Application of a rice husk-derived biochar in soil immobilization of iodide (I−) and iodate (IO3 −)

Purpose Radioiodine is an inevitable product of nuclear fission during nuclear fuel reprocessing and nuclear accident and finally is brought back to surface soil by fallout. Iodine is very active and mobile in soil and may adversely affect human health due to bioaccumulation through the food chain. The aim of this study was to evaluate the immobilization efficiency of biochar on the mobility of iodine (I − ) and iodate (IO 3 − ) in soil near Qinshan Nuclear Power Plant. Materials and methods Biochar was produced from a widely available agricultural waste (rice husk) at a pyrolysis temperature of 350 °C. Biochar was applied to the soil at five application rates (0, 0.33, 0.67, 1, and 1.33%). The affinities of I − and IO 3 − with soil/biochar, the mobility of I − and IO 3 − in biochar-amended soil, and effects of soil pH and ionic strength on immobilization of biochar were assessed by the standard batch sorption and desorption tests. Results and discussion Rice husk-derived biochar exhibited strong affinities for I − and IO 3 − as compared to that of soil, with immobilization ability ( K biochar / K soil ) of 936.6 and 309.9, respectively. Results showed that addition of 1% biochar to soil could significantly reduce desorption of I − and IO 3 − from soil. In addition, immobilization efficiency of biochar was not affected by soil physicochemical properties such as pH and ionic strength. Conclusions Results suggested that the easily synthesized biochar could be a promising and environmentally friendly amendment for the efficient immobilization of soil I − and IO 3 − .