The crude metal ruthenium is difficult to dissolve directly in aqua regia. The aqua regia at 90 °C dissolves for nearly half a month, and the dissolution rate is only less than 60%. If mixed in the ratio of Rh: Al: Fe ₂ 0 ₃ = 1:2: 0.2, smelting at 1000 ° C for 15 min, the resulting niobium-containing alloy is leached with 6 mol / L HCl, aluminum, iron , and then dissolved in aqua regia at 90 ° C At 20 min, the hydrazine dissolution rate reached 99%.
Obviously, the aluminothermic reduction smelting can convert all the insoluble metals in the insoluble state into an active and soluble state. However, the use of iron oxide in the process has the disadvantages of high melting temperature and sometimes inert atmosphere protection.
3.锍Fused aluminum thermal reduction leaching method This method first uses nickel or iron sulfide and the material to be treated to reduce and smelt to produce strontium containing precious metal, and then smelt it into aluminum alloy by aluminum, and the aluminum alloy dissolves nickel with acid. A base metal such as iron or aluminum produces a high-grade active precious metal concentrate, and finally dissolves the concentrate with HCl/Cl _{2 to} produce a high-concentration precious metal solution.
For example, low-grade precious metal materials that process the following ingredients (%):
Au Pt Pd Rh+Ir+Os+Ru Au+Pt Cu Ni Fe SiO ₂ CaO S
0.113 0.094 0.076 0.033 0.316 4.7 4.1 10.2 11.1 12.5 14.1
Process method: Material added borax, sodium carbonate, quartz sand at 1250 deg.] C melting, the melted base metal sulfide sulfonium trapped in the material of the noble metal, sulfonium separated slag to react with molten aluminum and aluminum alloyed with The acid dissolves the base metal in the alloy, and the residue is the active precious metal concentrate, which is dissolved by HCl/Cl ₂ , and the dissolution rate of all precious metals is greater than 99.8%.
For ten gold platinum group metals 7.748%, 19.1% base metal enrichment of noble metal, nickel sulfide was added to the smelting matte treated by the same procedure, the dissolution rate of the noble metal are all greater than 99.9%. The concentration of precious metals in the solution reaches 100 g/L. [next]
The Pt-Ir25 alloy waste was treated by the above process, and the first dissolution rate was >99%, and a high concentration platinum rhodium solution was produced. This method has also achieved very satisfactory results in the treatment of precious metal-containing waste residues accumulated in precious metal secondary resource refineries for decades.
For the rare ore-bearing concentrate (containing about 30% of Os and Ir) after the platinum-plated ore is extracted from platinum, the molten mineral can be decomposed and activated, and dissolved in sulfuric acid or hydrochloric acid. After the metal, the precious metal concentrate can be directly distilled in the sulfuric acid medium, absorbed by the lye, and then converted into an acidic medium to effectively oxidize and dissolve the cerium, platinum, etc., to obtain a high concentration cerium solution.
The barium metal in the dissolved aluminum alloy can use the acidic precious metal waste liquid generated in the precious metal refining process, and the precious metal in the waste liquid can be simultaneously replaced and recovered in the precious metal concentrate when the base metal is dissolved. If the waste liquid containing HCl ₂ mol/L, noble metal Ru 0.6%, Rh 0.5%, Ir 0.125 %, Pd 0.0735 is leached at 60 ° C for 6 h, the total precious metal concentration in the filtered ruthenium metal solution is reduced to less than 0.001%.
Compared with the above two methods, the method has the following characteristics.
1 Wide range of material composition, not only can handle high-grade materials, but also can deal with materials with precious metal grades as low as less than 1%, including precious metal enrichment of various grades in smelters, coarse concentrates, refineries Difficult to treat waste residue, secondary resources of various precious metals and insoluble niobium-containing alloys.
2 When treating waste slag and treating waste materials of insoluble crude metal strontium, strontium, strontium or precious metal alloy (such as platinum-bismuth alloy), firstly, it is melted with low-melting nickel bismuth (melting point 575 °C), and the nickel ruthenium infiltrates the precious metal. The ability to capture and shred is strong, the melting temperature is low, and there is no need to protect the atmosphere.
