Fixed Bed Column Studies for the Adsorption of Cadmium onto Cockle Shell (Anadara Granosa) Powder

Recently, the pollution of heavy metal ions is getting more attention due to economic development. A number of methods have been proposed for the removal of heavy metal ions in aqueous solutions, and the adsorption technique has been widely utilized due to the effectiveness and flexibility. Cockles are marine bivalve molluscs and their shells are discharged as waste by many restaurants and marine product manufacturers, which causes environmental problems. Cockle shells can be economically reused as an adsorbent for wastewater treatment. In this report, cockle shells were recycled as a material for the removal of cadmium (II) ion by adsorption in a fixed bed column. Experiments were designed according to the Box-Behnken scheme to investigate the effect of the column parameters such as inlet ion concentration, feed flow rate, and mass of adsorbent. The breakthrough curves from experiments were analyzed with Thomas, Bohart-Adams, and Yoon-Nelson models. The results also indicate that the powder derived from cockle shells can be used as a low cost and effective adsorbent for heavy metal removal such as cadmium in a fixed bed column. The observation suggests that the Thomas model and the Yoon-Nelson model are more suitable to predict the adsorption of cadmium (II) ions on onto cockle shell powder in fixed-bed operation mode.