A Comparative Study of Chemically Enhanced Crustacean Shell Carbons for Sustainable Adsorbent Development in Polycyclic Aromatic Hydrocarbon (PAH) Sequestration

The study aims to develop enhanced adsorbent Polycyclic Aromatic Hydrocarbon (PAH) Sequestration using crustacean shell carbons. Activated carbon was produced from periwinkle shells, clam shells, whelk shells, and a 1:1 composite of clam and whelk shells through carbonization at 450 °C under limited oxygen, followed by chemical activation with H₂SO₄ at 750 °C and KOH at 650 °C. This process resulted in eight adsorbents: Periwinkle Shell Acid-Activated Carbon (PSAAC), Periwinkle Shell Base- Activated Carbon (PSBAC), Clam Shell Acid-Activated Carbon (CSAAC), Clam Shell Base- Activated Carbon (CSBAC), Whelk Shell Acid-Activated Carbon (WSAAC), Whelk Shell Base- Activated Carbon (WSBAC), Clam-Whelk Shell Acid-Activated Carbon (CWSAAC), and Clam- Whelk Shell Base-Activated Carbon (CWSBAC). Characterization using Fourier Transform Infrared Spectroscopy (FTIR) and physicochemical analysis showed that CSBAC had the highest surface area (1288 m²/g) and bulk density (0.687 g/cm³). Batch adsorption experiments were conducted to evaluate the influence of adsorbent dosage and contact time on Polycyclic Aromatic Hydrocarbon (PAH) removal from contaminated water samples. CSBAC exhibited the highest removal efficiency, reaching 98.94% at a 1 g dosage with an adsorption capacity of 2.315 mg/g. Adsorption isotherms were analyzed using Langmuir, Freundlich, Henry, Elovich, and Janovich models. The Freundlich and Langmuir models best described adsorption for PSAAC, PSBAC, CSAAC, CSBAC, CWSAAC, and CWSBAC, with PSBAC achieving the highest Langmuir monolayer adsorption capacity (31.688 mg/g). In contrast, the Henry isotherm best represented PAH adsorption for WSAAC and WSBAC. Comparative analysis of acid and base-activated carbon indicated no statistical difference between acid and base activation on removal efficiency of PAH.