Composite flocculant for efficient mud-water separation as well as preparation method and application of composite flocculant

Abstract

The invention discloses a composite flocculant for efficient mud-water separation and a preparation method and application of the composite flocculant, and belongs to the technical field of mud treatment. 0.2% to 0.8% of an inorganic polymeric flocculant MPA; 0.07% to 0.15% of an organic polymeric flocculant CPAM; the C-type reagent is prepared from, by weight, 0.3%-0.7% of calcium oxide CaO and 96.85%-98.93% of water through MPF, MPA, CPAM and CaO. According to the reagent, the mud-water separation efficiency is remarkably improved through a bridge network effect, an electric neutralization effect and a Ca channel skeleton synergistic effect. Tests show that the C-type reagent can reduce the water content of sludge to 20.4% and the turbidity of wastewater to 36 NTU, and compared with a traditional flocculant, the water content of sludge is reduced by 20%, and the turbidity is reduced by 79%. The device is suitable for rapid dehydration and purification of high-viscosity and high-specific-gravity slurry.

Description

Technical Field

[0001] This invention relates to the field of mud treatment technology, and in particular to a high-efficiency composite flocculant for mud-water separation, its preparation method, and its application. Background Technology

[0002] In tunnel boring machine (TBM) construction, viscous slurry from viscous formations, even after screening and cyclone distillation, still exhibits high specific gravity and viscosity, necessitating the use of flocculants to assist in centrifugation and pressure filtration. Existing flocculants (such as polyaluminum chloride and polyacrylamide) suffer from drawbacks such as high slurry moisture content (30%–40%) and high wastewater turbidity (150–250 NTU), leading to high transportation costs and a high risk of secondary pollution. While inorganic flocculants can reduce turbidity, their slurry-water separation volume is small; organic flocculants, although offering large separation volumes, suffer from high turbidity. Furthermore, research on compound flocculants is largely limited to optimizing single mechanisms, failing to synergistically enhance bridging, charge neutralization, and mechanical dewatering performance. Therefore, there is an urgent need to develop a highly efficient composite flocculant to address these technical challenges.

[0003] Based on this, the present invention proposes a high-efficiency composite flocculant for mud-water separation, its preparation method, and its application. Summary of the Invention

[0004] This invention provides a high-efficiency composite flocculant for mud-water separation, its preparation method, and its application. By optimizing the ratio of inorganic / organic flocculants and introducing CaO, the bridging effect, charge neutralization effect, and Ca channel framework effect are synergistically enhanced, significantly reducing the water content of sludge and the turbidity of wastewater.

[0005] According to one aspect of this disclosure, a high-efficiency composite flocculant for mud-water separation is provided, the composite flocculant comprising the following components by mass fraction: inorganic polymeric flocculant MPF 0.5%-1.5%; inorganic polymeric flocculant MPA 0.2%-0.8%; organic polymeric flocculant CPAM 0.07%-0.15%; calcium oxide CaO 0.3%-0.7%; and water 96.85%-98.93%.

[0006] In one possible implementation, the inorganic polymeric flocculant MPF is a modified polymeric iron compound, the inorganic polymeric flocculant MPA is a modified polymeric aluminum compound, and the organic polymeric flocculant CPAM is a modified cationic polyacrylamide.

[0007] In one possible implementation, the amount of calcium oxide added is 0.5%, and the calcium oxide needs to be prepared and used immediately.

[0008] A method for preparing a composite flocculant, the method comprising the following steps: A. Dissolve inorganic polymeric flocculant MPF and inorganic polymeric flocculant MPA in water according to the preset ratio, and stir until completely dissolved; B. Add CPAM and control the stirring speed at 100-150 r / min for 10-15 minutes. C. Add CaO powder and stir to mix evenly to obtain a composite flocculant. The composite flocculant must be used immediately.

[0009] In one possible implementation, the dissolution temperature in step A is 20-30℃.

[0010] An application of a composite flocculant, wherein the composite flocculant is the composite flocculant of claim 1, is used for centrifugal separation and pressure filtration dewatering of shield tunneling mud, and the addition amount is 0.5%-1.2% of the dry weight of solids in the mud.

