Selective Uptake of Phosphate Ions on Nanocomposite of ZrO_2 and Layered Double Hydroxide

摘要

We synthesized novel nanocomposites (Zr-MgAl) of ZrO_2 and layered doublernhydroxide of MgII and AlIII, by adding a mixed solution of MgCl_2, FeCl_3, and ZrOCl_2 torndistilled water, adjusting a constant pH value of 10 with another mixed solution of 1MrnNa_2CO_3 and 1M NaOH. The content of Zr in the Zr-MgAl was varied over 1-20 wt%.rnThe Zr-MgAl exhibited only a poorly crystalline structure assigned to layered doublernhydroxide (LDH) from X-ray diffraction, with a decrease in strength with increasing thernZr content. XAFS characterization indicated that the Zr phase of the Zr-MgAl is almostrnidentical with amorphous ZrO_2, with a similar local structure around Zr to cubic ZrO_2.rnThe uptake of phosphate ions from P-enriched seawater (0.33 ppm-P) is stronglyrndependent on the Zr content, showing a maximal value of 18 mg-P/g at the Zr content ofrn14 wt%. The composite with a Zr content of 10-20 wt% exhibited a much greaterrnuptake of phosphate ions than amorphous ZrO_2 and binary Mg-Al LDH. This interestingrnselectivity toward phosphate ions is probably due to a composite structure ofrnnanoparticles of amorphous ZrO_2 with poorly crystalline Mg-Al LDH.