Sulfur potential diagram

Table V summarizes the experimental results of the tests with low oxygen content in the matte i.e., tests 1-5,9and 10. The matte conqxrsititMi and nramalized zinc solubility at Pzn=0.1 atm and 1350°C as reported Table III are repeated here. The zinc solubility has been converted into mole fractions to calculate the activity coefficient. The sulfur potentials at 1450 and 1200°C are taken from the reported activity diagrams for Fe-S-O matte (9), from which the sulfur potentials at 1350°C are estimated. The activities of ZnS in the matte were calculated from azns = K Pzn (Ps2), where K is the equilibrium constant for reaction Zn(g)+V2S2(g)=ZnS(l) and was estimated to be 64 at 1350 C. The activity coefficient of ZnS in the matte was estimated (Table IV). Although the estimated activity coefficient of ZnS varied from 7 to 22, it has an average value of 12.6 and is very close to the reported value, 10 (8). Considering the many possible sources of aror in the tests, it is not surprising that there is a large scatta in the estimated ZnS activity coefficient Nevertheless, the experimental data wae in close agreement with the theoretical predictions.

Fig. 16.21 Potential diagrams (values in V) for sulfur, selenium and tellurium at pH = 0.

As in the corresponding discussion for the halogens (Section 22-3), oxidation-reduction chemistry is a primary concern here. To assist in this discussion, we provide electrode potential diagrams for some important sulfur-containing species in Figure 22-13. 

Many of the sulfur oxoaeids and their salts are eonneeted by oxidation-reduetion equilibria some of the more important standard reduetion potentials are summarized in Table 15.19 and displayed in graphie form as a volt-equivalent diagram (p. 435) in Fig. 15.28. By use of the eouples in Table 15.19 data for many other oxidation-reduetion equilibria ean readily be ealeulated. (Indeed, it is an instruetive exereise to eheek the derivation of the numerieal data... 

In the lead-acid battery, sulfuric acid has to be considered as an additional component of the charge-discharge reactions. Its equilibrium constant influences the solubility of Pb2+ and so the potential of the positive and negative electrodes. Furthermore, basic sulfates exist as intermediate products in the pH range where Fig. 1 shows only PbO (cf. corresponding Pour-baix diagrams in Ref. [5], p. 37, or in Ref. [11] the latter is cited in Ref. [8]). Table 2 shows the various compounds. 

In Fig. 2.2, the potential-pH diagram is represented for the stable equilibria of the system sulfur-water at 25 °C, i.e., equilibria comprising the forms H28,... 

Table 2.1 states the redox relations at standard conditions. Extended information on the distribution of the redox pairs — still under equilibrium conditions but under varying redox potential and pH — is given in a Pourbaix diagram. Figure 2.4 is an example of such a diagram for the binary sulfur and oxygen system in water at 1 atm and 25°C with the sum of the concentrations of... 

Abstract This chapter first explains the natural flotability of some minerals in the aspect of the crystal structure and demonstates the collectorless flotaiton of some minerals and its dependence on the h and pH of pulp. And then the surface oxidation is analysed eletrochemically and the relations of E to the composition of the solutions are calculated in accordance with Nemst Equation. The E h-pH diagrams of several minerals are obtained. Thereafter, electrochemical determination such as linear potential sweep voltammetry (LPSV) and cyclic voltammetry (CV) and surface analysis of surface oxidation applied to the sulphide minerals are introduced. And recent researches have proved that elemental sulfur is the main hydrophobic entity which causes the collectorless flotability and also revealed the relation of the amount of sulfur formed on the mineral surfaces to the recoveries of minerals, which is always that the higher the concentration of surface sulphur, the quicker the collectorless flotation rate and thus the higher the recovery. 

This step is essential in the manufacture of detergent active ingredients as it converts the sulfonic acids or sulfuric acid esters (products produced by processes I-M) into neutral surfactants. It is a potential source of some oil and grease, but occasional leaks and spills around the pump and valves are the only expected source of wastewater contamination. A process flow diagram is shown in Figure 14. 

In other papers by the same group, the effects of sulfur adsorbed or segregated on the Ni surface on corrosion or passivation were described, including the sulfur-induced enhancement of dissolution and the blocking of passivation. It was shown how the conditions of stability of adsorbed sulfur monolayers could be predicted on thermodynamical grounds and this was illustrated by a potential-pH diagram for adsorbed sulfur on nickel in water at 25 °C. (See Refs. 22, 25-29 and papers cited therein.)... 

Figure 1. Tridimensional Pourbaix diagram. XYZ plot of redox potentials, MDC of sulfur and pH. Aqueous solutions at 25°C. X = redox potential, volt vs. NHE Y = log (MDCU defined by Equation 1, i — moieties identified on curves (Sc,...

Figure 22. Potential reaction diagram for N2 reduction in the absence and in the presence of metal-sulfur complexes.

Any species capable of oxidizing either Fe " or HjS at pH 6 cannot survive in this environment. According to the Pourbaix diagram for iron (Figure 5.11), the potential for the Fe(OH)j/Fe couple at pH 6 is approximately 0.3 V. Using the Latimer diagrams for sulfur in acid and base (see Resource Section 3), the S/H2S potential at pH 6 can be calculated as follows ... 

The driving force of the reaction at Eq. (1) comes from the thermodynamic instabihty of elemental sulfur in water. The Pourbaix diagram of the S8/H2O system at 20 °C shows elemental sulfur to exist as a separate phase only at very low pH values and redox potentials in the range 0.1-0.3 V [11]. 

FIGURE 22.24 Anodic polarization curves for passivation and transpassivation of metallic iron and nickel in 0.5 kmol m-3 sulfuric acid solution with inserted sketches for electronic energy diagrams of passive films [32] /ip = passivation potential, TP = transpassivation potential, fb = flat band potential, /Fe = anodic dissolution current of metallic iron, Nl = anodic dissolution current of metallic nickel, and io2 — anodic oxygen evolution current. 

Stability relatiMshipa and the sequence of formation of surface reaction layers can he predicted from potential-pH diagrams. The Cu-O-S-HjO system will be used as an example- Figure 93-6 represents the Cu-O-S-H.O system at S = 10". Stable regions for Cu2S and CuS indicate that sulfur films will not form adjacent to CujS since the reaction... 

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