[0011] Compared with the prior art, the beneficial effects of the present invention are: The composite flocculant of this disclosure comprises the following components by mass fraction: inorganic polymeric flocculant MPF 0.5%-1.5%; inorganic polymeric flocculant MPA 0.2%-0.8%; organic polymeric flocculant CPAM 0.07%-0.15%; calcium oxide (CaO) 0.3%-0.7%; and water 96.85%-98.93%. This invention forms a C-type reagent by compounding inorganic polymeric flocculants (MPF, MPA), organic polymeric flocculant (CPAM), and CaO. This reagent significantly improves sludge-water separation efficiency through bridging, charge neutralization, and the synergistic effect of the Ca channel framework. Experiments show that the C-type reagent can reduce the sludge moisture content to 20.4% and the wastewater turbidity to 36 NTU, representing a 20% reduction in sludge moisture content and a 79% reduction in turbidity compared to traditional flocculants. The present invention also discloses its preparation method and its application in shield tunneling mud treatment, which is suitable for rapid dewatering and purification of high viscosity and high specific gravity mud. Attached Figure Description

[0012] Figure 1 The results of a single-component experiment of the inorganic flocculant MPF according to an embodiment of the present disclosure are shown, demonstrating the relationship between volume ratio and turbidity.

[0013] Figure 2 The results of a single-component experiment of the inorganic flocculant MPA according to an embodiment of the present disclosure are shown, demonstrating the relationship between volume ratio and turbidity.

[0014] Figure 3 The results of a single-component experiment of the organic flocculant CPAM according to an embodiment of the present disclosure are shown, demonstrating the relationship between volume ratio and turbidity.

[0015] Figure 4The diagram shows the total interparticle potential energy curve calculated by EDLVO theory according to an embodiment of this disclosure, demonstrating that the C-type reagent has the lowest potential barrier.

[0016] Figure 5 A schematic diagram illustrating the formation and mechanism of the Ca channel framework is shown.

[0017] Figure 6 The graph shows the cumulative mercury infiltration rate in the mud after different reagents were used in a mercury intrusion porosimetry test according to an embodiment of the present disclosure.

[0018] Figure 7 The diagram shows the pore size density distribution of mud after different reagents were applied in a mercury intrusion porosimetry test according to an embodiment of the present disclosure, demonstrating how the Ca channel framework enhances porosity.

[0019] Figure 8 A schematic diagram illustrating the effect of a dispersant on a potential barrier according to an embodiment of the present disclosure is shown, illustrating the effect of SHMP in suppressing charge neutralization.

[0020] Figure 9 A schematic diagram of a filter press dewatering device is shown.

[0021] Figure 10 The graph shows the particle size distribution curves of mud particles after adding different reagents.

[0022] Figure 11 The graph shows the changes in zeta potential of mud after adding different reagents.

[0023] Figure 12 A flowchart illustrating a method for preparing a composite flocculant according to an embodiment of the present disclosure is shown.

[0024] Figure 13 The diagram shows the zeta potential change curves of mud after adding different flocculants according to an embodiment of this disclosure. Detailed Implementation

[0025] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0026] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0027] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0028] According to one aspect of this disclosure, a high-efficiency composite flocculant for mud-water separation is provided, the composite flocculant comprising the following components by mass fraction: inorganic polymeric flocculant MPF 0.5%-1.5%; inorganic polymeric flocculant MPA 0.2%-0.8%; organic polymeric flocculant CPAM 0.07%-0.15%; calcium oxide CaO 0.3%-0.7%; and water 96.85%-98.93%.

[0029] In one possible implementation, the inorganic polymeric flocculant MPF is a modified polymeric iron compound, the inorganic polymeric flocculant MPA is a modified polymeric aluminum compound, and the organic polymeric flocculant CPAM is a modified cationic polyacrylamide.

[0030] In one possible implementation, the amount of calcium oxide added is 0.5%, and the calcium oxide needs to be prepared and used immediately.

