A treatment process and system for slurry waste liquid in marble cutting

Abstract

The present invention discloses a treatment process and system for slurry waste liquid in marble cutting, including: collecting the waste liquid, pouring the waste liquid into a sedimentation tank, detecting the calcium ion concentration in the waste liquid, and adding a magnesium salt in proportion according to the calcium ion concentration; adding polyaspartic acid and stirring, carrying out reaction and flocculation, and regulating the pH value of the waste liquid in sections; before the flocculation is completed, uniformly adding modified vermiculite and polyacrylamide to the waste liquid for sedimentation for 0 to 60 minutes, and taking the supernatant for recycling. The present invention can quickly adsorb and precipitate marble powder and heavy metal ions in the waste liquid, and moreover, by adding a magnesium salt to induce the main component of marble powder, namely calcium carbonate, to precipitate in the metastable form of vaterite. In the prior art, calcium carbonate precipitates in the stable form of calcite, forming a dense hardening at the bottom of the sedimentation tank. The present invention not only improves the treatment speed of the slurry waste liquid generated by marble cutting, but also avoids the phenomenon of calcium carbonate solidification and hardening at the bottom of the sedimentation tank.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater, and in particular to a treatment process and system for slurry waste liquid in marble cutting. Background Art

[0002] Stone processing is currently the non-metallic mineral industry with the largest output value. The stone processing process flow is as follows: stone raw materials are cut by a sawing machine, then polished by a grinding machine, and the cutting machine cuts and forms them into finished products.

[0003] The slurry waste liquid in marble cutting mainly comes from the flushing water in the cutting and cooling processes, and contains stone powder, debris and cooling lubricant residues generated during the cutting process. According to the processing scale, the waste slurry volume can reach 20-30% of the weight of the processed rough stone.

[0004] The main pollutants in marble cutting wastewater include suspended particles (such as marble powder), Fe 3+ , Mn 2+ and other heavy metal ions. Existing treatment methods, such as coagulation precipitation, filtration and other methods, although they can also effectively treat the slurry waste liquid in marble cutting, have problems of long treatment time and difficult treatment of precipitates.

[0005] Therefore, it is necessary to provide a treatment process and system for slurry waste liquid in marble cutting to solve the above technical problems. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a treatment process and system for slurry waste liquid in marble cutting.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a treatment process for slurry waste liquid in marble cutting, comprising the following steps:

[0008] S1. Collect the waste liquid and filter out large particles therein;

[0009] S2. Pour the treated waste liquid into a sedimentation tank, detect the calcium ion concentration in the waste liquid, and add a magnesium salt in proportion according to the calcium ion concentration;

[0010] S3. Add polyaspartic acid and stir, carry out reaction and flocculation for 30-60 min, and at the same time, segmentally regulate the pH value of the waste liquid;

[0011] S4. 10-20 min before the completion of flocculation, uniformly add modified vermiculite and polyacrylamide to the waste liquid, sediment for 0-60 min, and take the supernatant for recycling.

[0012] In a preferred embodiment of the present invention, in the step S2, the magnesium salt is added according to the molar ratio of magnesium ion to calcium ion of 2.9-3.3:1.

[0013] In a preferred embodiment of the present invention, in step S3, the pH value is regulated in segments, specifically as follows:

[0014] Reaction stage: within 0 - 30 minutes after adding the magnesium salt, the pH of the waste liquid is regulated to 9.0 - 9.5;

[0015] Flocculation stage: within 30 - 60 minutes after adding the magnesium salt, the pH of the waste liquid is regulated to 8.0 - 8.5.

[0016] In a preferred embodiment of the present invention, the modified vermiculite is vermiculite particles after thermal expansion and surface treatment.

[0017] In a preferred embodiment of the present invention, the modification of the vermiculite specifically includes the following steps:

[0018] S41. Select vermiculite particles with a particle size of 50 - 100 μm;

[0019] S42. Place the vermiculite particles in a crucible and expand them at 800 - 900 °C for 20 - 30 s, then cool naturally;

[0020] S43. Immerse the thermally expanded vermiculite in a cetyltrimethylammonium bromide solution, ultrasonically treat it for 10 - 30 minutes, and then stir it at 50 - 70 °C for 3 - 5 hours;

[0021] S44. Filter, wash, and dry to obtain the modified vermiculite.

[0022] In a preferred embodiment of the present invention, in step S4, the mass ratio of the modified vermiculite to polyacrylamide is 1:80 - 100.

[0023] In a preferred embodiment of the present invention, in step S4, the dosage of the modified vermiculite is 0.5 - 1.5 g / L of the waste liquid.

[0024] In a preferred embodiment of the present invention, the polyacrylamide is cationic polyacrylamide.

