The Effect of Aeration on Mn(II) Sorbed to Clay Minerals and Its Impact on Cd Retention.

Manganese is a redox-sensitive element in soils and sediments that plays an important role in the retention of trace elements. Under anoxic conditions, clay minerals were shown to increase Cd retention by favoring the precipitation of Mn(II) phases. In this study, we investigated the influence of aeration on anoxically formed Mn solid phases and its impact on Cd retention in the presence of two clay minerals with low Fe contents, a natural kaolinite (KGa-1b) and a synthetic montmorillonite (Syn-1).

Surface precipitation of Mn on clay minerals enhances Cd sorption under anoxic conditions.

The influence of Mn on the sorption of metal(loid)s onto clay minerals is still unclear despite its relevance in suboxic and anoxic environments which often exhibit elevated dissolved Mn concentrations. In this study, the effects of Mn on Cd sorption to two types of clay minerals, a well-crystalline natural kaolinite (KGa-1b) and a synthetic montmorillonite (Syn-1), were investigated. Batch experiments on Mn and Cd sorption to Ca-saturated KGa-1b and Syn-1 were conducted under anoxic conditions.

Interactions of ferrous iron with clay mineral surfaces during sorption and subsequent oxidation.

In submerged soils and sediments, clay minerals are often exposed to anoxic waters containing ferrous iron (Fe2+). Here, we investigated the sorption of Fe2+ onto a synthetic montmorillonite (Syn-1) low in structural Fe (<0.05 mmol Fe per kg) under anoxic conditions and the effects of subsequent oxidation.