A Starting Point on Recycling Land and Sea Snail Shell Wastes to Manufacture Quicklime, Milk of Lime, and Hydrated Lime

The valorization of gastropod shell wastes in the production of lime is the topic of this study. First, shells from land snail and sea snail were characterized for their mineralogical, chemical, and thermal properties. Then, the shells were calcined at 1000 °C, and the obtained quicklimes were characterized for their specific surface area, pore diameter, and particle morphology, followed by evaluation of their reactivity in wet slaking tests. Comparisons were made with lime from limestone. It was found that both gastropod shell wastes were composed of aragonite as the dominant crystalline phase. The quicklime from land snail belonged to the most reactive class (R5) of the wet slaking reactivity, reaching 60 °C in about 5 min, whereas the quicklime from the sea snail belonged to the R4 class, reaching 60 °C in about 14 min. However, both were much less reactive than the lime from limestone (60 °C in 25 s). The lower reactivity of quicklime from sea snail shells compared to quicklime from land snail shells could be related to its higher sulfur content (as contaminant), lower pore diameter, and the presence of particles with rounder surfaces. The reference quicklime from limestone was more reactive, mainly due to the much higher specific surface area and lower particle size. It was concluded that the gastropod shell wastes can be used in lime manufacturing.