Study On Quaternized Poly (Phthalazinone Ether Sulfone Ketone) (QAPPESK) Nanofiltration And Anion-exchange Membranes

Poly(phthalazinone ether sulfone ketone) (PPESK) is a novel membrane material for filtration membrane with high glass-transition temperature, good solubility, well membrane-forming ability, good mechanical performance and chemical stability.Chloromethylated poly(phthalazinone ether sulfone ketone) (CMPPESK) was prepared from PPESK and chloromethyl octyl ether (CMOE) in concentrated sulfuric acid. The effects of reaction temperature, reaction time, the concentration of CMOE and polymer concentration on the degree of chloromethylation were investigated in detail. The technology conditions were optimized and the degree of chloromethylation could be controllable. The degree of chloromethylation could get to1.99 mmol·g^-1. The solubility and thermal properties of CMPPESK were also examined. CMPPESK had well solubility, which was soluble in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), and chloroform. It was found that the introduction of chloromethyl groups and quaternary ammonium groups into the polymer chains led to a decrease in the decomposition temperature. And with the increase of the degree of chloromethylation, the initial degradation temperature declined. The decomposition of CMPPESK maybe occurred by both the elimination of chloromethyl functional groups and a cross-linking reaction. The higher the degree of chloromethylation was, the more the residual quantity was. Quaternized poly(phthalazinone ether sulfone ketone) (QAPPESK) with different the ion exchange capacity (IEC) was prepared from CMPPESK and trimethylamine by quaternized modification. The solubility and thermal properties of QAPPESK were also examined. It was found that QAPPESK had better solvent resistance with the increase of the IEC. QAPPESK (IEC=1.18 mmol·g^-1) had excellent solvent resistance, which was partly soluble in sulfuric acid (98%) and swollen in N, N-dimethylformamide (DMF) and wan not soluble in NMP, DMAc and other organic solvents. The elimination of quaternary ammonium groups occurred at between 200 and 250℃. And with the increase of the IEC, the weight loss of QAPPESK was much more obvious.CMPPESK had good solubility, whereas QAPPESK had excellent solvent resistance. Therefore, positively charged QAPPESK NF membrane couldn't be directly prepared from QAPPESK, but could be obtained through the following two steps: (1) The preparation of CMPPESK asymmetric membrane by a phase inversion method. (2) QAPPESK NF membrane was prepared form CMPPESK asymmetric membrane by quaternized modification. Solvent and nonsolvent additives selected had effects on membrane structure and performance in the phase inversion process of preparing CMPPESK asymmetric membrane. The effects of polymer, solvent and nonsolvent on casting systems were investigated in detail by cloud titration method. The cloud of ternary phase system of CMPPESK/Solvent/NS A was tested at 25℃and the data were simulated linearly. The binodal lines of the ternary phase systems were calculated according to the linerized cloud point (LCP) correlation. Therefore, the maximum content of NSA in the casting solution can be calculated according to the bimodal lines of the system, which is a reliable basis for the establishment for the composition of casting solution.CMPPESK asymmetric membrane was prepared form CMPPESK membrane material. And positively charged quaternized poly(phthalazinone ether sulfone ketone) (QAPPESK) nanofiltration (NF) membranes were prepared from CMPPESK asymmetric membrane by quaternized modification. The effects of preparation conditions, such as casting solvent, nonsolvent additives, quaternization conditions and so on, were investigated and the technology conditions were optimized. QAPPESK NF membranes were obtained by optimal technology conditions, which the MgCl₂ rejection was 88% and the flux was 56 L·m^-2·h^-1 at 0.4 MPa. Quaternization conditions had much larger effects on the EEC and swelling rate of QAPPESK NF membrane. When much more quaternary ammonium groups were introduced, the membrane would get much more positive charges and the IEC of membrane would become much larger. At the same time, the swelling rate of membrane increased. And the swelling rate of membrane also increased with the reaction temperature. when trimethylamine concentration is 5.0 mol·L^-1, and quaternization time is about 5h, and quaternization temperature is 30℃, QAPPESK NF membrane had much better membrane performance.QAPPESK NF membranes with good integrated properties were prepared by optimal technology condition. Membrane parameters were calculated according to the irreversible thermodynamic model and the electrostatic and steric-hindrance (ES) model. The properties of QAPPESK NF membrane were studied, such as separating different inorganic salt, the thermal stability, chemical stability and desalination-purification for cation dye MB. The inorganic electrolytes rejection of QAPPESK NF membrane ranks: MgCl₂> MgSO₄> NaCl> Na₂SO₄, which is typical characteristics of a positively charged NF membrane. QAPPESK NF membranes exhibited good thermal stability and fouling resistance. QAPPESK NF membrane held the stable membrane separation performance in 120 h at 60℃. QAPPESK NF membrane showed good free chlorine resistance and oxide resistance, and could hold stable membrane separation performance when the pH of media solution was lower than 10. QAPPESK NF membrane was applied in the desalination-purification for cation dye MB, and the rejection for MB was kept at more than 99% and the flux waved about 40 L·m^-2·h^-1. The cation dye MB was almost desalinized through 7 times cycle.CMPPESK homogeneous membrane was prepared form CMPPESK membrane material. And QAPPESK anion-exchange membrane was prepared from CMPPESK homogeneous membrane by quaternized modification. The characteristic parameters, chemical stability and battery performance of QAPPESK anion-exchange membrane were investigated. QAPPESK membranes had good chemical stability. The vanadium redox flow battery (V-RFB) using QAPPESK anion-exchange membrane had better performance with 88.3% of overall energy efficiency, which had much higher energy efficiency than Nafion 112 and Nafion 117 at the same test conditions. So QAPPESK anion-exchange membrane is very useful as a separator for the V-RFB with high overall energy efficiency and has promising application prospect in the V-RFB.