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F.), nonhalogenated, low-odor, aliphatic, either linear or branched, with a carbon number of 8-16, most preferably 9-13, or mixtures thereof. Specific examples are given in Table 3. 

Suitable diluents can be water-immiscible aliphatic, aro› matic solvents or blends of such solvents. Most preferred are solvents that are classified nonflammable (flash point> 140° F.), nonhalogenated, low-odor aliphatic, aromatic, or a blend of aliphatic and aromatic solvents. The aliphatic diluent(s) can be linear but are preferably branched. The aromatic diluent(s) can be unsubstituted aromatic liquids but are 5 

preferably aliphatically-substituted aromatic liquid com› pounds. Extractant mixtures suitable for the invention con› tain at least 25% diluent (v/v), preferably 60% (v/v), and most preferably 85% (v/v). Specific examples of suitable diluents are shown in Table 3. 

For a further embodiment of the invention suitable reagents for stripping of metal ions, regeneration, solute concentration, and/or pH adjustment include mineral acids that do not cause decomposition of the extractant. Suitable strip acids are preferably selected from hydrochloric, sulfu› ric, phosphoric, blends of these and the like. Acid strength 

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1s 2-50% in the feed solution and the S2M mixture 1s preferably maintained at -pH 1-2 or less. Sl mixer pH is preferably maintained at pH 2-4, or less. Sulfate ions are subsequently stripped by basic reagents that do not cause decomposition of the extractant preferably selected from alkali and alkali metal hydroxides, and/or alkali carbonates. Base strength for sulfate ion stripping is preferably -pH 10-11 or greater. Specific examples of suitable of reagents for stripping and regenerating, and pH adjustment of the extractant are listed elsewhere herein. 

Referring to Table 3, effective "Type extractant phase" extract compounds of the invention. All of the components of the E-phase are oil soluble with a total carbon number of at least eight (8), can be charged or neutral, and can have additional functional groups such a halogens, ether linkages, ester linkages, alkyl phenolic, and the like, so long as the extraction chemistry and the oil solubility of the reagent is not adversely effected relative to the descriptions herein. 

Effective extractant compounds of the invention are all oil soluble with a total carbon number of at least eight (8), but preferably about 16, and most preferably about 25 or more, 

