Environment-friendly additive for preparing high-quality dredged sand

Abstract

The present application belongs to the technical field of flocculants for dredged sand, and discloses a green environmental protection additive for preparing high-quality dredged sand. The raw materials of the green environmental protection additive disclosed by the present application include: flocculation components and film-forming components; the green environmental protection additive is applied to the dredged sand at a mass ratio of 1:500-600. The green environmental protection additive includes the following components in parts by mass: 10-50 parts of anionic polyacrylamide, 50-100 parts of polyaluminum chloride, 8-15 parts of epoxy soybean oil, 2-5 parts of citrate, 1-3 parts of sodium bicarbonate, and 5-10 parts of natural latex. The present application aims to provide a green environmental protection additive for preparing high-quality dredged sand, which can improve the flocculation effect and obtain good mechanical strength when applied to concrete, in view of the problems of small cohesion, low structural strength and easy damage under shearing of flocculation groups in the process of using common flocculants at present.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flocculants for dredged sand, and particularly relates to a green environmental protection additive for preparing high-quality dredged sand. BACKGROUND

[0002] In order to improve the water quality of rivers and lakes, ensure the normal flood discharge capacity and navigation capacity of the river, large-scale dredging and desilting projects are carried out in the lakes and river channels in China. The dredged slurry has high water content and low density, and is difficult to be directly utilized. Flocculation refers to adding a flocculant to the slurry, and multiple small particles in the slurry form flocculation through electrical properties or bridging, which can reduce the blockage of filtration and improve the separation effect. Therefore, flocculation is the key to slurry filtration and separation. In the current process of using common flocculants, the flocculation particles have the characteristics of small cohesion, low structural strength and easy damage under shear. Therefore, it is of great significance to optimize the flocculant for the preparation of dredged sand, and a new product is needed to optimize the flocculation process. In addition, the application of flocculants in concrete is also very important. Therefore, the present application develops a green environmental protection additive which can improve the performance of concrete and meet the market demand. SUMMARY

[0003] In view of the problems of small cohesion, low structural strength and easy damage under shear of flocculation particles in the current process of using common flocculants, the present application aims to provide a green environmental protection additive for preparing high-quality dredged sand, which can improve the flocculation effect and form a film after mixing with the slurry, and can improve the overall mechanical strength when applied to concrete.

[0004] The present application aims to provide a green environmental protection additive for preparing high-quality dredged sand:

[0005] The processing raw material components of the above-mentioned green environmental protection agent include flocculation components and film-forming components. The green environmental protection agent is applied to the dredged sand at a mass ratio of 1:500-600.

[0006] Further, the flocculation components include anionic polyacrylamide and polyaluminum chloride, and the film-forming components include epoxy soybean oil, citric acid ester, sodium bicarbonate and natural latex.

[0007] Further, the green environmental protection agent includes the following components by mass fraction:

[0008] 10-50 parts of anionic polyacrylamide, 50-100 parts of polyaluminum chloride, 8-15 parts of epoxy soybean oil, 2-5 parts of citric acid ester, 1-3 parts of sodium bicarbonate and 5-10 parts of natural latex.

[0009] Further, the dredged sand is soil after the dredged slurry is dried, and the mass ratio of the green environmental protection agent to water is 1:1200-1600.

[0010] Further, the green environmental protection agent is applied in cooperation with the change of the stirring speed.

[0011] Further, the stirring speed is first set to 2000-3000 rpm, and the size of the mud flocculation group, the sedimentation rate of the mud and the clarity of the supernatant are observed synchronously during the stirring process; when small flocculation groups are formed or supernatant appears, the stirring speed is adjusted to 300-500 rpm and maintained for 0.5-2 h.

[0012] A processing method of a green environmental protection additive for preparing high-quality dredged sand: take the components with the mass fraction, and add them into a ball mill in sequence.

[0013] Further, the speed of the ball mill is 300-500 rpm.

