Development of high-performance CO2 adsorbents from urea-modified Leucaena leucocephala hydrochar

This study explores the development of urea-functionalized hydrochar from Leucaena leucocephala wood (LW) for CO2 capture. Hydrochar was produced via hydrothermal carbonization at 170 degrees C for 90 min and subsequently functionalized with urea. The effects of urea: hydrochar ratio (1:1 to 3:1), activation temperature (400-800 degrees C), and heating rate (5-15 degrees C/min) on CO2 adsorption capacity were investigated. Optimal conditions (2:1 urea: hydrochar ratio, 600 degrees C activation temperature, 5 degrees C/min heating rate) increased CO2 adsorption capacity from 13.09 mg/g to 76.20 mg/g. The modified adsorbent demonstrated high affinity towards CO2 over N-2, CH4, and O-2, and maintained performance over 11 adsorption-desorption cycles. Kinetic studies revealed physisorption as the primary adsorption mechanism. In fixed-bed column tests, best performing conditions within the tested ranges (30 ml/min flow rate, 15% CO2 concentration, 30 degrees C) yielded a CO2 uptake of 195.54 mg/g. This study demonstrates the potential of urea-functionalized hydrochar from Leucaena leucocephala as an efficient, sustainable adsorbent for CO2 capture.