Optimization of preparation conditions for activated carbon from Prosopis africana seed hulls using response surface methodology

Abstract

Optimal conditions for the preparation of Prosopis africana seed hulls-based activated carbon (PASH-AC) for removal of 4-chloro-2-methoxyphenol (4C2MP) from aqueous solution were investigated. The PASH-AC was prepared using physiochemical activation method which involved sodium acetate (CH₃COONa) treatment and carbon dioxide (CO₂) gasification. Central composite design (CCD) was used to study the effects of three preparation variables which were activation temperature, activation time, and impregnation ratio (IR) on the 4C2MP removal and Prosopis africana seed hulls (PASH)-derived activated carbon yield (PASH-AC yield). Based on the CCD, two quadratic models were developed for both PASH-AC yield and 4C2MP removal. The optimum conditions for preparing activated carbon from PASH for the removal of 4C2MP were found as follows: activation temperature of 795°C, activation time of 62 min, and IR of 2.45 showing PASH-AC yield of 20.01% and 4C2MP removal of 92.89%. The experimental results obtained agreed satisfactorily with the model predictions. The activated carbon prepared under optimum conditions was mesoporous with BET surface area of 1085.92 m²/g, total pore volume of 0.47 cm³/g, micropore volume of 0.35 cm³/g, and average pore size of 3.01 nm. The surface morphology and elemental composition of the activated carbon were determined by scanning electron microscopy and electron dispersive X-ray, respectively.

Keywords:

• Prosopis Africana seed hulls
• Activated carbon
• Central composite design
• Response surface methodology
• 4-chloro-2-methoxyphenol
• Adsorption

Acknowledgment

The authors acknowledge the financial support Universiti Sains Malaysia under Research University Grant – 1001/PKIMIA/854002 that has resulted in this article.