Abstract

The presence of cadmium (Cd) in aquatic systems can cause a serious risk to aquatic organisms and human health. In this study, biochar (BC) was prepared from blueberry pruning waste and activated via chemical (BCchem), biological (BCbio), and biochemical (BCbiochem) processes. BCchem corresponded to BC activated with polystyrene (PS) plastics, BCbio was a BC activated with vermicompost, and BCbiochem was a BC activated with PS plastics and vermicompost. The adsorbents were evaluated for the removal of cadmium (Cd2+) from aqueous systems. Surface characterization of the BCs was conducted using scanning electron microscopy coupled with energy- dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and BET-specific surface area (SBET) analyses. Different factors affecting Cd2+ adsorption by BCs, such as application dose, initial pH, adsorption time (adsorption kinetics), initial Cd2+ concentration (adsorption isotherms), and desorption studies were undertaken using batch systems. Characterization revealed that BCbiochem (64.2 m2 g-1) had a higher SBET than BC (6.2 m2 g-1), BCbio (16.7 m2 g-1), and BCchem (53.0 m2 g-1). The Elovich kinetic model described (r2 ≥ 0.927 and χ2 ≤ 0.17) the Cd2+ adsorption data better than the pseudo-second- order and pseudo-first-order kinetic models for all BC samples. The Langmuir model (r2 ≥ 0.98 and χ2 ≤ 0.10) fitted the Cd2+ adsorption isotherms well for the BCs, indicating that the Cd2+ adsorption occurred through a monolayer formation on a homogeneous surface. The BCbiochem showed the maximum Cd2+ adsorption capacity of 4.13 mg g-1, which was nearly double that of other BCs. After four desorption cycles, the BCbio retained 1.05, 1.24, and 1.91 times higher Cd2+ than BCbiochem, BCchem, and BC, respectively. This study demonstrated that BCbiochem was a highly efficient and economical alternative to conventional adsorbents for removing Cd2+ from aqueous systems.