ADSORPTION OF CADMIUM FROM AQUEOUS SOLUTIONS BY POLYETHYLENE MICROPLASTICS AND BAMBOO BIOCHAR

This study investigates the capability of cadmium (Cd) sorption on polyethylene (PE) microplastics and on bamboo biochar (BB) through adsorption isotherm studies. Cadmium was prepared at different concentrations (50-4000 µg/L). For batch sorption experiments, the PE or BB was separately added in the Cd solutions under controlled conditions at laboratory scale. The model-fittings of adsorption isotherms (i.e., Langmuir and Freundlich) were performed in non-linear regression. Biochar properties including Fourier transform infrared spectroscopy, X-ray powder diffraction, X-ray fluorescence and Brunauer–Emmett–Teller surface area were analyzed. Results show that the Cd sorption by BB was in good agreement with Freundlich model, implying that Cd could be sorbed on the BB via multilayer adsorption. The sorption of Cd on PE was well-described by Langmuir model. The maximum adsorption capacity of PE was 108.6 µg/g within 24 hr, which affirms the Cd sorption at homogenous sites of PE. This study highlights that PE can act an important vector to carry microplastic-metal co-contaminant properties, which pose serious threats to aquatic lives, while BB serves as a potential adsorbent for Cd removal from water. Further studies on the PE-Cd removal by biochars could be achieved to provide suitable treatments towards microplastic-metal co-contaminants from aquatic environments.