Mechanism of extracting trivalent gold from ether

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Ether (C 2 H 5 OC 2 H 5 ) extracts gold in view of the fact that diethyl ether can form a group cation with an acid in a high concentration hydrochloric acid solution, and combines with a complex anion of trivalent gold to form a neutral sheep salt. The reaction process is:

With R representing C 2 H 5 , the above formula can be simplified to (R 2 O-H) + Cl - .

Au 3 + +3Cl - AuCl 3 -

(R 2 O-H) + Cl - +AuCl 3 (R 2 O-H) + AuCl 4 -

Since the composition of the sheep salt has a hydrophobic hydrocarbon group R = C 2 H 5 , the sheep salt is soluble in an excess of diethyl ether and enters the organic phase, and is separated from the impurity element in the aqueous phase. This process is called the extraction of sheep salt.

From the above extraction process of producing sheep salt, it is known that the formation of adenine cation by diethyl ether requires a sufficient concentration of acid (H + ) in the solution, otherwise the sheep salt cannot be formed. At lower acid concentrations, even the formation of sheep salts is unstable, and the extracted metal must be capable of forming complex anions present in the solution. This complex anion must also have a certain hydrophobic property in order to enter the organic phase and be extracted. Therefore, metal ion sheep salts such as F - , Cl - , Br - , I - or CNS - are used, and oxyacids such as NO 3 - and SO 4 2 - are highly hydrophilic and are used less.

Since sheep salt can only be present in a high concentration of strong acid solution, it is unstable in low acidity or neutral solution, so water is used for back extraction of sheep salt. The addition of water to the stripping of the salt of the sheep is essentially due to the fact that a large amount of water molecules have taken away the H + in the sheep cation and destroyed the sheep salt. At this point, the ether is replaced and Au 3 + is stripped back into the aqueous phase:

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