A process for recycling wastewater from commercial concrete production

Abstract

This application relates to a process for recycling wastewater from commercial concrete production, and is in the field of wastewater treatment technology. The process includes the following steps: (1) collecting wastewater from commercial concrete production, performing preliminary sedimentation to remove large particulate impurities, and obtaining primary treated wastewater; (2) passing the primary treated wastewater through a filtration device to further remove small particulate impurities, obtaining secondary treated wastewater; (3) adding a slow-release flocculant to the secondary treated wastewater, allowing the slow-release flocculant to react with the slurry components, and then re-precipitating the secondary treated wastewater after the reaction. After separating the precipitate, tertiary treated wastewater is obtained. The precipitate is dried and crushed to obtain recycled concrete filler; (4) the tertiary treated wastewater is oxidized with an oxidant, and the pH is adjusted to neutral to obtain recycled wastewater. This application has the effect of improving the purity of recycled wastewater. The slow-release flocculant can exert a long-lasting flocculation effect, fully adsorbing impurities in the wastewater and improving the utilization value of the recycled wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to a commercial concrete production wastewater recycling process. BACKGROUND

[0002] At present, a large amount of wastewater is generated in the production process of commercial concrete, and the wastewater contains slurry. If the wastewater is directly discharged, environmental pollution will be caused. Traditional wastewater treatment methods include sedimentation, filtration and the like, but the treatment effect of these methods on the slurry is limited, and it is difficult to realize the recycling of the wastewater.

[0003] The existing concrete production wastewater treatment scheme usually adopts a chemical flocculant for rapid sedimentation, but the disadvantage of this method is that the treated wastewater still contains a large amount of impurities, and long-time flocculation cannot be realized, thereby limiting the recycling effect of the wastewater, and thus needs to be improved. SUMMARY

[0004] In order to improve the treatment effect of the wastewater, the present application provides a commercial concrete production wastewater recycling process.

[0005] The commercial concrete production wastewater recycling process provided by the present application adopts the following technical scheme:

[0006] A commercial concrete production wastewater recycling process comprises the following steps:

[0007] (1) Collecting commercial concrete production wastewater, performing preliminary sedimentation, removing large-particle impurities, and obtaining first-stage treated wastewater;

[0008] (2) Passing the first-stage treated wastewater into a filtering device, further removing small-particle impurities, and obtaining second-stage treated wastewater;

[0009] (3) Adding a slow-release flocculant to the second-stage treated wastewater, allowing the slow-release flocculant to react with slurry components, re-sedimenting the reacted second-stage treated wastewater, obtaining third-stage treated wastewater after separating the sediment, drying the sediment, and crushing the dried sediment to obtain recycled concrete filler;

[0010] (4) After the third-stage treated wastewater is treated by an oxidizing agent, adjusting the pH to neutral to obtain recycled wastewater.

[0011] The impurities such as sand and soil in the commercial concrete wastewater are effectively removed by the preliminary sedimentation, filtration, flocculation and oxidation treatment of the commercial concrete wastewater, and meanwhile, the separated impurities can be used as fillers to reduce the generation of solid waste; the slow-release flocculant has a long-acting flocculation effect, can remain in the wastewater for a longer time, fully contacts and reacts with the slurry components in the wastewater, effectively complexes and adsorbs the harmful components in the wastewater, so that the wastewater reaches the standard of recycling utilization, improves the utilization value of the recycled wastewater, reduces the discharge of the wastewater, and reduces the production cost and the risk of environmental pollution.

[0012] Preferably, the preparation raw materials of the slow-release flocculant include the following components in mass fraction: 3-5 parts of graphene loaded mesoporous titanium dioxide, 8-10 parts of organic titanium salt, 6-8 parts of composite inorganic salt, 20-30 parts of modified chitosan, 15-25 parts of branched polyethyleneimine and 10-15 parts of crosslinking agent.

[0013] The graphene loaded mesoporous titanium dioxide has good dispersion performance and high specific surface area, has high adsorption activity, can effectively adsorb the impurity components in the concrete wastewater, improve the effect and utilization rate of the slow-release flocculant, and reduce the amount of the slow-release flocculant; the organic titanium salt and the composite inorganic salt synergistically form colloidal particles, complex the particulate matters in the concrete wastewater, form larger lumps for sedimentation, and effectively remove the impurities in the concrete wastewater; the modified chitosan and the branched polyethyleneimine are in-situ polymerized on the surface of the graphene loaded mesoporous titanium dioxide, the organic titanium salt and the composite inorganic salt to form an inorganic-organic phase flocculant with core-shell structure, which effectively complexes the impurities in the concrete wastewater through the synergistic effect of the organic phase gel and the inorganic phase colloidal, and the high specific surface area filler, and improves the recycling value of the wastewater.

[0014] Preferably, the graphene loaded mesoporous titanium dioxide is prepared by the following steps:

[0015] Titanium tetrabutoxide, anhydrous ethanol and graphene oxide are mixed and dispersed to obtain a suspension, nitric acid aqueous solution is added under stirring to obtain a reaction liquid, the pH of the reaction liquid is adjusted to neutral after standing, and the reaction is carried out under heating, and then the graphene loaded mesoporous titanium dioxide is obtained after cooling, washing and drying.

