Sodium Hydroxide Extraction From Caustic Leaching Solutions

Abstract

SummaryThis report describes experiments conducted to demonstrate the proof-of-principle of a method to recover NaOH from Hanford tank sludge leaching solutions. Aqueous solutions generated from leaching actual Hanford tank waste solids were used. The process involves neutralization of a lipophilic weak acid (t-octylphenol was used in these experiments) by reaction with NaOH in the aqueous phase. This results in the transfer of Na into the organic phase. Contacting with water reverses this process, reprotonating the lipophilic weak acid and transferring Na back into the aqueous phase as NaOH.The work described here confirms the potential application of solvent extraction to recover and recycle NaOH from solutions generated by leaching Hanford tank sludges. Solutions obtained by leaching sludges from Tanks S-110 and T-110 were used in this work. It was demonstrated that Na + is transferred from caustic leaching solution to the organic phase when contacted with t-octylphenol solutions. This was accompanied by a concomitant decrease in the aqueous-phase hydroxide ion concentration. Seventy to 80% of the extracted Na was recovered by 3 to 4 sequential contacts of the organic phase with water. Cesium was co-extracted by the procedure, but Al and Cr remained in the feed stream.The results of this study revealed several areas that will require further investigation before the technology can be implemented.

Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation of Sodium Salts

“…14 Applied development was spun-off into a separately funded one-year project that demonstrated that recovery of NaOH from actual waste is possible for recycle to sludge washing. 21 Although the concept appears viable, issues identified include selectivity, phase behavior, and stripping efficiency. The first observation of SPHE was communicated, 22 wherein it was shown that enhanced NaOH extraction may be effected by combining fluorinated alcohols with macrocyclic extractants.…”

Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation of Sodium Salts

“…Although the donor-acceptor properties of 1-octanol are well-suited for PHE, its ability to solubilize appreciable amounts of water and its high viscosity are undesirable in an industrial application. At high sodium loading, expansion of the organic phase volume was observed with 1-octanol as the diluent , and in some cases, gelling of the loaded solvent occurred (Lumetta et al 2002). Aliphatic diluents are usually preferred for industrial solvent extraction processes.…”

Flowsheet Modeling and Testing of Pseudohydroxide Extraction from Aqueous Sodium Hydroxide Solutions with 3,5‐di‐tert‐Butylphenol in Isopar®L Modified with Exxal®8

“…At high sodium loading, the volume of 1-octanol organic phase volume expanded, [6] and in some cases, the loaded solvent gelled. [7] Aliphatic hydrocarbon diluents are usually preferred for industrial solvent extraction processes. However, they entail trade-offs, such as poor solvation of the ionic species leading to very weak extraction, particularly of the alkali metal ions.…”