Physicochemical properties of activated carbons produced from coffee waste and empty fruit bunch by chemical activation method

Abstract

In this study, coffee waste (CW) and empty fruit bunches (EFB) were employed as precursors for the production of activated carbons by a chemical activation method. KOH, ZnCl2, and H3PO4 were used as activating agents along with their three mixing ratios of 1:0, 1:1, 1:3, w/w, and carbonization temperatures of 600◦C, 700◦C, and 800◦C were used to prepare these activated carbons. The highest yields of produced activated carbons were observed at 600◦C with a value of 45.20% for coffee waste and 48.20% for empty fruit bunch, with a 1:3 w/w (H3PO4 ) ratio. However, the maximum specific surface area was 3068 m2 g−1, and 2147 m2 g−1 obtained at 800◦C for coffee waste and empty fruit bunch activated carbons, respectively. The surface features of these products exhibited acute morphological changes, as were clearly noticed via SEM studies. Moreover, in the Van Krevelen diagram, it was also observed that both the H/C and O/C ratios were dramatically decreased to 0.0019 and 0.0759, and 0.0066 and 0.1659 for coffee waste and empty fruit bunch at 800◦C with a (1:3) potassium hydroxide and zinc chloride ratio, respectively, and this similar phenomenon was also supported by a thermal gravimetric analysis. All these results, together with the specific characteristics of the products, suggest that this scheme can be an effective strategy for the activated carbon production from such residues.