The thermal reduction reaction of aluminum and aluminum is fast, and precious metal ruthenium is added to the molten aluminum at 800-1000 ° C, and the activation reaction is completed by instantaneous self-heating to incandescent high temperature.
4 The multi-component alloy dissolves the base metal with any precious metal acidic waste liquid in the acid or refining process, and obtains a high-grade active precious metal concentrate after filtration.
5 If the concentrate contains strontium or barium , it can be first oxidized by adding oxidant (such as hydrogen peroxide or sodium chlorate) to the dilute acid medium, and then absorbed by lye and hydrochloric acid respectively, then added with concentrated hydrochloric acid and heated with chlorine gas. Dissolved to obtain a high concentration precious metal solution with a simple medium property. The whole process takes only 1 day.
(II) Selective Sedimentation Separation Method This method mainly utilizes the difference in stability and solubility of the compounds of different precious metals and different states of the noble metal and the salts of the complexes.
The precious metal concentrate is directly dissolved by aqua regia, Cl ₂ + HCI, HCI+H ₂ O ₂ , or dissolved by alkali and then dissolved with hydrochloric acid, and the noble metal forms a corresponding chlorine anion or a sodium salt thereof. The addition of potassium or ammonium cations to the chlorine anion solution forms the corresponding potassium or ammonium salt of the chlorine complex. The complex salt formed by the platinum group metal chloride anion with K ⁺ , Na ⁺ , NH ₄ ⁺ cations, the solubility in water and dilute hydrochloric acid solution depends on the basicity of M ⁺ , and the stronger the basicity, the greater the solubility. The order of solubility is: sodium salt > potassium salt > ammonium salt. The valence state of the central ion of the platinum group metal also determines the solubility of the chlorinated acid salt, which is generally characterized by the low-value chlorine complex salt being easily soluble, and the high-valent chlorine complex salt being insoluble. [next]
In addition to bismuth, the chlorine-containing sodium salt of other platinum group metals (regardless of the oxidation state of the central ion) is mostly red and soluble in water. Sodium chlorate is a black crystal and is hardly soluble in water. The corresponding potassium salt, in addition to Rh(III), K ₃ [RhCl ₆ ]·H ₂ O or K ₃ [RhCl ₅ ·H ₂ O] is easily soluble in water, and the tetravalent chlorine complex potassium salt of other platinum group metals is The solubility in water is small. They have a regular octahedral crystal structure. For example, K ₂ PtCl ₆ (yellow) has a solubility of 1.12% in water, K ₂ IrCl ₆ (red) has a solubility of 1.25% in water, and K ₂ OsCl ₆ (yellow) is slightly soluble in cold water, and the solubility increases upon heating. K ₂ PdCl ₆ (dark red) is hardly soluble in water. K ₂ RuCl _{6 is} easily hydrolyzed to a complex containing K ₂ (RuH ₂ OCl ₅ ), which is slightly soluble in water. The tetravalent K ₂ PdCl ₆ and K ₂ RuCl ₆ are only stable in the presence of an oxidizing agent. Once azeotroped with water or hydrochloric acid, they can be reduced to a low-soluble chlorine-compatible potassium salt K ₂ PdCI ₄ and chlorine which are easily soluble in water. Hydrate with a potassium salt such as K ₂ RuH ₂ OCl ₅ .
The ammonium salt is similar to the potassium salt. The low-valent chlorine is compatible with the ammonium salt, and the high-valent chlorine is insoluble with the ammonium salt. For example, the low-valent cerium salt (NH4) ₃ RhCl ₆ (red), (NH ₄ ) ₃ [RhCl ₅ ·H ₂ O] (red) is easily soluble in water. The chlorine complex ammonium salts of other tetravalent platinum group metals are hardly soluble in water. For example, the solubility of (NH ₄ ) ₂ PtCl ₆ (yellow) water is only 0.77%, and it is further reduced to 0.003% in saturated ammonium chloride solution. (NH ₄ ) ₂ PdCl ₆ (red octahedron) slightly soluble in water, (NH ₄ ) ₂ lrCl ₆ (black crystal) has a solubility of 0.77% in water. Corresponding high-priced bismuth, bismuth chloride and ammonium salts are also difficult to dissolve. (NH ₄ ) ₂ PdCl ₆ is very unstable and is reduced to a readily soluble low-valent ammonium salt by boiling in water or dilute hydrochloric acid.
