Abstract: Complexation-ultrafiltration process for separation of palladium(II) from aqueous solution was investigated by using poly(acrylic acid) sodium (PAAS) as a complexing agent. The effects of polymer/metal mass ratio (rp/m), pH value and transmembrane pressure (Dp) on permeate flux (J) and palladium rejection coefficient (RPd) were investigated. It was found that J did not change with increasing of rp/m, and increased with pH or Dp. RPd increased with rp/m or pH, but did not vary with Δp. The concentration experiment was carried out at rp/m=2 and pH=6. The results showed that J declined slightly and RPd was about equal to 1 with increasing of volume concentration factor (Fv). Palladium concentration in the retentate (Cr) increased linearly with Fv, whereas palladium concentration in the permeate (Cp) was always about 0.07 mg/L. The decomplexation experiment was done at pH=3 by using the previous concentrated solution. Cr did not change but Cp increased gradually to 100.9 mg/L with increasing of decomplexation time. It took about 13 min to get the decomplexation equilibrium. The decomplexation rate of palladium(II)-PAAS complexes reached 56.3%. Further, an ultrafiltration experiment was carried out by using the washing water. If the volume of washing water was 3.5 times larger than the feed volume, Cr decreased from 179.3 to 5.2 mg/L, which corresponded to palladium removal rate of 97.1%.

Key words: complexation, ultrafiltration, poly(acrylic acid) sodium, palladium(II)

摘要： 以聚丙烯酸钠(PAAS)为络合剂，研究钯(II)的络合-超滤行为. 考察聚合物/金属质量比(rp/m)、pH、膜两侧压差(Δp)对膜通量(J)和钯截留系数(RPd)的影响，发现J不随rp/m变化，随pH增大而增大，随Dp增大呈线性递增；RPd随rp/m或pH增大而增大，与Dp无关. 控制rp/m=2和pH=6，PAAS-钯(II)溶液的浓缩结果表明，随体积浓缩因子增大，J略有下降，RPd接近1，截留液钯浓度(Cr)线性递增，渗透液钯浓度(Cp)约0.07 mg/L. 以浓缩液为研究对象，在pH=3下考察PAAS-钯(II)的解络合行为，随时间延长，Cr不变，Cp逐渐增至100.9 mg/L，解络合平衡时间为13 min，解络合率为56.3%. 对解络合液洗涤超滤，当洗涤液体积为原料液体积的3.5倍时，Cr从179.3降至5.2 mg/L，钯洗脱率为97.1%.

关键词: 络合, 超滤, 聚丙烯酸钠, 钯(II)