Chitosan Nanoparticles for the Efficient Inhibition of Sulfate-Reducing Bacteria in Inject Seawater

Abstract

Antimicrobial agents and corrosion inhibitors are widely used as biocides in the oil and gas industry to disinfect water and inhibit excessive biofilm formation caused mainly by sulfate reducing bacteria (SRBs). However, traditional biocides may induce bacterial resistance and/or be detrimental to environment by forming harmful disinfection byproducts. In this first systematic study, we synthesized a "green" and highly stable biocide formulations composed of ZnO-interlinked chitosan (Ch) nanoparticles (CZNCs) and evaluated their antimicrobial activity against mixed SRBs culture isolated from real oil field sludge. SEM, TEM, X-ray diffraction (XRD) and FTIR suggested the formation of stable nanocomposites with strong interaction between ZnO and Ch nanoparticles. Synthesized nanocomposites showed highly stable behaviors in the high salt concentrations of inject seawater. The inhibition of SRBs activity was concentration-dependent and more than 73% and 43% inhibition of sulfate reduction and total organic carbon (TOC) removal, respectively, was observed at 250 μg/mL CZNCs at 10% initial ZnO loading. Biocompatibility and environmental impact of the nanocomposite was evaluated by analyzing their potential toxicity in vivo using the zebrafish embryos. Neither mortality nor teratogenic effects were observed on zebrafish embryos using the acute toxicity assay. The hypothetical LC50 for the CZNCs was much higher than 250 μg/mL. It is expected that the new nanocomposite can contribute to the development of "green" biocides for oil/gas industries that will be eco-friendly and will have no adverse impact on the environment.