SPECTROPHOTOMETRIC DETERMINATION OF TOTAL CHROMIUM AND HEXAVALENT CHROMIUM IN WASTE WATER FROM THE URANIUM MINING AND HYDROMETALLURGICAL MILL

Hexavalent chromium is determined by reaction with diphenylcarbazide in acid condition, producing a red violet color compound. There is a sharp absorbency at 540nm. If total chromium is to be determined, it is necessary to oxidize the Cr(Ⅲ) to Cr(Ⅵ) by potassium permanganate before reacting with diphenylcarbazide. The concentration of Ca(Ⅱ) , Mg(Ⅱ) , SO42--, NO3-, and NH4+ up to 500mg/l, and the concentration of As(Ⅴ) , Pb(Ⅱ) , Hg(Ⅱ), Al(Ⅲ) , Cu(Ⅱ) , Fe(Ⅲ) , Mn(Ⅱ) , Si(Ⅳ) and F- up to lmg/ml can be tolerated. The range of chromium from 0.02-0.200mg/ml can be determined. The precision of the method is ±5%. The recovery of added standard sample is 95-105%.