Intercalation of Gastropod Shell Derived Calcium Oxide in Clay and Application in Phosphate Removal from Aqua Medium

The phosphate sorption potential of the layered framework of naturally occurring clay, which acts as a host in the sorption process, was boosted via intercalation of CaO derived from a Gastropod shell (GS). GS was used as precursor for the synthesis of the CaO in the perspective of waste recycling and cost minimization in environmental remediation. The phosphate sorption potential, PZC, and the surface area of raw clay sample were substantially enhanced by the intercalation process. The value of the Langmuir monolayer sorption capacity (<i>q</i>_m mg/g) increased from 49.02 to 71.43, PZC values increased from 4.70 to 7.20, and the surface area (m²/g) value increased from 23 to 103 after the intercalation process. The modification caused no change in the clay surficial microstructure but increased the lattice spacing of the clay framework. Increase in phosphate solution pH triggered monotonical reduction in the magnitude of phosphate sorbed while increase in phosphate solution ionic strength and concentration of anionic interferences caused an increase in the amount of phosphate sorbed per gram of sorbent. Phosphate sorption caused no change in the surficial microstructure of either sorbents but the crystallinity of the sorbent was considerably impacted, especially in the raw sampl