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Third, △ G - pH map and lgβ ' n - pH map (a) △ G - pH map
Anti-Qing medicament metal ions with mineral standard free energy change â–³ G and free energy change as a criterion, which calculates the relationship between the pH value and plotted for flotation mechanism to explain the best conditions, the flotation determined. It can then be used to select a solution for mineral flotation separation. It can also be used to discuss the mechanism of mineral flotation. In the calculation, if the anion's protonation reaction, the cation hydrolysis reaction, the mineral dissolution or oxidation are considered, the calculation results are more consistent with the experimental results.
The key fluorite flotation of scheelite is to find an efficient inhibitor. The single mineral test, mixed ore test and actual ore sorting results show that citric acid can effectively inhibit fluorite in the flotation separation of scheelite fluorite, thus achieving the separation of scheelite fluorite. Using citric acid as the inhibitor and F 306 as the collector, the crude product can reach the grade of 3.24% and the recovery rate is 88.45%. It indicates that citric acid has practical significance in the flotation of scheelite. According to the principle of solution chemistry, the selective inhibition mechanism of citric acid can be explained by investigating the change in free energy of formation of hydrophilic complexes on the surface of scheelite and fluorite.
In the entire pulp system, the following reactions exist:
The effect of citric acid (H 3 L) and water
Dissolution of scheelite and fluorite
Hydrolysis of Ca 2+
Surface reaction of citric acid and fluorite
Surface reaction of citric acid and scheelite
For the surface reactions (11), (12), (14), (15), since the K value is too small, the reaction is negligible, and only reactions (10) and (13) will be discussed here. The changes in the free energy of their surfaces are expressed as ΔG 1 and ΔG 2 :
ΔG 1 =-RTlnK 1 +RTln[F - ] 2 /[L3 - ]
ΔG 2 =-RTlnK 1 +RTln[WO 2- 4 ] /[L3 - ]
Initial reaction
а Ca 2+ =1+K ′ 1 [OH - ]+ k ′′ 2 [OH - ] 2
a WO 2- 4 =1+K H 1W [H + ]+K H 1W K H 2W [H + ] 2 [next]
It can be seen from Fig. 7 that cT=10-5 mol/L, when pH<8.5, ΔG 1 is negative, and ΔG 2 is positive, that is, the reaction of generating calcium citrate on the surface of fluorite can be spontaneously performed, and For scheelite, it cannot be spontaneously carried out, so that fluorite is inhibited and preferential flotation separation is achieved. With the increase of cT, △G 1 and △G 2 gradually become negative, when c T =10 -2 mol/L, pH When <8.5, ΔG 2 also becomes a negative value, and thus scheelite is also suppressed at this time.
The stoichiometric calculation of the above solution shows that the free energy change of citric acid on the surface of fluorite is ΔG 1 <0 in the wide range of citric acid concentration, and only when the concentration of citric acid is greater than 10 -2 mol/L. At the time, the free energy change of the hydrophilic complex formed on the surface of the scheelite is ΔG 2 <0. Therefore, citric acid is more likely to form a hydrophilic complex on the surface of the fluorite, thereby inhibiting it.
Fig.7 â–³G-pH diagram of scherichite fluorite and citric acid to form calcium citrate
1,2,3 is scheelite, cT is 10-5, 10-4, 10-2mol/L in order
4,5,6 are fluorite, cT is 10-5, 10-4, 10-2mol/L in order
(2) lgβ'n-pH diagram β' n is the conditional stability constant of the metal ion flotation agent complex. It is used as a criterion to reflect the ability of the metal ion to form a complex with the agent, and the flotation condition can be predicted.
