Characterization of acid-leaching cocoa pod husk (CPH) and its resulting activated carbon

In order to enhance the adsorption capacity of activated carbon (AC) from cocoa pod husk (CPH) and reuse the solution after the acid-leaching of CPH as a liquid fertilizer, CPH was first leached by acid and then used as a precursor (CPH-A) for preparing ACs by physical activation at a temperature range of 650–850 °C in this work. Based on the proximate analysis, mineral compositions, thermogravimetric analysis, and thermochemical properties, the differences between CPH and CPH-A were investigated. The chemical and pore properties of the resulting ACs were further studied. The results show that the pretreatment of CPH with hydrochloric acid led to removal of over 90% of the ash content in the CPH, mainly composed of potassium minerals. The Brunauer-Emmet-Teller (BET) surface area of the AC derived from CPH-A at 650 °C is 355.8 m²/g, significantly larger than that (i.e., 1.1 m²/g) of the AC derived from CPH. The higher activation temperature (e.g., 900 °C) is beneficial to the pore development of the resulting AC (e.g., BET surface area ˃ 1300 m²/g). In addition, the carbon (C) and sulfur (S) contents of the resulting ACs indicate an increasing trend as the temperature increased from 650 to 850 °C, but a decreasing trend in the hydrogen (H), nitrogen (N), and oxygen (O) contents.