Adsorption of cadmium and lead ions by phosphoric acid-modified biochar generated from chicken feather: Selective adsorption and influence of dissolved organic matter

To improve the adsorption efficiency, a H 3 PO 4 -modified biochar (CFCP) was prepared using chicken feather and applied to Cd 2+ and Pb 2+ adsorption. The pseudo-second-order model could explain the Cd 2+ and Pb 2+ adsorption behavior. CFCP had faster adsorption rate than non-modified biochar (CFC2). The Langmuir and Freundlich isotherm could better describe the Cd 2+ and Pb 2+ adsorption, respectively. The value of q m for Cd 2+ adsorption and K F for Pb 2+ adsorption by CFCP was 7.84 mg·g −1 and 24.41 mg 1−(1/n) ·L 1/n ·g −1 , which was 1.38 and 5.41 times of the corresponding results of CFC2. Relative to Cd 2+ , Pb 2+ was selectively adsorbed by biochars in the binary metal system. Phosphate precipitation explained in part the selective adsorption of Pb 2+ . Proline, glucose, and pH (4–6) had little influence on Cd 2+ and Pb 2+ adsorption. Electrostatic interaction, precipitation, and O–H bonds were the primary adsorption mechanisms. The increased N-containing heterocycles of CFCP accounted for the increased Cd 2+ and Pb 2+ adsorption.