Efficient degradation of chromium picolinate with simultaneous chromium removal from aqueous solutions using the Fenton process

Abstract

Chromium picolinate (Cr(pic)3) is widely used for feeding animals. Most Cr(pic)3 administered to animals is excreted without change. The land use of animal waste introduces Cr(pic)3 to the environment. Transformation of Cr(pic)3 in the environment releases hexavalent chromium (Cr(VI)), posing a chromium contamination risk. Because chromium (in trivalent valent) is complexed by picolinic acid (pic), removal of chromium in Cr(pic)3 form via direct adsorption and precipitation methods is rather difficult. Release of chromium from Cr(pic)3 first and then removal of it through the combination of adsorption and precipitation is advisable. To this end, the treatment of Cr(pic)3 using the Fenton process was first investigated in this work. Treatment parameters were optimized for Cr(pic)3 degradation and chromium removal (i.e., initial and final pH of 3.0 and 7.0, and the molar ratio of Fe(II) and H2O2 was 1:2). Adverse effects of the water constituents could be mitigated by flexible adjustment of the Fenton reagent dosages and the external addition of iron ions. The residual chromium in the aqueous phase was simultaneously lowered to the required standard, and Cr(VI) was barely detected in the aqueous phase. Mechanisms of Cr(pic)3 degradation and chromium removal were proposed by the intermediates determined. The results obtained indicate that the Fenton process is robust for degrading Cr(pic)3 and removing chromium simultaneously and is promising for treating Cr(pic)3-containing wastewater.