Synthesis and characterization of porous carbon from biomass using KOH and K2CO3 chemical activation

Abstract

Synthesis of activated carbon (AC) from agricultural waste is a research area that has gained high interest recently because of its double-faced potential in dealing with disposal challenges and also in converting such waste to useful products. Activated carbons were prepared from oil palm shell by chemical activation using both KOH and K2CO3 as chemical activants. The precursor was first carbonized at a temperature of 800°C under a nitrogen flow of 150cm3/min for 2 hours at 10°C/min.It was then impregnated with KOH or K2CO3 in the ratio 1:2. The mixture of both KOH or K2CO3 impregnated material were then loaded at different times into the reactor for subsequent heating. It was then pre-heated to a temperature of 800°C for 1 hour in the presence of nitrogen gas. The carbonized sample was then activated by heat treatment under the CO2 flow of 150cm3/min at 800°C for 1hr. Nitrogen adsorption analysis from BET surface area and pore volume were studied. The BET surface area and pore volume of the potassium hydroxide treated (PHAC) and potassium carbonate treated (PCAC) carbons were (305 m2/g and 0.16 cm3/g) and (708 m2/g and 0.31 cm3/g), respectively. The proximate analysis shows a high percentage of fixed carbon and low ash content which is an indication of good precursor for AC production. The FTIR spectra of both carbons showed hydroxyls, alkenes, alkynes, carbonyls and aromatics functional groups. The SEM micrographs showed that both carbons developed pores that are good enough for adsorption of contaminants. However, the results indicate that choice of chemical activant and other activation parameters enable tailoring the porosity of the carbons for a particular environment application.