Understanding the effect of experimental variables on the recovery of ²³¹Pa from siliceous cake using factorial design

Four-factor (oxalic acid concentration, contact time, temperature, ultra-sound), two-level experimental design was applied during the recovery of ²³¹Pa from siliceous cake—a solid radioactive-waste, produced in monazite processing. Oxalic acid (0.5 to 1.1 M) had the highest positive (F = 1018.6) and ultrasound had the least (F = 33.0) impact on recovery. All inter-factor interactions were significant, as F_calculated < F_critical and P < 0.05. Enthalpy of protactinium-oxalate complexation was found to be − 24.8 kJ mol⁻¹. The regression coefficient (0.9853), randomness and magnitude (< ± 2) of fitted residuals explicated the suitability of present statistical model for predictive analysis.