[0025] A treatment system for the slurry waste liquid in marble cutting includes:

[0026] A conveying component for conveying the waste liquid;

[0027] A sedimentation component where the waste liquid is treated. The sedimentation component includes a sedimentation tank and a stirring mechanism arranged on the sedimentation tank;

[0028] A monitoring component, which includes a calcium ion detection unit and a pH value detection unit;

[0029] Dosing assembly, the dosing assembly comprising: a magnesium salt dosing mechanism, a mixing mechanism, a pH adjustment mechanism, a flocculation dosing mechanism and a central control subsystem.

[0030] In a preferred embodiment of the present invention, the conveying assembly comprises: a conveying pipeline and a pump;

[0031] A first filtering unit and a second filtering unit are sequentially arranged on the conveying pipeline;

[0032] The first filtering unit is equipped with a coarse grille with a grid gap of 10 - 20 mm, and the second filtering unit is equipped with a fine grille with a grid gap of 3 - 5 mm.

[0033] The present invention solves the defects in the background art and has the following beneficial effects:

[0034] (1) The present invention provides a treatment process and system for slurry waste liquid from marble cutting, which can quickly adsorb and precipitate marble powder and heavy metal ions in the waste liquid. Moreover, by adding magnesium salt, the main component of marble powder, namely calcium carbonate, is induced to precipitate in the metastable form of vaterite. In the prior art, calcium carbonate precipitates in the stable form of calcite, forming a dense crust at the bottom of the sedimentation tank. The present invention not only improves the treatment speed of the slurry waste liquid generated from marble cutting, but also avoids the phenomenon of calcium carbonate solidification and crust formation at the bottom of the sedimentation tank, which is easy to clean.

[0035] (2) The present invention induces calcium carbonate in the waste liquid to precipitate in the form of vaterite by adding magnesium salt to the waste liquid, and controls the molar ratio of Mg 2+ to Ca 2+ within the range of 2.9 - 3.3:1. The sediment changes from a dense crust to a loose and porous state, reducing the cleaning difficulty. Moreover, the market value of vaterite is higher, and its recycling can offset the treatment cost of the waste liquid.

[0036] (3) The present invention modifies vermiculite through thermal expansion and CTAB surface treatment. After modification, the surface charge of vermiculite increases, and the Zeta potential rises from -35 mV to +20 mV (pH 8.0). Moreover, there are more adsorption sites. The surface of the modified vermiculite is positively charged, while the surface of marble powder (CaCO3) is negatively charged under neutral to alkaline conditions. Under the action of electrostatic force, the adsorption efficiency of marble powder is improved.

[0037] (4) By modifying vermiculite and controlling the mass ratio of the modified vermiculite to polyacrylamide within the range of 1:80 to 100, the present invention can balance charge neutralization and net capture, resulting in larger and looser flocs and better removal of suspended particles in the waste liquid. Compared with the sedimentation method in the prior art, the present invention achieves rapid treatment, low caking rate, and better effect in treating the slurry waste liquid from marble cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0039] Figure 1 It is a process flow diagram of treating slurry waste liquid in a preferred embodiment of the present invention.

[0040] Figure 2 It is a flow chart of the vermiculite modification method in a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0042] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0043] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0044] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "connected to" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific circumstances.

[0045] As Figure 1 shown, the present invention provides a treatment process for slurry waste liquid in marble cutting, including the following steps:

[0046] S1. Collect the waste liquid and filter out the large particles therein;

[0047] S2. Pour the treated waste liquid into a sedimentation tank, detect the calcium ion concentration in the waste liquid, and add a magnesium salt in proportion according to the calcium ion concentration;

[0048] S3. Add polyaspartic acid and stir, carry out reaction and flocculation for 30 - 60 min. At the same time, regulate the pH value of the waste liquid in sections;

[0049] S4. 10 - 20 min before the completion of flocculation, uniformly add modified vermiculite and polyacrylamide to the waste liquid, sediment for 0 - 60 min, and take the supernatant for recycling.

[0050] Through the above steps, the present invention can quickly adsorb and precipitate marble powder and heavy metal ions in the waste liquid. Moreover, by adding magnesium salts, the main component of marble powder, namely calcium carbonate, is induced to precipitate in the metastable form of vaterite. In the prior art, calcium carbonate precipitates in the stable form of calcite, forming a dense crust at the bottom of the sedimentation tank. The present invention not only improves the treatment speed of the slurry waste liquid generated by marble cutting, but also avoids the phenomenon of calcium carbonate solidification and crusting at the bottom of the sedimentation tank, which is easy to clean up.

[0051] The following is a detailed description of each of the above steps.

[0052] Step S1: Collect the waste liquid and filter out the large particles therein.

