Uptake properties of phosphate on a novel Zr-modified MgFe-LDH(CO3)

We prepare(d) a novel Zr-modified MgFe-LDH(CO3) composite by adding a mixed solution of MgCl2, FeCl3, and ZrOCl2 and another mixed solution of 1 mol/dm(3) NaOH and 1 mol/dm(3) Na2CO3 to distilled water at a constant pH of 10. The composite exhibited only a poorly crystalline structure, resembling that of layered double hydroxides (LDH) from X-ray diffraction. The phosphate uptake is dependent on pH, decreasing with an increase in pH. This composite shows a much greater uptake of phosphate ions in P-enriched seawater (0.33 mg-P/dm(3)) than amorphous zirconium oxide and MgFe-LDH(CO3). The uptake isotherm was fitted with a Freundlich relation. These phosphate-uptake behaviors closely resemble those of the relevant Zr-MgAl-LDH, which is estimated to be a composite of MgAl-LDH with amorphous zirconium hydroxide on the surface from X-ray absorption spectroscopy. Therefore, a similar structure of Zr-modified MgFe-LDH(CO3) composite probably causes the marked increase in phosphate uptake from P-enriched seawater. (C) 2010 Elsevier Inc. All rights reserved.