Adsorption and Separation of Metal Ions by Using Acryloylacetone Polymer

将丙烯酰丙酮在密封管中聚合，制备了聚丙烯酰丙酮(PAA)，并考察了其对金属离子的吸附性能。根据pH滴定实验数据测定了其与金属离子络合的解离常数和总结合常数，其稳定性顺序为：Cd(II)&Gt；Ni(II)&Gt；Co(II)&Gt；Cd(II)Sm(III)&Gt；Nd(III)&Gt；Pr(III)&Gt；Ce(III)&Gt；La(III)。金属离子在PAA上的吸附行为符合朗缪尔方程，而不符合Freundlich等温式。PAA对金属离子的最大吸附量很低，但对汞(II)和铜(II)有选择性吸附。稀土金属离子的最大吸附量比二价金属离子低一个数量级左右。吸附过程强烈依赖于溶液的pH值，吸附在PAA上的金属离子可被浓度大于10 mM的盐酸溶液洗脱。吸附速率采用双阻力模型，考虑了液相边界层中的传质和两种不同扩散系数的颗粒内固体扩散，其中DE0为β%PAA，其余为DE1。对模型方程进行了数值求解，通过将计算的摄取曲线与实验值进行拟合，确定了De_0和De_1。De_0=5×10^&lt；-8&gt；cm^2/S NAD_1=2-2.5×10^&lt；-9&gt；cm^2/S与初始浓度和所用金属形态无关。用PAA色谱柱对金属离子进行了分离和浓缩。通过逐步降低淋洗液的pH值，成功地实现了铜(II)与Co(II)、Cd(II)和Ni(II)的分离。该技术对稀土金属离子的色谱分离也取得了较好的分辨率。

Polyacryloylacetone (PAA) was prepared by polymerizing acryloylacetone in a sealed tube, and examined as an adsorbent of metal ions. Its dissociation constant and overall binding constants for complexing with metal ions were determined from experimental data on pH titration.The order of stability of metal complexes was as follows :Cu(II) > Ni(II) > Co(II) > Cd(II)Sm(III) > Nd(III) > Pr(III) > Ce(III) > La(III)The adsorption behaviors of metal ions on PAA conformed to the Langmuir rather than the Freundlich isotherm. The maximum adsorptions of metal ions by PAA were very low, but Hg(II) and Cu(II) were adsorbed selectively. The maximum adsorptions of rare earth metal ions were about one order lower than those of divalent metal ions. The adsorption was strongly dependent on the pH of the solution, and metal ions adsorbed on PAA could be eluted with HCl solution in a concentration above 10 mM.The adsorption rate was analyzed using a two-resistance model which involves a mass transfer in liquid phase boundary layer, and two intraparticle solid diffusions with different diffusion coefficients ; De_0 in beta% PAA and De_1 in all others. The model equations were solved numerically, and De_0 and De_1 were determined by fitting the calculated uptake curves to the experimental ones. De_0=5 X 10^<-8>cm^2/s nad De_1=2 - 2.5 X 10^<-9>cm^2/s were independent of the initial concentrations and of the metal species employed. The separation and concentration of metal ions using a PAA column were examined. The separations of Cu(II) from Co(II), Cd(II) and Ni(II) were achieved successfully by stepwise decrease in pH of the eluent. Good resolutions for chromatographic separation of rare earth metal ions were also achieved by the same technique.