Synthesis of gypsum fertilizer from waste eggshells for a sustainable environment

Abstract

In this research, waste eggshells were used as the source of calcium to synthesize valuable gypsum fertilizer. Three different routes were used to synthesis gypsum, namely (i) direct synthesis from raw eggshells; (ii) synthesis from calcium oxide as obtained after calcination of eggshell; and (iii) synthesis after production of calcium hydroxide from calcium oxide. Several batches from the three routes produced very similar results and the products were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric and energy dispersive X-ray (EDX) analyses. A set of test procedures such as free water calculation, combined water measurement, pH, and conductivity estimation were performed in addition to the highly sophisticated characterization techniques. A few properties of gypsum were compared in aqueous medium and soil extraction. Different crystallographic parameters such as lattice parameters, crystallite size, dislocation density, microstrain, and growth preference were computed from the XRD data.