Preparation And Performance Of Positively Charged2-hydroxypropyl Trimethyl Ammonium Chloride Chitosan (HTCC)/Poly (Polyether Sulfone) Composite Membrane

2-Hydroxypropyltrimethyl ammonium chloride chitosan (HTCC) with different substitution degrees were synthesized by reaction of chitosan (CTS) and glycidyl trimethyl ammonium chloride (GTMAC) in isopropanol. Then a positively charged composite nanofiltration membrane was prepared by using HTCC as the selective layer, PES UF membrane as support layer and epichlorohydrin (ECH) as cross-linking reagent. The prepared HTCC was characterized by Fourier transform infrared spectroscopy (FTIR),’H-NMR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of preparation conditions such as the concentration of HTCC and ECH, cross-linking time, ect. on membrane performance were studied and the membrane was characterized by SEM and atomic force microscope (AFM). The pure water permeability, molecular-weight cut-off (MWCO), charge performance, rejection performance, mechanical properties, swelling degree and antibacterial property of the composite membrane were also tested.The results indicated that the active amino groups of CTS were partly substituted by quaternary ammonium groups. As the substitution degree increases, the solubility, Zeta potential and hygroscopicity of HTCC enhanced. A HTCC/PES composite membrane from1.0wt%HTCC casting solution, cross-linked with1.9wt%ECH and0.3g KOH in50mL ethanol for21-22h was found to have optimum performance. The pure water permeability of the composite membrane is19.1kg·m-2·h-1·MPa-1, its MWCO is about968(nanofiltration range), mechanical strength234.53MPa, elongation at break20.75%, swelling degree80.51%and RMS29.2nm. The rejection of salt solutions follows the decreasing order of MgCl2. NaCl, KCl, MgSO4, Na2SO4, K2SO4, revealing the positively charged characteristic of the membrane. In addition, the antibacterial ability of the composite membranes enhanced along with the increasing DS of the HTCC used, and these membranes show greater antibacterial activity against G-ve bacteria E.coli than G+ve bacteria Bacillus subtilis.