Provided is a method for leaching nickel from a nickel oxide ore that enables a nickel sulfate production method which is easily carried out with a small amount of waste generation. The method for leaching nickel into an organic phase disclosed here includes the step of bringing a nickel ore into contact with an organic phase. The organic phase contains a hydrophobic deep eutectic solvent including a hydrogen bond donor and a hydrogen bond acceptor, and an organic acid. The hydrogen bond donor is an acidic hydrogen bond donor. The organic acid is a strong acid.

A process for recovery of one or more elements, selected from precious metals and chalcophile metals as herein defined, from materials containing precious and/or chalcophile metal/s, said process including: (i) a leaching step comprising contacting the material with an acidic solution containing a lixiviant comprising an aqueous amino acid-thiourea compound formed from an amino acid (as herein defined) and thiourea (as herein defined), in order to form a leachate containing the precious metal and/or chalcophile metal; and (ii) a recovery step comprising recovering the precious metal and/or chalcophile metal from the leachate.

Provided is a method for enabling recovery of metal element leaching capacity of a deep eutectic solvent used for leaching a metal element from an ore containing the metal element. A method for recycling a hydrophobic deep eutectic solvent disclosed here includes: preparing a hydrophobic deep eutectic solvent used for leaching a metal element from an ore containing the metal element; and bringing the hydrophobic deep eutectic solvent and hydrochloric acid into contact with each other. In the hydrophobic deep eutectic solvent, a hydrogen bond donor is a carboxy group-containing compound, and a hydrogen bond acceptor is chloride salt. The amount of use of the hydrochloric acid is such that hydrogen chloride is 1 mole or more with respect to 1 mole of the hydrogen bond acceptor.

Methods and systems for recovering or extracting rare earth elements under mild conditions include subjecting a material including rare earth element to a rare earth element crystallization medium under solvothermal conditions sufficient to form rare earth element crystals capable of gravity separation and purification.

The instant invention relates to a composition in form of a stable aqueous emulsion comprising a) 1-50 wt.-% of at least one water insoluble thionocarbamate collector selected from the group consisting of dialkyl thionocarbamates, alkyl alkoxycarbonyl thionocarbamates and alkyl allyl thionocarbamates, b) 1-50 wt.-% of one or a mixture of surface active agents of the general formula ##STR00001## wherein R.sup.1 is a saturated or unsaturated, branched or linear C.sub.3 to C.sub.30 aliphatic or aromatic hydrocarbon group, R.sup.2 and R.sup.3 are independently from each other hydrogen or a C.sub.1 to C.sub.4 alkyl group, R.sup.4 is hydrogen or CH.sub.2COOX where X is hydrogen or sodium salt or potassium salt or ammonium salt, and n and m are independently from each other 0 to 50, c) 0.1-20 wt.-% of a mixture of at least one alcohol and at least one ether and/or ester, e) 1-90 wt.-% of water.

The present invention relates to the field of chemistry, in particular the field of acids, and methods and processes relating to increasing the concentration, and decreasing the pH, of green organic acids (and thereby increasing their leaching ability), and especially from acids obtained as the by-process of biological processes such as pot-ale and pot-ale derived acids. More particularly, the present invention relates to apparatus and methods for removing minerals from a mineral containing substance using such acids. a method for removing minerals from a mineral containing substance, the method comprising taking a primary solution having a pH below 7 and containing one or more organic acids and water; freeze separating the primary solution to remove some of the water and thereby decreasing the pH of the primary solution to form a leachant; and applying the leachant to the substance to form a leachate.

The instant invention relates to a composition in form of a stable aqueous emulsion comprising a) 1-50 wt.-% of at least one water insoluble thionocarbamate collector selected from the group consisting of dialkyl thionocarbamates, alkyl alkoxycarbonyl thionocarbamates and alkyl allyl thionocarbamates, b) 1-50 wt.-% of one or a mixture of surface active agents of the general formula

##STR00001## wherein R.sup.1 is a saturated or unsaturated, branched or linear C.sub.3 to C.sub.30 aliphatic or aromatic hydrocarbon group, R.sup.2 and R.sup.3 are independently from each other hydrogen or a C.sub.1 to C.sub.4 alkyl group, R.sup.4 is hydrogen or CH.sub.2COOX where X is hydrogen or sodium salt or potassium salt or ammonium salt, and n and m are independently from each other 0 to 50, c) 0.1-20 wt.-% of a mixture of at least one alcohol and at least one ether and/or ester, e) 1-90 wt.-% of water.

A process for recovery of one or more elements, selected from precious metals and chalcophile metals as herein defined, from materials containing precious and/or chalcophile metal/s, said process including: (i) a leaching step comprising contacting the material with an acidic solution containing a lixiviant comprising an aqueous amino acid-thiourea compound formed from an amino acid (as herein defined) and thiourea (as herein defined), in order to form a leachate containing the precious metal and/or chalcophile metal; and (ii) a recovery step comprising recovering the precious metal and/or chalcophile metal from the leachate.

A process for recovery of one or more elements, selected from precious metals and chalcophile metals as herein defined, from materials containing precious and/or chalcophile metal/s, said process including: (i) a leaching step comprising contacting the material with an acidic solution containing a lixiviant comprising an aqueous amino acid-thiourea compound formed from an amino acid (as herein defined) and thiourea (as herein defined), in order to form a leachate containing the precious metal and/or chalcophile metal; and (ii) a recovery step comprising recovering the precious metal and/or chalcophile metal from the leachate.