[0031] like Figure 12 As shown, a method for preparing a composite flocculant, the method comprising the following steps: A. Dissolve inorganic polymeric flocculant MPF and inorganic polymeric flocculant MPA in water according to the preset ratio, and stir until completely dissolved; B. Add organic polymeric flocculant CPAM, and control the stirring speed at 100-150 r / min for 10-15 minutes. C. Add CaO powder and stir to mix evenly to obtain a composite flocculant. The composite flocculant must be used immediately.

[0032] In one possible implementation, the dissolution temperature in step A is 20-30℃.

[0033] An application of a composite flocculant, wherein the composite flocculant is the composite flocculant of claim 1, is used for centrifugal separation and pressure filtration dewatering of shield tunneling mud, and the addition amount is 0.5%-1.2% of the dry weight of solids in the mud.

[0034] For the preparation of type C reagents: Dissolve 0.5 g MPF and 0.2 g MPA in 50 mL of deionized water and stir until completely dissolved; Add 0.07 g CPAM and stir at 120 r / min for 12 minutes; Add 0.5 g CaO, mix quickly, and use immediately.

[0035] For mud treatment applications: The type C reagent prepared in Example 1 was added at 1% of the dry weight of the mud solids, mixed with the mud, and stirred rapidly for 1 minute, then allowed to settle for 1 hour. The supernatant volume ratio was 28.2%, and the turbidity was 36 NTU; after filtration for 60 minutes, the mud residue moisture content was 20.4%, and the filtrate volume was 85.65 mL.

[0036] Comparative Example: Effect of Traditional Flocculants: When MPA (0.5%) was used alone, the sludge moisture content was 33.1% and the turbidity was 189 NTU; when CPAM (0.1%) was used alone, the sludge moisture content was 39.5% and the turbidity was 216 NTU.

[0037] Experimental procedure: This experiment employed a flocculation and sedimentation test method, first conducting an optimal single-admixture screening test for six flocculants. The turbidity of the supernatant measured by a turbidity meter and the mud-to-water separation volume ratio read from a graduated cylinder were used as evaluation indicators to determine the optimal dosage of each flocculant (dosage = reagent dry weight / dry weight of solids in the slurry). The following tests were performed on the six flocculants in sequence: a certain amount of slurry was placed in five 500ml beakers, and different dosages of flocculant solution were added to beakers containing 50ml of distilled water. The dosage of each reagent was derived from preliminary experiments and engineering practice; specific dosages are shown in Tables 1 and 2. After mixing 50ml of flocculant solution with the slurry, the mixture was rapidly stirred (100 rpm) for 1 min, allowed to settle for 1 h, and then the turbidity of the supernatant and the mud-to-water separation volume ratio were measured (volume ratio = supernatant volume / total slurry volume). Based on the optimal dosage of each flocculant, the optimal flocculant type was determined. Following a similar method to the above experiment, the size of the floc was observed, and the turbidity of the supernatant and the volume ratio of mud to water were recorded every 20 minutes for a total of 120 minutes. The optimal reagents obtained from the above experiments were plotted in a three-factor, three-level orthogonal experimental table, and a compound orthogonal experiment was conducted to obtain the group with the best mud-water separation effect. Notably, the authors found that adding 0.5% Ca significantly improved the efficiency of subsequent mechanical dewatering of the mud.

[0038] Mechanical dewatering test of mud The sludge treated with flocculants was subjected to mechanical dewatering experiments using vacuum negative pressure to compare the effects of the new reagent with other flocculants in mechanical dewatering. Figure 9Using a filter press dewatering device, take 300ml of slurry from the bottom of the graduated cylinder after sludge-water separation. Thoroughly mix the slurry with reagents and pour it into a glass container above the dewatering device. Place filter paper underneath, connect the air pump, and perform filter press dewatering on the treated slurry. Record the amount of wastewater separated within 60 minutes, recording every 5 minutes. After mechanical dewatering, measure the moisture content of the sludge and the turbidity of the wastewater.

[0039] Flocculation Mechanism Analysis Experiment The mechanism of the difference between flocculation and mechanical dewatering effects observed in the experiment was studied using instruments such as scanning electron microscopy (SEM), zeta potential analyzer, Malvern 2000 laser particle size analyzer, and rotational viscometer.

