Treatment of a vanadium-containing effluent by adsorption/coprecipitation with iron oxyhydroxide

Competitive adsorption experiments showed that vanadate is slightly more strongly adsorbed than phosphate on iron oxyhydroxide. Spent corrosion inhibitor containing vanadate (10−4 M) and phosphate (10−2 M) was treated by selectively precipitating the phosphate as apatite by addition of lime. The vanadate was then coprecipitated by addition of waste pickle liquor (FeCl2(aq)) plus further lime, with aeration to convert Fe(II) to Fe(III). Residual vanadate was <2 × 10−6 M and phosphate <1.6 × 10−4 M. Adsorption of vanadate on apatite was negligible.