Composite flocculant for sedimentation of fine ore grains and application of composite flocculant

Abstract

The invention belongs to the technical field of ore pulp concentration and sedimentation, and particularly relates to a composite flocculant for sedimentation of fine ore grains and application of the composite flocculant. The composite flocculant is composed of polyaluminum chloride, sodium hexametaphosphate, polyacrylamide, polyoxyethylene and sodium alginate. The method for sedimentation comprises the following steps: preparing a solution A from polyaluminum chloride and sodium alginate, and preparing a solution B from sodium hexametaphosphate, polyacrylamide and polyoxyethylene; stirring the solution A and to-be-treated ore pulp at a high speed until the solution A and the to-be-treated ore pulp are uniformly mixed, finally adding the solution B, stirring at a low speed until the solution is uniformly mixed, and standing until settlement is completed. The composite flocculant has the characteristics of environment friendliness, wide raw material source, low cost and strong flocculation pertinence on fine ore grains. Through the synergistic effect of the components, the composite flocculant not only has higher flocculation speed and water adaptability, but also has the characteristics of compactness and high structural strength of generated floccules, and the flocculation effect is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of mineral slurry concentration and sedimentation technology, specifically relating to a composite flocculant for the sedimentation of fine mineral particles and its application. Background Technology

[0002] In the field of mineral processing, solid-liquid separation of slurry is a crucial technological step. Currently, the most common and economical method is to use gravity sedimentation to achieve solid-liquid separation of fine particles. In this process, flocculants are widely used to accelerate the sedimentation of fine particles.

[0003] As the characteristics of mineral raw materials—being scarce, fine-grained, complex, and dispersed—become increasingly prominent, finer grinding of the ore is necessary to achieve the individual liberation and effective separation of useful minerals and gangue. This results in a significant increase in the content of micro-particles (-20 micrometers) and even ultra-fine particles (-10 micrometers) in the grinding products. The finer the mineral particles, the more geometrically the specific surface area increases, leading to a sharp rise in surface energy. This results in particles exhibiting a strong Brownian motion tendency in water, exhibiting extremely high stability. Simultaneously, fine particles carry a larger total surface charge, and the electrostatic repulsion between particles is far greater than van der Waals attraction, further hindering particle proximity and aggregation. This phenomenon of "the finer the particle, the harder it is to settle" presents unprecedented challenges to subsequent solid-liquid separation operations such as concentration and dehydration.

[0004] Organic polymeric flocculants are among the most widely used flocculants, forming flocs through the adsorption and bridging of long molecular chains. For the sedimentation of fine particles, organic polymeric flocculants require relatively higher molecular weights. However, the higher the molecular weight, the longer the polymer chains, and the slower they entangle and unwind in water.

[0005] Polyacrylamide (PAM) is one of the most widely used organic polymeric flocculants in mineral processing and other fields. Taking PAM as an example, high molecular weight PAM may take several hours or even longer to completely dissolve, causing inconvenience to continuous and efficient industrial production. Furthermore, during the dissolution process, the outer layer of high molecular weight PAM particles swells rapidly upon contact with water, forming a gel-like coating that prevents water from penetrating the inner layer, thus forming incompletely dissolving clumps (commonly known as "fish eyes"). These "fish eyes" not only waste the agent but also clog pipes, pumps, and nozzles during addition, severely impacting production. Finally, excessively long molecular chains increase rigidity and entanglement tendency, making them unable to flexibly extend and adsorb onto multiple particles in a shear flow field. Instead, they are prone to curling or self-entanglement, resulting in a reduction in effective "adsorption sites" and decreasing the efficiency and probability of bridging.

[0006] Preparing composite flocculants is a promising direction for overcoming the shortcomings of traditional PAM flocculants. Patent CN102849831A discloses a composite flocculant formulation that combines sodium hexametaphosphate and polyacrylamide, solving the problem of rapid treatment of large quantities of sludge. However, when addressing the settling of extremely fine mineral sludge particles, the large surface charge of these particles, due to their small size, strengthens the obstacle of particle proximity and aggregation, limiting the effectiveness of this solution. Patent CN106219698A discloses a composite flocculant for wastewater treatment and its preparation method. The prepared flocculant has advantages such as short settling time, good effect, and low cost in wastewater treatment; however, the large number of reagents and complex formulation bring inconvenience to preparation and production.