[0040] To determine the optimal dosage of the two inorganic flocculants, multiple flocculation and sedimentation experiments were conducted. Table 1 shows the experimental results after adding flocculants to the mud 1 hour later. Figures 1-3 The diagrams show the flocculation effect of each group and the corresponding changes in turbidity and volume ratio.

[0041] Table 1. Flocculation Test Results of Inorganic Flocculants ; Figure 1 The image shows the slurry after MPF treatment. With increasing addition, the slurry-to-water volume ratio generally showed a trend of first increasing and then decreasing. The maximum volume ratio of 22.12% was reached at an addition of 1%. The supernatant turbidity reached its maximum of 43 NTU at an addition of 0.5%, and its minimum of 18 NTU at an addition of 1%. Considering both slurry-to-water separation and supernatant turbidity, the optimal addition of MPF for the interaction with the slurry was selected as 1%. Figure 2 The mud after MPA treatment is shown. Except for the group with 2% MPA, the mud-water separation effect was significant in all other groups. Furthermore, the mud-water separation volume ratio showed a trend of first increasing and then decreasing with increasing dosage. The maximum volume ratio (32.26%) was reached at 0.5%. Except for the group with 0.5% MPA, the supernatant of all groups was relatively clear. The supernatant turbidity was lowest at 0.5% MPA, at 16 NTU. Considering both indicators, the optimal dosage of MPA for interaction with mud was selected as 0.5%.

[0042] Table 2 shows the test results after adding organic flocculant to the mud 1 hour later. Figure 3 The diagram shows the CPAM flocculation effect and the corresponding changes in turbidity and volume ratio.

[0043] Table 2 Flocculation Test Results of Organic Flocculants ; The following is an orthogonal experiment on the coagulation of flocculants. This experiment uses a three-factor, three-level orthogonal experiment. The three factors are APAM, MPF, and MPA. The three levels are the constant values ​​of fluctuations around the optimal mass fractions of the three reagents obtained from the single-coagulation experiment. Three addition amounts were selected for each level. The specific factors at each level are shown in Table 3 below.

[0044] Table 3 Orthogonal Design Table and Experimental Results ; As shown in Table 4 of the range analysis, when the three reagents are co-mixed, the optimal combination of reagent additions, using turbidity as the evaluation index, is 0.5% MPF, 0.15% CPAM, and 0.5% MPA. MPF has the greatest impact on the turbidity of the supernatant, followed by CPAM, while MPA has the least impact. Using the volume of the separated supernatant as the evaluation index, the optimal combination of reagent additions is 0.5% MPF, 0.07% CPAM, and 0.2% MPA. CPAM has the greatest impact on the volume of the separated supernatant, followed by MPF, while MPA has the least impact. Considering both supernatant volume and turbidity, since CPAM has the greatest impact on supernatant volume, the optimal addition amount of MPA is 0.07%. MPA has the least impact on both indicators, and considering cost factors, the optimal addition amount of MPA is 0.2%. 0.5% MPF has a significant impact on both supernatant turbidity and supernatant volume; therefore, the optimal addition amount of MPF is 0.5%.

[0045] Table 4 Range Analysis Table ; In summary, the optimal blending combination is 0.5% MPF, 0.07% CPAM, and 0.2% MPF. After reacting with the mud, it rapidly flocculates to form large flocs and exhibits more pronounced mud-water separation, while also producing a clearer supernatant. Finally, to improve the mechanical dewatering effect of the mud, 0.5% CaO is mixed in (it must be prepared and used immediately). This reagent formulation is referred to as type C reagent.

[0046] The following section uses EDLVO theory to quantitatively analyze the effects of the charge neutralization of four reagents on mud flocculation and sedimentation. EDLVO theory posits that the total potential energy between particles... Energy from interparticle electrostatic interactions van der Waals interaction energy and spatial polarization energy Composition, as shown in equation (1). Total potential energy It is the result of the combined effect of repulsive potential energy and attractive potential energy. Both repulsive and attractive potential energy have a certain functional relationship with the distance between the particles.

