Synthesis And Biocidal Effects Of A Series Of Quaternary Ammonium Salts

With the wide application of quaternary ammonium compounds, their synthesis and functional discovery has become a hot research area. However, quaternary ammonium salts are very easy to foam accumulate in the soil, and resistance of bacteria and alga is beginning to show up. Thereby increasing their usage resulted in hight cost in water treatment, of the environment protection. Therefore, the development of novel quaternary ammonium compounds with high biocidal effects can reduce the cost of water treatment, and this is an important research topic.In this paper, using dimethylamine. tetradecane chloride and benzyl chloride as raw materials, a QAS of dimethylamine-tetradecane-benzyl ammonium chloride was prepared and characerized. An orthogonal experiment was designed, and the influences of temperature, synthetic time, ratio of raw materials and other factors on the yield were examined, and finally the synthetic conditions were optimized. For synthetic cost reduction, water was creatively used as solvent in QAS preparation and the QAS’s yield reached 92.11%. The molecular structures for the prepared QASs were proved to be the target products by the analysis of infrared spectroscopy and 1 H nuclear magnetic resonance.After purification, the QAS products were used as biocides in the experiments of sterilization and alga killing experiments. The determination results showed that QAS with one tetradecanyl, dimethyls and one benzyl provided strong bactericidal effect for Escherichia coli and Staphylococcus aureus, and the minimum inhibitory concentrations (MIC) were between 0.5～1.0mg/L at all. For evaluating biocidal effect of the QAS, a chlorophyll A determination method was creatively adopted, and optimal algae concentration of the QAS to remove Scenedesmus obliquus was 2.5mg/L. QASs were also selected as ideal algaecides, and they are worthy to be widely applied in practices. Finally, in natural water treatment, a spectrophotometric method based on bromothymol blue was applied in observing QAS’s degradation.In this dissertation. for exploring more efficiently synthetic method to prepare QASs which was easily degraded. a microwave irradiation assisted synthesis was employed during preparation of the series of four QASs with dialkyls and dihydroxyethyls. These QAS products were also successfully characterized by IR and 1H NMR spectra. Experiments indicated that the QASs with C12-C18 provided more efficient biocidal effect than the others during sterilization of Escherichia coli and Staphylococcus aureus.