[0014] Compared with the prior art, the application has the following advantages:

[0015] (1) The application uses anionic polyacrylamide (APAM) and polyaluminum chloride (PAC) to compound and strengthen the flocculation effect, but with the increase of APAM and PAC, the electric neutralization effect is gradually weakened, and the bridging effect is inhibited, resulting in an increase in the water content of the sediment; when the PAC dosage is small in the composite flocculation, the electric neutralization effect is beneficial to the bridging effect of APAM, more clay particles can be adsorbed, the water content of the sediment is reduced, and the supernatant of the mud after the composite flocculation of APAM and PAC is clear, the sedimentation rate is fast, the water content of the sediment is low, the permeability coefficient is high, and the flocculation and sedimentation effect is good; the larger the PAC addition amount, the slower the sedimentation rate and the permeability coefficient of the mud, so the PAC addition amount needs to be controlled; when the APAM addition amount is too large, not only the sedimentation rate of the mud cannot be increased, but also the water content of the sediment is too large, the permeability coefficient is reduced, and other problems occur; the application accurately controls the compound of APAM and PAC, and significantly improves the application effect of the flocculant.

[0016] (2) The green environmental protection agent prepared by the application can generate a protective film under the action of natural latex, epoxy soybean oil and the like during use, has an isolation effect on the sludge, assists in optimizing the flocculation effect, improves the cohesiveness of the flocculation particles, and improves the structural strength and is not easy to be damaged by shear force; especially when the green environmental protection agent is applied to the concrete, the mechanical properties of the concrete can be enhanced, which can be seen from the test part; after ball milling, the latex particles can move freely in the form of Brownian motion, and when the water evaporates, their movement is gradually restricted, and finally the latex particles approach each other to form a close accumulation; due to the protection of the double electric layer on the surface of the latex particles, the polymers in the latex cannot directly contact each other, but at this time, small gaps with small radii of curvature can be formed between the latex particles, which are equivalent to small "capillary tubes" filled with water; the capillary force caused by the surface tension of water can exert a large pressure on the latex particles, and especially the added sodium bicarbonate component can decompose carbon dioxide gas when applied to the concrete, increasing the internal gas pressure difference; as the water further evaporates, the surface pressure continuously increases, eventually overcoming the resistance of the double electric layer, so that the polymers in the natural latex directly contact each other; the contact between the polymers forms a polymer-water interface, and the interfacial tension causes a new pressure; the capillary force and the interfacial tension of the polymer and water complement each other, and this comprehensive force can deform the polymer particles and lead to the formation of a film, which can form an organic whole that can resist external stress and provide good mechanical properties when applied to the concrete. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 APAM and PAC composite flocculation slurry complete settling time curve.

[0018] Figure 2 PAC addition amount influence curve of sludge water content.

[0019] Figure 3 APAM addition amount influence curve of sludge water content.

[0020] Figure 4 PAC addition amount influence curve of sludge permeability coefficient.

[0021] Figure 5 APAM addition amount influence curve of sludge permeability coefficient. DETAILED DESCRIPTION

[0022] The following provides a specific embodiment of the application for preparing a green environmental protection additive for high-quality dredged sand. It is necessary to point out that the following examples are only used to more specifically illustrate the application, and do not narrow the protection scope of the application. Improvements and adjustments made by those skilled in the art after reading the application without departing from the concept of the application are within the scope of the application.

[0023] A green environmental protection additive for preparing high-quality dredged sand and a processing method thereof

[0024] The components of the green environmental protection agent include, in terms of mass fraction, 10-50 parts of anionic polyacrylamide, 50-100 parts of polyaluminum chloride, 8-15 parts of epoxy soybean oil, 2-5 parts of citrate, 1-3 parts of sodium bicarbonate, and 5-10 parts of natural latex.

[0025] The processing method is that the components in the above mass fraction are sequentially added and mixed, and ball milling is performed at 300-500 rpm for 1-2 h.

[0026] In application, the composite flocculating agent is mixed with water at a mass ratio of 1:1200-1600 before use. In application, the stirring speed is changed from fast to slow, which is beneficial to the flocculation process. The stirring speed is initially set to 2000-3000 rpm, and the size of the flocculation group, the sedimentation rate of the slurry, and the clarity of the supernatant are observed synchronously during the stirring process. When small flocculation groups are formed or supernatant appears, the stirring speed is adjusted to 300-500 rpm and maintained for 0.5-2 h.