[0047] (1) For particle size and The particles, and the van der Waals interaction energy between them. for: (2) (2) In the formula This represents the distance between particles. The effective Hamaker constant for the interaction between particle 1 and particle 2 in the medium is determined by the following equation (3). , , These represent the Hamaker constants of particle 1, particle 2, and the medium in vacuum, respectively. Since the main components of Zhanjiang clay are montmorillonite and kaolinite, after consulting... , , .

[0048] (3) Interparticle electrostatic interaction energy It is determined by equation (4). and These are the surface potentials of particles 1 and 2, respectively, and are approximately equal to their zeta potentials. The values ​​used here are for reference. Figure 13 . The dielectric constant of the medium is approximately equal to that of water due to the relatively small dosage of flocculant. . The Debye constant is determined by the ion concentration and valence of the flocculant; here we take... .

[0049] (4) Spatial polarization energy It is determined by equation (5). Here, is the attenuation constant, which is taken as 5nm. The energy constant for the spatial polar interaction is determined by the electron acceptor and donor components of particle 1, particle 2, and the surface energy of the medium. Reference values ​​are provided.

[86] .

[0050] (5) To simplify calculations, it is assumed that adjacent particles have the same particle size, i.e. For particles with a unit length diameter: (6) Figure 4The figure shows the curves of the total potential energy between mud particles of unit diameter as a function of particle spacing when four reagents are added at their optimal concentrations. It can be seen that the total potential energy curves for interparticle interaction of all four reagents show a trend of first rapidly increasing and then slowly decreasing, with the peak value of the curve being called the "potential barrier." The size of the potential barrier directly determines the ease of adsorption between clay particles; particles need to overcome this energy through thermal motion or other means to achieve adsorption and bonding. Therefore, the lower the potential barrier, the more conducive it is to improving the aggregation ability between mud particles. MPF, APAM, MPA, and type C reagents reached their respective potential barriers when the mud particles were 5.1 nm, 3.8 nm, 5.3 nm, and 7.5 nm apart, respectively. They are respectively , , and The strength of the potential barrier energy is: APAM > MPF > MPA > C-type reagent. The C-type reagent has the lowest potential barrier energy after neutralization, reducing it by 30.6% compared to the other three. This is the fundamental reason why the C-type reagent has the strongest charge neutralization ability. The zeta potential mentioned earlier represents the strength of charge neutralization from the perspective of macroscopic instrument measurements, while the potential barrier energy represents the strength of charge neutralization from the perspective of microscopic particles. Therefore, the strength of charge neutralization is: C-type reagent > MPA > MPF > APAM.

[0051] The fibrous crystals intertwine and connect, adsorbing onto the surface of the mud particles and encapsulating them, thus forming a framework of drainage channels between the mud particles. For example... Figure 5 As shown, the rigid drainage channel framework containing Ca expands the drainage channels between mud particles through its supporting effect, thus increasing the overall porosity of the mud. In ordinary mud, the drainage channels are quickly compressed under external forces such as pressure filtration, resulting in poor filtration efficiency. However, the rigid Ca-containing drainage channel framework delays the closure of the drainage channels, increasing the permeability of the mud and indirectly releasing more water, thereby improving the efficiency of mud pressure filtration and dewatering.

