Fine particle dressing agent (2)
4 flocculation copper minerals, affect the amount of potassium amyl xanthate with PEO (3mg / kg) FIG.
1—Chollanet; 2— Malachite
Zhongnan University of Technology investigated the flocculation behavior of wolframite and quartz , and investigated the benzyl phthalic acid or styrene phosphonic acid collector with flocculant CF 1 (PAMS: HPAM = 1:1), CF 2 (PAMS). : PAM = 1:1) Flocculation ability of the compound and PAMS to a single mineral, wherein PAMS and HPAM are sulfonates and partial hydrolyzates of polyacrylamide, respectively. Through experiments, the order of flocculation ability is CF 1 >CF 2 >PAMS, and also indicates that HPAM>PAM>PAMS, that is, the greater the degree of hydrolysis, the stronger the flocculation ability. The effective amount of the three flocculants is 2~80mg/L. When the dosage is too large, the flocculation ability is weakened due to the undulation of the polymer. Since pure quartz has few surface active points, the flocculant has no flocculation effect on quartz, and there is a dispersion phenomenon at high dosage. In addition to the amide group, PAM and PAMS contain active groups such as a carboxyl group and a sulfonic acid group, respectively, and have a certain selectivity to the wolframite. Therefore, the selectivity of CF 1 is good, and the optimum dosage is only 5 mg/kg. Carboxymethyl cellulose or corn starch as flocculants, dispersants, flocculation of the micro-fine apatite, calcite dispersion, and then mixed with the cooperation collector sarcosinate and polyoxyethylene nonyl phenyl ether, sorting jacupiranga Phosphate ore, ore containing 5.8% P 2 O 5 and less than 6μm ore content 4.2%, after a rough selection and secondary selection, a concentrate with 35% P 2 O 5 and a recovery rate of 65% can be obtained.
In addition, the use of a polymer flocculant in combination with an oil collector is also one of the ways to recover fines. It has been reported that an oil (isooctane) emulsion stabilized with cellulose xanthate can effectively sort less than 2 μm chalcopyrite from fine-grained quartz gangue under conditions of Ph11 and a slurry concentration of 5.1%. It is agglomerated with polymer-stabilized oil beads to separate from the quartz. At this time, the polymer xanthate plays a multiple role in the collection, flocculation and emulsification, and the oil beads are the carrier of the recovered ore particles in addition to the capture effect. However, at other pH conditions, the process loses selectivity due to the activation of the copper surface by the copper ions.
(2) with an activator or inhibitor complex with an anionic polymeric flocculant as polyvalent metal cations can often play a role in activation, similar to that selects flotation principle, as the case may be. The flocculant is used in combination with an inhibitor to prevent adsorption of the polymer on the surface of non-target minerals. Commonly used dispersing agents, such as water glass, sodium hexametaphosphate, etc., also disintegrate gangue minerals while also inhibiting them.
In summary, the use of inhibitors and activators increases the difference in surface properties between the separated minerals, thereby increasing the likelihood of selective adsorption of the flocculant.
4. Reasonable addition of flocculant On the basis of understanding the performance of flocculant, reasonable addition of flocculant is also an important factor to improve flocculation effect and selectivity. For example, the flocculation effect of the flocculant is related to the concentration of the flocculant. Generally, effective flocculation is ensured at a lower dosage, and excessive flocculant causes dispersion of the particles. For selective flocculation, the amount of flocculant is much less than the flocculation in solid-liquid separation. The appropriate amount should be determined by experiment according to the specific conditions. Generally, when the molecular weight is the same, the larger the molecular weight, the greater the sedimentation rate. If the same sedimentation rate is used for comparison, the larger the molecular weight of the polymer, the smaller the amount can be. When the amount of the polymer exceeds the optimum concentration, the flocculation settling velocity is rather lowered, and redispersibility of the particles occurs. The addition method and sequence of the flocculant also have a certain influence on the flocculation effect. Flocculants are often formulated as a dilute solution. Generally, a pH adjuster, a dispersant or other auxiliary agent is added first, followed by a flocculant. The auxiliary agent can be added to the grinding system in advance. Flocculation should be considered for batch addition or stepwise addition.
