Adsorption and Separation of Metal Ions by Using Acryloylacetone Polymer

通过在密封管中对丙烯酰丙酮进行聚合制备了聚丙烯酰丙酮（PAA），并对其作为金属离子吸附剂进行了研究。用pH滴定法测定了其解离常数和与金属离子络合的总结合常数。金属配合物的稳定性顺序为：Cu(II) > Ni(II) > Co(II) > Cd(II)Sm(III) > Nd(III) > Pr(III) > Ce(III) > La（III）金属离子在PAA上的吸附行为符合Langmuir等温线而不符合Freundlich等温线。PAA对金属离子的最大吸附量很低，但对Hg（II）和Cu（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。吸附在PAA上的金属离子与溶液的pH值密切相关，且浓度在10 mm以上的HCl溶液可以将金属离子洗脱。吸附速率采用液相边界层传质和不同扩散系数的颗粒内固体扩散的双阻力模型进行分析；β % PAA为De_0，其他均为De_1。对模型方程进行了数值求解，并将计算的吸收曲线与实验曲线拟合，确定了De_0和De_1。De_0=5 × 10^<-8>cm^2/s和De_1=2 - 2.5 × 10^<-9>cm^2/s与初始浓度和所用金属种类无关。研究了聚丙烯酸色谱柱对金属离子的分离和富集。通过逐步降低淋洗液的pH值，Cu（II）与Co（II）、Cd（II）和Ni（II）成功分离。该方法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.