Optimisation and Surface Morphological Analysis Of Activated Carbon from Agricultural Waste Products

Abstract

Many conventional or agricultural by-products and wastes go unused in Ghana. These wastes find their way into our water bodies and also sometimes become breeding grounds for mosquitoes and other insect pest causing diseases leading to severe health problems. These wastes sometimes are used as fillers in pot-holes which inadvertently blocks drainages during rainfall thereby leading to flooding in flood prone areas. The precursors used in this study to produce activated carbon were palm kernel shell and coconut shell. The produced activated carbon was activated chemically using three different activating agents, acid (H3PO4), base (NaOH) and a salt (CaCl2). The maximum yield of activated carbon, 26.3 g (PKS) and 22.9 g (CS), using H3PO4 as an activating agent were obtained at 400 oC, 1 h carbonisation time and an impregnation ratio of 1.2. Similarly, maximum yield of activated carbon, 22.4 g (PKS) and 17.3 g (CS), using NaOH as an activating agent was also obtained at 500 oC, 2.5 h and impregnation ratio of 1.2. Using CaCl2 as activating agent, the maximum yield of activated carbon were 25.5 g (PKS) and 20.8 g (CS), these maximum values corresponded to 400 oC, 1 h carbonisation time and an impregnation ratio of 1.2. The H3PO4 activated carbons were fairly better in the areas of ash content (7.17 %), moisture content (1.94 %), bulk density (0.65 g/cm3), pore volume (0.94 ml/g), iodine adsorption (743.02 mg/g) and porosity (0.49). On the other hand, the NaOH activated carbon was also advantageous in terms of carbon content (57.78 %). CaCl2 activated carbons, were also commendable in terms of volatile matter (30.46 %) and electrical conductivity (2130 μS/cm). Scanning Electron Microscopy (SEM) technique was employed to observe the surface physical morphology of the coconut shell and palm kernel shell activated carbons. Prior to chemical activation the surface morphology of the raw coconut shell compared to the palm kernel shell at a magnification of ×5000 did not show porous surface, while the external surfaces of the chemically activated carbon were rich with cavities.