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Study on Influencing Factors of Chemical Demulsification
Release Date：2018-6-12 Source：xiashundong Views：1268
1 Emulsion characteristics
Emulsions are diluted with emulsified oil and water. They are widely used in the mechanical processing industry and have cooling, lubrication and cleaning effects. Oil-in-water (O/W) emulsions are commonly used in metal processing, calendering, and hydraulic systems. Most are formulated with anionic emulsifiers. The main components of emulsified oil are various base oils, emulsifiers, emulsion stabilizers, additives, rust preventive oils, and defoamers. Because the emulsion contains a large amount of lubricating oils, surfactants, sodium salts of fatty acids, etc., it gradually deteriorates due to friction heat, metal dust, and surrounding environmental media (oxygen, carbon dioxide, microorganisms, etc.) during cyclic use. Deterioration of emulsified contaminants is generally high. The measurement data show that the emulsified wastewater contains up to 20,000 to 30000 mg/L of oil, CODCr up to 3,000 to 4000 mg/L, and BOD up to 9000 mg/L. Therefore, if the emulsion wastewater directly discharges into rivers and rivers, it will lead to serious pollution of water bodies.
As the emulsifier molecules are directionally adsorbed at the oil-water interface and form a strong interfacial film, the effective thickness of the diffusion double layer is also increased, and the potential distribution width and steepness of the double layer are increased, so that the oil is highly uniform. It is dispersed in water so that the emulsion has considerable stability. Therefore, in order to lose the stability of the emulsion, it is necessary to eliminate or weaken the ability of the emulsifier to protect the stability of the emulsion, that is, to break the adsorption film on the oil-water interface, and to reduce the amount of the same charge carried by the dispersed particles. Finally, the separation of oil and water to achieve the purpose of breaking the milk. Thus, demulsification is the key to the treatment of emulsion wastewater.
2 experiments and results analysis
2.1 The basic situation of the experiment
There are many types of demulsifiers used in chemical emulsion breaking. In this experiment, salt electrolytes and inorganic polymers are used as demulsifiers. In order to facilitate comparison, the salt electrolytes are all made of metal chlorides, mainly NaCl, CaCl2, AlCl3, and FeCl3. Polymeric polymer demulsifiers include polyaluminum sulfate and polyferric sulfate.
The composition of the emulsified oil used in the experiment was: 12% petroleum sulfonate, 2% OP-10, 30% triethanolamine oleate, 5% petroleum sulfonate, and 78% No. 15 mechanical oil.
2.2 Effect of Emulsion Concentration on Dosage
When emulsified oil is added into water to prepare the emulsion, its concentration is generally relatively small, but the concentration of the emulsion during actual use has a certain randomness. The concentrations used in this experiment are 2% and 4%, respectively. The 8%, 10% emulsions were used as the sample liquid, and NaCl, CaCl2, FeCl3, and polyaluminum sulfate were used as demulsifiers to determine the amount of emulsion breaking required for critical emulsion breaking. As the emulsion concentration increased, The dosage of demulsifiers does not increase proportionately, but only slightly. It can be considered that the concentration of the emulsion has little effect on the dosage and is generally negligible.
2.3 Effect of emulsion pH on demulsifier dosage
The emulsion is generally weakly alkaline, with a concentration of 4% emulsion as a sample, with 2mol/L H2SO4 to adjust the pH value, using NaCl, CaCl2, AlCl3, FeCl3 and polyaluminum sulfate as demulsifiers to determine them separately. The amount of critical demulsification needed under different pH conditions, for strong acid and alkali salts, because they do not hydrolyze in solution, as the pH value decreases, the H+ concentration increases, that is, the demulsification from H+. The effect is increased, so the amount of demulsifier is also gradually reduced until the pH is adjusted to about 3, and the emulsion is directly demulsified under the action of H+. Therefore, the amount of demulsifier required at this time is zero. However, for demulsifiers such as FeCl3 and polyaluminum sulphate, they are easily hydrolyzed in solution to form hydroxide polymers or complex ions, which play a role in flocculation and demulsification. When the pH value is too low, it will inhibit the hydrolysis of such substances. The flocculation and demulsification of polyaluminum sulfate and other materials is reduced, but at the same time, the demulsification effect of H-type demulsifiers does not change significantly due to the increase in the concentration of H+, that is, H+. The hydrolysis reaction proceeds sufficiently and it is necessary to add an appropriate amount of an alkaline regulator so that more positively charged metal hydroxide colloids are generated at a certain pH to increase the demulsification efficiency of such demulsifiers.
