Three core/shell/shell MgAl-LDH composites using
Fe<sub>3</sub>O<sub>4</sub> microspheres as the core, a SiO<sub>2</sub> matrix
as the inner layer and a MgAl-LDH layer as the outer shell have been
synthesized for the removal and recovery of phosphate and fluoride from water
by a magnetic separation technique. The synthetic mesoporous MgAl-LDH
composites show good magnetic separability, well-defined pore distributions,
and have specific surface areas of 73 m<sup>2</sup> g<sup>−1</sup>, 168 m<sup>2</sup>
g<sup>−1</sup>, and 137 m<sup>2</sup> g<sup>−1</sup> for Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>@LDH350,
Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>@<i>m</i>LDH350,
and <a></a><a>Fe<sub>3</sub>O<sub>4</sub>@<i>m</i>SiO<sub>2</sub>@<i>m</i>LDH350</a>, respectively. The
adsorption isotherms of both phosphate and fluoride on these MgAl-LDH
composites can be well fitted with the Langmuir model. The maximum adsorption
capacities of 57.07 mg g<sup>−1</sup> and 28.51 mg g<sup>−1</sup> were obtained
on Fe<sub>3</sub>O<sub>4</sub>@<i>m</i>SiO<sub>2</sub>@<i>m</i>LDH350 for phosphate and fluoride,
respectively, much higher than those of other LDH-type materials. The adsorbed
phosphate and fluoride could be successfully recovered by NaNO<sub>3</sub>-NaOH
solution, and the regenerated MgAl-LDH composites could be reused for phosphate
and fluoride removal. Owing to their high adsorption capacities of both
phosphate and fluoride, easy magnetic separation from solution, and great
reusability, the mesoporous MgAl-LDH composites are expected to have potential
applications in removal or recovery of fluoride or phosphate from water.
Three core/shell/shell MgAl-LDH composites using
Fe<sub>3</sub>O<sub>4</sub> microspheres as the core, a SiO<sub>2</sub> matrix
as the inner layer and a MgAl-LDH layer as the outer shell have been
synthesized for the removal and recovery of phosphate and fluoride from water
by a magnetic separation technique. The synthetic mesoporous MgAl-LDH
composites show good magnetic separability, well-defined pore distributions,
and have specific surface areas of 73 m<sup>2</sup> g<sup>−1</sup>, 168 m<sup>2</sup>
g<sup>−1</sup>, and 137 m<sup>2</sup> g<sup>−1</sup> for Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>@LDH350,
Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>@<i>m</i>LDH350,
and <a></a><a>Fe<sub>3</sub>O<sub>4</sub>@<i>m</i>SiO<sub>2</sub>@<i>m</i>LDH350</a>, respectively. The
adsorption isotherms of both phosphate and fluoride on these MgAl-LDH
composites can be well fitted with the Langmuir model. The maximum adsorption
capacities of 57.07 mg g<sup>−1</sup> and 28.51 mg g<sup>−1</sup> were obtained
on Fe<sub>3</sub>O<sub>4</sub>@<i>m</i>SiO<sub>2</sub>@<i>m</i>LDH350 for phosphate and fluoride,
respectively, much higher than those of other LDH-type materials. The adsorbed
phosphate and fluoride could be successfully recovered by NaNO<sub>3</sub>-NaOH
solution, and the regenerated MgAl-LDH composites could be reused for phosphate
and fluoride removal. Owing to their high adsorption capacities of both
phosphate and fluoride, easy magnetic separation from solution, and great
reusability, the mesoporous MgAl-LDH composites are expected to have potential
applications in removal or recovery of fluoride or phosphate from water.
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