Preliminary Laboratory Investigations into Zinc and Copper Adsorption by Crushed Bivalve Shells

Abstract

AbstractCrushed shells from three bivalve mollusc species (mussel, oyster and scallop) in two particle size ranges (63–150 μm and 710–1180 μm) were tested for their ability to remove dissolved copper and zinc ions from synthetic stormwater in a column. For comparison, zeolite (1–2 mm), which is commonly used for heavy metal ion capture, was also assessed. All shell types of both particle sizes were effective in removing zinc from solution with 97–100% removal efficiency which was similar to the removal efficiency by zeolite (97.6%). The removal of copper was most efficiently achieved with oyster shell with a particle size range of 710–1180 μm (83.6%), which was similar to the removal efficiency by zeolite (83.4%). Brunauear-Emmett-Teller (BET) surface area measurements showed significant decreases in the surface area of the shells after exposure to synthetic stormwater due to adsorption of heavy metals, visually confirmed by observation of a fine layer of metal precipitate adsorbed to the shell particle surfaces using Scanning Electron Microscopy (SEM). Overall, the results indicate that crushed bivalve shells have excellent potential for the removal of dissolved zinc and copper from stormwater and should be tested in more complex stormwater studies. This work has significant implications for stormwater infrastructure design using a local, cheap and readily accessible waste material.