Background and purpose: Recently, release of pollutants such as pharmaceuticals to the environment becomes one of the most important problems for soil and water. The present study was conducted to introduce walnut shell-based activated carbon (AC) as a new low-cost adsorbent for the removal of cephalexin (CFX) antibiotic from aqueous solutions.

Materials and Methods: This study was conducted in laboratory scale. To investigation of the morphology of the prepared walnut shell AC and nanoparticles, scanning electron microscopy analysis was applied. The effect of the presence of Fe2O3 and SiO2 nanoparticles on the adsorption of CFX on the walnut shell AC is also studied.

Results: The maximum removal efficiency (RE) was obtained 98.4% at 100 mg/L initial CFX concentration and decreased to 72.9% with increasing in the initial CFX concentration to 200 mg/L. The results showed that the presence of nanoparticles in the optimum increased the RE of CFX by about 2.1 and 6.5% for Fe2O3 and SiO2 nanoparticles, respectively.

Conclusion: Results suggest the potential of using the walnut shell AC as an adsorbent for effective treatment of pharmaceutical-contaminated wastewaters.