[0027] Example 1

[0028] A green environmental protection additive for preparing high-quality dredged sand and a processing method thereof

[0029] The components of the green environmental protection agent include, in terms of mass fraction, 50 parts of anionic polyacrylamide, 100 parts of polyaluminum chloride, 15 parts of epoxy soybean oil, 5 parts of citrate, 3 parts of sodium bicarbonate, and 10 parts of natural latex.

[0030] The processing method is that the components in the above mass fraction are sequentially added and mixed, and ball milling is performed at 400 rpm for 3 h.

[0031] Example 2

[0032] A green environmental protection additive for preparing high-quality dredged sand and a processing method thereof

[0033] The components of the green environmental protection agent include, in terms of mass fraction, 10 parts of anionic polyacrylamide, 50 parts of polyaluminum chloride, 8 parts of epoxy soybean oil, 2 parts of citrate, 1 part of sodium bicarbonate, and 5 parts of natural latex.

[0034] The processing method is that the components in the above mass fraction are sequentially added and mixed, and ball milling is performed at 400 rpm for 3 h.

[0035] Example 3

[0036] A green environmental protection additive for preparing high-quality dredged sand and a processing method thereof

[0037] The components of the green environmental protection agent include, in terms of mass parts: 40 parts of anionic polyacrylamide, 60 parts of polyaluminum chloride, 12 parts of epoxy soybean oil, 3 parts of citrate, 2 parts of sodium bicarbonate, and 7 parts of natural latex.

[0038] The processing method is as follows: the components are sequentially added and mixed, and then ball milled at 400 rpm for 3 h.

[0039] Comparative Example 1: substantially the same as Example 1, except that the film-forming component is absent.

[0040] Comparative Example 2: a certain composite flocculant commercially available in Nanjing (main components: ferrous sulfate heptahydrate, aluminum sulfate octadecahydrate).

[0041] I. Application in mechanical property test of concrete

[0042] The green environmental protection agent / composite flocculant obtained in Examples 1-3 and Comparative Examples 1 and 2 is subjected to compressive strength test according to GB / T 50081-2019 "Test methods for physical and mechanical properties of concrete", and the results are recorded in Table 1. Freeze-thaw cycle test is carried out according to GB / T 50082-2009 "Test methods for long-term performance and durability of ordinary concrete", and the freeze-thaw medium is 3.5% sodium chloride solution and 5% sodium sulfate solution, respectively. After freeze-thaw cycle for 300 times, the mass loss of the composite flocculant is detected, and the results are recorded in Table 1.

[0043] Table 1 Performance test

[0044]

[0045] It can be seen from Examples 1-3 and Comparative Examples 1 and 2 that the green environmental protection agent prepared in the present application has better mechanical properties when applied to concrete compared to Comparative Examples 1 and 2, the internal structure is compact, and has excellent compressive strength. At the same time, when sodium chloride solution and sodium sulfate solution are used as freeze-thaw medium, the mass loss of the concrete is small after 300 freeze-thaw cycles in salt-frozen environment, and the service life of the concrete is long. However, the absence of the film-forming component in Comparative Example 1 leads to a significant decrease in test performance.

[0046] II. Comparison test of flocculation components

[0047] Mud preparation: take the reservoir dredging soil sample, placed in the oven, constant temperature drying at 105℃ for 8h, the dried sample was crushed and ground after sealing, using the balance and weighing box to take 100g of treated soil sample, and transfer the measured soil sample to a beaker, add 500g of water, configure into 600g of mud with 500% moisture content. Then place it on a four-way stirrer, stir at 400 rpm for 5 minutes, mix thoroughly, the sample preparation is completed, and the powder clay ratio is 2.4. The composite test is divided into A, B, C, D, E five groups, each test condition is three parallel tests, A, B, C three groups are different adding amount of anionic polyacrylamide (APAM) and polyaluminum chloride (PAC) composite group, D is the optimal adding amount of APAM under the condition of the soil sample; E is the optimal adding amount of PAC under the condition of the soil sample. The test conditions are shown in Table 2.

