Comparison of adsorption properties for cadmium removal from aqueous solution by Enteromorpha prolifera biochar...

Using biochar to remove heavy metals from water is environmentally beneficial. In this study, three kinds of chemical reagents, including ZnCl₂, H₃PO₄ and KMnO₄, were introduced to modify the biochar derived from Enteromorpha prolifera. The performance of these modified biochar in removing Cadmium ions (Cd(II)) from water was investigated. The physicochemical properties of activated biochars were characterized by N₂-sorption, thermal gravity and differential thermal gravity (TG/DTG), scanning electron microscopy (SEM), elemental analysis and Fourier transform infrared spectroscopy (FTIR). The results showed that the removal rate of Cd(II) from water by EP biochar modified with H₃PO₄ was significantly increased, and the maximum adsorption capacity of Cd(II) reached to 423 mg/g for PBC. Moreover, the adsorption of Cd(II) from water by phosphoric acid modified biochar was very fast, and the saturation adsorption of Cd(II) was reached within 1 h. Compared with pseudo first-order model, pseudo secondary-order model was much more suitable for analyzing the adsorption kinetics data of Cd(II) onto KBC or ZBC. The adsorption of Cd(II) onto PBC was analyzed by the intra-particle diffusion kinetic model, where the value of R² was high as 0.98. The Langmuir model was fit for phosphoric acid modified biochar.