Abstract
There are several purposes for investigating hydrotalcite clays and one of them is due to its importance as an anionic adsorbent and ion exchanger, which make them capable of removing various pollutants from water. The most common hydrotalcite structure is based on double lamellar hydroxide of magnesium and aluminum, containing carbonate anions in the interlayer space. However, it is common to investigate the co-substitution of aluminum with other trivalent cations, especially transition metal cations, due to their binding properties. In this work, it was investigate the co-substitution of chromium (III) and aluminum in a sample of magnesium-aluminum carbonated hydrotalcite, comparing it with the same composition without this co-substitution. Thermal stability, crystallinity and morphology were investigated, showing that chromium contributes to the adsorptive capacity at low temperature.
Highlights
Hydrotalcite clay minerals are a class of anionic clays formed by Layered Double Hydroxide (LDH) with adsorbent properties and have compositions given by the general formula: M+2(1-x)M+3x(OH-)2(A-n)x/n.yH2O, where M+2 and M+3 are metallic cations with reduced ionic rays and A-n are interlayer anions (Belloto et al, 1996).The three-dimensional structure formed in hydrotalcites comes from the perpendicular interposition of lamellae, anchored by divalent or trivalent interlayer anions
It was investigating the co-substitution of chromium (III) and aluminum in a sample of magnesium-aluminum carbonated hydrotalcite, comparing it with the same composition without this co-substitution
The hydrotalcite possesses structure similar to Mg(OH)2 brucite, characterized by the Layered Double Hydroxide (LDH), but the magnesium can be partially replaced by other divalent cations, such as Zn+2, Ca+2, Ni+2, Cu+2, Mn+2, and Co+2
Summary
Hydrotalcite clay minerals are a class of anionic clays formed by Layered Double Hydroxide (LDH) with adsorbent properties and have compositions given by the general formula: M+2(1-x)M+3x(OH-)2(A-n)x/n.yH2O, where M+2 and M+3 are metallic cations with reduced ionic rays and A-n are interlayer anions (Belloto et al, 1996). The three-dimensional structure formed in hydrotalcites comes from the perpendicular interposition of lamellae, anchored by divalent or trivalent interlayer anions. The most common interlayer anion is carbonate CO3-2, due to the greater affinity with cations of alkaline earth metals, such as the magnesium one. The hydrotalcite possesses structure similar to Mg(OH) brucite, characterized by the Layered Double Hydroxide (LDH), but the magnesium can be partially replaced by other divalent cations, such as Zn+2, Ca+2, Ni+2, Cu+2, Mn+2, and Co+2. The more structurally stables compositions possesses partial substitution with trivalent cations, such as Sc+3, Al+3, Fe+3, and Cr+3 (Cavani et al, 1991, Crepaldi e Valim, 1998)
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