Potentials of emergent plant residue derived biochar to be alternative carbon-based phosphorus fertilizer by Fe(II)/Fe(III) magnetic modification
Hongjuan Xin, Jiao Yang, Yuanyuan Lu, Hekang Xiao, Haitao Wang, Kamel Mohamed Eltohamy, Xueqi Zhu, Chunlong Liu, Yunying Fang, Ye Ye, Xinqiang Liang
Abstract
Abstract Emergent plants have been remarkably effective in reducing phosphorus (P) discharge from ecological ditches; however, the treatment and recycling of these residues is a great challenge. In this study, magnetic biochars (MB s , i.e., MB- A , MB- C , and MB- T ) were fabricated from three emergent plant residues ( Acorus calamus L., Canna indica L., and Thalia dealbata Fraser, respectively) and modified with Fe(II)/Fe(III). Scanning electron microscopy-energy dispersive spectroscopy and X-ray diffraction spectra confirmed the successful loading of Fe 3 O 4 and FeO(OH) onto the surfaces of the MB s . Batch adsorption experiments showed that MB s exhibited a higher P adsorption capacity than that of the raw biochars. Within the range of 0.8–43.0 mg L −1 in solution, the adsorption capacities of P by MB- A , MB- C , and MB- T were 304.6–5658.8, 314.9–6845.6, and 292.8–5590.0 mg kg −1 , with adsorption efficiencies of 95.2–32.9%, 98.4–39.8%, and 91.5–32.5%, respectively. The primary mechanisms that caused P to adsorb onto the MB s were inner-sphere complexation and electrostatic attraction. Low pH conditions were more beneficial for the P adsorption of the MB s , while co-existing anions had a negative impact with the following order: HCO 3 − > SO 4 2− > Cl − ≈NO 3 − . The P-31 nuclear magnetic resonance results further demonstrated that the main adsorbed P species on the MB s was orthophosphate, followed by orthophosphate monoesters and DNA. Overall, MB s offer a resource utilization strategy for emergent plant residues and P-laden MB s are promising alternative P fertilizers. Graphical Abstract