[0007] Therefore, it is essential to provide new composite flocculants to solve the technical problems of long sedimentation time and poor settling effect of existing PAM flocculants. Summary of the Invention

[0008] To address the aforementioned technical problems, one objective of this invention is to provide a composite flocculant for the sedimentation of fine mineral particles.

[0009] The technical solution adopted in this invention is as follows: A composite flocculant for the sedimentation of fine mineral particles comprises, by weight, 50-100 parts of polyaluminum chloride, 10-20 parts of sodium alginate, 10-25 parts of sodium hexametaphosphate, 15-25 parts of polyacrylamide, and 5-10 parts of polyethylene oxide.

[0010] Preferably, the composite flocculant is a composition consisting of two independent components, component A and component B, wherein component A includes polyaluminum chloride and sodium alginate, and component B includes sodium hexametaphosphate, polyacrylamide, and polyethylene oxide.

[0011] Preferably, the polyacrylamide is anionic polyacrylamide with a molecular weight of 8000~20000 kDa.

[0012] In the above formulation, the purpose of polyaluminum chloride is to eliminate electrostatic repulsion between particles through charge neutralization, thereby destabilizing stable fine particles. This optimizes the slurry solution environment, which is beneficial for the subsequent polyacrylamide to expand more in the solution environment and expose more adsorption sites, thus significantly improving the flocculation activity and efficiency of polyacrylamide. The micro-flocs formed by polyaluminum chloride in the solution can also serve as "nuclei" or "seeds" for subsequent polyacrylamide. Polyacrylamide uses these as cores for bridging and encapsulation, resulting in a more compact internal structure and higher strength of the flocs, which are not easily dispersed by shear force, avoiding the problem of "bloated" flocs formed by traditional single polyacrylamide.

[0013] Sodium alginate provides diverse adsorption forces, including electrostatic attraction, hydrogen bonding, and coordination bonds. This greatly enhances its contact and capture probability with particles of different surface properties, such as metal oxides, silicates, and organic matter. Simultaneously, the molecular chains of sodium alginate and polyacrylamide intertwine within the flocs, forming a stable structure that provides strong skeletal support and cohesion for the flocs.

[0014] Sodium hexametaphosphate is used to optimize the ionic microenvironment surrounding polyacrylamide molecules, promoting the full extension of the molecular chains in water. This transforms the molecular chains from a coiled conformation to an extended linear conformation, which is more conducive to adsorption and bridging, thereby significantly improving the dissolution rate of polyacrylamide and the flocculation activity of the final solution. Based on this synergistic mechanism, this composite flocculant can also rapidly exert high efficiency in hard water or industrial reclaimed water.

[0015] Furthermore, polyacrylamide and polyethylene oxide exhibit a significant synergistic effect. Polyethylene oxide can preferentially and rapidly anchor to specific active sites (such as silanol groups) on the surface of fine particles through strong hydrogen bonding. Subsequently, the long molecular chains of polyacrylamide efficiently bridge these polyethylene oxide-modified particles through intermolecular hydrogen bonds and physical entanglement, forming a unique 'anchoring-bridging' structure that enhances the overall density and structural strength of the flocs.

[0016] The second objective of this invention is to provide the application of the composite flocculant for the sedimentation of fine mineral particles as described above in the sedimentation of fine mineral particles.

[0017] Preferably, the particle size of the fine mineral particles is less than 45 μm.

[0018] Preferably, the slurry is a fine-grained silicate slurry, and the fine mineral particles in the slurry account for more than 60% of the total mineral particle mass of the slurry.

[0019] Aluminosilicate fine-particle slurries present a significant sedimentation challenge in mineral processing and tailings treatment. The high content of fine particles in these slurries results in a large specific surface area and a strongly negatively charged surface, leading to predominantly electrostatic repulsion between particles and the formation of a highly stable colloidal suspension. Traditional flocculants struggle to effectively disrupt this stability, resulting in persistent problems such as slow sedimentation rates, low underflow concentrations, and turbid supernatant. The composite flocculant used in this application is specifically formulated to address the sedimentation problem of aluminosilicate fine-particle slurries.

