Ferrous chloride (FeCl 2 ) added to chromium-laden brines produced by strong base anion (SBA) exchange systems reduces hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) and precipitates the Cr(III) in a mixed chromium-iron hydroxide solid solution. A series of jar tests were conducted in which FeCl 2 was added to synthetic SBA exchange brines. The variables investigated were the initial Cr(VI) concentration, initial pH, and ferrous iron stoichiometric dose. This reduction-coagulation-flocculation (RCF) process was also tested on field brines with various compositions. The RCF process achieved >77% chromium removal efficiency at all tested conditions, except in brines with a bicarbonate matrix. Significant vanadium (V) and arsenic (As) removal (>78 and >49% removal, respectively) was observed in field brines with a chloride or sulfate matrix. Diffuse double-layer modeling suggests that adsorption to the precipitated solids was the predominant removal mechanism of V and As.
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