[0053] Specifically: The slurry waste liquid generated by marble cutting is centrally transported to the sedimentation tank through a conveying pipeline, and a first filtering unit and a second filtering unit are sequentially arranged on the conveying pipeline to intercept sundries such as fibers, plastic fragments, and metal chips in the cutting waste liquid. Among them, the first filtering unit is equipped with a coarse grille with a grid gap of 10 - 20 mm, and the second filtering unit is equipped with a fine grille with a grid gap of 3 - 5 mm.

[0054] Step S2: Pour the treated waste liquid into the sedimentation tank, detect the calcium ion concentration in the waste liquid, and add magnesium salts in proportion according to the calcium ion concentration.

[0055] The sedimentation tank includes: an inlet area, a sedimentation area, an outlet area, and a sludge area. The sedimentation tank is designed in a rectangular shape. The waste liquid flows in from one end, and after being evenly distributed through a perforated rectifying wall, it slowly flows horizontally and exits from the other end. The perforated rectifying wall is made of concrete bricks, and a number of perforations are evenly arranged on the surface. This enables the water flow entering the sedimentation area to be evenly distributed across the entire inlet cross-section, reducing the turbulence generated by the inlet water and minimizing the impact on the sedimentation of particles in the sedimentation area.

[0056] A number of calcium ion selective electrodes are evenly installed in the sedimentation area to continuously monitor the Ca 2+ concentration in the waste liquid. Preferably, METTLER TOLEDO Ca 2+ ISE is used, with a measuring range of 0.1 - 100 mmol / L.

[0057] Furthermore, magnesium salts (MgCl2·6H2O) are added in a molar ratio of Mg 2+ :Ca 2+ = 2.9 - 3.3:1, and the purity of the magnesium salts is ≥98%. Specifically, the dosage of the magnesium salts is calculated by the following formula:

[0058] , where M is the molar ratio of magnesium ions to calcium ions, C Ca 5 is the concentration, in mmol / L. For example: If the Ca in the waste liquid2+ When the concentration is 2.5 mmol / L and M is 3, the dosage of magnesium salt = 3×2.5×203.3 / 1000 ≈ 1.52 kg per ton of waste liquid.

[0059] A dosing pump is set in the precipitation area. According to the Ca concentration monitored by the calcium ion selective electrode, the dosage of magnesium salt is automatically calculated and magnesium salt is added to the precipitation area. 2+ Magnesium salt is added to the waste liquid to induce the precipitation of calcium carbonate in the waste liquid in the form of vaterite. Its loose and porous structure can solve the problem of dense hardening caused by the precipitation of calcite in the traditional precipitation method, and at the same time improve the precipitation rate and resource utilization value. Specifically:

[0060] 1) Mg in the magnesium salt has a strong affinity for the calcite crystal form of calcium carbonate, preferentially adsorbs on the calcite crystal surface, covers its active growth sites, and hinders the formation and expansion of calcite crystal nuclei. The Mg adsorbed on the calcite crystal surface forms an "ion barrier", significantly reducing the growth rate of calcite and forcing the crystallization path to turn to vaterite with a lower thermodynamic barrier.

[0061] 1) 2+ Mg has a strong affinity for the calcite crystal form of calcium carbonate, preferentially adsorbs on the calcite crystal surface, covers its active growth sites, and hinders the formation and expansion of calcite crystal nuclei. The Mg adsorbed on the calcite crystal surface 2+ forms an "ion barrier", significantly reducing the growth rate of calcite and forcing the crystallization path to turn to vaterite with a lower thermodynamic barrier.

[0062] 2) 2+ Mg reduces the free CO3 concentration in the waste liquid by complexing with CO3, making the supersaturation of CaCO3 close to the vaterite nucleation threshold (Ω≈3 - 5), rather than calcite (Ω≈10 - 20). 2- 2- concentration, making the supersaturation of CaCO3 close to the vaterite nucleation threshold (Ω≈3 - 5), rather than calcite (Ω≈10 - 20).

[0063] 3) 2+ Mg competes with Ca for binding to CO3, resulting in the local formation of amorphous calcium carbonate (ACC), which is more likely to transform into vaterite rather than calcite. 2+ 2- competes with Ca for binding to CO3, resulting in the local formation of amorphous calcium carbonate (ACC), which is more likely to transform into vaterite rather than calcite.

[0064] Based on the above reaction principle and the control of the molar ratio of Mg:Ca = 2.9 - 3.3:1, the precipitation form of calcium carbonate in the waste liquid is dominated by vaterite, reducing the occurrence of hardening phenomenon and facilitating cleaning. 2+ 2+ :Ca

[0065] Step S3: Add polyaspartic acid and stir, react and flocculate for 30 - 60 min. At the same time, the pH value of the waste liquid is regulated in segments.

[0066] When performing step S2, that is, when adding magnesium salt, polyaspartic acid is added synchronously, or magnesium salt and polyaspartic acid can be mixed and added. Polyaspartic acid and magnesium salt are added to the waste liquid at a mass ratio of 1:4 - 8.