[0020] Furthermore, the sedimentation method for fine mineral particles includes the following steps: S1. According to the required mass proportions, mix polyaluminum chloride and sodium alginate, and then prepare a solution A with a mass concentration of 1-3% by water; mix sodium hexametaphosphate, polyacrylamide and polyethylene oxide, and then prepare a solution B with a mass concentration of 0.1-0.5% by water. S2. First, add solution A to the slurry to be treated and stir at high speed until it is evenly mixed. Then add solution B and stir at low speed until it is evenly mixed. Let it stand until flocs are formed and settle.

[0021] Preferably, the mass concentration of the slurry is 15-50%, the volume ratio of solution A to slurry is (2-8):1000, and the volume ratio of solution B to slurry is (5-10):1000.

[0022] Preferably, the high-speed stirring is performed at a speed such that the Reynolds number of the slurry flow field is 1 × 10⁻⁶. 5 ~9×10 5 The speed of the high-speed stirring is such that the Reynolds number of the slurry flow field is between 4000 and 8000.

[0023] Preferably, in the settling condition, step S2 adopts a two-stage dosing method, wherein the mixing process of solution A and the slurry to be treated is completed in a stirring tank, and the mixing process of solution B and the slurry to be treated is completed in a thickening tank.

[0024] The mechanism of action of this composite flocculant is as follows: Component A consists of polyaluminum chloride and sodium alginate. In component A, the positively charged complex provided by polyaluminum chloride is strongly adsorbed onto the surface of negatively charged fine mineral particles, neutralizing the negative charge on their surface, thus reducing the Zeta potential of the colloidal particles and weakening or even eliminating the electrostatic repulsion. Under the influence of van der Waals forces, the fine mineral particles collide and aggregate, forming tiny flocs. Furthermore, the aluminum hydroxide in polyaluminum chloride has a certain degree of polymerization; when it co-polymerizes with sodium alginate, it reacts with the alginate ions in sodium alginate and the Al in the system. 3+ AlOH 2+ and Al(OH)2 +Cross-linking reactions occur, forming a denser network structure. This structure has a sufficiently large geometric volume to capture particles in the water under strong flow fields, forming flocs with larger volume and density. These flocs further grow into large and dense flocs under the action of flocculant B. The core function of flocculant B is adsorption bridging, and it strengthens the flocs through component synergy: both polyacrylamide and polyethylene oxide in flocculant B are long-chain polymers, exhibiting a significant synergistic effect. Polyethylene oxide is a non-ionic, highly flexible long-chain polymer that can form hydrogen bonds with the surface of suspended particles through ether oxygen atoms on its molecular chain, exerting a strong "entanglement" and "netting" effect to first link the particles or primary flocs. Subsequently, polyacrylamide, through strong charge neutralization and adsorption bridging, further "binds" and compresses the primary flocs, forming denser, structurally stronger, and larger flocs. In addition, sodium hexametaphosphate in flocculant B can enhance the flocculation effect by allowing polyacrylamide and polyethylene oxide to spread more freely in the liquid phase through competitive hydrogen bonding and steric hindrance.

[0025] Although the flocs formed by high molecular weight PAM are huge, their structure is often too loose and fragile, filled with water, and have very low strength. These "bloated" flocs are extremely easy to break when subjected to even very slight shear forces (such as stirring, pumping, or the pushing of a thickener rake). Once broken, the dispersed flocs are difficult to re-flocculate, causing the sedimentation process to reverse, the supernatant to become turbid, and the sedimentation effect to be completely wasted.

[0026] The beneficial effects of this invention are as follows: This application provides a novel composite flocculant for the sedimentation of fine mineral particles. The formulation contains only six raw materials, and it is characterized by being environmentally friendly, using widely available raw materials, low cost, simple preparation, and highly targeted at the flocculation of fine mineral particles during mineral processing. Through the synergistic effect between its components, the composite flocculant not only exhibits a faster flocculation speed and better water adaptability, but also produces flocs that are dense and have high structural strength, greatly improving the flocculation effect. Attached Figure Description

[0027] Figure 1 The results of particle size analysis of the slurry used for testing.

