Lignin-derived Porous and Microcrystalline Carbon for Flow-Electrode Capacitive Deionization

Capacitive deionization (CDI) is an emerging desalination technique with full potential to produce freshwater from brackish and sea water. To fulfill such potential, it is of great importance to prepare carbonaceous electrode with high desalination performance and low cost, and using environmental-friendly raw materials. Herein, we prepared a porous carbon by KOH activation of alkali lignin which is a by-product and organic pollutant of the pulp industry. It was shown lignin is a good carbon source due to a high carbon yield over 30%, yet a relatively high degree of graphitization can be obtained at 800 degrees C. The KOH-activated carbon exhibited a specific capacitance of 123.9 F g(-1) in a 1 M NaCl at 1 A g(-1), and a salt adsorption capacity of 11.4 mg g(-1) at a voltage of 1.4 V. Furthermore, the as-prepared carbon was dispersed into water and assembled into a flow-electrode CDI system, which displayed a salt removal rate of 0.00025 mmol cm(-2) min(-1) at a low voltage of 1.4 V and low concentration of feed solution. These results suggest porous carbons with high capacitive performance can be produced from lignin, which would extend the utilization of this organic pollutant.

Automated summary

Porous carbon prepared by KOH activation of alkali lignin exhibits high specific capacitance and salt adsorption capacity, making it suitable for use in capacitive deionization systems to effectively remove salt from solutions.