[0067] ​​​Polyaspartic acid can enhance the chelation-induced synergistic effect and shorten the reaction phase time, specifically:

[0068] The carboxylic acid group (-COOH) of polyaspartic acid reacts with free Ca 2+ Mg 2+ The formation of complexes slows the nucleation rate of calcium carbonate, that is, reduces the growth rate of calcite. In addition, polyaspartic acid adsorbs on the surface of vaterite to form an organic coating with a thickness of about 2 to 5 nm, inhibiting its transformation to calcite. It also prevents the aggregation of vaterite particles through electrostatic repulsion, maintaining the loose structure of the flocs.

[0069] Furthermore, the pH value is controlled in sections in step S3, specifically:

[0070] Reaction stage: 0-30 minutes after adding magnesium salt, the pH of the wastewater is regulated to 9.0-9.5. In this stage, NaOH solution or lime milk (Ca(OH)2) is added to the wastewater, and the amount of addition is adjusted according to the pH value of the wastewater detected by the pH probe. During the reaction stage, maintaining a high pH environment promotes CO3 - Generate (CO2+2OH - →CO3 2- +H2O) to increase the supersaturation of CaCO3 and accelerate the nucleation of vaterite.

[0071] Flocculation stage: 30 to 60 minutes after adding magnesium salt, the pH of the wastewater is adjusted to 8.0 to 8.5. In this stage, dilute hydrochloric acid or CO2 gas is added to the wastewater to reduce the pH value of the wastewater. - concentration, slowing down the crystal growth rate, preventing the excessive growth of vaterite leading to densification, and appropriately lowering the pH value of the waste liquid to 8.0-8.5, which can optimize the charge distribution of polyaspartic acid and enhance the flocculation synergistic effect with the modified vermiculite and polyacrylamide in step S4.

[0072] Step S4: 10 to 20 minutes before the completion of flocculation, the modified vermiculite and polyacrylamide are evenly added to the waste liquid, and the waste liquid is allowed to settle for 0 to 60 minutes, and the supernatant is collected and recycled.

[0073] That is, in the middle of the flocculation stage, modified vermiculite and polyacrylamide are evenly added to the wastewater, where the added polyacrylamide is cationic. The purposes of adding modified vermiculite and polyacrylamide to the wastewater during the flocculation stage are: modified vermiculite enriches vaterite, suspended particles, and metal ions through adsorption-netting; while cationic polyacrylamide forms large, loose flocs through charge neutralization and bridging, thereby preventing the occurrence of compaction.

[0074] It is worth noting that the modified vermiculite is vermiculite particles that have been thermally expanded and surface treated.

[0075] As shown Figure 2 below, the modification of vermiculite specifically includes the following steps:

[0076] S41. Select vermiculite particles with a particle size of 50 - 100 μm.

[0077] S42. Place the vermiculite particles in a high-temperature resistant ceramic crucible and expand them at 800 - 900 °C for 20 - 30 s. Rapid expansion can avoid excessive sintering due to too long a time. Then, cool them naturally to room temperature to avoid the collapse of the expanded structure caused by rapid cooling;

[0078] After being treated by step S42, the volume expansion rate of the vermiculite particles is 8 - 10 times, the specific surface area increases from 5 m 2 / g to 250 - 300 m 2 / g, and the interlayer porosity increases from 20% to 60 - 70%. The vermiculite after high-temperature expansion has a larger volume, a higher specific surface area, and an interlayer porosity, and can have more adsorption sites.

[0079] S43. Immerse the thermally expanded vermiculite in a CTAB (cetyltrimethylammonium bromide) solution and perform ultrasonic treatment at 40 kHz for 10 - 30 min with a power density of 0.5 W / cm 3 to promote the entry of CTAB molecules into the interlayer of vermiculite. Then, stir at 50 - 70 °C for 3 - 5 h at a rotation speed of 150 rpm to form a stable organic-inorganic complex.

[0080] It should be noted that CTAB is dissolved in an ethanol-water mixed solution with a volume ratio of 1:1 to prepare a CTAB solution with a concentration of 2 - 5% (w / w).

[0081] S44. Filter with a 200-mesh nylon filter cloth, rinse with ethanol 3 times, and finally dry in an oven at 60 °C to constant weight to obtain modified vermiculite with a moisture content < 2%.

[0082] For the modified vermiculite, the surface charge increases, the Zeta potential rises from -35 mV to +20 mV (pH 8.0), and moreover, it has more adsorption sites. The surface of the modified vermiculite is positively charged, while the surface of marble powder (CaCO3) is negatively charged under neutral to alkaline conditions. Under the action of electrostatic force, the adsorption efficiency for marble powder is improved.

