Comparison of the Adsorption and Inactivation of Soil Cadmium by Two Biochars Derived from Mulberry and Cinnamon Branches

Objective  The study was conducted to explore the remediation effects of biochars derived from mulberry and cinnamon branches on cadmium(Cd) pollution in water and soil environments, with a view to providing a theoretical basis for the resource utilization of woody agroforestry wastes and the remediation of Cd-contaminated environment.

Method  Both mulberry and cinnamon branches were slowly pyrolyzed under 400℃ for 2 h. The obtained biochars were tested for their isothermal adsorption of Cd, and then added into the Cd contaminated soil grown with Brassica chinensis L. in a pot experiment.

Result  Adsorption of Cd b y either mulberry biochar (MB400) or cinnamon biochar (CB400) could be fitted by Langmuir isothermal equation, and the maximum adsorption capacities (Q⁰) were 4 305.61 mg/kg and 442.77 mg/kg, respectively. It was obvious that MB400 had much higher capacity for adsorption of Cd than that of CB400 treatment, which may be attributed to its higher values in pH, ash and CEC and available phosphorus(AP). Furthermore, MB400 addition significantly reduced the content of available cadmium(AvCd) while it showed little effect under CB400 treatment. The dry matter of B. chinensis L. was remarkably enhanced by adding both biochars. The bioconcentration factor(BCF) of Cd decreased from 5.95 in the control to 4.29 (MB400) and 4.85 (CB400).

Conclusion  Both biochars had high adsorption capacity for Cd, and could inactivate Cd availability and thereafter inhibited Cd accumulation in cabbage tissue. MB400 showed better effect than CB400.