Synthesis of Gypsum Utilizing Waste Eggshell

Background: Eggs being a nutrition rich source of food is used in large quantities resulting in eggshell generated as waste in abundance globally every year. Although these shells have found some uses like catalysts, calcium supplements still is mostly sent to landfills.
Scope and approach: Gypsum is used mainly in construction as well as insulation works. Gypsum is either mined or synthesized from Cao using sulfuric acid. Eggshells being rich in CaCo₃ (approx. 95% w/w) gives an excellent opportunity for gypsum synthesis from them giving double fold advantage of reduction of landfill requirement as well as synthesis of gypsum.
Result and conclusion: Dilute sulphuric acid was used to treat washed and dried eggshells directly as well as calcined shells. Calcination and then neutralization yielded 89% calcium sulphate compared to direct neutralization using eggshell. The reaction order was found to be of first order.