Preparation and Characterization of Calcium Hydroxide from Cockle Shell Waste via Sol-Gel Method: Effect of HCl Concentration

Continuous cockle shell dumping in open areas has become a global problem which generate major environmental issues. The conversion of the wastes into value-added products is highly desirable and economic. This work aimed to investigate the influence of sol-gel processing parameter on the properties of the synthesized calcium hydroxide (Ca(OH)2). In this study, cockle shell waste was used as calcium carbonate (CaCO3) precursor in the preparation of Ca(OH)2 via sol-gel method and the processing parameter varied was hydrochloric acid (HCl) concentration (0.5, 1.0 and 2.0 M). The cockle shell based CaCO3 and the prepared Ca(OH)2 powders were characterized by X-ray diffraction (XRD), Fourier transform infra-Red (FTIR), field emission scanning electron microscopy with energy dispersive X-ray (FESEM-EDX), X-ray fluorescent (XRF) and particle size analyzer (PSA). The XRD analysis indicates that the calcium carbonate obtained from cockle shell was mainly in the form of aragonite polymorph. Upon sol-gel processing, the analysis of the sample shows the presence of portlandite and small traces of aragonite in all samples suggesting an incomplete reaction of the hydrolysis process. Ca(OH)2 powder prepared using 1M HCl yields the smallest particle size.