The process flow for group dissolution and selective precipitation separation is shown in Figure 1. This is a classic method used by the world's major platinum group metal refineries for a long time before the 1970s. Firstly, the precious metal ore extracted from the mineral or secondary resources is mixed with an appropriate amount of sulfuric acid, calcined and calcined, and then the ruthenium metal is separated by dilute sulfuric acid to reduce the content of bismuth metal in the precious metal concentrate to less than 1%, and the roasting process The para-platinum group metal is also converted into a state in which the aqua regia is insoluble.

[next]

The separation and refining process includes at least 8 separation procedures and hundreds of chemical reactions, smelting and dissolving alternately, filtration, and precipitation intermittent operations for a period of several months. The main procedures are as follows.
1. Wangshui dissolves platinum and gold. Firstly boil the concentrate with hydrochloric acid, then add nitric acid in a ratio of HCI: HNO ₃ ≈3:1 and dilute it twice with distilled water, continue to boil and add hydrochloric acid and nitric acid to dissolve gold platinum palladium . The dissolution reaction of platinum is as follows:
HNO ₃ +3HCl====Cl ₂ +NOCI+2H ₂ O
Pt+2Cl ₂ ====PtCl ₄
Pt+4NOCl====PtCl ₄ +4NO
PtCl ₄ +2HCI====H ₂ PtCl ₆
Total reaction Pt+8HCl+2HNO ₃ ====H ₂ PtCl ₆ +2NOCl+4H ₂ O
The dissolution reaction is similar to platinum to form H ₂ PdCl ₆ . The gold in the concentrate and a small amount of base metal are also dissolved to form chlorine acid and chloride such as HAuCl ₄ , FeCl ₃ , CuCl ₂ and NiCl ₂ . When the aqua regia is dissolved, platinum will form a poorly soluble nitroso complex (NO) ₂ PtCl ₆ yellow precipitate. After the dissolution, add hydrochloric acid to boil and evaporate to a paste. Repeat several times to completely convert the platinum into a soluble chlorine complex. . After filtration, the filtrate is mainly composed of platinum, rhodium and gold, and contains a small amount of base metal and ruthenium, osmium and iridium. The insoluble slag contains silver and a platinum group metal. This dissolution process can now be carried out by introducing chlorine gas into the hydrochloric acid medium, or adding sodium chlorate solution or adding hydrogen peroxide to avoid nitroso-nitrogen pollution.
2. Separation of gold, platinum and palladium (1) Separation and extraction of gold Because gold is more than platinum, easy to reduce and precipitate, first separation can avoid the subsequent gold separation and precipitation interference during the separation of platinum, and at the same time reduce the gold to reduce the ruthenium in the solution. It is in a low-cost state to reduce the coprecipitation of ruthenium when separating platinum. In addition, in the traditional process, the ammonia separation method is used, and if the solution contains a large amount of gold, it will generate an explosive "Rainjin" (Au ₂ O ₃ · 4NH ₄ ), which brings operational danger.
