Optimised Process to Produce Calcium Acetate from Waste Blue Mussel Shells and its Use as a De-icer

The preparation of calcium acetate from mussel (Mytilus edulis) shells and acetic acid was optimised via design of experiments. The solid product was identified as the monohydrate via powder X-ray diffraction, IR spectroscopy and Thermogravimetric analysis. Comparisons were made to optical grade calcite in place of the bio-sourced calcium carbonate for the synthesis. An exploratory central composite design compared the yield of calcium acetate with respect to shell material used (shells dried in air at room temperature, dried at 220 °C or calcined), concentration of acetic acid, and time. The yield of Ca(CH₃COO)₂·H₂O was optimized further using heated, crushed shells using a custom optimal design. A maximum yield of 93% was reached after 32 h using 9% v/v CH₃COOH or an 85% yield using food-grade white vinegar after 24 h. De-icing experiments showed that Ca(CH₃COO)₂·H₂O produced from waste blue mussel shells melted 6 wt.% of ice at a concentration of 30% (m/v). For comparison, 11 wt.% defrosted using CaCl2 30% (m/v) and 13 wt.% defrosted using NaCl 30% (m/v).