ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Walnut shells-derived activated carbon for utilization in the removal of heavy metal ions

Wahran M. Saod, Abdulsalam M. Aljumialy, Nahla Hilal, Mohammed Faiad Naief, and May Fahmi Abdulrahman

Department of Chemistry, College of Science, University of Anbar, Ramadi, Iraq

E-mail: abdulsalam.mohammed@uofallujah.edu.iq

Received: 6 December 2025  Accepted: 12 March 2026

Abstract:

Activated carbon derived from walnut shells as a precursor has the potential to be an economically attractive product for the adsorption of heavy metals (HMs) from aqueous solutions. Activated carbons were prepared from walnut shells using ZnCl₂ as the activating agent. The walnut shells were soaked in a 20% ZnCl₂ solution and then carbonised in a furnace at 550 °C for 2 h. The prepared activated carbon was characterized using Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The prepared activated carbon was employed as an adsorbent to evaluate its effectiveness in adsorbing heavy metal ions (Zn(II), and Ni(II)) from standard aqueous solutions. The adsorption process was investigated under various influencing parameters (contact time, pH of the solution, initial concentration of HMs, and dosage of AC) to determine the optimal conditions for the removal of heavy metal ions. The optimal adsorption conditions were found to be: pH = 6, contact time = 60 min, temperature = 298 K, initial metal ion concentration = 100 mg/L, and adsorbent mass = 0.01 g. The adsorption of heavy metal ions on the AC fits well with the Langmuir isotherm model, suggesting monolayer adsorption. The maximum adsorption capacities (q_max) for Zn(II), and Ni(II) were 40.16 and 39.21 mg/g, respectively. The results indicate that the pseudo-second-order model is more suitable for describing the adsorption kinetics, indicating chemical interactions between the heavy metal ions and activated carbon.

Keywords: Walnut shells; Adsorption; Activated carbon; Heavy metal

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04809-2

Chemical Papers 80 (6) 6973–6983 (2026)