[0083] In step S4, the mass ratio of modified vermiculite to polyacrylamide is 1:80-100, and the amount of modified vermiculite added is 0.5-1.5 g / L of waste liquid. By controlling the amount of modified vermiculite and polyacrylamide added, the sedimentation of suspended particles in the waste liquid and the loosening of flocs are maximized, which improves the processing speed of the slurry waste liquid generated by marble cutting, avoids the solidification and hardening of calcium carbonate at the bottom of the sedimentation tank, and facilitates cleaning.

[0084] The following comparative experiments are set up to verify the treatment effect of the present invention.

[0085] Example 1:

[0086] Based on the above-mentioned marble cutting slurry waste liquid treatment process, the collected waste liquid is treated.

[0087] First, the waste liquid is filtered to remove large particles. The filtered waste liquid is divided into 12 parts, each of which has 10 tons of initial waste liquid. One part is randomly selected as the initial waste liquid of this example. The initial waste liquid: 1500 mg / L of suspended particles, of which calcium carbonate accounts for 1200 mg / L, pH value 8.5, temperature 25 ° C, Cu 2+ Concentration 15mg / L.

[0088] 1) Pour a portion of the initial wastewater into a sedimentation tank. Eight calcium ion selective electrodes are evenly distributed on the sedimentation tank to detect the Ca 2+ =3.0mmol / L. According to the molar ratio of Mg 2+ :Ca 2+ =3.0:1, magnesium salt is added to the initial waste liquid, and the addition amount is 1.83kg / ton of waste liquid.

[0089] 2) Polyaspartic acid and magnesium salt are added to the waste liquid simultaneously at a mass ratio of 1:6.

[0090] 3) The pH value of the wastewater was monitored in real time by a pH probe. The pH value was controlled at 9.2±0.2 in the first 30 minutes and at 8.3±0.2 in the last 30 minutes.

[0091] 4) Vermiculite particles with a particle size of 50-100 μm were selected and expanded at 850°C for 25 seconds, with the volume expanding by about 9 times. The expanded vermiculite was immersed in a 3% (w / w) CTAB solution and ultrasonically treated for 20 min (40 kHz, power 0.5 W / cm 3 ), then stirred at 60 °C for 4 h (150 rpm), filtered using a 200-mesh nylon filter cloth, rinsed with ethanol three times, and finally dried in an oven at 60 °C to constant weight to obtain modified vermiculite with a moisture content of <2%.

[0092] 5) At the 20th minute after the start of the flocculation stage, modified vermiculite was added at a dosage of 1.0 g / L of the waste liquid, and polyacrylamide was added at a mass ratio of modified vermiculite to polyacrylamide of 1:90. After sedimentation for 40 minutes, the vaterite proportion (%) in the sediment, compressive strength (MPa), suspended solid concentration (SS, mg / L), turbidity (NTU), porosity (%) and floc diameter D50 (μm) were respectively detected and recorded.

[0093] Example 2:

[0094] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that according to the molar ratio Mg 2+ :Ca 2+ = 2.9:1, magnesium salt was added to the initial waste liquid at a dosage of 1.76 kg per ton of waste liquid. Similarly, after sedimentation for 40 minutes, the vaterite proportion (%) and compressive strength (MPa) in the sediment were respectively detected and recorded.

[0095] Example 3:

[0096] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that according to the molar ratio Mg 2+ :Ca 2+ = 3.3:1, magnesium salt was added to the initial waste liquid at a dosage of 2.01 kg per ton of waste liquid. Similarly, after sedimentation for 40 minutes, the vaterite proportion (%) and compressive strength (MPa) in the sediment were respectively detected and recorded.

[0097] Comparative Example 1:

[0098] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that according to the molar ratio Mg 2+ :Ca 2+ = 2.5:1, magnesium salt was added to the initial waste liquid at a dosage of 1.52 kg per ton of waste liquid. Similarly, after sedimentation for 40 minutes, the vaterite proportion (%) and compressive strength (MPa) in the sediment were respectively detected and recorded.

[0099] Comparative Example 2:

[0100] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that according to the molar ratio Mg 2+ :Ca 2+ = 4:1, magnesium salt was added to the initial waste liquid at a dosage of 2.44 kg per ton of waste liquid. Similarly, after sedimentation for 40 minutes, the vaterite proportion (%) and compressive strength (MPa) in the sediment were respectively detected and recorded.

[0101] Comparative Example 3:

[0102] Select an initial waste liquid for treatment. The specific treatment process includes:

[0103] Add 2.0 mg / L of ordinary flocculant (anionic polyacrylamide) to the initial waste liquid, stir and react for 30 min. Add dilute hydrochloric acid to the reacted waste liquid to adjust the pH to 7.0 - 7.5. After sedimentation for 120 min, detect and record respectively: the vaterite proportion (%) in the sediment, turbidity (NTU), compressive strength (MPa), and suspended solid concentration (SS, mg / L).

