Preparation and phosphate ion-exchange properties of a hydrotalcite-like compound

Abstract

A Cl'-intercalated hydrotalcite-like compound (HTAL) was prepared by neutralizing magnesium and aluminum chlorides with sodium hydroxide. The HTALs were characterized by chemical analyses, X-ray diffraction (XRD), differential thermal (DTA)/thermogravimetry (TG) analyses, and scanning electron microscopic (SEM) observation. The HTAL crystal with a single unit cell, aa = b0 = 0.31 and c0 = 2.33 nm as the lattice constant, was formed by aging at 353 K. The crystal growth proceeded for all three axes a, b, and c up to 5 h of aging, while the stacking along the c axis was preferentially observed by aging beyond 5 h. Phosphate ion-exchange properties of HTAL were investigated by a batch method. The HTAL obtained by longer aging time showed a slightly larger phosphate uptake, owing to better crystallization of the hydrotalcite structure. The pH dependence of the phosphate ion exchange showed that phosphate uptake has a maximum around pH 7. Chemical analyses of HTALs before and after the phosphate loading showed that phosphate ions are mostly ion-exchanged with interlayer Cl' ions, and the composition of phosphate ions in the solid phase is similar to that in the solution phase. The isotherm for phosphate uptake followed the Langmuir equation at pH 7.53 and 310 K; it gave an ion-exchange capacity of 2.37 mmol of P/g for phosphate.

Phosphate adsorption from sewage sludge filtrate using zinc–aluminum layered double hydroxides

“…Due to the high charge density of the sheets from M 2+ substitution by M 3+ and the exchangeability of the interlayer anions as well, LDHs have been employed in several studies for removing phosphate in different environment, such as phosphate solutions [13,[17][18][19], drain effluent [20] and seawater [21].…”

On the Existence of Hydrotalcite-Like Phases in the Absence of Trivalent Cations

“…The various minerals referred to above differ from each other in the identity of the metals M and M , or the A anions involved. In view of the possible application of LDHs as catalysts (10), anion exchangers (11), precursors to oxides (12), and electrodes for alkaline secondary cells (13), there has been considerable interest in the synthesis of these minerals by chemical routes that involve precipitation (14), hydrothermal (15), or electrochemical reactions (16).…”

“…On the other hand, the a parameter (3.102 A s for HT) shows little change. The presence of anions in the interlayer region confers unique anion-exchange properties to LDHs (11).…”

Continuous Treatment of Bisphenol A and Diethyl Phthalate Solutions Using Dodecylsulfate-Intercalated Mg-Al Layered Double Hydroxide Particles Packed in Column

“…Mg-Al LDH is known to function as an effective anion exchanger in the removal of phosphate. [4][5][6] The uptake of phenols, anionic surfactants, and colored organics from aqueous solutions has also been examined. [7][8][9][10][11] Based on the anion exchange characteristics of Mg-Al LDH to intercalate various types of organic and inorganic anions in interlayers, we have carried out a series of experiments to develop organic-inorganic composite materials by intercalation of organic anions having functional groups in their structure into the interlayers of Mg-Al LDH.…”