Box-Behnken Design Optimization of Eco-Friendly Walnut Shell-Derived Activated Carbon for Enhanced Paracetamol Adsorption

Mariem Ouled Mohamed (Applied Thermodynamic Laboratory, National School of Engineers of Gabès (ENIG), University of Gabes, 6072, Zrig)
Leila Khalfa (Applied Thermodynamic Laboratory, National School of Engineers of Gabès (ENIG), University of Gabes, 6072, Zrig||Tunisia National School of Engineers of Gafsa (ENIGA), University of Gafsa, 2112)
Noureddine Hamdi (Higher Institute of Water Sciences and Techniques, University of Gabes, 6072, Zrig, Tunisia, Laboratory of Composite Materials and Clay Minerals, National Center for Research in Material Sciences (CNRSM), 8020, Soliman, Bordj Cedria)
Walid Maherzi (Department of Civil Engineering and Environmental, IMT Lille Douai, EA 4515 - 10 LGCgE, University of Lille, F-59000 Lille)
Mohamed Bagane (Applied Thermodynamic Laboratory, National School of Engineers of Gabès (ENIG), University of Gabes, 6072, Zrig)

Bulletin of Chemical Reaction Engineering & Catalysis
2027: BCREC Volume 22 Issue 1 Year 2027 (April 2027) (Issue in Progress)

In this work, a low-cost activated carbon derived from walnut shells (WSAC) was developed through pyrolysis coupled with chemical activation using ZnCl₂. The preparation process was statistically optimized using the Box–Behnken design (BBD) to assess the influence of impregnation ratio, carbonization time, and carbonization temperature on the textural properties of the material. The optimal conditions, predicted by Design Expert, corresponded to a carbonization temperature of 450 °C, a carbonization time of 90 min, and an impregnation ratio of 1:1 (w/w). Under these conditions, the WSAC achieved a high specific surface area of 873 m²/g and a total pore volume of 0.490 cm³/g, indicating a predominantly mesoporous structure. The physico-chemical properties of WSAC, including thermogravimetric analysis, crystalline structure, morphology, functional groups, and surface area, were investigated using various techniques such as TGA-DTG, SEM, XRD, FTIR, pHZPC, and BET analysis. The adsorption behavior of paracetamol (PCT) from aqueous solution was systematically evaluated as a model pharmaceutical contaminant. The effects of solution pH, temperature, initial concentration, and adsorbent dosage were investigated. The adsorption data were best described by the Langmuir isotherm, with a maximum monolayer adsorption capacity of 62.06 mg.g-1, while the kinetic results followed a pseudo-second-order model (R2 = 0.999). It was found that the adsorption mechanism involves hydrogen bonding and phi–phi interactions. Thermodynamic parameters revealed that the adsorption process is spontaneous and exothermic. These results show that WSACs can be an efficient adsorbent for the removal of PCT or other pharmaceutical pollutants from water. Copyright © 2027 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).