Activation of blueberry pruning waste biochar for enhanced removal of cadmium from aqueous systems

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 (BC chem ), biological (BC bio ), and biochemical (BC biochem ) processes. BC chem corresponded to BC activated with polystyrene (PS) plastics, BC bio was a BC activated with vermicompost, and BC biochem was a BC activated with PS plastics and vermicompost. The adsorbents were evaluated for the removal of cadmium (Cd 2+ ) 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 (S BET ) analyses. Different factors affecting Cd 2+ adsorption by BCs, such as application dose, initial pH, adsorption time (adsorption kinetics), initial Cd 2+ concentration (adsorption isotherms), and desorption studies were undertaken using batch systems. Characterization revealed that BC biochem (64.2 m 2 g -1 ) had a higher S BET than BC (6.2 m 2 g -1 ), BC bio (16.7 m 2 g -1 ), and BC chem (53.0 m 2 g -1 ). The Elovich kinetic model described ( r 2 ≥ 0.927 and χ 2 ≤ 0.17) the Cd 2+ adsorption data better than the pseudo-second-order and pseudo-first-order kinetic models for all BC samples. The Langmuir model ( r 2 ≥ 0.98 and χ 2 ≤ 0.10) fitted the Cd 2+ adsorption isotherms well for the BCs, indicating that the Cd 2+ adsorption occurred through a monolayer formation on a homogeneous surface. The BC biochem showed the maximum Cd 2+ adsorption capacity of 4.13 mg g -1 , which was nearly double that of other BCs. After four desorption cycles, the BC bio retained 1.05, 1.24, and 1.91 times higher Cd 2+ than BC biochem , BC chem , and BC, respectively. This study demonstrated that BC biochem was a highly efficient and economical alternative to conventional adsorbents for removing Cd 2+ from aqueous systems.