Dados do Trabalho

Título

SYNTHESIS OF CALCIUM CARBONATE FROM EGGSHELL

Introdução

Chicken eggshells, a waste product primarily used in agriculture to amend acidic soils, have significant potential for recovery. Composed mainly of calcium carbonate (CaCO3), eggshells can be utilized in construction, paper, and rubber industries, as well as in plastics, paints, pharmaceuticals, and cosmetics. Based on this context, this research aimed to synthesize calcium carbonate from eggshells to prevent waste disposal.

Material e Métodos

To this end, firstly, the white and red hen's eggshells, previously cleaned and ground (127 mesh sieve), were characterized for the presence and quantity of Ca2+ and CaCO3. Calcium carbonate was synthesized from red eggshells using the carbonation method: i) the shells were calcined at 850ºC to produce lime; ii) the lime was dissolved in water at 30ºC; iii) the resulting solution was reacted with CO2. After precipitation, the CaCO3 was vacuum filtered and dried at 110ºC for 1.5 hours. Both shells and synthesized CaCO3 were analyzed for thermogravimetric decomposition (thermobalance model STA 8000, Perkin Elmer) from 25 to 1000ºC and structure by scanning electron microscopy (SEM) using EVO LS15 (Zeiss) equipment.

Resultados e Discussão

The results showed a calcium content of 74 ± 1% for red eggshells and 66 ± 6% for white eggshells (p > 0.05), with both samples containing 96.5% CaCO3. From the reactions carried out, very satisfactory yields of 87 to 94% were obtained. When compared to a commercial sample, the synthesized CaCO3 was more soluble in water and thermally decomposed at 751ºC, about 10°C lower than the commercial carbonate. SEM analysis revealed that both the synthesized and commercial CaCO3 had the same vaterite-type structure.

Conclusão

These findings suggest that calcium carbonate synthesized from eggshells could potentially replace commercial CaCO3, offering a more sustainable production method. This approach not only enhances the utility of eggshells but also supports better waste management practices.