Stone sulphur

Lime sulfur method for extracting gold, is China's first new non-cyanide gold leaching technology. Zhang Jian and others have done a lot of research on this. The stone sulphur mixture is made of cheap and easily available lime and sulfur, which is non-toxic and environmentally friendly.
At present, the leaching gold process of the Lime-Sulfur-Synfur-Synfur-Solution (LSSS) method has just started, and the theoretical research on the mechanism of leaching gold is still rare. The main components of the stone sulphur mixture are calcium polysulfide (Cat S.) and calcium thiosulfate (CaS ₂ 0 ₃ ). Therefore, the gold leaching process of the sulphur sulphur method is a combination of both polysulfide leaching gold and thiosulfate leaching gold, so the use of the stone sulphur mixture method has superior leaching gold properties, and is more suitable for treating carbon and arsenic. , antimony, copper, lead refractory gold Ore. However, this method is still immature in technology and cannot handle more refractory gold mines, which needs further study.
Stone Sulfur (ISSS) is a new type of non-toxic synthetic leaching agent synthesized from cheap lime, sulfur and suitable additives. It can effectively dissolve gold and silver in an alkaline medium in the presence of additives, and the effect is better than a single agent.
It is well known that elemental sulfur has a strong electronegativity and is prone to form polysulfides or thiosulfates with alkali metal or alkaline earth metal ions. The precious metal has a strong affinity with sulfur, and it is easy to form sulfide. The polysulfide is soluble. This is the theoretical basis for the dissolution of gold and silver by the stone sulfur mixture (calcium sulfide + calcium thiosulfate).
The nature of the stone sulphur mixture reacts different proportions of lime and sulphur in solution to form different polysulfides and thiosulfates:

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Thus, calcium polysulfide solution is a rather complex solution, which contains not only sulfur, also contain various valence sulfide, elemental sulfur is reacted is usually present in the most stable form of a ring of eight ₈ sulfur S, When it is dissolved, the S ₈ structure is attacked by S ² and SO ₃ ^2- present in the solution, and ring-opening generates linear sulfur. Various reactions occur between them, which makes it difficult to further analyze and understand the solvent. It is self-evident that the stone sulphur mixture can react with many metal ions.
When lime or slaked lime, sulfur and additives are used in boiling water, the possible reactions are:
1 when pH=6~8

4S+3H ₂ 0 ==== 2HS ^- +S ₂ 0 ₃ +4H ⁺ +2e ^-

â‘¡ When pH≥14, the above formula HS ^-, H ⁺ reacts as follows:

HS ^- +OH ^- ==== S ^2- +H ₂ 0

H ⁺ +OH ^- ==== H ₂ 0

Therefore, the reaction of sulfur in this action is:

4S+60H ^- ==== 2S ^2- +S ₂ O ₃ ^2- +3H ₂ 0

S+60H ^- ==== SO ₃ ^2- +3H ₂ 0

The principle of leaching gold from the stone sulphur mixture method 1) General chemical principle The sulphur sulphur mixture contains S _x ^2- , S ₂ 0 ₃ ^2- , S ₃ ^2- , S ^2- plasma, which form a stable complex with gold. Polysulfide ions, like peroxygen ions (0 ₂ ^2- ), are oxidizing and can oxidize Au (0) to Au(I). The resulting Au(I) can form a stable complex with various coordination ions in solution. As the concentration of Au(I) is continuously lowered, Au (0) is continuously dissolved.
The key to leaching gold is not only the oxidation of Au (0) by oxidants, but more importantly, the oxidized Au(I) forms a stable complex with the coordination ions in the solution. Cyanide and sulfur W (Thio) are the most famous leaching gold solvents, and they form a stable complex with Au(I) in the presence of oxidant. The complexes formed by S ₂ 0 ₃ ^2- , SO ₃ ^2- , S ^2- and Au(I) have higher stability than the complexes of sulfur veins and Au(I), close to the complex of cyanide and gold. , the order is:

Ligand ThiO < S ₂ 0 ₃ ^2- < SO ₃ ^2- < S ^2- < CN ^-

1gβ 25.3 29.3 30.0 39.8 41.0

This is the main principle and basis for the leaching of gold from stone sulphur.
Since the 1950s, Soviet scholars have studied the thermodynamics and kinetics of gold extraction with thiosulfate and polysulfide, respectively, and believe that both reagents can leach gold. In the future, many scholars used these two reagents to carry out leaching gold experiments and research from mineral raw materials, and published many theoretical and applied papers and special issues. These work have important enlightenment and reference for the study of gold sulphur leaching agent.
In the polysulfide gold extraction system, there are mainly polysulfide ions S ₄ ^2- and S ₅ ^2- , which can form stable five-membered ring and six-membered ring conjugate with gold. The reaction may be:

Au+S ₄ ^2- —→[AuS ₄ ] ^- +e ^-

Au+S ₅ ^2- —→[AuS ₅ 〕 ^- +e ^-

In a polysulfide system, sulfur atoms are interconnected by a common pair of electrons to form a polysulfide ion S _x ^2- , which has a dual role of oxidation and coordination during the gold dissolution process. [next]