[0104] Summarize the test results of the above Examples 1 - 3 and Comparative Examples 1 - 3 as shown in Table 1:

[0105] Table 1. Test Results

[0106]

[0107] It can be concluded from Table 1 that the vaterite proportion in the sediments of Example 1 (3.0:1), Example 2 (2.9:1), and Example 3 (3.3:1) is all > 90%, and the compressive strength ≤ 0.08 MPa. It can be seen that in the range of molar ratio Mg 2+ :Ca 2+ = 2.9 - 3.3:1, vaterite formation can be effectively induced and calcite formation can be inhibited. While the vaterite proportion in the sediment of Comparative Example 1 (2.5:1) is only 65%, and the compressive strength increases to 0.40 MPa, indicating that insufficient Mg 2+ results in an increase in the calcite proportion; and the vaterite proportion in the sediment of Comparative Example 2 (4:1) is 84%, which is higher than that of Comparative Example 1 but lower than those of Examples 1, 2, and 3, because excessive Mg 2+ competes with Ca 2+ for adsorption, interfering with the crystallization path.

[0108] Example 4:

[0109] Based on Example 1, select an initial waste liquid for treatment. The difference is that in step 5, modified vermiculite is added at 0.5 g / L of waste liquid, and polyacrylamide is added according to the mass ratio of modified vermiculite to polyacrylamide of 1:90. After sedimentation for 40 min, detect and record respectively: suspended solid concentration (SS, mg / L), turbidity (NTU), compressive strength (MPa), and porosity (%).

[0110] Example 5:

[0111] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that in step 5, modified vermiculite was added at a dosage of 1.5 g / L of the waste liquid, and polyacrylamide was added at a mass ratio of modified vermiculite to polyacrylamide of 1:90. After sedimentation for 40 min, the suspended solid concentration (SS, mg / L), turbidity (NTU), compressive strength (MPa), and porosity (%) were respectively detected and recorded.

[0112] Comparative Example 4:

[0113] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that in step 5, modified vermiculite was added at a dosage of 1.0 g / L of the waste liquid, and polyacrylamide was added at a mass ratio of modified vermiculite to polyacrylamide of 1:50. After sedimentation for 40 min, the suspended solid concentration (SS, mg / L), turbidity (NTU), compressive strength (MPa), and floc diameter D50 (μm) were respectively detected and recorded.

[0114] Comparative Example 5:

[0115] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that in step 5, modified vermiculite was added at a dosage of 1.0 g / L of the waste liquid, and polyacrylamide was added at a mass ratio of modified vermiculite to polyacrylamide of 1:120. After sedimentation for 40 min, the suspended solid concentration (SS, mg / L), turbidity (NTU), compressive strength (MPa), and floc diameter D50 (μm) were respectively detected and recorded.

[0116] Comparative Example 6:

[0117] Based on Example 1, an initial waste liquid was selected for treatment. The difference is that in step 5, vermiculite (unmodified) was added at a dosage of 1.0 g / L of the waste liquid, and polyacrylamide was added at a mass ratio of vermiculite to polyacrylamide of 1:90. After sedimentation for 40 min, the suspended solid concentration (SS, mg / L), compressive strength (MPa), and vaterite proportion (%) were respectively detected and recorded.

[0118] The detection results of the above Examples 1, 4, and 5 and Comparative Examples 3 - 6 are summarized in Table 2 as follows:

[0119] Table 2. Detection Results

[0120]

[0121] As can be seen from Table 2 above:

[0122] The data of Examples 1, 4, and 5 show that the addition amount of modified vermiculite is positively correlated with the waste liquid treatment effect. When the addition amount of modified vermiculite increases from 0.5 g / L to 1.5 g / L, the SS concentration decreases from ≤50 mg / L to ≤25 mg / L, and the removal efficiency increases by 50%. The increase in the addition amount of modified vermiculite reduces the compressive strength from 0.15 MPa to 0.05 MPa because vermiculite disperses particles through entrapment and reduces dense packing. The porosity increases from 60% to 72%, indicating that the precipitation structure is looser, which is beneficial for subsequent cleaning. It should be noted that although the addition amount of 1.5 g / L of modified vermiculite has the best effect, the cost of vermiculite will also increase accordingly. Therefore, an addition amount of 1.0 g / L of modified vermiculite is preferably selected to balance the waste liquid treatment effect and cost.

[0123] In Comparative Example 4, the mass ratio of modified vermiculite to polyacrylamide is 1:50. The excess of polyacrylamide results in dense flocs (compressive strength 0.20 MPa) and slow sedimentation speed (floc particle size 150 μm), and the SS removal rate decreases.

[0124] In Comparative Example 5, the mass ratio of modified vermiculite to polyacrylamide is 1:120. Too little polyacrylamide results in loose but weakly bound flocs, and the SS removal rate is only ≤45 mg / L.