[0052] To quantitatively describe the changing trends of pore size and porosity in mud after the action of different reagents and to analyze the supporting effect of the Ca channel framework, mercury intrusion porosimetry (MIP) was conducted. Figure 6 and Figure 7The figures show the cumulative mercury ingress curves and pore size density distribution curves of the mud after mechanical filtration and treatment with different reagents. The pore size distribution of the original mud was mainly concentrated between 3515 and 58562 nm. After mechanical dewatering, the mercury ingress rate of the mud decreased significantly, with the pore size distribution mainly concentrated between 98 and 1589 nm, a reduction of 69% to 78% compared to the original mud. This indicates that the drainage channels were significantly compressed during mechanical dewatering. The mud with the addition of MPF, MPA, and APAM all showed varying degrees of increase in total pore size, with the pore size mainly distributed between 245 and 4654 nm, an average increase of approximately 17% compared to the original mud. This is because the small particles aggregated into larger particles, and the small gaps between the particles merged into larger pores. The mud treated with reagent C showed an even greater increase in total pore size. Notably, the support effect of reagent C at a distance of 8 cm was most significant, with the pore size mainly concentrated between 346 and 8656 nm, an increase of approximately 41% compared to the original mud. The change in porosity within a 1cm gap was not significant, with the pore size mainly concentrated between 289 and 2954 nm, increasing by only about 15%. This indicates that the supporting effect of the Ca drainage channel framework is somewhat limited. The reason is that during the drainage consolidation process of the mud under radial mechanical action, the soil near the center is more fully consolidated, resulting in higher density and limiting mercury inflow into the pores early on. Conversely, the density is relatively lower further away, leading to a relatively higher total porosity. This explains the supporting effect of the Ca element drainage channel framework, which, on average, increases the drainage channel porosity by about 29%, promoting mechanical drainage of the mud.

[0053] Figure 8 The figure shows the curves of the total potential energy between clay particles of unit diameter as a function of particle spacing when soaking mud cake with four dispersants at their optimal concentrations. It can be seen that the total potential energy curves of the interparticle interactions for all four dispersants exhibit a trend of first rapidly increasing and then slowly decreasing; the peak value of the curve is called the "potential barrier." The size of the potential barrier directly determines the ease of adsorption between clay particles; particles need to overcome this energy through thermal motion or other means to achieve adsorption bonding. Therefore, the higher the potential barrier, the more beneficial it is to reducing the adhesion force between clay particles. PASS, TSPP, PCAC, and the S-type reagent reached their respective potential barriers when the clay particles were spaced 2.6 nm, 3.2 nm, 2.9 nm, and 2 nm apart, respectively. They are respectively... , , and The strength of the potential barrier energy is as follows: S-type reagent > PASS > PCAC > TSPP. The S-type reagent has the highest potential barrier energy after action, increasing it by 20.6% compared to the other three. This is the fundamental reason why the S-type reagent has a better viscosity-reducing effect.

[0054] Inorganic flocculants MPF (modified polyferric oxide) and MPA (modified polyaluminate) compress the electric double layer through charge neutralization. Organic flocculant CPAM (cationic polyacrylamide) aggregates fine particles through bridging; generating cementitious substances such as CaSiO3·H2O to form the drainage channel framework. The optimal blending ratio was determined through orthogonal experiments: MPF 0.5%, CPAM 0.07%, MPA 0.2%, and CaO 0.5%.

[0055] like Figure 10 As shown, after adding the same mass fraction of flocculant and dispersant, the curves of the four types of samples shifted to the right relative to the original mud. The shift trend is CPAM+SHMP>CPAM>MPA≈MPA+SHMP>original mud; the greater the shift trend, the stronger the bridging and trapping effect of the reagents. In the mud after the reaction of CPAM and MPA, the particle size distribution of particles larger than 50μm accounted for 43.69% and 26.88%, respectively, therefore, the bridging and trapping effect of CPAM is stronger than that of MPA. Under the action of gravity, larger flocs have better sedimentation effect. Compared with the original mud of 21.88%, the bridging and trapping effect of inorganic flocculant MPA only increased the particle size distribution of 50μm particles in the mud by 5.0%, therefore, the main reason for flocculation by MPA may not be the bridging and trapping effect. After adding dispersant SHMP, the particle size distribution of MPA in the mud remained basically unchanged, therefore, dispersant SHMP had almost no effect on the bridging and trapping effect of inorganic flocculants. The particle size distribution of CPAM in the slurry increased slightly, with particles larger than 50 μm increasing by 5.88%. Therefore, the dispersant SHMP can enhance the bridging and trapping effect of the organic flocculant CPAM to a certain extent, accelerating the flocculation and sedimentation of the slurry. The reason why SHMP can enhance the bridging and trapping effect of the organic flocculant CPAM is related to the special molecular structure of CPAM. After the polymer dissolves in water, the extension of its long chains is limited. When SHMP is added, the dissociation of CPAM is promoted, the long chains are further extended, and more adsorption sites of slurry particles are activated, thereby promoting the bridging and trapping effect of CPAM. Bridging effect: CPAM long chains adsorb fine particles, forming flocs with a diameter >50 μm (increased by 30%). Charge neutralization effect: MPF / MPA reduces the mud zeta potential to -12.6 mV, reducing interparticle repulsion; Figure 11The graph shows the trend of zeta potential of slurry after the addition of two flocculants, measured using a zeta potential meter. The value of zeta potential also reflects the stability of the dispersion system; the larger the absolute value of zeta potential, the more stable the system; conversely, the system is more prone to sedimentation. The initial zeta potential of the slurry was -30 mV. After adding the same mass fraction of organic flocculant CPAM and inorganic flocculant MPA, the potentials rose to -21.9 mV and -12.6 mV, respectively. The stability of the slurry is broken by the charge effect of the flocculant, which is one of the mechanisms of flocculant action: charge neutralization. However, the decrease in zeta potential of the slurry after adding organic flocculant CPAM was less than that of inorganic flocculant MPA. Therefore, the charge neutralization effect of inorganic flocculant MPA is stronger because MPA contains more metal cations such as aluminum. Thus, at the same addition amount, the cation concentration of inorganic flocculant MPA is higher.