When reducing gold, the gold concentration in the solution should be greater than 20g / L, the acidity of the solution is less than 0.5mol / L, to avoid the production of fine black gold or colloidal gold, generally with ferrous salts (FeSO ₄ , FeCl ₂ ), SO ₂ , oxalic acid ( H ₂ C ₂ O ₄ ) and other reducing agents of moderate reduction ability, based on the premise of reducing platinum and palladium at the same time, reducing the crude gold produced and refining to produce pure gold. The reaction with ferrous sulfate and oxalic acid as a reducing agent is: [next]
AuCl ₃ +3FeSO ₄ ====Au↓+Fe ₂ (SO ₄ ) ₃ +FeCl ₃
2AuCl ₃ +3H ₂ C ₂ O ₄ ====Au↓+6HCl+6CO ₂
(2) Separation and extraction of platinum The precipitated gold was added with ammonium chloride to precipitate egg yellow chloroplatinate. The response is:
H ₂ PtCl ₆ +2NH ₄ Cl====(NH ₄ ) ₂ PtCl ₆ ↓+2HCl
The solubility of ammonium chloroplatinate in water is 0.77%, but the solubility in the 17.7% concentration ammonium chloride solution is reduced to 0.003%, so the ammonium chloride should be excessive in the precipitation of platinum. The base metal does not form a similarly insoluble salt with ammonium chloride, and most of the residue is separated in the solution, but the ammonium chloroplatinate precipitates a small amount of base metal and is deeply separated when the platinum is refined. When the solution is in a low-cost state of Pd(II) or Ir(III), the resulting ammonium salts (NH ₄ ) ₂ PdCl ₄ and (NH ₄ ) ₃ IrCl _{6 are} soluble. However, when the Pd(IV) and Ir(IV) are in a high valence state, an ammonium salt (NH ₄ ) ₂ PdCl ₆ and (NH ₄ ) ₂ IrCl ₆ which are heteromorphous with ammonium chloroplatinate are also coprecipitated, and It is difficult to separate by washing and precipitation, and it must be deeply separated during platinum refining. Therefore, the solution should be boiled before the precipitation of platinum to reduce the hydrazine to a low price.
(3) Separation and extraction of palladium The filtrate after filtering ammonium chloroplatinate is mainly used, and can be extracted from the solution by the following three methods.
1 Precipitating chlorine to ammonium chloride method The platinum-plated filtrate is supplemented with a part of ammonium chloride, and chlorine gas is added or nitric acid is added to precipitate a red chlorine to acid ammonium. The reaction is as follows:
(NH ₄ ) ₂ PdCl ₄ +Cl ₂ ====(NH ₄ ) ₂ PdCl ₆ ↓
Ammonium chloropalladate is very unstable and is reduced to soluble ammonium chloropalladate when boiled in water. The base metal does not form an ammonium salt precipitate, but when the concentration of the base metal is high, the crystal of the complex salt formed by the chloride and ammonium chloride contaminates the palladium ammonium salt and turns it into a purplish red color. The ruthenium metal can be separated by repeated precipitation (at least three times), but a large amount of palladium-containing mother liquor is produced separately, and the direct yield of palladium is not high. High-valent ions such as Pt(IV), Ir(IV), and Rh(III) also form similar chloroformammonium salts. Therefore, the precipitation method cannot completely separate palladium from platinum, rhodium, and ruthenium.
2 Precipitating dichlorodiammonia palladium method The filtrate after platinum is heated and added with ammonia water, and the ruthenium metal is hydrolyzed into a hydroxide precipitate, and at the same time, the pink dichlorodiamine palladium salt is precipitated, and the reaction is:
2H ₂ PdCl ₄ +8NH ₄ OH====Pd(NH ₃ ) ₄ ·PdCl ₄ ↓+4NH ₄ Cl+4H ₂ O
Continue to add ammonia, the dichlorodiamine palladium salt precipitates into a soluble and colorless dichlorotetraammine palladium salt, the reaction is:
Pd(NH ₃ ) ₄ ·PdCl ₄ +4NH ₄ OH====2Pd(NH ₃ )4Cl ₂ +4H ₂ O[next]
After the hydrolyzed precipitation of the base metal by filtration, the palladium-containing filtrate was slowly neutralized with hydrochloric acid to pH = 0.5, and a yellow powder of dichlorodiamine palladium salt was reprecipitated. This property is palladium-specific and can be separated by filtration to separate other soluble precious metal impurities.
3 Combination method When the content of noble and bismuth metal impurities in the palladium solution is high, the above two methods can be used in combination. That is, the ammonium chloropalladate is first precipitated to separate the ruthenium metal impurities, and then the noble metal impurities are separated by the ammonia complex method, and each of the precipitates is repeatedly precipitated several times to obtain a pure metal.
3. The insoluble residue of aqua regia is recovered from the insoluble residue of aqua regia. It mainly contains silver chloride, strontium, barium and strontium. It also contains a small amount of platinum and palladium. The rest is silica, which is mainly used for separation and extraction of platinum group metals. purpose.