[0125] Compared with Comparative Examples 4 and 5, in Example 1, the mass ratio of modified vermiculite to polyacrylamide is 1:90, which is actually the best ratio. The charge neutralization and entrapment effects are balanced, the floc particle size is 220 μm, the compressive strength is 0.08 MPa, and the SS removal rate is the best (≤30 mg / L).

[0126] Compared with the unmodified vermiculite used in Comparative Example 6, in Example 1, the vermiculite is modified in Step 4 by thermal expansion, which increases the specific surface area of the modified vermiculite from 5 m² / g to 250 m² / g, increases the adsorption sites, and increases the SS removal rate from ≤80 mg / L to ≤30 mg / L. By surface treatment, the surface potential of vermiculite is increased from -35 mV to +20 mV, enhancing the electrostatic adsorption effect on negatively charged particles (CaCO3, heavy metals). Further, the modified vermiculite adsorbs Mg 2+ to maintain a local high concentration, increasing the vaterite proportion from 70% to 92% and reducing the compressive strength by 84%.

[0127] In summary, for the treatment process of the slurry waste liquid from marble cutting of the present invention, by adding a magnesium salt and controlling the molar ratio of Mg 2+ to Ca 2+ within the range of 2.9 - 3.3:1, vaterite is induced to form and calcite formation is inhibited. The sediment changes from dense and compact to loose and porous, reducing the cleaning difficulty. Moreover, vaterite has a higher market value, and its recycling can offset the treatment cost of the waste liquid;

[0128] Moreover, by modifying vermiculite and controlling the mass ratio of modified vermiculite to polyacrylamide within the range of 1:80 - 100, the charge neutralization and net trapping effects can be balanced, resulting in larger and looser flocs, and better removal effect of suspended particles in the waste liquid. Compared with the sedimentation method in the prior art, the present invention realizes rapid treatment, low caking rate and better effect for the slurry waste liquid treatment of marble cutting.

[0129] The present invention also provides a treatment system for the slurry waste liquid of marble cutting, including: a conveying component, a sedimentation component, a monitoring component and a dosing component.

[0130] The conveying component includes: a conveying pipeline and a corresponding pump; and a first filtering unit and a second filtering unit are sequentially arranged on the conveying pipeline for intercepting sundries such as fibers, plastic fragments, and metal chips in the cutting waste liquid. Among them, the first filtering unit is installed with a coarse grid with a grid gap of 10 - 20 mm, and the second filtering unit is installed with a fine grid with a grid gap of 3 - 5 mm.

[0131] The sedimentation component includes: a sedimentation tank and a stirring mechanism arranged on the sedimentation tank; wherein, the sedimentation tank includes: a water inlet area, a sedimentation area, a water outlet area and a sludge area, and a perforated rectifying wall is arranged between the water inlet area and the sedimentation area; the sedimentation tank is of a rectangular design, the waste liquid flows in from one end, after being evenly distributed by the perforated rectifying wall, it slowly flows along the horizontal direction and flows out from the other end; the perforated rectifying wall is made of concrete bricks, and a number of perforations are evenly arranged on the surface. It can make the water flow entering the sedimentation area evenly distributed on the entire water inlet cross-section, reduce the turbulence generated by the water inlet, and reduce the influence on the particle sedimentation in the sedimentation area.

[0132] The stirring mechanism includes: an X / Y axis displacement platform arranged above the sedimentation area, a driving unit arranged on the X / Y axis displacement platform, the output end of the driving unit is arranged downward and is connected with a stirring paddle. The stirring paddle vertically penetrates into the sedimentation area, drives the stirring paddle to rotate through the driving unit, stirs the waste liquid in the sedimentation area, and adjusts the position of the stirring paddle through the X / Y axis displacement platform to complete the stirring work of the waste liquid in the entire sedimentation area.

[0133] The monitoring component includes: a calcium ion detection unit and a pH value detection unit; the calcium ion detection unit preferably uses a calcium ion selective electrode, and a number of calcium ion detection units are evenly installed in the sedimentation area to monitor the Ca 2+ concentration in the waste liquid in real time; and the pH value detection unit preferably uses a pH probe, and a number of pH value detection units are evenly installed in the sedimentation area to monitor the pH value of the waste liquid in real time.

[0134] The dosing component includes: a magnesium salt dosing mechanism, a mixing mechanism, a pH adjustment mechanism, a flocculant dosing mechanism and a central control subsystem.

[0135] The magnesium salt dosing mechanism includes a chemical storage tank for storing magnesium salt and a metering peristaltic pump connected to the chemical storage tank. The metering peristaltic pump calculates the dosing amount of magnesium salt based on the Ca 2+ concentration output by the calcium ion detection unit and automatically doses it.

[0136] The mixing mechanism is a dynamic mixer, which is connected in parallel with the magnesium salt dosing pipeline and doses polyaspartic acid proportionally and synchronously.

