Assessing the Potential of Chemically Activated Crustacean Shells for Persistent Organic Pollutants Removal in Contaminated Water

Activated Carbon Samples were produced from periwinkle shells, clamshells, whelk shells, and a 1:1 composite of clam/whelk shells at a carbonization temperature of 450 °C under limited-oxygen conditions and then activated using KOH at an activation temperature of 650 °C. This produced Periwinkle, clam, whelk, and clam/whelk composite base activated carbons noted PSBAC, CSBAC, WSBAC, and CWSBAC respectively. The properties of these adsorbents were characterized by scanning electron microscopy energy dispersive X-ray analysis (SEM-EDX), Fourier Transform Infrared spectrometry (FTIR), and physicochemical analysis. The examination indicated that CSBAC had the highest surface area at 1288 m2/g. The effect of the activated carbon dosages and contact times on the adsorption of PAHs was studied in batch adsorption experiments at a temperature of 25oC and pH of 6. The results indicated that CSBAC had the highest removal efficiency at 1g of 98.94%. The adsorption of PAHs was modeled using Langmuir, Freundlich, Henry, Elovich, and Janovich isotherms. The Freundlich and Langmuir models described the sorption equilibrium data for PSBAC, CSBAC, and CWSBAC with PSBAC having a Langmuir maximum monolayer adsorption capacity of 31.688mg/g. Henry Isotherm best described the sorption equilibrium data for WSBAC. Kinetic studies indicated that the adsorption processes of PAHs agreed well with a pseudo-second-order kinetic model. This study demonstrated that modified Crustacean shells are excellent low-cost alternatives for removing PAHs from contaminated water.