The fate of char in controlling the rate of heavy metal transfer from soil to potato

In this research, the influence of the biochar produced from the gasification of poplar wood and the char obtained from the gasification of the mixture of poplar wood, grass, carton, tire and plastic at 850 °C on the control of transfer of heavy metals [lead (Pb), nickel (Ni) and cadmium (Cd)] in contaminated soil to potato was investigated. A lab-scale reactor was used to produce char. The effect of char structure on the adsorption capacity of heavy metals by potato was determined. In addition, natural zeolite, which was mainly used for the control of heavy metals adsorption from soil to plants, was tested as a reference. The results showed that biochar obtained from poplar wood could reduce the adsorption of the heavy metals up to a higher extent compared to the char produced from mixed wastes. This was because of more amorphous structure, the higher abundance of oxygen-containing functional groups and the higher amount of inorganics in the poplar wood-derived biochar, which increased the rate of physical separation, complexation and ion-exchange of the heavy metals with the biochar. In addition, our results demonstrated that natural zeolite was a suitable material to decline the adsorption of heavy metals by potato, but its effect was weaker than that of poplar wood-derived biochar. Additionally, zeolite negatively affected the growth of potato. The transfer of the metals from contaminated soil to the potato was very sensitive to the amount of char in the soil. Graphic abstract