In situ process for producing layered double hydroxide (LDH) and further recycling of the LDH

A process for simultaneously removing silica and reducing Total Hardness of water containing silica and scale-forming ions, the process comprising:

• adding (i) magnesium hydroxide or a precursor of magnesium hydroxide to said water and (ii) a soluble aluminate compound or a precursor of aluminate to said water;
• forming a treated water, while maintaining the pH of said treated water at pH>8 to produce layered double hydroxide in situ;
• wherein the layered double hydroxide incorporates the scale-forming ions in a lattice of the layered double hydroxide and silica is incorporated in the lattice of the layered double hydroxide as an interlayer anion and/or bound by the layered double hydroxide via one or more binding modes to simultaneously remove silica and reduce Total Hardness of said water,
• wherein the density of the layered double hydroxide is approximately 2.0 g/cm3,
• wherein said water is selected from the group comprising surface water, produced water, municipal water, process water, stormwater, waters derived from industrial processing, agricultural processing, mineral processing, mine pit waters, ore overburden or waste rock seepage or drainage waters, concentrate streams from desalination plants, ion-exchange waters, boiler waters, and oilfield waters, and
• wherein silica is present in said water in two or more forms selected from dissolved, polymeric, colloidal or particulate, and the two or more forms of silica are simultaneously removed from the treated water by incorporation into or binding with the layered double hydroxide as it forms in situ;
• separating the layered double hydroxide and one or more of the silica and scale-forming ions and polymeric, colloidal and particulate forms sequestered thereof by the layered double hydroxide during formation by mechanical and/or chemical means;
• and
• recycling the layered double hydroxide produced in situ and mixing the layered double hydroxide with a further water stream to remove contaminants therefrom.