[0048] Table 2 APAM and PAC composite flocculation test conditions

[0049]

[0050]

[0051] Table 3 summary of flocculation and sedimentation index

[0052] Test group Flocculant Floc size Supernatant turbidity A PAC+APAM Large Clear B PAC+APAM Large Clear C PAC+APAM Large Clear D APAM Large Turbid E PAC Small Clear

[0053] (2) Test results and analysis

[0054] 1) APAM and PAC composite flocculation and sedimentation index

[0055] As shown in Table 3, the data in the table shows that the flocs of APAM and PAC composite flocculation group are larger and the supernatant is clear, which combines the advantages of APAM and PAC single flocculation.

[0056] 2) Effect of APAM and PAC composite flocculation on complete sedimentation time of mud

[0057] The complete sedimentation time of D test group with single addition of APAM and E test group with single addition of PAC is about 45min and 105min respectively, Figure 1The relationship curve between the complete sedimentation time of slurry and the PAC addition amount is listed. As can be seen from the curve in the figure, with the increase of the PAC addition amount, the complete sedimentation time of the slurry in each test group changes little; in the composite flocculation test, the complete sedimentation time of the slurry in the A test group is the longest, about 48 min, the complete sedimentation time of the slurry in the C test group is the shortest, about 37 min, and the complete sedimentation time of the slurry in the B test group is 43 min. Comparing the C test group in the composite flocculation test with the D test group in which APAM is added alone, it can be seen that the complete sedimentation time of the slurry in the C test group in which PAC is added is slightly delayed; and comparing the E test group in which PAC is added alone with the A3, B3 and C3 test groups in the composite flocculation test, it can be seen that the complete sedimentation time of the slurry in the E test group is much higher than that in the composite flocculation test groups.

[0058] 3) Effect of APAM and PAC composite flocculation on the water content of the sludge

[0059] The water content of the sludge in the D test group in which APAM is added alone is 130.7%, the water content of the sludge in the E test group in which PAC is added alone is 156%, and the water content change curves of the sludge in the A, B and C test groups in the composite flocculation test are shown in Figure 2 , 3 , wherein Figure 2 is the effect curve of the PAC addition amount on the water content of the sludge in the composite flocculation, Figure 3 is the effect curve of the APAM addition amount on the water content of the sludge in the composite flocculation. As can be seen from the figure, with the increase of the addition amounts of PAC and APAM, the water content curves of the sludge all show an upward trend, the larger the addition amounts of PAC and APAM, the greater the water content of the sludge, the water content of the sludge in the A group increases from 120.69% to 123.9%, the water content of the sludge in the B group increases from 124.26% to 126.3%, and the water content of the sludge in the C group increases from 126.34% to 130.1%, wherein the water content of the sludge in the A1 group is the smallest, 120.69%. The possible mechanism is that as the APAM and PAC increase, the electric neutralization effect is gradually weakened, the bridging effect is inhibited, and the water content of the sludge increases. Comparing the water content of the sludge in the A1 test group in the composite flocculation test with the D group in which APAM is added alone and the E group in which PAC is added alone, it can be seen that the water content of the sludge in the composite flocculation test group is slightly lower than that in the group in which APAM is added alone and much lower than that in the group in which PAC is added alone. It is indicated that when the PAC amount is small in the composite flocculation, the electric neutralization effect of PAC will be beneficial to the bridging effect of APAM, more clay particles can be adsorbed, and the water content of the sludge is reduced.

[0060] 4) Effect of APAM and PAC composite flocculation on the permeability coefficient of the sludge

