Figure 1. Kinetics and isotherms of Zn²⁺ sorption on different biochars.

(a) Kinetics of Zn²⁺ sorption on raw biochars (the initial concentration of Zn was 150 mg L⁻¹; the solution pHs were ranged from 6.5 to 7.5 (see Fig. S3) without adjustment; (b) kinetics of Zn²⁺ sorption on de-ashed biochars (the initial concentration of Zn was 50 mg L⁻¹; the solution pHs were controlled to 7.0); (c) isotherms of Zn²⁺ sorption on raw biochars (the solution pHs were not adjusted); (d) isotherms of Zn²⁺ sorption on de-ashed biochars (the solution pHs were controlled to 7.0). Error bars represent ± SE (SE is the standard error of estimate). The experiments were conducted in duplicate (n = 2).