In addition, when adding flocculant, the heart must control the stirring strength, because the molecular chain of the flocculant is long, can not withstand strong shearing action, easily cause breakage, cause degradation of flocculant, and redisperse the suspension. Moderate agitation, no turbulence.
(3) Flocculation mechanism [next]
Polymeric surfactant flocculation is a complex physical and chemical process, and the mechanism of action is still limited to qualitative interpretation. It is generally considered to be a bridging mechanism as shown in Figure 5.
Figure 5 Coagulant bridging mode
The polymeric surfactants are all high molecular weight long chain macromolecules having a plurality of repeating hydrophilic, hydrophobic based structural units. When a polymer surface active molecule collides with a particle, certain functional groups in the molecule are adsorbed on the surface of the particle, and other portions extend into the solution. The same adhesion occurs if the second particle with some adsorption vacancies contacts the overhang of the polymer molecule. Thus, the two particles form aggregates by means of polymer molecules, in which case the polymer molecules act as a bridge, as shown in FIG. If the second particle is not encountered, the overhanging portion of the polymer molecule may adsorb to other locations of the originally adsorbed particle, at which point the polymer molecule no longer functions as a bridge, as shown in FIG. When the flocculant is added in excess, the surface of the particles is saturated by the polymer molecules, and the surface of the particles has no adsorption vacancies, so that the polymer loses bridging effect. At the same time, due to the steric hindrance effect of the polymer molecular adsorption film, the particles repel each other and the particles are again stably dispersed, as shown in Fig. 5. In some cases, strong or prolonged agitation causes the floc to break, and the overhanging portion of the polymer molecule is in turn adsorbed to other vacancies on the surface of the original adsorbent particle, thereby redispersing the particle, as shown in Figure 5 6. [next]
The essence of the bridging action is that the flocculant molecules are adsorbed on the surface of more than two particles at the same time, and the particles are joined together by their long chain characteristics. The necessary conditions are: 1 the polymer has enough adsorption groups, the molecular chain is stretched by its own charge; 2 the surface of the mineral particles has enough vacancies for further adsorption; 3 the polymer concentration should be appropriate, and the particle suspension is excessive stability. An important feature of the bridging action is that under appropriate conditions, the adsorbed polymer molecules can bridge across the electric double layer between the two particles. However, due to the difference in composition and structure of different types of surfactants, there are some differences in the flocculation mechanism.
The -CONH 2 groups on the molecular chain of the nonionic polymer surfactant are attracted to each other by hydrogen bonding, and thus the molecules are easily present in a bent torsion state in water. Since there is no dissociated ionic group in its molecular chain, it has no special electrostatic interaction with the particles, but is close to the particles by stirring, and the amide group forms a hydrogen bond with the particles to combine. The non-ionic polymer molecules are mostly cyclically adsorbed on the surface of the particles, and when they are close to the particles, they rapidly brid to form flocs. Since the chain-like bridging effect is less, the particles are closer to each other, and it is easy to form small and tight flocs. The electrical properties of the surface of the particles have an effect on the flocculation effect. For example, at high pH values, the repulsion between the particles increases due to the increase of the negative charge on the surface of the particles, which is difficult to access each other, and the bridging flocculation between them is disadvantageous.
The morphology of anionic polymer surfactants is different due to the introduction of a negatively charged anion group -COO - in the molecular chain of the non-polar polymer, the molecular chain stretching by the electrostatic repulsion between the anionic groups, and stretching The state is fixed to the surface of the particles. This chain-like fixation is more likely to contact the particles than the chain and chain, and achieve bridging flocculation. However, studies have shown that the pH of the medium has an important effect on the flocculation of anionic polymers. In addition, the hydrolyzed polyacrylamide has a carboxyl group and can interact with the particles by chemisorption, so the flocculation effect is also related to the degree of hydrolysis.
The cationic polymer is mainly flocculated by the electrostatic adsorption of the cationic group dissociated in water and the negative charge on the surface of the particle by the electrostatic adsorption of the particles and the polymer. First, a part of the polymer is adsorbed on the surface of the particles, so that the potential of the particles is lowered, the distance between the particles is shortened, and then flocculation is achieved by bridging with other unreacted polymers. Since the adsorption of particles by the cationic polymer has the effect of lowering the surface charge and compressing the electric double layer, the molecular length required for the bridging effect of the cationic polymer is smaller than that of the nonionic polymer, that is, the molecular weight can be smaller. . In contrast, anionic polymers do not have a large molecular weight for negatively charged particles due to electrostatic repulsion.
