Adsorption and Oxidation of Thallium(I) by a Nanosized Manganese Dioxide

The adsorption and oxidation of thallium(I) by nanosized manganese dioxide (nMnO(2)) may have an impact on the removal of Tl from waters in engineered applications, as well as the fate and transport of Tl in natural waters. The fundamental data on the adsorption and oxidation of Tl(I) by nMnO(2) were obtained here. The results show that Tl was adsorbed by nMnO(2) within 15 min at pH 7.0. Moreover, Langmuir fitting indicated a maximum adsorption capacity of similar to 58.48 mg/mmol (i.e., similar to 672 mgTl/gMnO(2)). The presence of Ca2+, Mg2+, SiO3 (2-), PO4 (3-), and CO3 (2-)decreased the removal of Tl(I) to a certain extent; however, it was increased by a pH from 4.0 to 9.0. The oxidation of Tl(I) was proposed at pH 4.0 based on the observation of Mn release and nMnO(2) aggregation, while the oxidation of Tl(I) might not be favored at neutral and basic conditions. The presence of 3 mg/L humic acid hindered the adsorption of Tl(I) on nMnO(2). These results indicate that nMnO(2) could help to remove Tl from water in engineered applications and might deepen our understanding of the transport of Tl in natural waters.