2.4 Polymer Demulsifier
Polymers include various water-soluble inorganic polymers and organic polymers. Treatment of oily wastewater with macromolecule polymer can make the fine beads present in the water coarser, so as to improve the separation efficiency, and has the advantages of low capital investment, strong adaptability, and simple operation and management. Inorganic polymers can be divided into aluminum salts and iron salts according to the composition of metal salts, and can be classified into hydrochloric acid and sulfuric acid by anion components. The main varieties were in the order of time of development: polyaluminum sulphate (PAS), polyaluminum chloride (PAC), polyferric sulfate (PFS), and basic silicic acid first developed by Handy Chemicals in January 1989. Aluminum sulfate (PASS). The low-cost, self-made PAS and PFS are now used for the demulsification test. The emulsion used has a concentration of 4% and a pH of 8.5. After the emulsion is demulsified by PAS, the water is acidic, and it needs to be neutralized with alkaline substances such as lime milk to achieve the discharge requirement of pH value. The milk of lime has a certain coagulation aid effect and is an inexpensive acid conditioner. Compared with PAS, using PFS as a demulsifier has the advantages of less dosage, good water quality after demulsification and so on.
Regarding the demulsification of macromolecules, we believe that it can be explained by two reasons. The first is due to the bridging effect between the liquid beads, polymer nonionic polymers and agglomerating agents with the same charge cause flocculation and demulsification by bridging; while the other is considered to be caused by neutralization of the surface charge of the liquid beads. Adding an agglomerating agent with an opposite charge to the surface of the bead can cause flocculation and demulsification due to charge neutralization. In fact, in the actual demulsification process, not only one of these theories has played a role, but both of them have only contributed to the demulsification.
In general, when the pH is greater than 4, hydroxyl ions increase, and bridging bonding occurs between the hydroxyl groups of the ions. Further hydrolysis results in insoluble hydroxide colloids. These colloids are generally relatively long linear molecules. These extended linear molecules can be adsorbed by van der Waals forces in the water under the physical and chemical action of coordination bonds. When the charge of the coagulant polymer is opposite to the charge sign of the oil droplets in the emulsion, the electrostatic attraction becomes the basis of the interaction. These extended molecules are easily adsorbed by several or even many oil droplets, causing aggregation. At the same time, the high-valent positive ions can also compress and diffuse the electric double layer at the same time, lower the kinetic potential, promote the oil beads to be close to each other, and cause condensation, and become alum aggregates to break emulsion of the emulsion.
For PFS put into use in the early 1980s, it is necessary to analyze its characteristics. PFS is a basic, non-toxic, chemically stable, persistent, water-soluble basic iron sulfate polymer with a multinuclear complex ion structure in its molecule. The Fe in PFS is easily hydrolyzed in aqueous solution and can generate a large number of hydrophobic hydroxide polymers, such as: [Fe(H2O)6]3+, [Fe2(OH)3]3+, [Fe8(OH) 20] 4+ and other complex ions, using OH- as a bridge to form multi-nuclear complex ions, thus becoming a huge inorganic polymer compound. The reason why PFS is superior to other inorganic flocculants in terms of high flocculating ability and good demulsification effect is that PFS can provide a large amount of complex ions as described above, and can strongly absorb oil droplets in emulsions through adhesion, bridging, Cross-linking action promotes the condensation of oil beads. At the same time, physical and chemical changes have also taken place, neutralizing the surface charge of the oil droplets, lowering their kinetic potential, and allowing oil droplets to attract and accumulate. Because PFS itself has a certain degree of alkalinity, the range of pH value adaptation is relatively wide. In general, pH values vary from 4 to 11 with different degrees of treatment effect. In addition, it also has the advantages of high speed, large particles and good sedimentation performance. Therefore, it is a kind of demulsifier with promising development.
3 conclusions
The amount of demulsifier does not increase significantly with increasing emulsion concentration.
Due to the effect of H+ itself, the smaller the pH value, the lower the amount of alkali metal and alkaline earth electrolyte demulsifier used, and the pH of 3 can be achieved without adding any demulsifier. However, due to the increase of H+, the hydrolysis of transition metal ions will be inhibited, so the influence of the amount of such demulsifier is not obvious.
PFS is a new type of inorganic polymer flocculant, which has a certain degree of alkalinity, has a huge flocculation force, and has a wide range of pH value adaptation. It has a fast speed, large particles, good sedimentation performance, and sludge formation. Small, clear and transparent water is a cost-effective demulsifier.