[0061] The permeability coefficient of the sludge in the D test group in which APAM is added alone is 3.34 x 10 -5cm / s, the sediment permeability coefficient of the E test group with single PAC addition was 1.269 x 10 -5 cm / s, the sediment permeability coefficient curves of the A, B and C groups in the composite flocculation test are shown in Figure 4 , 5 , wherein Figure 4 is the influence curve of PAC addition amount on the sediment permeability coefficient in the composite flocculation test, Figure 5 is the influence curve of APAM addition amount on the sediment permeability coefficient in the composite flocculation test. It can be seen from Figure 4 that with the increase of PAC addition amount, the sediment permeability coefficient curves of the A1-A3, B1-B3 and C1-C3 groups generally show a downward trend, the sediment permeability coefficient of the A group decreases from 2.71 x 10 -5 cm / s to 2.02 x 10 -5 cm / s, the sediment permeability coefficient of the B group decreases from 3.26 x 10 -5 cm / s to 2.86 x 10 -5 cm / s, and the sediment permeability coefficient of the C group decreases from 2.46 x 10 -5 cm / s to 2.31 x 10 -5 cm / s, indicating that the greater the PAC addition amount in the composite flocculation test, the smaller the sediment permeability. It can be seen from Figure 5 that with the increase of APAM addition amount, the sediment permeability coefficient curves of the A1-C1, A2-C2 and A3-C3 groups all show a first-increasing and then-decreasing trend, and the permeability coefficient of each group is the largest when the APAM addition amount is 240 g / t, wherein the sediment permeability coefficient of the B1 group is the largest, which is 3.26 x 10 -5 cm / s. Comparing the sediment permeability coefficients of the B1 group in the composite flocculation test with the D group with single APAM addition and the E group with single PAC addition, it can be seen that the sediment permeability coefficient of the composite flocculation test group is slightly lower than that of the group with only APAM addition, and is much higher than that of the group with only PAC addition. This is because when the addition amounts of PAC and APAM are too large in the composite flocculation, the electric neutralization effect of the flocculant is reduced, the molecular force shows repulsion, and the bridging effect is inhibited, so the sediment permeability coefficient decreases.

[0062] 5) According to the above composite test results, it can be found that after the APAM and PAC composite flocculation, the mud liquid is clear, the sedimentation rate is fast, the sediment moisture content is low, and the permeability coefficient is high, and the flocculation and sedimentation effect is good. The greater the PAC addition amount, the slower the mud sedimentation rate and the lower the sediment permeability coefficient, so the PAC addition amount should not be too large; when the APAM addition amount is too large, it not only cannot increase the mud sedimentation rate, but also causes the problems of excessive sediment moisture content and reduced permeability coefficient.

[0063] Description: The above examples are only used to illustrate the technical solutions described in the present application and do not limit the present application; therefore, although the present application has been described in detail with reference to the above various embodiments, those of ordinary skill in the art should understand that the present application can still be modified or equivalently replaced; and all technical solutions and improvements that do not deviate from the spirit and scope of the present application should be covered within the scope of the claims of the present application.

Claims

1. A green and eco-friendly additive for preparing high-quality dredged sand, characterized in that, The green environmental protection additive raw material components include flocculation components and film forming components; the green environmental protection additive is applied to the dredged sand at a mass ratio of 1:500-600; The flocculation components include anionic polyacrylamide and polyaluminum chloride; the film forming components include epoxy soybean oil, citrate, sodium bicarbonate and natural latex.

2. The green and eco-friendly additive for producing high quality dredged sand according to claim 1, characterized in that, The green environmental protection additive includes the following components by mass fraction: 10-50 parts of anionic polyacrylamide, 50-100 parts of polyaluminum chloride, 8-15 parts of epoxy soybean oil, 2-5 parts of citrate, 1-3 parts of sodium bicarbonate and 5-10 parts of natural latex.

3. The green and eco-friendly additive for producing high quality dredged sand according to claim 1, characterized in that, The dredged sand is soil after the dredged slurry is dried; the mass ratio of the green environmental protection additive to water is 1:1200-1600.

4. The green and eco-friendly additive for producing high quality dredged sand as claimed in claim 1, wherein, The green environmental protection additive is applied in coordination with the change of the stirring speed.

5. The green and eco-friendly additive for producing high quality dredged sand according to claim 4, characterized in that, The stirring speed is first set to 2000-3000 rpm, and the size of the slurry flocculation group, the slurry sedimentation rate and the clarity of the supernatant are observed simultaneously during the stirring process; when small flocculation groups are formed or supernatant appears, the stirring speed is adjusted to 300-500 rpm, and the stirring is maintained for 0.5-2 h.

6. The green and eco-friendly additive for producing high quality dredged sand as claimed in claim 2, wherein, The processing method of the green environmental protection additive is that the components are sequentially added into a ball mill for mixing.

7. The green and eco-friendly additive for producing high quality dredged sand according to claim 6, characterized in that, The speed of the ball mill is 300-500 rpm.

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