Effects of lamellar reconstruction routes in the release of molybdate encapsulated in Mg–Al layered double hydroxides

• Lamellar reconstruction effect in the release of MO4−2MO4−2 in Layered Double Hydroxides.
• Choosing the reconstruction route allows to modulate the liberation of MO4−2MO4−2 by LDH.
• Reconstruction of LDH with terephtalate leads to slower MO4−2MO4−2 release than glycerol.

Effects of lamellar reconstruction methods in the release of molybdate ions encapsulated in Layered Double Hydroxides (LDH) are evaluated. The methodology consisted of two stages: i) treatment of LDHs and interlayer substitution with molybdate; ii) characterization of morphology and kinetics of molybdate release in chloride solution and deionized water. Commercial hydrotalcite (HT) was calcined and then reconstructed in water (HTCCa), terephthalic acid (HTCTe), glycerol (HTCGl) and in molybdate solution (HTCMo). XRD showed that lamellar reconstruction succeeded only with HTCCa, HTCTe and HTCGl. Afterwards, substitution of interlamellar anions by molybdate was done. Molybdate release over time, monitored by ion chromatography, was higher in chloride solution suggesting ion exchange. Increasing temperature to 85 °C doubled the molybdate released by HTCTe-Mo, accelerating the kinetic process compared with room temperature. The kinetics release was different for each LDH doped with molybdate. Gradual liberation of molybdate characterizes HTCTe-Mo while HTCGl-Mo promotes quick release. Therefore by the choice of reconstruction routes it is possible to modulate the liberation of molybdate by LDH.

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