Patent EP-3771690-A1 (EP)
Inventor: CIPOLLINA ANDREA
IPC: C22B26/10
Filed: 2020-08-01
Abstract: The present invention discloses a procedure for extracting minerals from the waste brine of saltern plants , where said brine is also called "bittern", wherein said bittern comprises a quantity of sodium ions Na<sup>+</sup> ranging from about 18 to about 78 g/l, a quantity of potassium ions K+ ranging from about 3 to about 17 g/l, a quantity of magnesium ions Mg<sup>2+</sup> ranging from about 10 to about 60 g/l, a quantity of chlorine ions Cl<sup>-</sup> ranging from about 178 to about 292 g/l, a quantity of sulphate ions SO4<sup>-</sup> ranging from about 43 to about 114 g/l, a concentration of calcium ions Ca<sup>2+</sup> less than 1 g/l, a concentration in trace elements ranging from 10<sup>-6</sup> to 1 g/l, and is substantially inorganic carbon free, wherein said procedure comprises the following steps:a) obtaining said bittern from a saltern by way of a fractioned evaporation and crystallization of calcium and chlorine salts, such as for example sodium chloride;b) sending said bittern to a first reactive crystallizer for magnesium hydroxide;c) extracting magnesium hydroxide from said bittern by way of a reactive crystallization, wherein the reagent is alkaline solution of alkaline hydroxides, such as, for example, NaOH and KOH or mixtures thereof, and obtaining a magnesium-free waste brine;d) sending the magnesium-free waste brine to a trace element separation unit;e) separating a solution from the magnesium-free waste brine comprising at least one of the trace elements included in the group formed of alkaline, alkaline-earthy, transition, and post-transition metals, at a concentration ranging from 10<sup>-4</sup> to 100 g/l, so as to obtain a waste brine deprived of one or several trace elements;f) sending the solution to a second reactive crystallizer;g) extracting at least one of the trace elements of a group including alkaline, alkaline-earthy, transition, and post-transition metals from the solution by way of a reactive crystallization, wherein the reagent is an acidic solution, formed of a mixture of HCI and H<sub>2</sub>SO<sub>4</sub>, and/or an alkaline solution, formed of a mixture of NaOH and KOH;h) sending the waste brine deprived of one or several trace elements to an electrodialysis with bipolar membranes unit;i) submitting the waste brine deprived of one or several trace elements to electrodialysis with bipolar membranes, so as to convert a part of the sodium, potassium, and chloride ions and the water of the solution into hydrochloric acid (HCI), sulphuric acid (H<sub>2</sub>SO<sub>4</sub>), and sodium/potassium hydroxides (NaOH/KOH) in solution, thus obtaining acidic solutions, alkaline solutions, and a salt-concentrated waste brine;j) diluting said salt-concentrated waste brine for obtaining a diluted waste brine and recycling it in the saltern or in the sea,wherein the electrical energy necessary for implementing steps b) thru j) of the procedure is generated starting from said waste brines jointly with and/or alternatively to the electrical energy produced by at least one renewable energy source ,wherein said procedure for extracting minerals from said bittern is closed cycle one, wherein the waste product of each individual step of the procedure feeds another step of the procedure itself, and wherein the final waste product of the procedure is re-used in the saltern itself or in the sea.The present invention also describes a plant for extracting minerals from a bittern that uses the above-described procedure.