[0137] The pH adjustment mechanism includes an alkaline chemical tank, an acidic chemical tank, and chemical dosing pumps respectively connected to the alkaline chemical tank and the acidic chemical tank, which control the addition of alkaline chemicals or acidic chemicals during the reaction stage and the flocculation stage to control the pH value of the waste liquid within a set range.

[0138] The flocculation dosing mechanism includes a modified vermiculite storage bin and a PAM (polyacrylamide) dissolution and dosing unit; the modified vermiculite storage bin is equipped with a screw feeder with a dosing amount of 0.5 - 1.5 g / L; the PAM dissolution and dosing unit is dosed synchronously with the modified vermiculite at a mass ratio of 1:80 - 100.

[0139] The central control subsystem integrates the Ca 2+ concentration, pH value, and flow rate data, and automatically calculates and controls the dosing amount and time of the magnesium salt dosing mechanism, the mixing mechanism, the pH adjustment mechanism, and the flocculation dosing mechanism.

[0140] Regarding the detailed design of the treatment system for the slurry waste liquid from marble cutting, the present invention will not be described in detail, as it is well-known to those skilled in the art.

[0141] Based on the ideal embodiments of the present invention as inspiration, through the above description, relevant personnel can make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and must be determined according to the scope of the claims.

Claims

1. A treatment process for slurry waste liquid in marble cutting, characterized in that, It includes the following steps: S1. Collect the waste liquid and filter out the large particles therein; S2. Pour the treated waste liquid into a sedimentation tank, detect the calcium ion concentration in the waste liquid, and add a magnesium salt according to a ratio based on the calcium ion concentration; wherein, the molar ratio of magnesium ions to calcium ions is 2.9 - 3.3:1; S3. Add polyaspartic acid and stir, carry out reaction and flocculation for 30 - 60 min, and at the same time, regulate the pH value of the waste liquid in stages; S4. 10 - 20 min before the completion of flocculation, uniformly add modified vermiculite and polyacrylamide into the waste liquid according to a mass ratio of 1:80 - 100, sediment for 0 - 60 min, and take the supernatant for recycling.

2. The treatment process of slurry waste liquid for marble cutting according to claim 1, characterized in that: In the said S3, regulating the pH value in stages specifically means: Reaction stage: 0 - 30 min after adding the magnesium salt, regulate the pH of the waste liquid to 9.0 - 9.5; Flocculation stage: 30 - 60 min after adding the magnesium salt, regulate the pH of the waste liquid to 8.0 - 8.

5.

3. The treatment process of slurry waste liquid for marble cutting according to claim 1, characterized in that: The said modified vermiculite is vermiculite particles after thermal expansion and surface treatment.

4. The treatment process of the slurry waste liquid for marble cutting according to claim 1, characterized in that: The modification of the vermiculite specifically includes the following steps: S41. Select vermiculite particles with a particle size of 50 - 100 μm; S42. Place the vermiculite particles in a crucible, expand them at 800 - 900 °C for 20 - 30 s, and cool naturally; S43. Immerse the thermally expanded vermiculite in a cetyltrimethylammonium bromide solution, carry out ultrasonic treatment for 10 - 30 min, and then stir at 50 - 70 °C for 3 - 5 h; S44. Filter, wash, and dry to obtain the modified vermiculite.

5. The treatment process of slurry waste liquid for marble cutting according to claim 1, characterized in that: In the said S4, the dosage of the modified vermiculite is 0.5 - 1.5 g / L of the waste liquid.

6. The treatment process of slurry waste liquid for marble cutting according to claim 1, characterized in that: The said polyacrylamide is cationic polyacrylamide.

7. A treatment system for slurry waste liquid in marble cutting, based on the treatment process for slurry waste liquid in marble cutting according to any one of claims 1-6, characterized in that, It includes: A conveying component for conveying the waste liquid; A sedimentation component where the waste liquid is treated, and the sedimentation component includes a sedimentation tank and a stirring mechanism arranged on the sedimentation tank; A monitoring component, and the monitoring component includes: a calcium ion detection unit and a pH value detection unit; A chemical dosing component, and the chemical dosing component includes: a magnesium salt dosing mechanism, a mixing mechanism, a pH adjustment mechanism, a flocculation dosing mechanism, and a central control subsystem; Wherein, the mixing mechanism is a dynamic mixer, is connected in parallel with the magnesium salt dosing mechanism, and synchronously doses polyaspartic acid according to a ratio.

8. The treatment system for slurry waste liquid in marble cutting according to claim 7, wherein: The conveying component includes: a conveying pipeline and a pump; A first filtering unit and a second filtering unit are sequentially arranged on the conveying pipeline; The first filtering unit is equipped with a coarse grille with a grid gap of 10 - 20 mm, and the second filtering unit is equipped with a fine grille with a grid gap of 3 - 5 mm.

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