Preparation of Activated Carbons from Hydrolyzed Dipterocarpus alatus Leaves: Value Added Product from Biodiesel Production Waste

A solid waste is generated in the production of biodiesel from the leaves of the Dipterocarpus alatus tree. This waste was hydrolyzed by oleaginous yeast and was employed as the precursor for preparing activated carbon by chemical activation. This work investigated the effect of types of chemical agent i.e. acid (H3PO4 and HNO3), base (KOH and NaOH) and chloride (ZnCl2 and FeCl2) on the porous properties of the resulting activated carbons. The dry leaves prior to hydrolysis were also used for comparison. The experiment was conducted as an activator to a biomass impregnation ratio of 1:2 for 1 h, followed by carbonization at 500 °C for 1 h. The raw materials and activated carbons were analysed using proximate analysis and the porous properties by using nitrogen adsorptiondesorption isotherms and thermogravimetric analysis (TGA). According to proximate analysis, fixed carbon contents of 9.27 and 16.25 dry wt% were found for the hydrolyzed material and dry leaves, respectively. This indicated that both materials served as good precursors to produce carbons. The results of porous properties show that the maximum surface area of 456 m2/g was produced using ZnCl2 activation. The prepared carbons from hydrolyzed leaves had surface areas comparable with carbons prepared from dry leaves for ZnCl2, H3PO4, HNO3 and NaOH activation. However, activation of hydrolyzed leaves with FeCl2 and KOH gave activated carbons with a lower surface area than dry leaves. Moreover, Dipterocarpus alatus leaf activated carbons had a higher surface area than several other literature examples of activated carbons. Therefore, hydrolyzed Dipterocarpus alatus leaves are a good precursor for the preparation of economical activated carbon.