Emulsions are diluted with emulsified oil and water. They are widely used in the mechanical processing industry and have cooling, lubrication and cleaning effects. Oil-in-water (O/W) emulsions are commonly used in metal processing, calendering, and hydraulic systems. Most are formulated with anionic emulsifiers. The main components of emulsified oil are various base oils, emulsifiers, emulsion stabilizers, additives, rust preventive oils, and defoamers. Because the emulsion contains a large amount of lubricating oils, surfactants, sodium salts of fatty acids, etc., it gradually deteriorates due to friction heat, metal dust, and surrounding environmental media (oxygen, carbon dioxide, microorganisms, etc.) during cyclic use. Deterioration of emulsified contaminants is generally high. The measurement data show that the emulsified wastewater contains up to 20,000 to 30000 mg/L of oil, CODCr up to 3,000 to 4000 mg/L, and BOD up to 9000 mg/L. Therefore, if the emulsion wastewater directly discharges into rivers and rivers, it will lead to serious pollution of water bodies.
As the emulsifier molecules are directionally adsorbed at the oil-water interface and form a strong interfacial film, the effective thickness of the diffusion double layer is also increased, and the potential distribution width and steepness of the double layer are increased, so that the oil is highly uniform. It is dispersed in water so that the emulsion has considerable stability. Therefore, in order to lose the stability of the emulsion, it is necessary to eliminate or weaken the ability of the emulsifier to protect the stability of the emulsion, that is, to break the adsorption film on the oil-water interface, and to reduce the amount of the same charge carried by the dispersed particles. Finally, the separation of oil and water to achieve the purpose of breaking the milk. Thus, demulsification is the key to the treatment of emulsion wastewater.
2 experiments and results analysis
2.1 The basic situation of the experiment
There are many types of demulsifiers used in chemical emulsion breaking. In this experiment, salt electrolytes and inorganic polymers are used as demulsifiers. In order to facilitate comparison, the salt electrolytes are all made of metal chlorides, mainly NaCl, CaCl2, AlCl3, and FeCl3. Polymeric polymer demulsifiers include polyaluminum sulfate and polyferric sulfate.
The composition of the emulsified oil used in the experiment was: 12% petroleum sulfonate, 2% OP-10, 30% triethanolamine oleate, 5% petroleum sulfonate, and 78% No. 15 mechanical oil.
2.2 Effect of Emulsion Concentration on Dosage
When emulsified oil is added into water to prepare the emulsion, its concentration is generally relatively small, but the concentration of the emulsion during actual use has a certain randomness. The concentrations used in this experiment are 2% and 4%, respectively. The 8%, 10% emulsions were used as the sample liquid, and NaCl, CaCl2, FeCl3, and polyaluminum sulfate were used as demulsifiers to determine the amount of emulsion breaking required for critical emulsion breaking. As the emulsion concentration increased, The dosage of demulsifiers does not increase proportionately, but only slightly. It can be considered that the concentration of the emulsion has little effect on the dosage and is generally negligible.
2.3 Effect of emulsion pH on demulsifier dosage
The emulsion is generally weakly alkaline, with a concentration of 4% emulsion as a sample, with 2mol/L H2SO4 to adjust the pH value, using NaCl, CaCl2, AlCl3, FeCl3 and polyaluminum sulfate as demulsifiers to determine them separately. The amount of critical demulsification needed under different pH conditions, for strong acid and alkali salts, because they do not hydrolyze in solution, as the pH value decreases, the H+ concentration increases, that is, the demulsification from H+. The effect is increased, so the amount of demulsifier is also gradually reduced until the pH is adjusted to about 3, and the emulsion is directly demulsified under the action of H+. Therefore, the amount of demulsifier required at this time is zero. However, for demulsifiers such as FeCl3 and polyaluminum sulphate, they are easily hydrolyzed in solution to form hydroxide polymers or complex ions, which play a role in flocculation and demulsification. When the pH value is too low, it will inhibit the hydrolysis of such substances. The flocculation and demulsification of polyaluminum sulfate and other materials is reduced, but at the same time, the demulsification effect of H-type demulsifiers does not change significantly due to the increase in the concentration of H+, that is, H+. The hydrolysis reaction proceeds sufficiently and it is necessary to add an appropriate amount of an alkaline regulator so that more positively charged metal hydroxide colloids are generated at a certain pH to increase the demulsification efficiency of such demulsifiers.
