Physical–chemical and microstructural study of shells of the Lucina Pectinata species

Abstract

Lucina pectinata, popularly called Lambreta, is a delicacy very consumed in Bahian cuisine. The shell is composed of nacreous layers formed by keratin, collagen, and elastin, interspersed with layers of calcium carbonate, predominantly calcite, and aragonite phases, which provides protection to the mollusk. As these shells do not readily degrade, provoking environmental imbalance due to their accumulation, this work aims to evaluate the physicochemical and microstructural properties of shells of the species L. pectinata, focusing on the reuse of the solid residue generated by the consumption of this mollusk. The shells were washed, crushed, and subjected to chemical treatment and dried. Subsequently, the physical–chemical and microstructural properties of the samples LN—in nature and LB were treated with sodium hypochlorite. The samples were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), zero load potential (pHpcz), pH determination, moisture content (%), ash content (%), specific surface area, and pore volume by the BET method, scanning electron microscopy (MEV), thermogravimetric/derivate thermogravimetry (TG/DTG), and differential thermal analysis (DTA). The results revealed that calcite and argonite phases are present in the two samples with high calcium carbonate content (95%) and that thermal decomposition occurs in the range of 575 to 810 °C, producing CaO and CO2. Treatment with sodium hypochlorite (sample LB) promoted leaching in the solid by dragging possible lamellae, which culminated in superficial erosion of solids, resulting in a better cavity and pore distribution profile on the surface, besides increasing the specific surface area in relation to sample LN.