For cationic polymers with a long molecular chain length relative to the particles, Gregory proposes a mosaic-like, chain-like sturdy model on the surface of the particles. As a result of this fixation, an uneven distribution of the surface charge of the particles is caused, and the adjacent oppositely charged particles attract each other to flocculate. This effect is similar to compressing the electric double layer to cause the colloidal particles to agglomerate, which is called an electrostatically combined model.
Second, the hydrophobic agglomeration sorting agent For the fine particle material with particle size less than 10μm, the conventional flotation method is not effective, and the selective hydrophobic agglomeration method is often used to obtain good results.
Any process in which the surface of a mineral particle is selectively hydrophobized to form a hydrophobic agglomerate and then separated by a suitable physical method is referred to as a hydrophobic agglomeration sorting method. For example, emulsification flotation, pellet agglomeration, two-liquid separation, shear flocculation-flotation, carrier flotation, etc. are all classified as hydrophobic agglomeration. Among them, shear flocculation-flotation and carrier flotation can not effectively separate the fine-grained minerals, so it will not be introduced.
(1) Characteristics of hydrophobic agglomeration sorting
The various sorting processes for hydrophobic agglomeration sorting, although with different characteristics, have the following common features:
1 by selectively adding the necessary surfactants and adjusting agents to selectively hydrophobize the surface of the mineral particles;
2 by stirring, a certain mineral grain forms a hydrophobic agglomerate with a certain strength, while other mineral particles remain dispersed, and moderate or strong agitation is required to make the slurry in a strong turbulent state, and the stirring time is usually greater than 10 min;
3 separating the hydrophobic agglomerates and the dispersed ore particles by appropriate physical means, and the separation method may be flotation, magnetic separation, deliming, sieving, phase separation, etc.;
4 Neutral oil is often added during agitation to enhance hydrophobic agglomeration.
All processes have similar basic processes: adding chemicals, vigorously stirring, forming hydrophobic agglomerates, and agglomerating separation. The only difference between them is that the amount of non-polar oil added is different (from zero to more than 10% of the volume of the slurry) and the physical means used in the separation process are different.
The non-polar oil is used instead of the surfactant, which is shear flocculation; when the oil-water ratio is about 0.1%, it is the oil-powder mixed flotation, and the ratio of the non-polar oil to the surfactant is about 1:1; When the oil-water ratio is further increased to about 1.0%, it corresponds to the case of emulsification flotation; the oil-water ratio of the pellet agglomeration is about 5%; for the two-liquid separation, the oil-water ratio can be as high as 10% to 20%. Apolar oils have been shown to enhance the formation of agglomerates of hydrophobic particles, and non-polar oils should be used in an emulsified form to achieve good sorting results. [next]
The hydrophobic agglomeration process does not follow the DLVO theory. The formation of particle agglomerates is mainly dependent on the "hydrophobic association energy" produced when the hydrophobic particles are in direct contact. Professor Lu Shouci studied quartz in 1983 -, dodecylamine Ling manganese ore - sodium oil hematite - changes in the relationship between hydrophobicity and flocculation of oil sodium system, and the use of water structure theory and modern micelle formation principle, The quantification theory of hydrophobic interaction energy was first proposed. He pointed out that the hydrophobic interaction between mineral particles can have two components, namely hydrophobic interaction energy based on interfacial water structure change and hydrophobic association energy based on hydrocarbon chain intercalation association.
(B) the role of surfactants in the classification of hydrophobic clusters
The surfactant mainly functions as a collector and an emulsifier in the hydrophobic agglomeration sorting process.
1. Use as a collector The principle of hydrophobic agglomeration sorting is to use the action between particles with a hydrophobic surface in water. As mentioned above, when the hydrophobic particles enter the water, it will inevitably lead to an increase in the free energy of the system. Hydrophobic ore particles will be strongly repelled by surrounding water molecules, forcing them to move closer together, forming agglomerates, reducing the free energy of the system in a way that reduces the solid-liquid boundary area, which is the essence of hydrophobic action. Therefore, the mineral surface must be selectively hydrophobized prior to hydrophobic agglomeration sorting.