(1) Separation of silver and platinum to gold First, the precious lead is smelted, that is, two times the amount of precious metal is added to lead oxide or lead carbonate as a collector, and 75% of the amount of residue is added to borax, and 175% is added to soda. The flux is subjected to reduction smelting at 1000 ° C or higher. The precious lead water enriched in precious metals is crushed into granules, and lead and silver are boiled and dissolved in nitric acid. The filtrate is boiled with sulfuric acid to precipitate insoluble lead sulfate. After filtration, the lead sulfate is thermally decomposed into lead oxide or converted to carbonic acid with sodium carbonate. Lead returns to smelting precious lead. The silver-containing solution after filtering lead sulfate is added with hydrochloric acid or sodium chloride to precipitate AgCl, and then smelted with charcoal and soda into crude silver for electrolytic refining.
The nitric acid insoluble slag is first calcined at 600 ° C and then dissolved again with aqua regia. The platinum-containing gold solution is incorporated into the main solution to separate and extract the three metals.
(2) Separation and extraction é“‘ Wangshui insoluble slag is melted with sodium hydrogen sulphate, cooled and then leached with dilute sulfuric acid to obtain a soluble Rh ₂ (SO ₄ ) ₃ solution, which can form a special property of sulphate, which is:

This solution is used as a raw material for refining crucibles.
(3) Separation and extraction of ruthenium The ruthenium and osmium are very special in nature. The melting point and density of the metal are very high, but they are easily oxidized to low-boiling high-valent oxides (boiling point: OsO ₄ 131.2 ° C, RuO ₄ 65 ° C). Therefore, they are easily lost during metallurgical enrichment and the recovery rate is low. They have many kinds of compounds, which can form chlorinated anions and related salts from central cations, and can also form citrates and citrates by using acid oxides. Therefore, the separation and extraction methods of lanthanum and cerium are mainly oxidative volatilization and selective absorption. . [next]
The above materials containing ruthenium and osmium are mixed with 3 parts of Na ₂ O ₂ and 1 part of NaOH, heated to 700 ° C in iron crucible, cooled, and then leached with water to obtain sodium citrate (Na ₂ OsO ₄ ) and sodium citrate ( Na ₂ RuO ₄ ) alkaline solution. The response is:
2Os+6Na ₂ O ₂ +2NaOH====2Na ₂ OsO ₄ +5Na ₂ O+H ₂ O
2Ru+6Na ₂ O ₂ +2NaOH====2Na ₂ RuO ₄ +5Na ₂ O+H ₂ O
The filtrate is vented with chlorine gas at about 80 ° C to volatilize OsO4 and RuO4. The reaction is as follows:
Na ₂ OsO ₄ +Cl ₂ ====OsO ₄ ↑+2NaCl
The reaction of the two high-valent oxides to the acidic sulfur vein solution shows red and blue, respectively, so the cotton ball wetted with sulfur veins can be used to periodically monitor the volatilization process and the end point in the gas outlet pipe. RuO _{4 is} absorbed by an appropriate amount of alcohol with a concentration of 5 mol/L HCl, and reduced to a stable H ₂ RuCI ₅ . The reaction is as follows:
2RuO ₄ +20HCl====2H ₂ RuCl ₅ +8H ₂ O+5Cl ₂
OsO ₄ is absorbed by 20% NaOH plus an appropriate amount of alcohol solution, and reduced to form sodium citrate solution, the reaction is:
2OsO ₄ +4NaOH====2Na ₂ OsO ₄ +2H ₂ O+O ₂
Each of the 3~4 stages is connected in series, and the absorption system is connected to a negative pressure of 100~200Pa. The enthalpy absorbed in the é’Œ absorption liquid is also converted into an unstable H ₂ OsCl ₆ state, which can be directly or concentrated and then added with a small amount of nitric acid or hydrogen peroxide to oxidize and boil. The hydrazine is reoxidized to OsO _{4 and} volatilized into the alkali absorption system. Generally, the first-stage absorption liquid having a higher concentration is separately sent for refining, and the other stages are sequentially moved forward.
