Chromium (VI) Sorption with Different Heavy Metals in Inceptisols

Abstract

Chromium (Cr) (VI) sorption in soils having high pH (pH > 7.0) is negligible because of the soil's negative surface charge, which aggravates the negative sorption of Cr (VI) by negative leaching phenomenon. However, the sorption of Cr (VI) is influenced by the presence of different heavy metal cations in these soils. For a better understanding of mechanisms responsible for differential sorption of Cr (VI) in soil, laboratory experiments were conducted. This study evaluated the effect of different heavy metals, viz. Pb, Cd, Ni and Zn, on Cr (VI) sorption in Inceptisols. Kinetic study revealed that cation sorption was more rapid and took place during the first hour, whereas sorption of Cr (VI) was slower. The presence of heavy metal cations in the solution matrix increased the sorption of Cr (VI) by the Inceptisols, but Cr (VI) sorption was negligible, in the range of 0—0.03 mM, in the absence of heavy metal cations. In the presence of cations, sorption of Cr (VI) was first observed at an equilibrium concentration of 0.008 mM for the Delhi (Delhi, Typic Ustochrept) soil and 0.02 mM for the Hisar (Hisar, Typic Ustochrept) soil. Based on the calculated distribution coefficient (Kd) for those metals, Pb generally exhibited the highest affinity for soil sorption. An investigation was also conducted to determine the individual effect of heavy metals on Cr (VI) sorption, and it was found that amongst the studied heavy metal cations Pb strongly influenced the sorption of Cr (VI) in soil.