A method for preparing a suspension of LDH particles comprising the steps of: preparing LDH precipitates by coprecipitation to form a mixture of LDH precipitates and solution; separating the LDH precipitates from the solution; washing the LDH precipitates to remove residual ions; mixing the LDH precipitates with water; and subjecting the mixture of LDH particles and water to a hydrothermal treatment step by heating to a temperature of from greater than 80 C. to 150 C. for a period of about 1 hour to about 144 hours to form a well dispersed suspension of LDH particles in water, wherein said LDH particles in suspension comprise platelets having a maximum particle dimension of up to 400 nm.

Exemplary layered double hydroxides (LDHs) may comprise a compound of formula Mg.sub.4-yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01?y?1. Exemplary layered double hydroxide hydrogels (LDH-gels) may comprise a hydrogel and at least one LDH. Exemplary hydrogels may comprise polyethylene (glycol) diacrylate (PEGDA) or polyacrylamide (PAAm). Exemplary LDH-gels may comprise at least one LDH comprising a compound of formula Mg.sub.4-yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01?y?1.

Exemplary layered double hydroxides (LDHs) may comprise a compound of formula Mg.sub.4-yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01?y?1. Exemplary layered double hydroxide hydrogels (LDH-gels) may comprise a hydrogel and at least one LDH. Exemplary hydrogels may comprise polyethylene (glycol) diacrylate (PEGDA) or polyacrylamide (PAAm). Exemplary LDH-gels may comprise at least one LDH comprising a compound of formula Mg.sub.4-yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01?y?1.

The present invention relates to a process for modifying a layered double hydroxide (LDH), the process comprising, a. providing a water-wet layered double hydroxide of formula:

[M.sup.z+.sub.1-xM.sup.y+.sub.x].sup.a+(X.sup.n).sub.a/r.bH.sub.2O (1) wherein M and M are metal cations, z=1 or 2; y=3 or 4, x is 0.1 to 1, preferably x<1, more preferably x=0.1-0.9, b is greater than 0 to 10, X is an anion, r is 1 to 3, n is the charge on the anion X and a is determined by x, y and z, preferably a=z(1-x)+xy-2; b. maintaining the layered double hydroxide water-wet, and c. contacting the water-wet layered double hydroxide with at least one solvent, the solvent being miscible with water and preferably having a solvent polarity (P) in the range 3.8 to 9,
as well as to a layered double hydroxide prepared according to that process.

The present invention relates to a process for modifying a layered double hydroxide (LDH), the process comprising, a. providing a material comprising a layered double hydroxide of formula: [M.sup.z+.sub.1-xM.sup.y+.sub.x(OH).sub.2].sup.q+(X.sup.n).sub.q/n.bH.sub.2O wherein M and M are metal cations, z is 1 or 2, x is 0.1 to 1, b is 0 to 5, y is 3 or 4, X is an anion, n is 1 to 3 and q is determined by x, y and z, b. optionally washing the material at least once with a mixture of water and a mixing solvent miscible with water, and c. washing the material obtained in step a or b at least once with at least one first solvent, the first solvent being miscible with water and having a solvent polarity P.

Layered double hydroxides having a high surface area (at least 125 m.sup.2/g) and the formula (I)
[M.sup.z+.sub.1?xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.sub.+bH.sub.2O.c(AMO-solvent)(I)
wherein M and M are different and each is a charged metal cation (and must be present), z=1 or 2; y=3 or 4, 0<x<0.9, b is 0 to 10, c=0 to 10, X is an anion, n is the charge on the anion, and a=z(1?x)+xy?2; AMO-solvent is aqueous miscible organic solvent, may be prepared by a method which comprises a) precipitating a layered double hydroxide having the formula
[M.sup.z+.sub.1?xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n?).sub.a/n.sub.+bH.sub.2O wherein M, M, z, y, x, a, b and X are as defined above from a solution containing the cations of the metals M and M and the anion X.sup.n?; b) ageing the layered double hydroxide precipitate obtained in step a) in the original solution; c) collecting, then washing the layered double hydroxide precipitate; d) dispersing the wet layered double hydroxide in an AMO solvent so as to produce a slurry of the layered double hydroxide in the solvent; e) maintaining the dispersion obtained in step d); and f) recovering and drying the layered double hydroxide. The high surface area products have low particle size and are particularly suitable for use as catalysts, catalyst supports, sorbents and coatings.

Layered double hydroxides organo-modified by 3-(4-hydroxyphenyl)propionic acid (HPPA), by 2-(4-hydroxyphenyl)ethylsulfonic acid or by a hydroxyphenylpropenoic acid, and to composite polymer materials having same. The composite materials are advantageously made of biosourced polymers such as poly(butylene succinate). These composite materials have improved properties over the polymers that make up the composition thereof, and over the composites of the prior art.

The present invention relates to a method for extracting magnesium and lithium and also producing layered double hydroxides (LDH) from brine, comprising the steps of: adding an aluminum salt to brine, to prepare a mixed salt solution A for preparing MgAl-LDH; adding an alkaline solution to carry out co-precipitation, followed by crystallization; after the crystallization is complete, performing solid-liquid separation to obtain a solid product of MgAl-LDH and a filtrate; concentrating the filtrate by evaporation to obtain a lithium-rich brine, adding an aluminum salt thereto to prepare a mixed salt solution B for preparing LiAl-LDH; adding the mixed salt solution B to an alkaline solution to carry out precipitation; after the precipitation is complete, performing solid-liquid separation to obtain a solid product of LiAl-LDH and a filtrate; and concentrating the filtrate by evaporation, returning the solution concentrated by evaporation to the lithium-rich brine for recycled use. This method uses mild reaction and simple equipment, has a small loss of Li, can achieve isolation of resources from salt lakes, and can also obtain functional materials having a high added value.

A process for preparing particles of a layered double hydroxide of the general formula

[M.sub.p.sup.z+M.sub.q.sup.y+(OH).sub.2].sup.a+(X.sup.n).sub.a/n.bH.sub.2O(I)

wherein M.sup.z+ and M.sup.y+ are metal cations or mixtures of metal cations, z=1 or 2; y=3 or 4; p+q=1; b=0 to 10, X.sup.n is an anion, n is 1 to 5 and a is determined by p, q, y and z such that a=zp+yq2, comprises (a) mixing, in aqueous solution, M.sup.z+ cations, M.sup.y+ cations and X.sup.n anions, with a base; and (b) allowing the layered double hydroxide of formula (I) to precipitate from the solution mixed in step (a).

Preferably, M is Li, Mg, Zn, Fe, Ni, Co, Cu, Ca, or a mixture of two or more. Preferably, y is 3, and M is Al, Ga, In, Fe or a mixture of two or more thereof. Also provided are particles obtainable by the process, especially wherein M is Ca, M is Al, and X.sup.n is NO.sub.3.sup.. Particles of a layered double hydroxide wherein the particles have a particle size of not greater than 2000 nm, preferably not greater than 300 nm and especially not greater than 100 nm, are also provided. The layered double hydroxides according to the invention are useful in certain applications, for example, as adsorbents, coatings and catalyst supports.

Exemplary layered double hydroxides (LDHs) may comprise a compound of formula Mg.sub.4-yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01y1. Exemplary layered double hydroxide hydrogels (LDH-gels) may comprise a hydrogel and at least one LDH. Exemplary hydrogels may comprise polyethylene (glycol) diacrylate (PEGDA) or polyacrylamide (PAAm). Exemplary LDH-gels may comprise at least one LDH comprising a compound of formula Mg.sub.4-yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01y1.