China's priority oxidative distillation recovery scheme is beneficial to improve the recovery rate of hydrazine. Precious metal concentrate (%) for the following ingredients:
Cu Ni Pt Pd Rh Ir Os Ru Au
1.1 4.0 2.84 0.83 0.185 0.28 0.18 0.41 0.55
The coarse concentrate is slurried into the distillation pot with sulfuric acid slurry, and the mixture is heated to 80 ° C or higher, and the sodium chlorate solution is slowly added to oxidize and volatilize the hydrazine, and is respectively absorbed by the acid or the alkali solution. The recovery rate of ruthenium is greater than 85% and 95%, respectively, and at the same time, 95% of platinum, and more than 85% of ruthenium and osmium are dissolved in the distillation residue, and further separated and recovered from the solution.
(4) The residue obtained after extracting the crucible is enriched with the most chemically inert crucible, and the crucible is generally in the IrO ₂ state. Dissolved with aqua regia, the reaction is:
31rO ₂ +18HCl+4HNO ₃ ====3H ₂ lrCl ₆ +8H ₂ O+O ₂ +4NO ₂
While maintaining the oxidizability of the solution (with a small amount of nitric acid or chlorine gas) to ensure that the ruthenium is in the high valence state of Ir(IV), ammonium chloride is precipitated to precipitate a mercerized ammonium chlororuthenate (NH ₄ ) ₂ IrCl ₆ black precipitate. Further, it is further refined into metal ruthenium using ammonium chloroantimonate as a raw material. [next]
4. Treatment of low-concentration precious metal solution and waste liquid A large amount of low-concentration solution produced in the refining process and precious metals in the waste liquid are recovered by the following methods.
(1) The composition of the concentration method is simple, and the single solution of the precious metal species is directly boiled and concentrated, and then returned to the main process.
(2) The replacement method uses a metal powder such as magnesium , zinc , nickel, iron, aluminum or copper , a wire or a sheet to displace the precious metal from the solution. When the solution contains only platinum, palladium or gold, the precious metal can be quantitatively replaced by zinc powder, and the concentration of precious metal in the displaced liquid can reach the lower limit of analytical sensitivity (<0.2 mg/L). However, the replacement rate for cockroaches is slow, and the replacement rate for cockroaches is not high. When the solution contains a platinum group metal, it needs to be replaced by zinc and then replaced with magnesium powder. Since zinc and magnesium consume a large amount of acid and quantitatively replace copper, the method is only suitable for solutions containing low copper and low acidity.
The replacement of precious metals with copper or activated sponge copper as a displacer, the replacement rate is not as fast as zinc-magnesium powder, but less limited by acidity and solution composition, and the noble metal grade of the replacement product is higher. For example, for chloride solution containing (g/L) Cu 2.1, Ni 2.6, Fe 2.0, Pt 0.34, Pd 0.2, HCl 5mol/L, copper replacement at 80 ° C for 1 h, the concentration of platinum and palladium in the mother liquor can be reduced to 0.0002 g /L and 0.0009g/L levels, the replacement rates were 99.9% and 99.5%, respectively.
The speed and efficiency of copper replacement of precious metals are closely related to temperature, medium properties (sulfuric acid or hydrochloric acid system), acidity, etc., and generally need to be replaced in a solution above 60 ° C, preferably above 90 ° C and in a higher acidity. The order of displacement speed is Au>Pd>Pt>Rh》Ir, that is, the substitution effect on gold palladium platinum is good, 铑 is slower, and 铱 is the slowest, so copper substitution can be used as a method for crude separation of gold platinum palladium ruthenium. The first substitution was 99.5% gold, palladium and platinum, about 15% Rh and 5% Ir; the second substitution was about 94% hydrazine, and most of the hydrazine remained in the replacement mother liquor. Since the amount of copper powder is difficult to control accurately, the replacement product contains high copper. Although it can be redissolved by nitric acid, copper is easily dissolved and dispersed. Replacement with copper wire or sheet can reduce the inclusion of copper in the replacement product, but the silk and sheet have poor activity, and the replacement efficiency is poor and the speed is slow.
(3) Precipitation method The noble metal containing sodium salt solution is passed through hydrogen sulfide or sodium sulfide is added to convert all precious metals except the cerium into a sulfide precipitate, and the concentration of precious metal remaining in the mother liquor can be reduced to less than 1 mg/L. When the sodium sulfide is excessive, the thios salt of the corresponding metal is formed, and the sodium chlorogalladium solution is precipitated by sodium sulfide as an example:
Na ₂ PdCl ₄ +2Na ₂ S====Na ₂ PdS ₂ ↓+4NaCl
NaAuCl ₄ , Na ₂ PtCl ₆ , Na ₃ RhCl ₆ and the like in the solution are also precipitated by the above reaction to form a thio salt such as Na ₃ AuS ₃ , Na ₂ PtS ₃ or Na ₃ RhS ₃ .