For mineral particles with a hydrophilic surface, it is necessary to use the action of a surfactant. The surfactant selected should be preferentially adsorbed on the mineral particles to be sorted by hydrophobic agglomeration to hydrophobize the surface of the particles. The choice of surfactant is similar to that of the float collector.
In order to strengthen the hydrophobic agglomerate, a non-polar oil and a modifier are also added. The non-polar oil has three functions: one is to enhance the hydrophobicity of the particles; the other is to form an oil bridge to enhance the strength of the agglomerates; and the third is a carrier for the hydrophobic particles. As the amount of oil increases, its above functions gradually appear in turn. Many experiments have shown that the adhesion of a non-polar oil between two hydrophobic particles can form an oil ring, and the production of the oil ring further increases the strength of the hydrophobic agglomerates, resulting in a significant increase in the size of the agglomerates. The adjusting agent mainly includes common flotation adjusting agents such as sodium silicate, starch and dextrin.
2. The hydrophobic floc formed by using the emulsifier single collector is small in size and uneven, and the floc structure is loose and the stability is poor. In practice, the method of adding non-polar oil is used to strengthen the hydrophobic floc formed by the collector. group. According to the different amount of non-polar oil added, the flocculation of hydrophobic flocs with non-polar oil can be divided into oil-powder flotation (oil-water ratio is about 0.03~0.15) and emulsification flotation (oil-to-drug ratio is about 0.6). ~2.0). In both methods, the non-polar oil is emulsified and dispersed by adding an appropriate amount of emulsifier, and the dispersed oil beads are used as a bridging medium to realize the flocculation between the ore particles, and then the bubble flotation is most effective. The difference is that emulsified flotation is more suitable for fine-grained materials. Since the fine-grained material has a larger surface area, the amount of the non-polar oil used for the emulsification flotation is correspondingly increased, and it must be used as an emulsion with a collector or/and an emulsifier. In addition to natural hydrophobic minerals such as graphite , natural sulfur , molybdenite and coal , the process has industrial applications in phosphate rock and manganese ore.
Commonly used emulsifiers are nonionic and anionic surfactants. Nonionic surfactants are commonly used in the form of polyoxyethylene ethers, and alkylphenol ethoxylates are most effective.
(3) Emulsion flotation Emulsation flotation (Emulsion), also known as agglomeration flotation, the ratio of oil to medicine is 0.6~2.0. The non-polar oil is emulsified and dispersed, and the dispersed oil beads are used as a bridging medium to achieve agglomeration between the ore particles, and then separated by bubble flotation. Emulsified flotation is very suitable for fine particles and particulate materials. There are many kinds of suitable ores, easy to realize industrialization, easy to control the production process, and stable sorting index. At present, the process has industrial applications in phosphate rock and manganese ore in addition to natural hydrophobic minerals such as graphite, natural sulfur, molybdenite and coal. The only drawback is the high energy consumption and the large amount of chemicals used, resulting in high production costs.
Since the fine-grained material is larger than the surface, the amount of the non-polar oil used for the emulsification flotation is correspondingly increased, and it must be used as an emulsion with the collector or/and the emulsifier. The amount of the main agent in the emulsion varies depending on the type of ore. The emulsifier is added in an amount of about 3% by weight of the oil, and a polyoxyethylene ether nonionic surfactant and a petroleum sulfonate anionic emulsifier can be used. The emulsification effect of the emulsifier on the non-polar oil is crucial for the sorting effect.
(4) Oil agglomeration sorting
Oil agglomeration, also known as Spherical agglomeration, is one of the effective methods for processing fine-grained materials. The principle of the method is to finely grind the ore, dissociate the mineral, treat the slurry with a regulator and a collector, make certain minerals selectively hydrophobic, and then add a non-polar oil to wet the hydrophobic ore. Under the action of extrusion and kneading, the particles covering the oil adhere to each other and form pellets, and finally the pellets can be physically separated from the hydrophilic particles which are still in a dispersed state. Separation methods for pellets and dispersed minerals are sieving and water washing. The former is suitable for pellets with a relatively large particle size, and the latter is suitable for smaller pellets. Since the pellet agglomeration method can obtain pellets having a larger particle size and higher strength, the sorting purpose can be achieved by simple screening.
