Evaluation of extractant-coated ferromagnetic microparticles for the recovery of hazardous metals from waste solution

A magnetically assisted chemical separation (MACS) process developed at Argonne National Laboratory is a compact method for the extraction of transuranic (TRU) metals from, and volume reduction of, Liquid waste streams that exist at many DOE sites. The MACS process utilized the selectivity afforded by solvent extractant/ion-exchange materials in conjunction with magnetic separation to provide a more efficient chemical separation. Recently, the principle of the MACS process has been extended to the evaluation of acidic organophosphorus extractants for hazardous metal recovery from waste solutions. Moreover, process scale-up design issues were addressed in respect to particle filtration and recovery. Two acidic organophosphorus compounds have been investigated for hazardous metal recovery, bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex(R) 272) and bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex(R) 301). These extractants coated onto magnetic microparticles demonstrated superior recovery of hazardous metals from solution as compared with data from solvent extraction experiments. The results illustrate the possibility for diverse applications of this technology far dilute waste streams. Preliminary process scale-up experiments with a high-gradient magnetic separator at Oak Ridge National Laboratory revealed the potential for very low microparticle loss rates.