Using cocoa (Theobroma cacao) shell-based activated carbon to remove 4-nitrophenol from aqueous solution: Kinetics and equilibrium studies

The cocoa shell (CS) flake was ground, sieved and pressed into pellets. The pellets were carbonized at 800 °C and subjected to activation at 850 °C under a flow of CO2 for several activation burn off. The cocoa shell-based activated carbon (CSAC) showed moderate surface area (248 m2 g−1), a low mesoporosity ratio with a pore size in the range between 2 and 4 nm. CSAC also displays the presence of aliphatic, aromatic hydrocarbons, CO and a near absence of C–O. CSAC was evaluated for its ability to adsorb 4-nitrophenol (4-NP). The adsorption time and initial dye concentration study on adsorption performance was carried out in a batch system. The results indicate that the Freundlich, Temkin and Langmuir isotherms fit well (R2 > 0.9). The results from the kinetic study show that 4-NP adsorption follows pseudo-second-order and Boyd models.

► An activated carbon was produced from cocoa (Theobroma cacao) shell (CS).
► The raw CS was grinded, formed into pellets, carbonized to form carbon monolith and activated with CO2.
► The products had well developed porosity with significant amount of mesopore.
► The products showed adsorption activity towards 4-NP (167.17 mg g−1) and comparable with others activated carbon.