[0028] Figure 2 These are micrographs of the floc morphology of Example 3 and Comparative Examples 1-8.

[0029] Figure 3 The results are the floc strength test results for Example 3 and Comparative Examples 1-3. Detailed Implementation

[0030] To facilitate understanding, the technical solution of the present invention will be described in more detail below with reference to embodiments. Unless otherwise stated, the terms used herein have the meanings conventionally understood by those skilled in the art.

[0031] A composite flocculant for the sedimentation of fine mineral particles comprises 50-100 parts of polyaluminum chloride, 10-20 parts of sodium alginate, 10-25 parts of sodium hexametaphosphate, 15-25 parts of polyacrylamide, and 5-10 parts of polyethylene oxide.

[0032] The composite flocculants of Examples 1-3 were prepared according to the formulas, and the specific formulas are shown in Table 1.

[0033] Table 1. Composite flocculant formulation (unit: parts)

[0034] The flocculants from Examples 1-3 were used for flotation, and the methods were as follows: First, mix polyaluminum chloride and sodium alginate, and then prepare a 1.5% solution A with water; mix sodium hexametaphosphate, anionic polyacrylamide and polyethylene oxide, and then prepare a 0.3% solution B with water. Then, solution A was added to the frothy slurry after reverse flotation of a certain iron ore at a volume ratio of 2:1000, and stirred for 5 minutes at a Reynolds number of 30,000. Then, solution B was added at a volume ratio of 5:1000, and stirred for 5 minutes at a Reynolds number of 5,000. The mixture was then transferred to a container and allowed to stand. The settling time, slurry layer height, and particulate matter content in the clarified water were then tested.

[0035] The foam slurry used in the above tests had a mass concentration of 15%. The main chemical composition of the minerals is shown in Table 2, and the particle size distribution is as follows: Figure 1 The mineral particles are relatively fine, with an average particle size of 24.90 μm.

[0036] Table 2 Main Chemical Components of Minerals in Reverse Flotation Foam Products

[0037] To verify the effectiveness of the flocculant, comparative examples 1-8 were set up to conduct flocculation tests on the same type of foamed mineral slurry.

[0038] Comparative Example 1 was formulated with reference to the formula of patent CN102849831A, and Comparative Example 2 was formulated with reference to the formula of patent CN106219698A. Specific information is shown in Table 3.

[0039] Table 3. Formulas for Comparative Examples 1-8 (Unit: portions)

[0040] The test results of Examples 1-3 and Comparative Examples 1-8 are shown in Table 4. See the microscopic photographs of the floc morphology for details. Figure 2 .

[0041] In addition, based on the floc morphology diagrams, Examples 3, 1, 2, and 3, whose floc sizes were not significantly different, were selected for floc strength testing. The flocs generated under each formulation were broken up under strong stirring at 4000 rpm. The average particle size (D50) of the flocs before and after breaking up was measured using a laser particle size analyzer, and the floc strength factor was calculated. S f To evaluate the strength of the flocs: .

[0042] In the formula, d 1 It is the average particle size of the flocs before they break down. d 2 It is the average particle size of the fragmented flocs. Intensity factor S f The larger the size, the higher the structural strength of the floc. The test results are shown below. Figure 3 .

[0043] Table 4. Flocculation and sedimentation effects of Examples 1-3 and Comparative Examples 1-8

[0044] It can be seen that Examples 1, 2, and 3 have shorter settling times and lower supernatant solid content compared to Comparative Examples 4-8. Comparative Examples 4-8 each have one less component than the Examples, resulting in poorer flocculation and settling effects. This indicates that the presence of each component in this invention has a positive impact on the flocculation and settling effect. Among them, Example 3 exhibits the best settling effect in terms of both settling time and supernatant solid content. Comparative Example 1 consists of 4.5 parts sodium hexametaphosphate and 2 parts anionic polyacrylamide. Compared to the Examples, this formulation has a similar supernatant solid content, but a slower settling speed.

