An efficiency of rare earth (europium, Eu) removal from aqueous solutions by polymer enhanced ultrafiltration (PEUF) process was investigated using two water-soluble polymers polyacrylic acid (PAA) and polyethylenimine (PEI). The effects of loading ratios of Eu to PAA or PEI, pH of solution and the added salt on Eu removal were evaluated. It was shown that the binding capacities for PAA and PEI to Eu ions were 0.8g Eu/g PAA and 0.5g Eu/g PEI, respectively. Eu ion rejection R decreased significantly at a low pH compared to the results at high pH, regardless of using PAA or PEI. Compared to the PAA case, PEI enhanced UF was more sensitive with changing pH. The effect of the added salt was slightly weak at pH 4-5.At the decomplexation stage, when permeate volume was equal to three times than that of the retentate, Eu removal efficiency (X) of Eu-PAA enhanced UF was 79.5% while that of Eu-PEI enhanced UF was 76.1%, and the polymer PAA and PEI could be recovered more than 97% and 93%, respectively. Eu in the retentate could be extracted effectively and the purified PAA and PEI solution were obtained. The recovered PAA and PEI solution was same as the fresh PAA and PEI solution in PEUF processes carried out by using the recovery recovered PAA and PEI as complex agents.
Conformation of Water Soluble Polymers in Aqueous Solution
