Alkaline Hydrolysis of Tri-iso-amyl Phosphate in n-dodecane Using Sodium Hydroxide: Part 1—Factors Affecting the Hydrolysis Process

Tri-iso-amyl phosphate (TiAP) is being proposed as a suitable alternate to tri-butyl phosphate mainly for the reprocessing of high-Pu-content spent fuel from fast reactors. After its use in a few cycles, the solvent has to be categorized as organic waste, which needs further treatment and disposal. Toward this, systematic studies have been carried out on the alkaline hydrolysis of TiAP in n-dodecane (n-DD) using sodium hydroxide (NaOH). The experiments were carried out in a stainless steel autoclave with a reactor vessel having a 1 L processing capacity. The parameters, such as mixing intensity, temperature, aqueous-to-organic phase volume ratio, and initial NaOH concentration, that can affect the kinetics of the hydrolysis reaction were studied. During each experiment, the TiAP concentration in the organic phase decreased steadily with time followed by a sudden decrease, which could be due to the autocatalytic hydrolysis of TiAP. After the completion of the hydrolysis reaction, the organic phase was mainly n-DD with iso-amyl alcohol, suggesting complete hydrolysis of TiAP to its aqueous-soluble hydrolysis products. Based on the studies, it was observed that temperature and initial NaOH concentration, among other parameters, highly influence the rate of hydrolysis of TiAP.