2.4 Polymer Demulsifier
Polymers include various water-soluble inorganic polymers and organic polymers. Treatment of oily wastewater with macromolecule polymer can make the fine beads present in the water coarser, so as to improve the separation efficiency, and has the advantages of low capital investment, strong adaptability, and simple operation and management. Inorganic polymers can be divided into aluminum salts and iron salts according to the composition of metal salts, and can be classified into hydrochloric acid and sulfuric acid by anion components. The main varieties were in the order of time of development: polyaluminum sulphate (PAS), polyaluminum chloride (PAC), polyferric sulfate (PFS), and basic silicic acid first developed by Handy Chemicals in January 1989. Aluminum sulfate (PASS). The low-cost, self-made PAS and PFS are now used for the demulsification test. The emulsion used has a concentration of 4% and a pH of 8.5. After the emulsion is demulsified by PAS, the water is acidic, and it needs to be neutralized with alkaline substances such as lime milk to achieve the discharge requirement of pH value. The milk of lime has a certain coagulation aid effect and is an inexpensive acid conditioner. Compared with PAS, using PFS as a demulsifier has the advantages of less dosage, good water quality after demulsification and so on.
Regarding the demulsification of macromolecules, we believe that it can be explained by two reasons. The first is due to the bridging effect between the liquid beads, polymer nonionic polymers and agglomerating agents with the same charge cause flocculation and demulsification by bridging; while the other is considered to be caused by neutralization of the surface charge of the liquid beads. Adding an agglomerating agent with an opposite charge to the surface of the bead can cause flocculation and demulsification due to charge neutralization. In fact, in the actual demulsification process, not only one of these theories has played a role, but both of them have only contributed to the demulsification.
In general, when the pH is greater than 4, hydroxyl ions increase, and bridging bonding occurs between the hydroxyl groups of the ions. Further hydrolysis results in insoluble hydroxide colloids. These colloids are generally relatively long linear molecules. These extended linear molecules can be adsorbed by van der Waals forces in the water under the physical and chemical action of coordination bonds. When the charge of the coagulant polymer is opposite to the charge sign of the oil droplets in the emulsion, the electrostatic attraction becomes the basis of the interaction. These extended molecules are easily adsorbed by several or even many oil droplets, causing aggregation. At the same time, the high-valent positive ions can also compress and diffuse the electric double layer at the same time, lower the kinetic potential, promote the oil beads to be close to each other, and cause condensation, and become alum aggregates to break emulsion of the emulsion.
For PFS put into use in the early 1980s, it is necessary to analyze its characteristics. PFS is a basic, non-toxic, chemically stable, persistent, water-soluble basic iron sulfate polymer with a multinuclear complex ion structure in its molecule. The Fe in PFS is easily hydrolyzed in aqueous solution and can generate a large number of hydrophobic hydroxide polymers, such as: [Fe(H2O)6]3+, [Fe2(OH)3]3+, [Fe8(OH) 20] 4+ and other complex ions, using OH- as a bridge to form multi-nuclear complex ions, thus becoming a huge inorganic polymer compound. The reason why PFS is superior to other inorganic flocculants in terms of high flocculating ability and good demulsification effect is that PFS can provide a large amount of complex ions as described above, and can strongly absorb oil droplets in emulsions through adhesion, bridging, Cross-linking action promotes the condensation of oil beads. At the same time, physical and chemical changes have also taken place, neutralizing the surface charge of the oil droplets, lowering their kinetic potential, and allowing oil droplets to attract and accumulate. Because PFS itself has a certain degree of alkalinity, the range of pH value adaptation is relatively wide. In general, pH values vary from 4 to 11 with different degrees of treatment effect. In addition, it also has the advantages of high speed, large particles and good sedimentation performance. Therefore, it is a kind of demulsifier with promising development.
3 conclusions
The amount of demulsifier does not increase significantly with increasing emulsion concentration.
Due to the effect of H+ itself, the smaller the pH value, the lower the amount of alkali metal and alkaline earth electrolyte demulsifier used, and the pH of 3 can be achieved without adding any demulsifier. However, due to the increase of H+, the hydrolysis of transition metal ions will be inhibited, so the influence of the amount of such demulsifier is not obvious.
PFS is a new type of inorganic polymer flocculant, which has a certain degree of alkalinity, has a huge flocculation force, and has a wide range of pH value adaptation. It has a fast speed, large particles, good sedimentation performance, and sludge formation. Small, clear and transparent water is a cost-effective demulsifier.