The advantage of the oil agglomeration separation process is that dehydration is also carried out while separating the fine minerals. Therefore, the solid-liquid separation process can be simplified. The disadvantage is that the amount of the agent is large, which leads to an increase in production cost. When the collector of the non-polar oil cannot be recycled, the application prospect of the process is limited. Therefore, the process can only be used to sort out the value of the beneficiation product, or to select the refractory ore with poor effect by other methods. In order to reduce costs, it is necessary to consider setting up a drug recovery system.
The collector used should be highly hydrophobic to the surface of the target mineral to ensure that the bridging liquid can spontaneously wet, generally 10 to 100 times the amount of conventional flotation. Titanium ore sorting Studies show that when the liquid mixture containing the bridging collector when the lowest impurity content of MgO pellets about 20%, at this time, the lowest moisture pellets. The emulsification caused by an excessive amount of collector increases the moisture and hydrophilic mineral inclusions in the pellet. Most of the oil used is petroleum products, which are immiscible with water. The modifiers added to increase the selectivity of the separation are not the same as the conventional flotation regulators.
Wei Dawei has carried out pellet agglomeration on the artificial mixed ore of fine-grained black tungsten ore (15μm). Under the condition of Ph=7.3 and raw ore containing 6.83% WO 3 , the grade is 70.65% WO 3 , and the recovery rate is obtained. It is 91.62% black tungsten concentrate. The main factors affecting the oil agglomeration separation process are: adjusting agent, slurry concentration and temperature, collector amount, stirring time and stirring speed (1800r/min), oil filling rate in hydrophobic ore pores (60%~80) %)Wait. The oil agglomeration separation process has been used for the sorting of various ores, such as coal, iron ore, ilmenite, cassiterite , barite and gold. Among them, coal oil agglomeration has been successfully industrialized. At present, the United Kingdom, the United States and Canada have corresponding devices of different scales. [next]
(5) Separation of two liquids
The two-liquid separation method is to add a collector to the adjusted slurry to hydrophobize the surface of the target mineral, and then inject a non-polar oil, and in the shear field, the hydrophobic particles adhere to the oil beads and A stable emulsion is formed and then sent to a separation device to raise the oil particles covering the hydrophobic particles to the upper part of the slurry to form an oil layer rich in hydrophobic minerals, and then the phase separation method is used to separate the hydrophobic mineral from the hydrophilic mineral. The sorting effect of the method is related to the pH value of the pulp, the concentration of the slurry, the type and amount of the collector, the type of oil, the oil-water ratio and the ratio of the oil to the drug, the stirring method and the strength. The two-liquid separation method has been applied to the separation of cassiterite, kaolin , hematite, fluorite and barite, and some have been used in industrial practice, and the particle size of the treated materials is mostly less than 10 μm.
III. Research and application of new pharmaceuticals (1) Using the principle of isomerism to find new medicaments
The idea of ​​finding new agents using the principle of isomeric is proposed by Zhu Jianguang. The arguments are the isomers with the same functional group, the chemical properties are very similar, the isomers with similar functional groups, the chemical properties are similar, and the mineralization characteristics of the flotation reagent are a comprehensive reflection of its chemical and physical properties. . Therefore, the same series of isomers with the same functional group have very similar collection performance, and similar functional groups are similar, and the collection performance is similar. When looking for new collectors, you can design an easy-to-synthesize isomer that synthesizes a good collector. The latter is an ideal new collector, and it is easy to synthesize and cheaper. This view is applicable to various fields such as collectors, foaming agents, and conditioners. The use of isobutyl xanthate instead of n-butyl xanthate for industrial production is an application example of the theory of isomeric isomers. For example, all the factories selected by the Dongchuan Mining Bureau replaced the n-butyl xanthate with isobutyl xanthate, and obtained the flotation index better than the n-butyl xanthate, which reduced the cost of the beneficiation operation and the economic benefits were significant. The scheelite and cassiter collector benzyl decanoic acid, which has been in use since 1980, is also a typical example of the application of this argument to guide synthesis.
