The aging effects of biochar and Zn²⁺ on adsorption and desorption kinetics of Pb²⁺ in a calcareous sandy soil

ABSTRACT

Adsorption and desorption rates play an important role in the availability and mobility of Lead (Pb²⁺) in soils treated with biochar. However, information is still limited about the effects of pyrolysis temperature, presence of Zn and incubation times on these processes. This study was performed to investigate the effects of 1% (w/w) walnut leaves biochars produced at different temperatures (200 °C (B200), 400 °C (B400) and 600 °C (B600)) on adsorption and desorption kinetics of Pb²⁺ in the presence of Zn²⁺ at two incubation times (30 and 90 d). Results explained that the adsorption rate of Pb²⁺ was decreased with increasing the pyrolysis temperature, whereas the desorption rate of Pb²⁺ was increased. In the presence of Zn²⁺, there was a decrease in the adsorption sites for Pb²⁺, while there was an increase in the available desorption sites for Pb²⁺. The rate of Pb²⁺ adsorption in 90 d of incubation was higher than 30 d of incubation, whereas the rate of Pb²⁺ desorption in 90 d of incubation was slower than 30 d of incubation. It can be concluded that 1% (w/w) walnut leaves biochar could not immobilize Pb²⁺ in the soil because more than 74% adsorbed Pb²⁺ desorbed in DTPA-TEA solution.

KEYWORDS:

• Competitive system
• kinetics models
• incubation time

Disclosure statement

The authors declare no conflicts of interest.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This study supported by funds allocated by the Vice President for research of Shahrekord University.