An Efficient Phosphorus Scavenging from Aqueous Solution using Magnesiothermally Modified Bio-Calcite.

Abstract

The excessive discharge of phosphorus (P) from sewage treatment plants and runoff from agricultural fields is causing a rapid contamination of water resources worldwide. Several materials have been evaluated for the removal of excess P from waste supplies, but designing a cost-effective and environmental friendly substrate is essential for the efficient P removal. In this study, bio-calcite (BC) derived from waste hen eggshell was subjected to thermal treatments (CBC). The BC and CBC further modified via magnesiothermal treatments to produced MBC and MCBC, respectively, and evaluated as a novel green sorbent for P removal from aqueous solutions. The removal efficiency of P from aqueous solutions by the modified bio-calcite materials were investigated in the batch experiments. Modified bio-calcite exhibited improved structural and chemical properties, such as porosity, surface area, thermal stability, mineralogy and functional groups, than pristine material. Langmuir and Freundlich models well described the P sorption onto both thermally and magnesiothermally sorbents, respectively, suggesting mono and multi-layer sorption of P onto these sorbents. Langmuir predicted highest P sorption capacities were in order of: MCBC (43.33 mg g(-1)) > MBC (35.63 mg g(-1)) > CBC (34.38 mg g(-1)) > BC (30.68 mg g(-1)). The MBC and MCBC removed 100% of P from aqueous up to 50 mg P L(-1), which reduced to 35.43% and 39.96%, respectively, when P concentration was increased up to 1000 mg L(-1). Dynamics of P sorption was well explained by the pseudo-second order rate equation, with the highest sorption rate of 4.32 mg g(-1) min(-1) for the MCBC. Hydroxylapatite [Ca10(PO4)6(OH)2] and brushite [CaH(PO4).2H2O] were detected after P sorption onto the modified sorbents by X-ray diffraction analysis, suggesting chemisorption as the operating sorption mechanism. This study suggested that magnesiothermally modified bio-calcite may be used as an efficient sorbent and promising technology for removal of excessive P from water bodies.