A Review: Coffee and Tea Potential Materials for Carboneous Material Synthesis

Coffee and tea are classified as the biomass due to their characteristic lignocellulosic main content, including lignin, cellulose, and hemicellulose. However, their each most content is cellulose and lignin, respectively. Both coffee and tea have been used for preparation of biochar, activated carbon, and CNM/CNS. Biochar and activated carbon (AC) has different chemically structure, especially related to oxy groups and hydrocarbon aliphatic chain. CNM can has same or different crystal structure with activated carbon depend on the preparation way. As the adsorbent, activated carbon had higher average specific surface area (11x) and higher average pore volume (6X) than biochar. In other side, it had higher average specific surface area (4X) but same average pore volume compared to CNT. Using 3 different activators (H3PO4, KOH, CO2), hydrothermal pyrolysis produced the activated carbon which had 86X higher specific surface than without activator. In other side, it gave 6X higher specific surface area than slow pyrolysis method with those 3 activators. For the same metal cation adsorbate (Cu2+), each maximum adsorption ratio of AC to biochar, AC to CNT, and NaOCl-modified CNT to AC was about 2.4. For 4 different metal cations (Cu2+, Ni2+, Pb2+, Cd2+), the average maximum adsorption ratio of the functionalized CNT to AC was about 3.2.