Fabrication of Bifunctional Chitosan-Based Flocculants: Characterization, Assessment of Flocculation, and Sterilization Performance

Abstract

In this study, a series of chitosan-based quaternary ammonium graft flocculants, namely chitosan-<i>graft</i>-poly(acrylamide and methacryloyl ethyl trimethyl ammonium chloride) [CTS-<i>g</i>-P(AM-DMC)], was successfully synthesized by plasma initiation, and the as-prepared [CTS-<i>g</i>-P(AM-DMC)] had both flocculation and sterilization functions. Various characterization techniques were used to study the structure and physicochemical properties of the chitosan-based flocculants. ¹H nuclear magnetic resonance spectroscopy (¹H NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), and thermogravimetric analysis/differential scanning calorimetry (TG/DSC) confirmed the successful synthesis of CTS-<i>g</i>-P(AM-DMC). Scanning electron microscopy (SEM) analysis exhibited that CTS-<i>g</i>-P(AM-DMC) contained a smooth convex and porous structure with an enormous surface area. CTS-<i>g</i>-P(AM-DMC) was then used to flocculate the simulated wastewater of the kaolin suspension and the <i>Salmonella</i> suspension. Besides external factors, such as the dosage of flocculant and pH, the effect of the internal factor graft ratio was also evaluated. The experimental results showed that CTS-<i>g</i>-P(AM-DMC) also revealed a strong sterilization effect, aside from the excellent flocculation effect. Moreover, the sterilization mechanism was investigated through a series of conductivity measurements and the analysis of fluorescence-based cell live/dead tests. The results indicated that CTS-<i>g</i>-P(AM-DMC) destroyed the cell membrane of <i>Salmonella</i> through its grafted quaternary ammonium salt, thereby exhibiting sterilization property.