6Au+2S ^2- +S ₄ ^2- —→6AuS ^-

8Au+3S ^2- +S ₅ ^2- —→8AuS ^-

6Au+2HS ^- +20H ^- +S ₄ ^2- —→ 6AuS ^- +2H ₂ 0

8Au+3HS ^- +30H ^- +S ₅ ^2- --→ 8AuS ^- +3H ₂ 0

In the gold dissolution system in the thiosulfate solution, an oxidant is present, and S ₂ 0 ₃ ^2- is a gold ligand, and the reaction is:

1
Au+4S ₂ 0 ₃ ^2- +——0 ₂ +H ₂ 0 —→ 2[Au(S ₂ 0 ₃ ) ₂ ] ^3- +20H ^-
2

In the presence of Cu(NH ₃ ) ₄ ²⁺ , the reaction proceeds rapidly:

Au+2S ₂ 0 ₃ ^2- +Cu(NH ₃ ) ₄ ²⁺ —→ [Au(S ₂ 0 ₃ ) ₂ ] ^3- +Cu(NH ₃ ) ²⁺ +2NH ₃

Many studies have shown that good results are obtained by leaching gold from ore with a single polysulfide or thiosulfate.
Combining the two for gold extraction will definitely achieve good results. The stone sulphur mixture is a mixed solution mainly composed of polysulfide and thiosulfate. The practice of leaching gold shows that the stone sulphur mixture is an excellent gold solvent for leaching.
2) Electrochemical principle Yu Nengwen and Zhang Jian conducted electrochemical research on the stone sulfur mixture system. Five stone sulphur mixture compositions were selected, as shown in Table 1, and electrochemical measurements were performed using a HDV-7 potentiostat.

Note: G is an oxidant.

Determination of the potential of the 1LSSS system. Figure 1 below shows the potential-time curve of the LSSS system. As can be seen from the figure, each curve has its maximum potential value range. Curves 1, 2, 3, and 4 have higher potential stability than curve 5 except for the higher potential value. From an electrochemical point of view, that is, adding Cu ²⁺ , NH ₃ , Na _{2 to} LSSS. The effect of S0 ₃ on the system potential is not as obvious as the addition of oxidant G. Curve 5 also shows that the potential of the ISSS leaching gold system containing oxidant G will become extremely unstable after 3-4 hours, which will be detrimental to the dissolution of gold. Because the usual gold-smelting process takes 4-6 hours, the process of leaching gold for some gold mines is even 8~12h. Therefore, it is important to select the appropriate oxidant for the LSSS leaching gold system.
Figure 1 also shows that the composition potentials of the curves 3, 4 and 1, 2 are significantly improved, and the variation law is basically similar to the curves 1, 2 . This proves that the electrochemical-catalytic mechanism of Cu ²⁺ and NH _{3 ^{in the}} process of leaching gold _^from LSSS, that is, in the presence of copper and ammonia, can significantly promote the dissolution of gold. In addition, it has been confirmed that except for the LSSS composition shown by the curves 3 and 4, the composition of the curves 1, 2 can dissolve gold and silver at room temperature and pH>14. [next]
The activation energy of the gold electrode reaction in the 2LSSS system is based on the theoretical expression of activation energy:

i(y)=Bexp[-E(y)/RT]

Where i(y) - current density, A / m ² ;
E(y) - activation energy, kJ/mol;
T - temperature, K;
R——gas constant, 8.314 J/(mol·K);
B - is constant for a specific electrode;
y - the electrode overpotential is constant.
Take the logarithm of the two sides of the above formula:

Ln i(y)=ln B-[E(y)/RT]

This formula shows that ln i(y ) is linear with 1/T and its slope is [-E(y)/R].
Based on the results of the potential measurements of curves 3 and 4, a representative ISSS system with Cu ²⁺ and NH ₃ added was selected. The relationship between ln i(y)-1/T at the same overpotential was measured by experiments. ,as shown in picture 2. The activation energy of the gold electrode reaction can be obtained from the slope of the line in Figure 2:

[-E(y )/R]=k

E(y)=-kR=-(-0.2025)× 8.314=16.835(kJ/mol)

Figure 1 Figure 2

According to the principle of electrochemistry:
The gold electrode reaction is controlled by diffusion in the LSSS system. Therefore, in the LSSS method of leaching gold, by adjusting the stirring speed of the process, the leaching time is appropriately extended, and the LSSS normal temperature and atmospheric pressure leaching gold process can be completely realized.

Highway Sound Barrier

Brief introduction
Acoustic Barrier For Highway is mainly used as a noise reduction of road, highway, viaduct and other noise sources. It is a kind of barrier set at the side of road or railway in order to reduce the impact of vehicles' noise on residents nearby.
Specification
1.Material: PC Acrylic board,Plastic panle, steel sheet or aluminium sheet
2.Inner material: Glass wool
3.Sheets thickness: 0.8-1mm,but we can also design as our clients request.

4.Panel size: Width-500mm,Length2000mm is standard size ,the panel can be longer ,but no more than 4meters.