[0056] Ca channel framework: CaO reacts to form fibrous crystals, which increases porosity (by 41%) and enhances dehydration permeability.

[0057] Adhering to the concept of green and efficient construction, a novel flocculant suitable for on-site mud-water separation was developed through a combination of indoor orthogonal experiments and field tests. The study revealed the changes in the mud-water separation volume ratio, supernatant turbidity, particle size distribution, and zeta potential of the mud from both flocculation and mechanical dewatering perspectives. The reasons and mechanisms by which the novel flocculant outperforms commonly used flocculants were explored. Research shows that the C-type reagent can reduce the water content of the mud sludge by approximately 20% and the turbidity of the supernatant by 79%. The C-type reagent mainly releases more bound water by improving the charge neutralization effect of the bridging network, enhancing the pore size distribution of the mud, and reducing the viscosity of the mud, thereby improving the mechanical dewatering efficiency of the mud.

[0058] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A high-efficiency composite flocculant for mud-water separation, characterized in that, The composite flocculant is composed of the following components by mass fraction: inorganic polymeric flocculant MPF 0.5%-1.5%; inorganic polymeric flocculant MPA 0.2%-0.8%; organic polymeric flocculant CPAM 0.07%-0.15%; calcium oxide CaO 0.3%-0.7%; and water 96.85%-98.93%.

2. The composite flocculant for efficient mud-water separation according to claim 1, characterized in that, The inorganic polymeric flocculant MPF is a modified polymeric iron compound, the inorganic polymeric flocculant MPA is a modified polymeric aluminum compound, and the organic polymeric flocculant CPAM is a modified cationic polyacrylamide.

3. The composite flocculant according to claim 1, characterized in that, The amount of calcium oxide added is 0.5%, and the calcium oxide must be prepared and used immediately.

4. A method for preparing a composite flocculant, characterized in that, The method is used to prepare the composite flocculant according to claim 1, and includes the following steps: A. Dissolve inorganic polymeric flocculant MPF and inorganic polymeric flocculant MPA in water according to the preset ratio, and stir until completely dissolved; B. Add organic polymeric flocculant CPAM, and control the stirring speed at 100-150 r / min for 10-15 minutes. C. Add CaO powder and stir to mix evenly to obtain a composite flocculant. The composite flocculant must be used immediately.

5. The preparation method according to claim 4, characterized in that, The dissolution temperature in step A is 20-30℃.

6. The application of a composite flocculant, characterized in that, The composite flocculant is the composite flocculant described in claim 1, used for centrifugal separation and pressure filtration dewatering of shield tunneling mud, and the addition amount is 0.5%-1.2% of the dry weight of solids in the mud.

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