Process optimization of K2C2O4-activated carbon from Prosopis africana seed hulls using response surface methodology

• Activated carbon was produced from PASH by physicochemical activation.
• Potassium oxalate, nitrogen gas and carbon (IV) oxide were used for the activation.
• Response surface methodology was used to optimize preparation conditions.
• Optimum activated carbon resulted into good yield and desirable 4CG removal.

Potassium oxalate was used as an activating agent for the preparation of activated carbons using Prosopic africana seed hulls (PASH) as a newly discovered precursor. The preparation conditions were optimized by using central composite design (CCD), a subset of response surface methodology (RSM) to maximize the activated carbon yield as well as percentage removal of 4-chloroguaiacol (4CG). The activated carbon was produced at the optimum conditions of 780 °C activation temperature, 63 min activation time and 3.19 IR resulting in 91.65% of 4CG removal and 21.43% yield. The experimental values obtained were in good agreement with the values predicted from the models with relatively small errors. The activated carbon prepared under optimum conditions was mesoporous with BET surface area, Langmuir surface area, total pore volume and the pore size of 1095.56 m2/g, 1205.70 m2/g, 0.50 cm3/g and 3.08 nm respectively. Scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX) were used to investigate the obtained optimal activated carbon. The results revealed that PASH could be recommended as a promising effective precursor for producing activated carbons with excellently developed pores, good yield and potentially desirable 4CG percentage removal.