Ultra-efficient adsorption of diclofenac sodium on fish-scale biochar functionalized with H3PO4 via synergistic mechanisms
Jia Xie, Minghua Liu, Miao He, Yifan Liu, Jian Li, Fangxia Yu, Yuancai Lv, Chunxiang Lin, Xiaoxia Ye
Abstract
Developing safe and efficient diclofenac sodium (DS) removal technology has become a critical issue. This study synthesized the fish-scale biochar by co-pyrolysis of fish scale and phosphoric acid (H 3 PO 4 ). In addition to increasing the specific surface area and pore volume of fish-scale biochar, H 3 PO 4 assisted in the formation of Graphitic N and sp 2 C, as well as reacting with C═O groups to form a significant number of phosphorus-containing groups. All these functional groups could act as major active sites for DS adsorption. Adsorption data could well fit pseudo-second-order and Langmuir models. The maximum adsorption capacity of FSB 600-15 for DS was 967.1 mg g −1 , which was much better than that reported in the literature. Under the synergistic effect of various mechanisms (pore-filling effect, electrostatic attraction, H-bonding, π-π, and n-π electron donor-acceptor interactions), the DS ultra-efficient adsorption on FSB 600-15 was realized. Meanwhile, the DS adsorption by FSB 600-15 was an endothermic, spontaneous, and entropy-increasing process. Furthermore, the DS adsorption capacity was more than 426.5 mg g −1 in the actual water, which was sufficient for practical applications.