Investigating triple superphosphate for lead removal from aqueous solutions

Abstract

The aim of this research is to investigate monocalcium phosphate monohydrate [Ca(H₂PO₄)_2. H₂O] also called triple superphosphate (TSP) for the removal of lead (Pb) from aqueous solutions. In this study, TSP was selected amongst various phosphate-based materials and fertilizers to act as the source of orthophosphate (PO₄^3-) which is a powerful tool for metal fixation in soil and water. Thermodynamic equilibrium dissolution-precipitation relationships for the systems of Pb-H₂O and Pb-PO₄^3--H₂O were drawn with the aid of Eh-pH stability diagrams to determine the predominance areas of different species. The lead phosphate compounds, identified through the stability area diagrams, were verified with the batch precipitation tests performed with standard solutions of lead and TSP at different conditions. It was observed that, depending upon solution conditions, TSP can precipitate 99.9% of the lead from the solution. Lead precipitates, analyzed by x-ray diffraction, showed the formation of lead phosphate compounds. The mechanism of TSP for the removal of lead from aqueous solutions is discussed.

Keywords:

• Triple superphosphate
• lead removal
• precipitation
• stability
• metal ions
• Eh-pH diagram

Acknowledgment

Financial support for the present work from Dokuz Eylul University Scientific Research Projects Coordination council (BAP) with a project number 2020.KB.FEN.022 gratefully acknowledged.

Data availability statement

The data that support the findings of this study are available from the corresponding author, [M.C.S.G], upon reasonable request. Data were produced from chemical laboratory in Dokuz Eylul University, Mining Engineering Department.

Additional information

Funding

Dokuz Eylül Üniversitesi.