Evaluation of Layered Double Hydroxide Synthesised from a Green Biogenic Precursor for Phosphate Removal: Characterisations and Isotherms

Abstract

CaCr LDH materials were synthesized by the co-precipitation method, using Gastropod shell as a biogenic source of Ca2+. The mineralogical, surficial morphology and elemental composition analysis of the materials showed characteristics typical of hydrotalcite-like materials, composed of Ca, Cr, O, C and Cl. Batch equilibrium adsorption studies showed that phosphate sorption on the LDH reached equilibrium within 5 min with about 98% removal. The sorption of phosphate was well described by the Langmuir isotherm model. The monolayer adsorption capacity of the CaCr LDH for phosphate was 142.86 mg/g. Mechanistic studies of phosphate removal by the LDHs was elucidated via instrumental analysis, vis-a viz, SEM-EDX, XRD and FTIR. Results revealed that phosphate was removed via the combination of ion exchange and precipitation. It could be inferred that CaCr LDH synthesised using Gastropod shell as a biogenic source of Ca2+ is a suitable adsorbent for phosphate removal from aqua system.