ABSTRACT
60Seleniferous soil collected from the wheat-grown agricultural land in Punjab (India) was characterized for pH, organic matter, moisture content, cation exchange capacity, bulk density, heavy metals and total Se concentration. Further, the Se concentration in various soil fractions was determined through two different sequential extraction procedures. The soil had a total Se content of 4.75 (±0.02) mg Se kg−1, of which 45% was observed in the oxidisable soil fraction. Both in situ and ex situ techniques were involved for Se contaminated soil remediation and process efficiency comparison. Soil flushing process was involved as an in situ technique and performed to simulate Se migration pattern in case of rainfall or irrigation. A lower Se removal efficiency with increasing layers of the soil column was observed. Also, significant migration of Se from the upper layer to the lower layers was observed during water percolation through the soil column. For ex situ treatment, the soil washing technique was optimized by varying different parameters such as treatment time, temperature, pH and liquid to solid (L:S) ratio. The soil washing extraction efficiency of Se was further evaluated in the presence of competing ions and oxidizing agents. Results showed that Se extraction from soil was significantly improved by the presence of oxidizing agents in the washing solution. Around 38% Se was removed from the soil in the presence of 0.5% KMnO4. In contrast, other parameters such as treatment time, temperature, pH, L:S ratio and competing ions showed no significant enhancement of the Se extraction efficiency.
