Low-temperature hydrothermal carbonization of activated carbon microsphere derived from microcrystalline cellulose as carbon dioxide (CO2) adsorbent

Activated carbon material produced by the low-temperature hydrothermal processes was needed to further decrease the production cost of CO2 adsorbent materials. In this study, we fabricated cellulose hydrochar microspheres (CHM) materials with a relatively low hydrothermal temperature (200 °C) with prolonged hydrothermal reaction time (48 h) using microcrystalline cellulose as a feedstock. The CHM is then further activated using a thermal and chemical agent. The activated carbon microsphere was then characterized using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), and Fourier transforms infrared (FTIR) spectroscopy. The Brunauer–Emmett–Teller (BET) surface area (SBET) of the thermal activation (ACS) activated carbon was enhanced significantly with further chemical activation with KOH and NaOH, from 589 m2/g to 1334 m2/g and 2296 m2/g, respectively. Moreover, CHONS elemental analysis suggests that the chemical activation process enhances the surface functional group. Increasing textural properties and enrichment of the functional group of the ACS-NaOH and ACS-KOH samples gave a CO2 adsorption capacity up to 7.07 mmol/g after 300 min of contact. This finding enables the possibility of producing cellulose hydrochar microspheres using a low hydrothermal temperature that can be further activated to become CO2 adsorbent materials with great CO2 capture capabilities.