Cadmium immobilization in contaminated soil by nano-biohar and Fe-modified nano-biochar

In the past few decades, accumulation of heavy metals in soils has increased as a result of human activities. The objective of this study was to evaluate the effect of common reed nano-biochar and Fe-modified nano-biochar on cadmium (Cd) mobility and fractionation in a Cd-contaminated soil. This study was carried out in 1399-1400 as a factorial experiment based on a completely randomized design (CRD) with two factors including absorbent type (at four levels including biochar, modified biochar, nano-biochar and modified nano-biochar), and biochar application levels (0, 0.5 and 1% w/w) in three replications under laboratory conditions. After treatments’ application, the soil samples were incubated for 90 days. At the end of incubation period, Cd availability and fractionation were measured and Cd mobility factor was determined. The results indicated that with the application of all absorbents (especially at 1% w/w level), concentration of available Cd, exchangeable and Cd bound to carbonate fraction were significantly decreased, while Cd bound to Fe-Mn oxides, Cd bound to organic matter and residue fraction of Cd significantly (P<0.05) increased. The Cd availability in modified nano-biochar treatment (1%) decreased by 26.37 % compared to the control. Results also indicated that nano-biochar had a more significant impact than raw biochar on the immobilization of Cd and decrease its mobility in the soil. In addition, modified-biochar and nano-biochar had more efficiency than raw biochars on the Cd stabilization in the soil. In general, the results revealed that common reed nano-biochar and modified nano-biochar with FeCl2 can be suitable absorbent for stabilization of Cd in contaminated soils.