Beneficiation of low-grade Uranium ore from the Atomic Energy Commission (Mark-‘MM’)

Abstract

A low grade uraniferous quartzite received for investigation, contained apatite, magnetite and an opaque black, feebly magnetic mineral all of which were radioactive. The principal gangue minerals present were quartz, hornblende, biotite and tourmaline. Traces of torbernite, autunite, rutherfordite and epidote were also present. The sample assayed 0.033 percent U3O8 equivalent (radiometric) and gave 21.0 counts/ gram/hour. The sample assayed percent 1.49 percent P2O5 (i.e. roughly 3.4 percent apatite).Magnetic separation of the -10+20 mesh and -20 mesh fractions of the ore, under a strong field gave an overall recovery in the magnetic product of 55.08 percent in terms of counts with a grade of 37.9 counts/gm/ hr. The finer fraction, however, yielded a higher grade of concentrate viz., 60.4 counts/gm/hr. Tabling of the sample ground to -35 mesh yielded a concentrate consisting mostly of magnetic minerals and giving 55.9 counts with a recovery of 26.8 percent in terms of counts. After magnetic separation, this table concentrate yielded a magnetic concentrate giving 87.1 counts /gm/hr with a recovery of 18.7 percent in terms of counts. Straight soap flotation with two cleaning operations yielded the highest grade of apatite concentrate assaying 30.91 percent P2O5 with a grade of 134.6 counts/gm/hr assaying 0.135 percent U3O8 equivalent (radiometric). But the loss in the tailings was high; this was due to the presence in it of magnetic minerals and slime which do not float readily. The slime gave about 80 counts/ gm/hr and assayed 0.11 percent U3O8 equivalent (radiometric).Magnetic separation prior to floatation, followed by desliming of the flotation feed, and floatation to concentrate the apatite were found to be essential for obtaining a high recovery of the radioactive minerals. This yielded (i) a magnetic concentrate giving 93.5 counts/gm/hr and assaying 0.096 percent U3O8 equivalent (radiometric) with a recovery of 21.5 percent in terms of counts,(ii)a slime giving 45.0 counts/gm/hr and assaying 0.078 percent U3O8 equivalent (radiometric) with recovery of 10.0 percent in terms of counts, (iii) a floatation concentrate giving 123.1 counts/gm/hr and assaying 0.134 percent U3O8 (radiometric)after two cleanings with a recovery of34.1 percent in terms of counts,(iv)cleaner tailing giving 36.3 counts/gm/hr with a recovery of 29.8 percent in terms of counts and (v)a primary floatation tailing very low in counts the loss due to this tailing being 4.6 percent in terms of counts. When the product (iv) is returned to the floatation circuit as will be the case in practice, a further recovery of about 25 percent could be expected in the cleaner concentrate, maintaining the same grade viz. ,0.134 percent U3O8, resulting in an overall recovery of about 90 percent when the products (i)and (ii) are also mixed, in which case the will be lowered to0.111 percent U3O8 equivalent (radiometric).