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根据固定电荷模型和非线性最小二乘法,研究膜体积电荷密度为定值和其大小随电解质主体溶液浓度呈指数变化的两种初始条件下,五种纳滤膜(NTR7450,ESNA1,ESNA1-LF,LES90和UTC60)在不同浓度的氯化钠和氯化钾溶液中的膜电位,获得膜体积电荷密度与电解质主体溶液浓度的关系.结果表明,当体积电荷密度随浓度呈指数变化时,拟合的膜电位与实验结果更接近,得到的固定电荷密度更精确.膜电位的大小与膜两侧电解质溶液浓度的比值相关.在较高浓度时,膜电位的值还与扩散系数相关;其中阴阳离子的扩散系数之比大于1.0是膜电位反号的标志.在中间浓度时,膜电位随电解质主体溶液浓度近似呈线性变化.
According to the fixed charge model and the nonlinear least square method, two kinds of nanofiltration membranes (NTR7450, ESNA1, ESNA1-LF) were studied under the two initial conditions that the membrane volume charge density is a constant value and its size varies exponentially with the concentration of the electrolyte solution. , LES90 and UTC60) in different concentrations of sodium chloride and potassium chloride solution to obtain the relationship between the membrane volume charge density and the concentration of the electrolyte solution.The results show that when the volume charge density changes exponentially with the concentration, The resultant membrane potential is closer to the experimental one and the resulting fixed charge density is more accurate.The magnitude of the membrane potential is related to the ratio of electrolyte solution concentrations on both sides of the membrane and at higher concentrations the membrane potential is also related to the diffusion coefficient Diffusion coefficient ratio of anion to cation is greater than 1.0, which is a sign of the reverse sign of membrane potential. At intermediate concentration, the membrane potential changes approximately linearly with the concentration of electrolyte solution.