Benzohydroxamic acid and salicylaldoxime are isomers, and they should have similar collection properties according to the principle of isomeric isomerization. Therefore, benzyl hydroxamic acid is synthesized and used for flotation of Shizhuyuan nonferrous metal ore black tungsten. fine mud, industrial test results show that containing WO 3 1.94% for the ore, using benzohydroxamic based mixed collector BH, AD obtained composition containing an inhibitor WO 3 52.77%, 62.38% recovery operations wolframite Concentrate.
(2) Polymer 5 Surfactant Polymers In recent years, studies on macromolecular polymer-small molecule surfactant complexes and their flotation properties have received increasing attention from flotation workers and have become new and efficient. The way to develop flocculants and collectors. There are two main categories:
(1) The chemically active functional group in the small molecule flotation agent is chemically introduced into the macromolecular chain to form a complex having both chemical activity and macromolecular properties of the small molecule, which can be used alone as a selective flocculant and flocculation. Flotation flocculant-collector. For example, xanthate is an effective collector for chalcopyrite, and its complex with hydroxypropyl cellulose can selectively floculate chalcopyrite without causing flocculation on quartz. For example, in order to reduce the sulfur content in coal, it is necessary to separate fine coal from pyrite. When PAM is used as a flocculant, if polyacrylic acid PAA is used as a dispersant, both coal and pyrite will be dispersed without selectivity. Instead of using polyacrylic acid xanthate PAAX as a dispersing agent, the pyrite remains in a dispersed state, and the coal particles form a floc.
2 The polymer and surfactant are added to the solution in sequence, and the two interact in solution or on the surface of the mineral to improve the flocculation or flotation behavior of the mineral. For example, if polyvinyl acetate (PVAC) is directly added to an aqueous solution of dodecylamine hydrochloride (DDA) or sodium dodecylsulfate (DDSNa), the magnetite is floated, and the obtained indexes are superior to those used alone. DDA or DDSNa, and the pH range of flotation is widened, which is less affected by metal ions and mineral surface potential.
(III) Biosurfactant Flocculant Biosurfactant is more and more popular because of its low toxicity, natural biodegradability, ecological safety, high surface activity and physiological activity compared with synthetic surfactant. Most biosurfactants have a liposome structure. Like synthetic surfactants, biosurfactants are amphiphilic with both hydrophilic and hydrophobic groups. The hydrophobic group is generally a fatty acid or a hydrocarbon, and the hydrophilic group is a sugar, a polyol, a polysaccharide, a peptide, and the like. Under appropriate conditions, microbial bacteria can produce and accumulate biosurfactants in large quantities in vitro. Surfactants that bind to polysaccharides, proteins, and lipid nucleic acids interact with the surface of the particles to cause flocculation. Tenney Busch believes that when the biosurfactant flocculates the suspension by bridging, emulsification can occur between the flocculant molecules and the particles to promote flocculation. Lyons and Hough pointed out that flocculation is due to the bridging effect of phosphodiester on the cell surface, while some believe that this bridging effect is carboxyl, and the effect of flocculation is directly related to the number of carboxyl groups exposed on the cell surface. Numerous studies have shown that Ca 2+ plays a bridging role in flocculation and enhances the flocculation effect, but its dosage has a critical value. Above this value, flocculation is weakened.
At present, biosurfactants have been used to treat various minerals such as kaolin, hematite and bentonite . Smith et al. showed that M. phlei is a highly negatively charged and highly hydrophobic microorganism with many groups on its surface, which can be used as phosphate rock, hematite, coal, calcite. And flocculants of minerals such as kaolinite. The use of this bacteria to treat phosphate mud in Florida is effective. When the bacteria were added, the effect of flocculation and sedimentation was produced in 4 minutes without adding the bacteria, and the sedimentation effect was not obtained in 45 minutes. When the iron ore is treated with the bacteria, the hematite can be obviously settled within 4 minutes, and the same effect can not be achieved in 30 minutes without adding time. It can be seen that this biosurfactant can be used as a good selective flocculant, and the filtration performance of the precipitate after flocculation is obviously improved. Polyacrylamide flocculating material is used. When the concentration reaches 400mg/kg, the sedimented material is very sticky, and it is difficult to further dehydrate. However, the mycobacteria are hydrophobic, and the material after flocculation is more easily dehydrated.
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