Rare earth elements (REE) are present at low concentrations (hundreds of ppm) in phosphoric acid solutions produced by the leaching of phosphate ores by sulfuric acid. The strongly acidic and complexing nature of this medium, as well as the presence of metallic impurities (including iron and uranium), require the development of a particularly cost effective process for the selective recovery of REE. Compared to the classical but costly solvent extraction, liquid-solid extraction using commercial chelating ion exchange resins could be an interesting alternative. Among the different resins tested in this paper (Tulsion CH-93, Purolite S940, Amberlite IRC-747, Lewatit TP-260, Lewatit VP OC 1026, Monophos, Diphonix,) the aminophosphonic IRC-747, and aminomethylphosphonic TP-260 are the most promising. Both of them present similar performances in terms of maximum sorption capacity estimated to be 1.8 meq/g dry resin and in adsorption kinetics, which appears to be best explained by a moving boundary model controlled by particle diffusion.

A flowsheet for a novel GANEX (Grouped ActiNide EXtraction) process has been tested in a spiked flowsheet trial in a 32 stage plutonium-active centrifugal contactor rig with a simulant feed that contained 10 g/L plutonium as well as some fission products and other transuranic actinides. The solvent system used was a combination of 0.2 mol/L N,N,N’,N’-tetraoctyl diglycolamide (TODGA) and 0.5 mol/L N,N‘-(dimethyl-N,N‘-dioctylhexylethoxy-malonamide (DMDOHEMA) in a kerosene diluent that co-extracted actinides and lanthanides. Actinides were subsequently selectively co-stripped away from the lanthanides using a sulphonated and, therefore, hydrophilic bis-triazinyl pyridine (BTP) complexant in conjunction with acetohydroxamic acid (AHA). Plutonium and americium recoveries were high with decontamination factors across the strip contactors of ~14,000 and ~390 respectively. However, approximately 30 % of neptunium was lost to the aqueous raffinate which was due to a large recycle within the first extract-scrub section. Some recycle of strontium was also observed but in this case it was fully directed to the raffinate stream. In the stripping section, a small fraction of europium (taken as a model lanthanide ion), ca. 7 %, was found in the actinide product stream. Modelling of selected data using the PAREX code has shown that, even with a relatively simplistic treatment, reasonable agreement between modelling and experiment can be obtained; giving confidence in the use of modelling to refine the GANEX flowsheet design prior to further testing with irradiated fast reactor fuel.JRC.E.5-Nuclear chemistr

We report first results on the development of a new system for a GANEX 2nd cycle developed by the “ACSEPT” project. A solvent system consisting of 0.2 M N,N,N’,N’-tetra-n-octyl-diglycolamide (TODGA) + 0.5 M N,N’-dimethyl-N,N’-dioctyl-2- (2-hexyloxyethyl)malonamide (DMDOHEMA) in kerosene was formulated which co-extracts TRU elements and lanthanides with high distribution ratios and allows for Pu(IV) loading up to ~40 g·L1 at 3 M HNO3. Neptunium redox chemistry and extraction in the TODGA/DMDOHEMA phase has been studied in order to identify optimum conditions for Np extraction. Further, the behaviour of non-lanthanide fission products was investigated to identify a substitute for oxalic acid (used as a Zr masking agent in DIAMEX processes where there is no Pu in the feed). 1,2-cyclohexanediaminetetraacetic acid (CDTA) efficiently suppresses the extraction of Zr and also masks Pd which would otherwise be co-extracted.JRC.E.5-Nuclear chemistr