The application of nanoemulsion as a novel sustainable industrial fluid

• Main Authors: Shang-Jie Lin, 林上傑
• Other Authors: 張書奇
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/53667077770371580647

碩士 === 國立中興大學 === 環境工程學系所 === 96 === The need for effective industrial water management requires better strategies for industrial fluid formulation, in-process fluid management, and end-of-life fluid management. The earlier the changes in its life cycle, the greater the benefit will be. Industrial fluids are subject to biodeterioration in a variety of industrial operations, including oil exploration, cooling water systems, filtration systems, desalination, and metalworking processes. Thus, resources and time have been expended to prevent microbial growth and consequential impacts on fluid integrity and functionality. Among these various industrial fluids, water-based metalworking fluid has been one of the most vulnerable fluids since it has suitable oil-to-water ratios for microbial proliferation. Therefore, biocide addition is inevitable and dosage elevation is required due to microbial resistance. Consequently, workers are exposed to high level of biocides and endotoxins released from killed Gram-negative bacteria. The working hypothesis of this study is that metastability of nanoemulsion will exhibit high emulsion stability and high biostability due to membrane disruption without adding any biocides. Nevertheless, nanoemulsion will be easily biodegraded when in wastewater treatment processes due to coalesce in diluted concentration range. In this study, with industrial-grade components, a novel and highly stable nanoemulsion with average mineral oil droplet diameters as small as 10 nanometers has been prepared through phase inversion temperature method and its biocidal effects were tested on Pseudomonas aeruginoasa (Gram negative) and Mycobacterium immunogenum (Gram positive). Side by side, two commercially available biocides, Kathon and Preventol, were also tested for their biocidal effects in phosphate buffer saline with two commercially available metalworking fluids. In pure cultures, this nanoemulsion successfully achieved a killing efficacy on Pseudomonas aeruginosa higher than 5 log decades and that on Mycobacterium immunogenum higher than 6 log decades within 15 minutes. In an equal-volume mixed culture, this nanoemulsion showed a killing efficacy on Pseudomonas aeruginosa and Mycobacterium immunogenum higher than 7 log decades within 15 minutes and 5 log decades within 30 minutes, respectively. These results suggest that such mineral oil nanoemulsion has high biocidal effects on bacteria comparable to commercially available biocides. A soybean oil nanoemulsion with droplet diameters less than 15 nanometers has also been prepared but showed insignificant biocidal effects on both bacteria. This result implied that, apart from the size of oil droplets, the molecular structures of oils and surfactant composition may have also contributed to their biocidal effects.