Insight into the adsorption isotherms and kinetics of Pb (II) on pellet biochar via in-situ non-destructive 3D visualization using micro-computed tomography

Abstract

The micro-CT technique was applied in adsorption visualization of Pb (II) on the pellet biochar derived from wheat straw to provide information on understanding the complex heavy metal-biochar interaction during the process. The 3D distribution of Pb (II) on the biochar was well in line with the results of isothermal and kinetic adsorption experiments as well as those of simulation with Langmuir and Weber-Morris intraparticle diffusion (IPD) models. It was shown that Pb (II) was preferentially adsorbed on the surface of the biochar at an initial Pb (II) concentration of 50 mg/L. However, at a higher initial concentration of 100 mg/L, the adsorption process occurred in a two-stage regime, namely rapid surface adsorption followed by slow intraparticle diffusion. This research offered a new way for investigation of the complex adsorption behavior of heavy metals on biochar, as well as construction and optimization of related adsorption models.

Keywords: Adsorption behavior; Heavy metal adsorption; Normalized in-situ 3D characterization; Wheat straw biochar; micro-CT.