Anodizing of sulfur in electrolytic slurry

A significant advantage of the slurry electrolysis process is that during the pulp electrolysis process, the sulfur in the mineral is produced in the form of elemental sulfur and can be extracted and recovered. The elemental sulfur produced is easy to store and transport, and solves the problem of SO ₂ pollution and excessive sulfuric acid production by pyrometallurgical smelting, and difficult transportation and sales of sulfuric acid.

When Bismuthinite ore slurry electrolysis process yield of elemental sulfur slurry is an important aspect of an electrolytic anodization process, Wang Chengyan, Qiu Fan et mapping the set S ⁰ and H ₂ S polarization curve on the graphite anode.

The test conditions were as follows: 333K, NH ₄ Cl was 200g ∕L, H ⁺ was 1g ∕L, stirring speed was 600min ^-1 , scanning speed was 1mV ∕s, and the measured anodic polarization curve is shown in Fig. 1.

Figure 1 Anodization curve of S and H ₂ S

1-NaCl (200 g ∕ L) + H ⁺ (1 g ∕ L);

2-NaCl(200g∕L)+H ⁺ (1g∕L)+S (L:S=10:1);

3-NaCl (200 g ∕L) + H ⁺ (1 g ∕ L) + Na ₂ S (0.01 mol ∕ L);

It can be seen from Fig. 1 that line 1 and line 2 are substantially coincident, indicating that elemental sulfur is not substantially oxidized on the anode, and line 3 has a significant anode current, indicating that an oxidation reaction of S ^{2 -} occurs at the anode due to The study carried out in the acidic system can be considered as the oxidation reaction of H ₂ S produced by Na ₂ S acid dissolution on the anode:

It can also be seen from the figure that when the anode current density is greater than 7 mA/cm ² (70 A/m ² ), the anode will undergo an oxygen evolution reaction. Therefore, under actual slurry electrolysis conditions (anode current density is 15 to 25 mA ∕ cm ² ), the oxidation reaction of H ₂ S on the anode is not dominant. The main anodic reaction is the oxidation reaction of Fe ^{2 +.}

Due to kinetic reasons, the oxidation of S ⁰ by Fe ^{3 +} is very slow, indicating that elemental sulfur is relatively stable under the conditions of slurry electrolysis. The related research work shows that the oxidation of elemental sulfur to SO ₄ ^{2 -} and HSO ₄ ^- in aqueous solution is extremely slow. This is why the pulp electrolysis process can achieve a higher elemental sulfur yield.

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