Gastropod Shell for Phosphate Removal and Recovery via Calcium Phosphate Minerals Crystallization

Abstract

Waste biogenic Gastropod shell was used for the removal and recovery of phosphate via calcium phosphate mineral (CPM) crystallization. Removal efficiency values 99% was achieved when 2g of snail shell was used in water of phosphate concentrations that ranged between 25-1000mg/L. pH and ionic strength exhibited no influence on the removal efficiency. Concomitant removal of phosphate and organic matter revealed that phosphate removal efficiency was not impacted but the magnitude of the organics removed increased with increase in the organic load. Kinetic analysis showed that second order kinetic model gave a better description of the process. XRD analysis of the derived sludge showed the crystallinity and peaks synonymous with the presence of whitlockite, hydroxyapatite and calcium phosphate hydrate were detected. The FTIR of the sludge showed the disappearance of some naturally occurring functional groups and the appearance of phosphate peaks which confirmed the formation of CPM.