Effects of pH and uranium concentration on the removal of uranium from drinking water by ion exchange

Effects of pH in the range of 5 to 8 and uranium concentration in the range of 0.02 mg/l to 25 mg/l on the removal of uranium with a strong base anion exchange resin (SBA) and a chelating aminophosphonate resin were studied. The results of the batch and column mode experiments clearly showed that the aminophosphonate resin was an efficient exchanger for the removal of uranium at pH values close to 5 and the SBA resin at higher pH values. In the column experiments, where altogether 2000 bed volumes of drinking water simulant were processed with these exchangers, the uptake of uranium was as high as 99.8% by the aminophosphonate resin at pH 5 and 99.7% by the SBA resin at pH 8.

Soluble and particle-bound 234,238U, 226Ra and 210Po in ground waters

Water of five drilled wells was filtered with three membranes (pore size 0.45 µm-5 kD) to determine the soluble and particle-bound forms of 234,238U, 226Ra and 210Po. Three of the waters were of Ca-HCO3 type and two of Na-Cl type. Some of the waters also exhibited high concentrations of Fe, Mn and humic substances. 234,238U was present entirely in soluble form in all waters, probably as uranyl ion (UO2 2+) in soluble carbonate complexes. 226Ra was in soluble form in the waters with low concentrations of Fe and Mn, but 10% of the total 226Ra activity was bound to particles in the Fe-Mn-rich waters. The behaviour of Po varied with water composition. Particle-bound 210Po was observed to correlate with the combined concentration of iron and manganese in the raw waters. In the two of waters of Na-Cl type, in which the concentrations of Fe, Mn and humic substances were high, salinity of the waters did not enhance the solubility of polonium. Polonium was present in both soluble and particle-bound forms in all the ground waters.

Removal of234,238U,226Ra,210Po and210Pb from drinking water by ion exchange

Six organic and five inorganic ion exchangers were studied for the removal of natural radionuclides from drinking water. In the first phase, distribution coefficients (KD) of uranium and radium were determined in three model solutions: a good quality water, an Fe-Mn-rich water and a saline water simulant. The exchangers showing highest KD´s for U and Ra were tested in column mode experiments for the removal of U,226Ra,210Po and210Pb from a real ground water. Considering the total 1800 processed bed volumes, the best decontamination factors (DF) for U, 20-120, were obtained with the strong base anion exchange resin. The most efficient exchangers for the removal of226Ra were the weak and strong cation resins and zeolite A. With use of long regeneration intervals, conventional organic resins are thus most suitable for the removal of radionuclides. When only a few hundred bed volumes were processed, with the corresponding regeneration interval about one week, the aminophosphonate resin was most effective for the removal of both uranium and radium.210Po and210Pb in ground water were mainly bound in particles and adsorbed on the surface of the anion resins. The use of the aminophosphonate resin to remove uranium and radium would therefore require an anion resin to take up polonium and lead.