Pili (Canarium ovatum Engl.) nut shell activated carbon: Surface modification, characterization and application for carbon dioxide capture

• Main Author: Yao, Marina Gaviola
• Format: text
• Language: English
• Published: Animo Repository 2012
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/4112
• Institution: De La Salle University

Activated carbon, derived traditionally from wood, is an important material for industrial adsorption. To maintain ecological balance, new sources of activated carbon for environmental applications are desired. This study explores the Pili (Canarium ovatum Engl.) nut shell, which is a waste material in Pili food processing, as a potential source of activated carbon. The fixed carbon content of charred Pili nut shell was determined to be high (86.81%) making it an ideal carbon precursor for the production of activated carbon. Nitrogen sorption analysis of the Pili nut shell activated chemically by NaOH showed high surface area (SBET = 817 m2/g) and large pore volume (VDR = 0.54 cm3/g) compared to the unactivated Pili nut shell. To enhance the adsorption capacity for CO2 capture application, the surface of the activated carbon was modified through acid-base treatment. Treatment with 10M nitric acid resulted to incorporation of carboxylic acid moieties (0.71 mmol/g) as determined by Boehm titration. Further treatment with SOCl2 followed by wet impregnation with different amines (triethylenetetramine, pentaethylenehexamine and polyethyleneimine) resulted to amine-terminated moieties on the surface with the formation of amide group as shown in IR spectra. Low surface areas and total pore volumes (PSAC-NP=85.60m2/g, 0.10cm3/g, PSAC-NT=362.0m2/g, 0.29 cm3/g, and PSC-NT=2.630m2/g, 0.01 cm3/g) and dramatic change in morphology (from uniform geometric shape to spongy microstructures) were observed via nitrogen sorption analysis and scanning electron microscopy, respectively. XRD patterns of PSAC samples showed a turbostatic structure, vii intermediate structures between graphite and amorphous state. PSAC-NT and PSAC-NP gave slight decrease in interlayer spacing (d(002)) values resulting to a small crystallites that may promote high CO2 adsorption. PSAC-NP having a low surface area of 85.60m2/g and narrower micropore volume of 0.212cm3/g gave the highest CO2 adsorption as determined in CO2 sorption analysis. The CO2 capture mechanism in the amine-treated activated carbon from Pili nut shell is proposed to operate via chemisorptions compared to the conventional physisorption, due to the observed low surface area and narrower pore volume.