A method for preparing an anion adsorbent may be provided, which comprises the steps of: mixing at least two metal salts with each other, thereby forming a stack structure in which cationic compound layers and anionic compound layers containing anions and water of crystallization are alternately stacked on one another; performing a first heat treatment on the stack structure to expand between the cationic compound layers, thereby preparing a preliminary anion adsorbent; and performing a second heat treatment on the preliminary anion adsorbent to remove the anions and the water of crystallization from the anionic compound layers while allowing at least one of the anions to remain, thereby preparing the anion adsorbent.

A method for producing hydrotalcite particles includes dissolving aluminum hydroxide in an alkaline solution to prepare an aluminate solution, causing a reaction of the aluminate solution prepared in the first step with carbon dioxide to precipitate a low-crystallinity aluminum compound, causing a first-order reaction by mixing the low-crystallinity aluminum compound with a magnesium compound to prepare a reactant containing hydrotalcite nuclear particles, and causing a hydrothermal reaction of the reactant to synthesize hydrotalcite particles. The hydrotalcite particles can impart excellent heat resistance, transparency, flowability, and are useful as a resin stabilizer.

A method for producing hydrotalcite particles includes dissolving aluminum hydroxide in an alkaline solution to prepare an aluminate solution, causing a reaction of the aluminate solution prepared in the first step with carbon dioxide to precipitate a low-crystallinity aluminum compound, causing a first-order reaction by mixing the low-crystallinity aluminum compound with a magnesium compound to prepare a reactant containing hydrotalcite nuclear particles, and causing a hydrothermal reaction of the reactant to synthesize hydrotalcite particles. The hydrotalcite particles can impart excellent heat resistance, transparency, flowability, and are useful as a resin stabilizer.

With respect to a plate-shaped hydrotalcite in which the average width of primary particles is increased, (1) the aspect ratio of secondary particles is increased by suppressing aggregation of primary particles by relatively reducing the average thickness thereof, and 2) the formation of a by-product that impairs the transparency of a resin is suppressed. Provided is a plate-shaped hydrotalcite represented by a formula (1) below:

(M.sup.2+).sub.1x(M.sup.3+).sub.x(OH).sub.2(A.sup.n).sub.x/n.mH.sub.2O(1) where M.sup.2+ indicates at least one divalent metal, M.sup.3+ indicates at least one trivalent metal, A.sup.n indicates an n-valent anion, n indicates an integer of 1 to 6, and x and m are within respective ranges of 0.1x0.33 and 0m10, the formula (1) satisfying (A) to (D) below: (A) the average width of primary particles as measured using an SEM method is 1 m or greater; (B) the average thickness of primary particles as measured using an SEM method is 80 nm or less; (C) the degree of monodispersity of width is 50% or greater; and (D) the degree of monodispersity of thickness is 50% or greater.

A heat-ray-blocking fluororesin film includes a heat-ray-blocking metal oxide and a hydrotalcite-type compound represented by Chemical Formula [1], wherein the content of the hydrotalcite-based compound is 0.03 to 1.0 wt %. The heat-ray-blocking fluororesin can exhibit excellent heat-ray-blocking performance while keeping the properties inherent in fluororesin films such as mechanical properties, transparency and long-term weatherability and is transparent and can be used out of doors for a long period of time, wherein
Mg.sup.2+.sub.1a.Al.sup.3+.sub.a(OH.sup.).sub.2.AN.sup.n.sub.a/n.cH.sub.2O
where 0.2a0.35 and 0c1; AN.sup.n indicates n-valent anion.

Provided are a hydrotalcite substance composition having excellent dispersibility, and an additive using the hydrotalcite substance composition. The hydrotalcite substance composition of the present invention contains a hydrotalcite substance and a surface treatment agent containing an organic compound. The hydrotalcite substance is in a state in which at least part thereof is coated with the surface treatment agent. The amount of an extract to be extracted from the composition by hot toluene treatment is 1 wt % or less with respect to the composition, and the content of calcium in the extract is 500 ppm or less with respect to the weight of the composition.

A hydrotalcite is represented by formula (1):

(M.sup.2+).sub.1-X(M.sup.3+).sub.X(OH).sub.2(A.sup.n).sub.X/n.mH.sub.2O(1), wherein M.sup.2+ indicates a divalent metal, M.sup.3+ indicates a trivalent metal, A.sup.n indicates an n-valent anion, n indicates an integer of 1 to 6, 0.17x0.36, and 0m10. The hydrotalcite has (A) a lattice strain in the <003> direction is 310.sup.3 or less as measured using an X-ray diffraction method; (B) primary particles with an average width between 5 nm and 200 nm inclusive per a SEM method; and (C) a degree of monodispersity of 50% or greater (degree of monodispersity (%)=(average width of primary particles as measured using the SEM method/average width of secondary particles as measured using a dynamic light scattering method)100). A resin containing the hydrotalcite, a suspension containing the hydrotalcite and a method for producing the hydrotalcite are disclosed.

The present disclosure relates to a method for producing lanthanide doped layered double hydroxides (Ln-doped LDHs). The method includes the steps of preparing a carbonate free alkaline solution; preparing a solution of metal salts comprising a salt of a lanthanide; co-precipitating the alkaline solution and the solution of metal salts to form a mixture and Ln-doped LDH precipitate wherein the pH of the mixture is maintained at a constant value; aging the precipitate; and separating the precipitate from the solution. The alkaline solution is an aqueous ammonia solution. The present disclosure is also related to lanthanide-doped layered double hydroxides (La-doped LDHs) obtainable by such a method, as well as to the use of the lanthanide-doped layered double hydroxides obtainable by such a method.

The present disclosure relates to a method for producing lanthanide doped layered double hydroxides (Ln-doped LDHs). The method includes the steps of preparing a carbonate free alkaline solution; preparing a solution of metal salts comprising a salt of a lanthanide; co-precipitating the alkaline solution and the solution of metal salts to form a mixture and Ln-doped LDH precipitate wherein the pH of the mixture is maintained at a constant value; aging the precipitate; and separating the precipitate from the solution. The alkaline solution is an aqueous ammonia solution. The present disclosure is also related to lanthanide-doped layered double hydroxides (La-doped LDHs) obtainable by such a method, as well as to the use of the lanthanide-doped layered double hydroxides obtainable by such a method.

A process is disclosed for treating a Bayer process waste comprising a slurry containing bauxite residue and dissolved aluminum. The process comprises supplying the waste to a settling area to cause the bauxite residue to settle out of the slurry, thereby producing a supernatant liquor. The process further comprises neutralizing the supernatant liquor with a solution containing magnesium and calcium to produce a neutralized slurry containing precipitated hydrotalcites and thickening the neutralized slurry to produce a clarified effluent and a compacted slurry containing the precipitated hydrotalcites, part of said compacted slurry being recirculated to the supernatant liquor to be neutralized and/or directly to the neutralizing step. The clarified effluent and the compacted slurry are disposed of separately. Also disclosed is a plant for treating a Bayer process waste.