Synthesis and Characterization of Activated Carbon Prepared from Pomegranate Peel for Efficient Adsorptive Removal of a Cationic Dye

Abstract

The accumulation of cationic textile dyes in natural waters is still a stubborn environmental problem, and low-cost adsorbents obtained from food waste continue to attract attention as a practical remedy. In the present work, activated carbon was prepared from pomegranate (Punica granatum) peel — an abundant agro-industrial residue — by chemical activation with KOH followed by carbonisation at 600 °C, and was then examined as an adsorbent for the removal of the cationic dye Basic Blue 41 (BB41) from aqueous solution. The textural and chemical features of the prepared carbon (denoted PPAC) were probed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM); the analyses together described an amorphous, highly porous material (Sʙᴇᴛ = 875 m² g⁻¹, Vp = 0.52 cm³ g⁻¹, Dp = 2.8 nm) carrying oxygen-containing surface groups. Batch experiments evaluated the effect of solution pH (2–10), adsorbent dosage (0.5–3.0 g L⁻¹), contact time (0–180 min), initial dye concentration (25–200 mg L⁻¹) and temperature (298–328 K). The highest uptake was recorded at pH 8, where the dye removal reached 96.8 %. Kinetic data were better represented by the pseudo-second-order model (R² = 0.9985), which points to chemisorption as the rate-controlling step, while the equilibrium results were well described by the Langmuir isotherm with a monolayer capacity of 285.7 mg g⁻¹. The thermodynamic parameters indicated a spontaneous (ΔG° = −3.55 to −6.41 kJ mol⁻¹) and endothermic process (ΔH° = +24.85 kJ mol⁻¹; ΔS° = +95.3 J mol⁻¹ K⁻¹). Overall, the findings suggest that pomegranate-peel activated carbon is a cheap, effective and environmentally sound adsorbent for BB41-bearing effluents, and that valorising this waste offers a sensible route towards cleaner water treatment.