Abstract
Carbonized sorbents were prepared from walnut and pistachio shells and comprehensively characterized using optical microscopy, SEM, FTIR spectroscopy, BET surface area analysis, and EDAX. The sorbents were evaluated for phenol removal from aqueous solutions under varying conditions, including particle size, pH, carbonization temperature (500–900 °C), and contact time. SEM analysis revealed the formation of porous structures, with needle-like particles observed on pistachio carbon surfaces at high magnification. FTIR confirmed the decomposition of cellulose, hemicellulose, and lignin after carbonization, with a simultaneous increase in aromatic C=C bonds. EDAX analysis demonstrated significant enrichment of carbon and persistence of mineral inclusions (K, Si, Ca), potentially influencing surface activity. Adsorption experiments showed that walnut shell sorbents exhibited higher phenol removal efficiency (R%) than pistachio shell sorbents. Maximum removal was observed at acidic pH (3–5), smaller particle sizes, and carbonization temperature at 800 °C. The results confirm that walnut and pistachio shells can serve as effective precursors for carbon sorbents, with walnut shell carbon showing superior performance for phenol removal.