Xanthate can precipitate the platinum and palladium xanthate from the platinum, palladium, silver and nitric acid solution. Taking palladium as an example, the reaction is:
Pd ²⁺ +2C ₂ H ₅ OCSS-====Pd(C ₂ H ₅ OCSS) ₂ ↓
The xanthate is combined with mercaptobenzothiazole or p-phenylthiol to precipitate palladium, platinum and rhodium in a stepwise manner. [next]
Thiourea can form a soluble complex with all noble metal chloro complexes, but is converted to a sulfide precipitate by adding concentrated sulfuric acid and heating above 170 °C.
The alkaline solution of NaBH ₄ can efficiently and completely reduce the precipitation of precious metals from the waste liquid, which is limited by the expensive application of the reagent.
(4) Adsorption method After the activated carbon is pre-oxidized with nitric acid, it is used for selective adsorption of platinum from a silver nitrate solution containing platinum, and the adsorption capacity is 60-70 mg Pd/g carbon and about 13 mg Pt/g carbon, respectively, and nitric acid is used. Desorb platinum and put it. The activated carbon of thiourea can effectively adsorb gold from the ruthenium metal solution containing precious metal, the residual liquid concentration is less than 0.4mg/L, and then re-dissolve from the activated carbon with aqua regia to obtain a high concentration precious metal solution. The anion exchange resin can exchange a trace amount of precious metal with an anion in the adsorption solution, but it is difficult to desorb the precious metal and the recycled resin with other reagents, and the precious metal is recovered by incineration of the resin.
All of the above methods can simultaneously recover trace precious metals, but cannot selectively separate precious metals. Various methods have different application ranges and operating conditions for solutions of different acidity and composition, and must be selected after testing according to specific conditions.
The selective precipitation separation process has been used for nearly one hundred years, but there are obvious shortcomings, such as: repeated smelting-leaching-precipitation, fire, wet process alternate operation, long process flow and treatment cycle, low work efficiency of intermittent and batch operation, labor intensity Large, there is the problem of environmental pollution; the selectivity of separation is not high, the reagent consumption is high, the index is unstable, and various metals in a large number of intermediate products contain each other, which requires repeated treatments and is accompanied by a large amount of intermediate products such as dilute solution and insoluble slag. Backlog and turnover, the primary yield of precious metals is not high; smelting, dissolving, sedimentation, filtration equipment , energy consumption, equipment corrosion.
Since the 1980s, selective precipitation separation processes have been gradually replaced by advanced solvent extraction separation processes. However, some of the techniques in the selective precipitation process are still an important method for refining pure metals and extracting various precious metal compound products of different purities.
(3) Solvent extraction separation solvent extraction technology uses a special organic compound to form a new organic compound (extracted compound) with a noble metal according to a specific mechanism, and selectively extracts the noble metal into the organic phase, and other metals. Separation, if each metal is separated by extraction technology, the separation process formed by the combination is called "full extraction separation process" in metallurgy. This technology has been widely used in the separation and refining of precious metals. Compared with the traditional selective precipitation separation process, there are many advantages, such as simplifying the process, shortening the cycle, reducing the backlog of precious metals and the turnover of various intermediate products that need to be returned to the treatment, reducing energy consumption and processing costs, and improving The direct yield and the safety of the production operation have great flexibility for material adaptability and process configuration.
1. Extraction system and extraction mechanism After the precious metal concentrate is dissolved in aqua regia or HCl/Cl ₂ , the seven precious metals contained in the solution are in the form of chlorine anion or hydrated chlorine and anion. Under different acidity and oxidation-reduction conditions, Various metals have complexes in different valence states and different states in solution, which have different properties and are in complex equilibrium in solution. Solvent extraction technology is in this system, the use of different valence states and the difference in the properties of different state complexes, the precious metals are separated from each other. [next]
The precious metal extraction mechanism mainly includes three kinds of ion pair formation, compound formation and solvation.
