Fumigating fresh longan with sulfur dioxide (SO2) is commonly used in Thailand
as an effective postharvest method to controll saprophytic surface fungi and prevent
skin browning. However, SO2 residues is a problem for exportation. In this work, the
impregnated activated carbon was used to remove sulfur dioxide residue in fresh
longan. The commercial activated carbon (AC) was impregnated with alkaline
compound as potassium hydroxide (KOH) at verious concentration in the range of 0-8
wt%. The surface area of activated carbons and impregnated activated carbon were
characterized by BET. The phase formation, morphology and functional groups on the
surface of activated carbon samples were investigated by x-ray diffraction (XRD),
scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR),
respectively. The surface area analysis of activated carbons and impregnated activated
carbon was 773 m2/g and it was continuously decreased when the concentration of
KOH increased. SEM micrographs showed the agglomeration of activated carbon
powders. The functional groups of activated carbon were found in FTIR spectrum which
were there composition. The results indicated that the activated carbons and
impregnated activated carbon showed usability to be used as sulfur dioxide sorbent.
In additionally, the activated carbons without impregnation show the maximum ability
absorption SO2 residues in the fumigation fresh longan.