Example 1: rutile, complexing collector during flotation hematite selected Italian scholars Marabini et al conditions are selected with the size of the stability constants of the various flotation collector and determining the flotation conditions, respectively, FIGS. 8 and 9 It is a calculated conditional stability constant for the complexation reaction of salicylic acid and N-benzoyl-N-phenylhydroxylamine (NBNPH) with TiO 2+ and Fe 3+ . It can be seen that at pH=3, lgβ' n is the largest, indicating that rutile (TiO 2+ and hematite are the best floatability at this time, and because the β'n of the agent and TiO 2+ is larger than the β' of Fe 3+ n, so rutile should show better floatability than hematite, as shown in Figure 10 and Figure 11.
Figure 8 lgβ'n-pH diagram of complexation of TiO 2+ and Fe 3+ with salicylic acid
Figure 9 lgβ'n-pH diagram of TiO 2+ and Fe 3+ complexation with NBNPH [next]
Figure 10 Rutile (1) and hematite (2)
Relationship between flotation recovery rate R and pH (salicylic acid as collector)
Figure 11 Rutile (1) and hematite (2)
Flotation recovery ratio R to pH (NBNPH) as collector
Effect of Surfactant Adsorption on Properties of Suspended Particles and Suspension Systems (I) Surface Wettability
The adsorption of the surfactant at the solid/liquid interface can change the wettability of the solid surface, hydrophobize the hydrophilic surface or hydrophilize the hydrophobic surface. On the surface of the polar solid, the surfactant adsorbs on the solid with a hydrophilic group, and the lipophilic group faces the water, so that the hydrophobicity of the surface is increased, and it is easy to be wetted by the oil. When the surfactant adsorbs on the surface of the non-polar solid, its hydrophilic group faces the aqueous solution, thus increasing the hydrophilicity of the surface of the adsorbent (for the ionic surfactant, it also increases the surface charge), making it easier for The water is wet.
(2) Changing the mechanical strength of the ore particles The adsorption of surfactant molecules on the particles causes dislocation migration of the surface layer lattice, which causes defects in dots or lines, promotes the generation and expansion of cracks, and thereby reduces the strength and hardness of the particles.
(3) Changing the aggregation/dispersion state The surfactant is added to the solid/liquid suspension system. Due to the adsorption of the surfactant at the solid/liquid interface, the solid/liquid interfacial tension is lowered, the surface free energy is greatly reduced, and the solid is reduced. The tendency of particles to coalesce with each other. At the same time, due to the adsorption of the surfactant, an adsorption film is formed on the surface of the particles, and the particles are prevented from coming close to each other due to the spatial barrier. If it is an ionic surfactant, its adsorption will also charge the surface of the particles, creating an electrostatic repulsion barrier, which further hinders the particles from colliding with each other, thereby preventing re-aggregation.
In a system in which water is used as a dispersion medium, if the surface of the solid is hydrophilic, after the surfactant is added, the hydrophilic hydrocarbon chain is adsorbed on the solid, and the hydrophobic hydrocarbon chain is oriented to extend into the water to make the original hydrophilicity. The solid surface becomes a hydrophobic surface, the solid/liquid interfacial tension increases, and the contact angle between the water and the solid surface increases, resulting in solid particles condensed from the water or displaced to the gas/liquid interface, and the long-chain surfactant ratio The short chain acts as a larger coagulation. Conversely, the adsorption of the surfactant changes the surface of the lipophilic solid particles in the oil dispersion medium to precipitate or coagulate from the oil phase.
Adding an appropriate amount of polymer in the solid/liquid dispersion system, because a plurality of hydrophilic groups in one molecule adsorb to the solid particles to bridge, thereby causing the particles to aggregate with each other to cause coagulation or flocculation. If the concentration of the polymer is too large, it encapsulates the suspended particles to make the suspension system more stable.
