SELECTIVE EXTRACTION OF RARE-EARTH ELEMENTS FROM ROCKS USING A HIGH-CAPACITY CIS-1,4-BUTANEDIOIC ACID-FUNCTIONALIZED RESIN

A high-capacity carboxylic acid functionalized resin prepared by ring- opening metathesis polymerization containing cis-1,4-butanedioic acid (succinic acid) units was used for the extraction of rare-earth elemen ts (REEs) from rock digests. Extraction efficiencies measured by means of ICP-AES were found to be in the range of 90-100% for standards con taining 5 and 500 ppb of each REE, respectively. The optimum extractio n pH was found to be between 5.3 and 5.5. Three different rock standar d reference materials (SRMs), GSR-1 granite, GSR-2 andesite and GSR-3 basalt, were digested by fusion of the corresponding rock with lithium metaborate (LiBO2) and subsequent dissolution in nitric acid. As a co nsequence of the different compositions of the three investigated SRMs , the resulting digest showed different concentrations of the REEs as well as of SiO2, Fe, Al, Mg, and Ca. The entire extraction procedure w as additionally supported by masking of the interfering metal ions usi ng 5-sulfosalicylic acid. Small amounts of methanol were added to prev ent silicate from precipitating, Following this setup, REEs occurring in the digest solutions in the range of 40 ppt to 150 ppb were retaine d selectively, with recoveries ranging for most elements from 75 to 11 0%, The high performance of the entire system is underlined by the fac t that relative standard deviations were <10% for most of the REEs.