[0045] from Figure 2 Photos of fluffy clumps and Figure 3 The results of the floc strength test show that Comparative Example 1, which uses only sodium hexametaphosphate and polyacrylamide, can increase the particle size of mineral flocs, but its floc density and floc strength are not as good as those of the Example. Compared with the Example, Comparative Example 2, although the sedimentation rate and supernatant solid content are not significantly different under this formulation, uses a complex preparation scheme with 11 raw materials, which is not conducive to production. Comparative Example 3 uses the most commonly used combination of polyaluminum chloride and polyacrylamide in the field of slurry flocculation and sedimentation. With the same total reagent dosage, the flocculation and sedimentation effect of Comparative Example 3 is significantly different from that of the Example.

[0046] from Figure 2 The floc structure shows that the flocs formed in Example 3 are large and dense, which determines that the reagent scheme of Example 3 can quickly achieve sedimentation of the slurry. The flocs in Comparative Example 1 are also large, but looser and more prone to breakage, resulting in a decrease in sedimentation effect, which was verified by subsequent strong stirring tests. The flocs in Comparative Example 2 are large and dense, with no significant difference from those in Example 3. The flocs in Comparative Example 3 are large and loose. The flocs in Comparative Examples 4-8 have significantly smaller particle sizes, which is also the main reason for the poor sedimentation effect. Comparing the sedimentation results, it can be seen that the key to efficient sedimentation lies in forming large and dense flocs, which is the main advantage of this invention. In addition, strong stirring tests further confirmed that the flocs formed in the embodiments of this invention have high structural strength, can remain intact under external force interference, are not easily broken, and can maintain good sedimentation performance in water flow while ensuring that the solid content of the supernatant is at a low level.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite flocculant for the sedimentation of fine mineral particles, characterized in that, By weight, it includes 50-100 parts of polyaluminum chloride, 10-20 parts of sodium alginate, 10-25 parts of sodium hexametaphosphate, 15-25 parts of polyacrylamide, and 5-10 parts of polyethylene oxide.

2. The composite flocculant for the sedimentation of fine mineral particles as described in claim 1, characterized in that, The composite flocculant is a composition consisting of two independent components, component A and component B. Component A includes polyaluminum chloride and sodium alginate, while component B includes sodium hexametaphosphate, polyacrylamide, and polyethylene oxide.

3. A composite flocculant for the sedimentation of fine mineral particles as described in claim 1 or 2, characterized in that, The polyacrylamide is anionic polyacrylamide with a molecular weight of 8000~20000 KDa.

4. The application of a composite flocculant for the settling of fine mineral particles as described in any one of claims 1-3 in the settling of slurry containing fine mineral particles.

5. The application as described in claim 4, characterized in that, The particle size of the fine mineral particles is less than 45 μm.

6. The application as described in claim 5, characterized in that, The slurry is a fine-grained silicate slurry, and the fine mineral particles in the slurry account for more than 60% of the total mineral particle mass of the slurry.

7. The application as described in claim 4, characterized in that, The settlement method includes the following steps: S1. According to the required mass proportions, mix polyaluminum chloride and sodium alginate, and then prepare a solution A with a mass concentration of 1-3% by water; mix sodium hexametaphosphate, polyacrylamide and polyethylene oxide, and then prepare a solution B with a mass concentration of 0.1-0.5% by water. S2. First, add solution A to the slurry to be treated and stir at high speed until it is evenly mixed. Then add solution B and stir at low speed until it is evenly mixed. Let it stand until flocs are formed and settle.

8. The application as described in claim 7, characterized in that, The slurry has a mass concentration of 15-50%, and the volume ratio of solution A to slurry is (2-8):1000; the volume ratio of solution B to slurry is (5-10):1000.

9. The application as described in claim 7, characterized in that, The high-speed stirring is performed at a rate such that the Reynolds number of the slurry flow field is 1 × 10⁻⁶. 5 ~9×10 5 The speed of the high-speed stirring is such that the Reynolds number of the slurry flow field is between 4000 and 8000.

10. The application as described in claim 7, characterized in that, In the settling process, step S2 adopts a two-stage dosing method, wherein the mixing process of solution A and the slurry to be treated is completed in the mixing tank, and the mixing process of solution B and the slurry to be treated is completed in the thickening tank.

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