(IV) Rheological properties of the suspension In the solid/liquid suspension system, the surfactant is adsorbed at the solid/liquid interface, which in turn affects the rheology of the suspension system. The rheological properties of the suspension refer to the response of the suspension to shear, and the primary indicator of such rheology is the viscosity of the suspension system. In the absence of a surfactant, the solid particles in the suspension system are easily agglomerated. When subjected to shearing, the shear plane will inevitably pass through these agglomerates, causing greater mechanical resistance. At the same time, the mechanical shearing causes the suspended particles to be divided into more small particles, which produces many new phase interfaces, which increases the free energy of the system, and accordingly consumes additional shearing work (the shearing work per unit volume of fluid is shearing) The shear rate and the shear stress multiply increase the shear stress and the viscosity of the fluid. When the surfactant makes the solid particles in a good dispersion state, the particles are separated from each other, and the surface of the particles has an adsorbed surfactant interface film and a hydration film, and no new phase interface is generated when shearing, and the friction between the particles is also It is much smaller, and therefore, the viscosity of the suspension system is lowered.
(5) Influence on the bridge of high polymer
The combination of surfactant and polymer is beneficial to improve the selectivity of flocculation system and flotation system. In flocculation, a surfactant is first added, which is hydrophobic due to its preferential adsorption on a certain mineral particle. Strengthening the hydrophobic interaction between the particles. At this time, the polymer flocculant is added, and the floc is easily generated due to the bridging action of the flocculating agent itself and the hydrophobic action of the surfactant preferentially adsorbed on the mineral surface, thereby improving the minerals. Selective flocculation. For example, anionic polymer flocculants have strong flocculation ability, but the selectivity is often insufficient. In order to improve the selectivity, a surfactant can be used in combination. The results of flocculation separation test on 1:1 mixed ore of hematite and quartz show that the combined use of hydrolyzed polyacrylamide (HPAM) and sodium oleate can increase the flocculation separation index by 0.085 compared with HPAM alone. When the concentration of sodium oleate is 5 × 10-4mol/L and the concentration of HPAM is 2mg/kg, the flocculant is added at one time, and after three times of de-mudging, a flocculating product with an iron grade of 62.7% can be obtained. Professor Lu Shouci believes that the addition of surfactant can first form the dispersed hematite particles into a hydrophobic floc. After the flocculant is added, the polymer bridges to form a plurality of hydrophobic flocs to form a large floc. The effect of the flocculant and the hydrophobic floc is attributed to the hydrophobic interaction between the long carbon chain of the flocculant and the surfactant hydrocarbon chain adsorbed on the mineral surface. [next]
In the flotation, when the polymer is opposite to the electrical property of the collector, the flotation of the collector can be activated, and vice versa. For example, the cationic polymer PAMA (copolymer of methacrylamide-propyltrimethylammonium chloride) and sodium dodecylbenzenesulfonate (NaDDS) can activate the flotation of quartz by sodium dodecylbenzenesulfonate. This is because the cationic PAMA adsorbs on the negatively charged quartz surface to form the first adsorption layer, and the sodium dodecylbenzenesulfonate is adsorbed on the cationic group on the quartz surface by electrostatic force to form a second adsorption layer, so that the ore particles The surface becomes hydrophobic and floats; conversely, if the collector is dodecylamine (DDA), the PAMA is adsorbed on the negatively charged quartz surface, covering the adsorbed dodecylamine molecules, making the surface hydrophilic. Thereby, the flotation of the British is suppressed, as shown in FIGS. 12, 13, and 14.
Figure 12 Effect of cationic polymer PAMA concentration on dodecyl flotation quartz (pH=6.5±0.3)
1—no PAMA; 2—0.5 mg/kg PAMA;
3-1.0mg/kg PAMA; 4-10.0mg/kg PAMA
Figure 13 Effect of cationic polymer PAMA concentration on sodium dodecyl sulfonate flotation quartz (pH = 6.1 ± 0.6)
1—no PAMA; 2—1.0 mg/kg PAMA;
3-10.0mg/kg PAMA; 4-100.0mg/kg PAMA
Figure 14 cationic polymer PAMA and DDA and
Schematic diagram of NaDDS interaction on quartz surface
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