The side reaction coefficient a M(OH) is calculated as follows:
Coefficient calculation troublesome side effects, can be used various hydroxyl FIG IgC-pH complex metal ions is obtained at the various pH values affect the solubility of the solubility of sulfide e acidity of insoluble metal sulfides having particular solubility Importance. The hydrolysis of S 2- and the hydrolysis of metal ions are closely related to the pH value. In addition, when excess hydrogen sulfide is present in the solution, the solution may contain significant concentrations of molecular metal sulfides and various thio complexes of metals. . Most of the metal thiosulfate complex equilibrium constant is unknown, the solubility of heavy metal sulfide molecules also unmeasured, metal sulfides thus calculated exactly conditional solubility product Ks * difficulty, when considering only S 2- The influence of the hydrolysis and the formation of the hydroxy complex on the solubility of the metal sulfide can be roughly calculated by the following equation: the conditional solubility product K s * of the divalent metal sulfide at each pH condition:
Wherein the primary and secondary ionization constants of K 1 , K 2 ——— H 2 S.
If the precipitant to be added is chemically equivalent to the metal ion to be precipitated, and the pH is not too high, the residual metal ion concentration is estimated by the following formula.
It is worth noting that the residual metal ion concentration does not always decrease with the increase of the amount of the sulfide precipitant. For example, when the mercury is precipitated by H g S, the excess sulfide precipitant will make the mercury Hg(Hs) 2 and HgHS 2 . - The morphological dissolution of HgS 2 2- increases the residual mercury content.
B Precipitation Flotation Mechanism Precipitation flotation is similar in many respects to mineral flotation, which does not require the addition of a chemical amount of surfactant. Flotation collector of non-sulfide ores may also be used a hydroxide, carbonate, phosphate precipitation flotation; sulfide mineral collector flotation agent can be used to sulfide precipitation. The adsorption of the collector on the surface of the precipitated particles is the same as that on the surface of the mineral, and there are physical adsorption and chemical adsorption. [next]
However, because the nature of the precipitated particles is different from that of the mineral particles, it is not the same as the mineral flotation. The aggregate of the precipitate particles is in the form of a loose floc, and the water content of the aggregate is 99 to 99.9%. The hydrophobicity of the surface of the sediment is lower than that of the mineral flotation. Usually only a few milligrams of collector per liter is required, and the addition of flocculant is more important. Each individual unpolymerized precipitate has a particle size on the order of micrometers or nanometers and is in a reactive state, making it difficult to float. Once a flocculent precipitate is formed, it can sometimes be floated without the addition of a collector, since natural water typically contains several milligrams of organic matter per liter, and the resulting hydrophobicity is sometimes sufficient to cause the floc to float.
The adhesion mechanism between the particles and the bubbles is also not identical. In the flotation of minerals, the adhesion between the ore particles and the bubbles is mainly collision adhesion, followed by the precipitation of bubbles on the mineral surface. The adhesion between the solid particles and the bubbles increases with the hydrophobicity of the solid surface, that is, as the contact angle θ increases, and the hydrophobicity is the main factor affecting the adhesion probability.
During precipitation flotation, the precipitation of bubbles on the precipitate is the main form, and during the precipitation formation process, the entrained gas is included, which creates favorable conditions for the precipitation of bubbles. The mechanical adhesion and filtration entrainment associated with the flocculent structure (the flocculated sediment meets the floating bubbles during the sedimentation process, and the network structure of the floc retains the mechanical entrainment of the bubbles inside the floc). The probability of adhesion of particles to bubbles. Therefore, when the flotation is carried out, the adhesion rate between the bubbles and the particles depends not only on the surface hydrophobicity, but also on the floc structure.
(3) Adsorption flotation The objects of adsorption flotation treatment are ions, molecules, micelles, bacteria, algae, micro-granule minerals, etc. The usual adsorption carriers are activated carbon, diatomaceous earth , molecular sieve, activated alumina, sulfonated coal. , ion exchange resins, ferric hydroxide, aluminum hydroxide and the like. Since the adsorption flotation is achieved by the flotation carrier to achieve the enrichment and sorting of the object, the adsorption characteristics, adsorption capacity, regeneration performance and flotation characteristics of the carrier are important factors affecting the adsorption flotation.
The adsorption carrier is an adsorbent. The solid composition, structure, surface state and specific surface area of ​​the carrier have a great influence on the adsorption characteristics and adsorption capacity. A substance having a large specific surface area and a high total surface energy is expected to be an excellent adsorbent. The adsorption of solids in solution can be expressed mostly by the Freundlich empirical formula or the Langmuir formula. Multilayer adsorption for adsorbents lacking pores can be expressed by the BET formula.
The logarithmic form of Freundlich's adsorption isotherm is:
IgΓ becomes a straight line with IgK as the intercept and 1/n as the slope. From the experiment, according to the formula (10), several enthalpy and C are obtained under isothermal conditions; the constants 1/n and K can be obtained, and the most suitable adsorbent can be selected as a criterion.
Where m—the mass of the adsorbent, g;
V———solution volume, L;
C 0 , C———the initial concentration of adsorbate and the equilibrium concentration of adsorption, moI/L. [next]
Figure 4 is the adsorption isotherm of different types of activated carbon. The adsorption capacity of a is the strongest, and the adsorption capacity of c is stronger than that of b at low concentrations. It is appropriate to use a or b under the conditions of adsorption flotation.
If the added adsorption carrier is an iron salt or an aluminum salt, the main mechanism is to use the co-precipitation effect of adsorption, absorption, mixed crystal, wrap, agglomeration, etc. during the precipitation process of iron hydroxide or aluminum hydroxide to take the object from the solution. It is enriched in a carrier of hydroxide. In this case, the addition time, location, and pH of the medium have a great influence on the adsorption co-precipitation capacity.
As with the flotation flotation, the carrier is both reliable in its own floatability and reliable in the hydrophobicity caused by the collector. This mineral flotation is similar and need not be detailed.
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