Interim Report - Hanford Site

Table 7. (contd)
Phosphate Source
Sodium
hexametaphosphate
Sodium
hexametaphosphate
Sodium
hexametaphosphate
Sodium
hexametaphosphate
Sodium
hexametaphosphate
Sodium
hexametaphosphate
Phosphorus Conc.
(ppm) Calcium Source
1,500 Calcium
chloride
1,500 Calcium
chloride
2,000 Calcium
chloride
2,000 Calcium
chloride
2,500 Calcium
chloride
2,500 Calcium
chloride
Calcium Conc.
(ppm)
1,000
1,500
1,000
1,500
1,000
1,500
Uranium Conc.,
(μg/L)
10 1,000
0.00
10 1,000
0.00
10 1,000
0.00
10 1,000
0.00
10 1,000
0.00
10 1,000
0.00
Figure 12 displays the percent of calcium and phosphorus removed from solution as a function of the
calcium to phosphorus molar ratio in the presence of 10 and 1,000 ppb uranium. The objective of these
tests was to identify the calcium-to-phosphorus molar ratio for maximum removal from the aqueous
phase. The mechanisms of removal may include sorption and precipitation; however, no attempt was
made to discern the degree of removal based on these respective mechanisms. Greater than 90% removal
of calcium and phosphorus from solution was achieved in the presence of sodium orthophosphate, sodium
pyrophosphate, sodium tripolyphosphate, respectively, with calcium-chloride (Figure 12). The optimum
molar ratio of calcium to phosphorus for sodium orthophosphate and sodium pyrophosphate is 1.5;
whereas, the optimum calcium-to-phosphorus molar ratio for sodium tripolyphosphate is ~2.4. Moreover,
the uptake of uranium was rapid (