Mechano-chemical effects on surface properties and molybdate exchange on hydrotalcite

The effects of mechano-chemical treatment on the surface characteristics and sorption properties of hydrotalcite were studied. Non-milled (crushed) and milled samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis and specific area. A milling time of 2 h decreased the particle size of the hydrotalcite samples from 21 to 8.0 nm, the specific area from 97 to 5.7 m (super 2) g (super -1) and the total pore volume from 0.41 to 0.01 cm (super 3) . After the crushed and milled samples had been separately calcined at 500 degrees C, they were agitated with 10 (super -2) M Na (sub 2) MoO (sub 4) aqueous solutions for 48 h. The molybdate ion content in the regenerated non-milled hydrotalcite samples (HT (sub c) -MoO (sub 4) ) was found to be 6.0 meq g (super -1) while in the milled hydrotalcite (HT (sub m) -MoO (sub 4) ) samples this content was 2.5 meq g (super -1) . The lower molybdate content was thought to be a result of compaction and, hence, reduced reactivity of the milled HT samples.