Sulfide solubility

Tall oil rosin is a by-product of paper manufacturing. Raw wood chips are digested under heat and pressure with a mixture of sodium hydroxide and sodium sulfide. Soluble sodium salts of lignin, rosin, and fatty acids are formed, which are removed from the wood pulp as a dark solution. The soaps of the rosin and fatty acids float to the top of the mixture, where they are skimmed off and treated with sulfuric acid to free the rosin and fatty acids. This mixture, known as cmde tall oil (CTO), is refined further to remove color and odor bodies fractional distillation separates the tall oil rosin acids from the fatty acids (see Tall oil). 

Clarke, E.C.W. and D.N. Glew (1971), Aqueous nonelectrolyte solutions, Part VIII. Deuterium and hydrogen sulfides solubilities in deuterium oxide and water, Can. J. Chem., 49, 691-698. Corsi, R.L., S. Birkett, H. Melcer, and J. Bell (1995), Control of VOC emissions from sewers A multi-parameter assessment, Water Sci. Tech, 31(7), 147-157. 

Part VIII. Deuterium and Hydrogen Sulfides Solubilities in Deuterium Oxide and Water," Can. J. Chem., 1971, 49, 691-98. 

The water dissociation equilibrium constant, Kw, and the first acid dissociation constant of H28, Ki, are both well documented. 8everal studies have confirmed that K2, the second acid dissociation constant of H28, has a value of 10 [38-43], and not as previously assumed 10 [38]. This results in a substantial revision of known metal sulfide solubilities [44]. Noticeably, the concentrations of... 

Sodium Sulfide Soluble No Low Not Applicable Moderate Moderate Minimal... 

Dilute hydrochloric acid or sulfuric acid Silver nitrate Lead acetate Sodium nitroprusside solution Sulfides, S2 Hydrogen sulfide gas is evolved and detected by odor or lead acetate paper Black precipitate of silver sulfide soluble in hot, dilute nitric acid Black precipitate of lead sulfide Transient purple color in the presence of solutions of alkalis... 

The above approximations would not be vahd for sulfides, like CuS, which are much more insoluble than MnS. First, the water dissociation would begin to play an important role in determining [OH-]. Second, the second stage of hydrolysis, which produces [H2S], would not be negligible compared with the first. Even for MnS, an additional complication arises because of the complexation of Mn2+ with OH-. The full treatment of sulfide solubilities is a complicated problem because of the multiple equilibria that must be considered. 

Sulfide produces an undesirable rotten-egg odor and is toxic when in the HjS gas form. Since the first pKa of H2S is 7.24, it is necessary to maintain pH 9 or above to completely prevent evolution of H2S gas (Fig. 12.7). Although excess H2S is necessary for the precipitation reaction, the excess must be kept to a minimum. Furthermore, although metal-sulfide solubility with respect to pH exhibits U-shaped behavior (Fig. 12.8), its solubility within the desirable pH range is extremely small (MCLs are met) (Fig. 12.9). Precipitation of metal-sulfides is normally carried out using Na2S or NaHS. However, not all metals precipitate effectively by sulfide. For example, chromium (Cr3+) precipitates effectively as a hydroxide rather than sulfide. 

An example is given in Figure 6.11, giving both complex stabilities and sulfide solubility products. 

A quantitative calculation of metal sulfide solubility requires treating several simultaneous equilibria, as the following example illustrates. 

Properties Orange-yellow powder odorless. Insoluble in water soluble in concentrated hydrochloric acid with evolution of hydrogen sulfide soluble in alkali. Decomposes on heating. 

Properties Yellowish-gray or grayish-white powder odor of hydrogen sulfide. Soluble in acids insoluble in water and alcohol. Noncombustible. 

Effect of hydrogen sulfide solubility and water volatility on analysis of process. The solubility of hydrogen sulfide and the volatility of water introduce changes in flow rates of gas and liquid and deuterium concentrations at the top and bottom of the hot and cold towers. Figure 13.34 illustrates the flow scheme and nomenclature to be used in working out these effects. 

Hemley, J.J., Cygan, G.L., Fein, J.B., Robinson, G.R. and D Angelo, W.M., 1992. Hydrothermal ore - forming processes in the light of studies in the rock-buffered systems 1. Iron-copper-zinc-lead sulfide solubility relations. Economic Geology, 87 1-22. 

Brown powder. Decomposed by atmospheric oxygen or heat, forming cobalt sulfide. Soluble in NHg, pyridine and ethylene-diamine, forming deep dark-red solutions. 

The ZnS in the FeS matte shows a positive deviation from Raoult s law. The activity coefficient of molten zinc sulfide in molten ZnS-FeS matte was estimated as 5, Yzns=5,. from the optimized FeS-ZnS phase diagram (2). Zinc sulfide in molten metallic iron and iron oxide should also display a positive deviation from Raoult s law. Therefore, a yzns>5 is expected in the Fe-S-O matte. In fact, the ZnS activity coefficient in an Fe-S-O-Pb matte has been reported (2) to be about 10, a value which was confirmed by our experimental work to be described later in this p ier. Consequently, when the activity of molten ZnS in the Fe-S-O matte is maintained to less than 0.05, the expected zinc sulfide solubility in the Fe-S-O matte should be less than 1 mole %. 

Metal Sulfide Solubility Product Constant (Ksffi... 

---