Fabrication of phosphorus doping porous carbon derived from bagasse for highly-efficient removal of La3+ ions via capacitive deionization

Heteroatom doping is an effective method to improve the electrochemical properties of carbon materials. In this work, the bagasse-based phosphorus-doped porous carbon (PC-90 0) was prepared by phytic acid as activator and phosphorus dopant under hydrothermal conditions, which is evaluated for removal of La3+ in water via capacitive deionization (CDI) technology. The influence of working voltage and initial concentration of La3+ solution on the CDI process were analyzed. The results show that the activation of phytic acid promotes the formation of the well-developed microporous and mesoporous composite structure, and successfully achieved P-doping of porous carbon, which is essential for improving the electrosorption performance of La3+. The adsorption value is as high as 88.89 mg g(-1) at the optimal working voltage of 1.8 V, which is 86% higher than that of un-doped carbon. Furthermore, PC-900 has also excellent selective behavior for La3+ in the La3+/Na3+ and La3+/Ca2+ co-existence system, and the selection rate can reach 94.08% and 90.98%. The analysis of electrochemistry and capacitance contribution theory shows that PC-90 0 has pseudocapacitance and ideal electric double layers (EDLs) behavior. P-doping is conductive to enhance EDLs adsorption and introduce Faraday adsorption active sites such as C-P-O, C-P = O and P-O-P. Under the coordination and electrostatic attraction of these active sites, PC-900 exhibits excellent electrosorption capacity. Driven by the electric field, La3+ can not only enter the pore structure of PC-900 to form EDLs, but also form P2-O-(La3+) and La-O-P with surface groups through Faraday reaction. Phosphorus-doped porous carbon shows broad prospects for separation of rare earths in the application of CDI technology. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Heteroatom doping, specifically phosphorus doping, has been demonstrated to enhance the electrochemical properties of carbon materials. In this study, a bagasse-based phosphorus-doped porous carbon material (PC-900) was synthesized using phytic acid as an activator and phosphorus dopant under hydrothermal conditions. The PC-900 material showed high adsorption capacity for La3+ ions in water through capacitive deionization (CDI) technology. The activation of phytic acid promoted the formation of a well-developed microporous and mesoporous composite structure, which contributed to the improved electrosorption performance of La3+. The PC-900 material also exhibited excellent selectivity for La3+ ions in the presence of Na3+ and Ca2+. The electrochemical analysis confirmed the presence of pseudocapacitance and ideal electric double layers behavior in PC-900. The phosphorus doping facilitated the enhancement of electric-double-layer adsorption and the introduction of active sites for Faraday adsorption. The PC-900 material showed great potential for separating rare earth ions in CDI applications.