Optimization of preparation conditions for activated carbon from Brachystegia eurycoma seed hulls: A new precursor using central composite design

• Optimal activated carbon was produced from a new precursor Brachystegia eurycoma seed hulls.
• Three preparation variables were optimized with the aid of a central composite design.
• The optimal BESH-AC was mesoporous with BET surface area of 1217.52 m2/g.
• BESH-AC has maximum adsorption capacity of 370.37 mg/g.
• Optimal BESH-AC was superior than many adsorbents reported in the literature.

One of the drawbacks troubling agrarian countries like Nigeria is handling so many agricultural by-products lying as wastes thereby causing environmental contamination. Activated carbon production is a significant way of managing such waste materials which result in to waste minimization as well as massive cost saving. Physiochemical activation method was employed in this work for activated carbon production using Brachystegia eurycoma seed hulls (BESH) as new precursor materials. The preparation method involved treatment with potassium carbonate (K2CO3) as chemical activating agent. Central composite design (CCD) was applied to study the influence of activation temperature, chemical impregnation ratio (IR) and activation time on the physicochemical activation process. Based on the CCD, a quadratic model and a two-factor interaction (2FI) model were established for malachite green (MG) elimination in percentage and BESH-AC yield respectively. The prime conditions for BESH-AC production were found as 760 °C (activation temperature), IR of 1.00 and 117 min (activation time) ensuing into 91.41% of MG removal and 19.24% of BESH-AC yield. Characterization of the adsorbent revealed it to be mesoporous with large surface area attributed to intercalation of potassium ion. The equilibrium data for adsorption of MG on the optimum activated carbon were well represented by the Langmuir isotherm, giving maximum monolayer adsorption capacity as high as 370.37 mg/g at 30 °C.

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