(1) Forming an ion pair to extract a noble metal chloride anion as an anionic group can form an ion pair with a plurality of basic organic cationic groups (mainly various amine organic substances) to extract precious metals into the organic phase, which is in the complex The process of attracting and generating organic compounds soluble in organic solvents by positive and negative ions. The charge number and ion size of the chlorine anion have a great influence on the rate at which the ion pair is formed. The more the charge number, the slower the ion pair is formed with the organic cationic group, ie the rate at which the ion pair is generated is (MCI ₆ ) ^3- <(MCI ₆ ) ^2- <(MCl ₆ ) ^- , that is, (MCl ₄ ) ^- >(MCl ₄ ) ^2- ≈(MCI ₆ ) ^2- >(MCI ₆ ) ^3- . The order of the ion pairs formed by ion exchange for each metal is: (AuCl ₄ ) ^- > (PdCl ₄ ) ^2- ≈ (PtCl ₄ ) ^2- > (PdCl ₆ ) ^2- ≈ (PtCl ₆ ) ^2- ≈ ( IrCl ₆ ) ^2- 》(RhCl ₆ ) ^3- ≈(IrCl ₆ ) ^3- .
The reaction of extracting platinum with a tertiary amine (Am) is:

(2) generating extracted precious metal chloro complex compound ligand anion Cl ^- in other organic compounds can be substituted with groups, such as thioether, carboxylic acid, sulfonic acid, alkyl (hydrocarbyl) phosphoric acid, hydroxy oxime, i.e. The complex exchange of the ligand inner boundary forms a new compound or chelate soluble in an organic solvent, and the precious metal is extracted into the organic phase. Since the structure of most platinum group metal chloride anions is relatively tight, the rate of ligand substitution exchange (coupling) reaction is generally slow.
According to the speed of MCl _m + nS (organic chelating reagent) → -MCI _mn · nS + nCl ^- reaction, precious metals of different valence states can be divided into four categories:
Pt(IV), Ir(IV), Os(IV) are very inert, difficult to exchange Pt(II), Pd(IV), Ru(IV) moderately inert, can exchange Ru(III), Ru(IV), Ir( III), Os(III) is moderately unstable, exchanges fast Pd(II), Au(III) is unstable, and the fastest application of exchange is more thioether or a chlorine-containing anion extracted by a lipid organic compound, such as thioether. (r ₂ S) extraction of palladium, the reaction is:

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A good night's sleep is a key element to a great outdoor experience
We are often asked, "Is it cold to camp outdoors, especially in winter, sometimes in the snow?" "What brand and
model of Sleeping Bag do you have and what is the temperature limit?" This is a very difficult question to answer,
as there are many factors that can affect sleep at night in outdoor camping.

1. choice of campsite, and what to sleep on?
The location of the campsite is key to choosing, flat, sheltered from the wind, and dry - uneven ground directly
affects the sleeping body, even if you are using an air mattress try to find a flat surface.
When camping outdoors, blowing wind can take away body temperature and it can make the outdoor environment
very noisy, so it is also important to choose a campsite that is sheltered from the wind.

2. selection of sleeping gear
In some tests, researchers have found that heat loss through the ground is three times greater than heat loss
through the air. Poor-quality pads can make an expensive sleeping bag feel more or less useless, while a good
sleeping pad may improve the quality of your sleep. A good sleeping pad will keep you comfortable on the
uneven ground of a worse campsite, while also providing a key barrier against heat loss.

3. Keep your sleeping environment dry
What protection do you have to keep you and your sleeping bag dry and windproof?
Where do you sleep, a hut, a tent, a snow cave, or an alpine hut? All of these can affect your sleep. Staying
dry is not only about protecting yourself from precipitation, but it is equally important to deal with condensation.
If your sleeping bag gets damp, try to dry it out in the sun or build a fire to dry it out before you go to bed.

As a professional supplier of camping outdoor products, we are committed to bringing our customers a great
outdoor experience and high-longevity outdoor sleeping products, and we look forward to working with you
in the future.

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Ningbo Autrends International Trade Co., Ltd. , https://www.zjouterlead.com