[0016] The graphene oxide has good adsorption activity and large specific surface area, and can effectively adsorb and complex various impurities; the in-situ synthesis of mesoporous titanium dioxide on the surface of the graphene oxide can improve the dispersion performance of the graphene oxide, reduce the agglomeration, and thus improve the adsorption performance; the mesoporous titanium dioxide has a rich and ordered pore structure, can store the organic titanium salt and the composite inorganic salt particles, improve the adsorption and complexing efficiency, and provide a slow-release effect, so as to improve the long-acting flocculation performance and water purification performance of the slow-release flocculant.

[0017] Preferably, the raw materials for preparing the organotitanium salt include titanium tetrachloride and dodecylmethyldihydroxyethylammonium bromide.

[0018] The organic titanium salt obtained by reacting titanium tetrachloride and dodecylmethyldihydroxyethylammonium bromide has good flocculation performance. By introducing quaternary ammonium salt, the adsorption effect on small molecule organic matter can be improved, and it can also perform preliminary sterilization and disinfection on concrete wastewater, thereby improving the water purification performance of slow-release flocculants.

[0019] Preferably, the composite inorganic salt includes aluminum sulfate, ferric chloride, and calcium carbonate.

[0020] The synergistic effect of aluminum sulfate, ferric chloride and calcium carbonate forms a colloid that effectively flocculates particulate matter in concrete wastewater, thereby enhancing the water purification effect of the slow-release flocculant.

[0021] Preferably, the raw materials for preparing the modified chitosan include carboxymethyl chitosan and polyquaternium-7.

[0022] Carboxymethyl chitosan has good water solubility and reactivity, and is more prone to cross-linking reactions. Polyquaternium-7 has quaternary ammonium salt groups and acrylamide groups. By modifying carboxymethyl chitosan, the charge density on the surface of chitosan can be enhanced, and the adsorption capacity can be improved. This allows the modified chitosan to effectively adsorb and encapsulate particles in water, thereby improving the flocculation effect.

[0023] Preferably, the mass ratio of carboxymethyl chitosan to polyquaternium-7 is 1:(0.28-0.46).

[0024] The modified chitosan prepared according to the above mass ratio has good flocculation properties.

[0025] Preferably, the raw materials for preparing the branched polyethyleneimine include polyethyleneimine, chlorohexane, and epoxysilane.

[0026] Modifying polyethyleneimine with chlorohexane and epoxy silanes introduces hydrophobic silane molecules into the branched chains of polyethyleneimine, giving the resulting polyethyleneimine a certain degree of negative charge, enabling it to adsorb positively charged impurities. Simultaneously, the increased branching degree increases steric hindrance, improving the dispersibility of polyethyleneimine and slowing down the flocculation and sedimentation rate of the flocculant, allowing the slow-release flocculant to function for a longer period. Branched polyethyleneimine exhibits good reactivity; through in-situ polymerization with modified chitosan on the inorganic phase surface for secondary coating, the slow-release performance can be further enhanced, extending the working time of the slow-release flocculant and improving its water purification performance.

[0027] Preferably, the mass ratio of the polyethyleneimine, chlorohexane and epoxysilane is (4-6):0.25:1.

[0028] The branched polyethyleneimine prepared according to the above mass ratio has good reactivity and adsorption properties.

[0029] Preferably, the slow-release flocculant is prepared using the following steps:

[0030] Graphene-supported mesoporous titanium dioxide was dispersed in deionized water and sonicated to obtain a graphene dispersion. An organic titanium salt and a composite inorganic salt were added to the graphene dispersion and stirred to obtain a mixed dispersion. Modified chitosan and branched polyethyleneimine were mixed and dispersed in deionized water to obtain an organic phase solution. A crosslinking agent was dissolved in deionized water to obtain a crosslinking agent solution. The organic phase solution and the crosslinking agent solution were added to the mixed dispersion under stirring conditions. After reaction, a slow-release flocculant solution was obtained. Acetone was added to the slow-release flocculant solution to precipitate the product. The product was dried to obtain the slow-release flocculant.

[0031] The slow-release flocculant prepared according to the above steps has long-lasting flocculation performance and good water purification effect.

[0032] In summary, this application includes at least one of the following beneficial technical effects:

[0033] 1. By performing preliminary sedimentation, filtration, flocculation, and oxidation treatment on the wastewater from commercial concrete production, impurities such as sand and mud in the wastewater are effectively removed. At the same time, these separated impurities can be used as fillers to reduce the generation of solid waste. The slow-release flocculant has a long-lasting flocculation effect and can remain in the wastewater for a longer period of time, fully contacting and reacting with the mud components in the wastewater. It effectively complexes and adsorbs harmful components in the wastewater, enabling the wastewater to meet the standards for reuse, improving the utilization value of recycled wastewater, reducing wastewater discharge, and lowering production costs and the risk of environmental pollution.

[0034] 2. Graphene-supported mesoporous titanium dioxide possesses excellent dispersibility and high specific surface area, exhibiting high adsorption activity. It effectively adsorbs impurities in concrete wastewater, enhancing the efficacy and utilization of slow-release flocculants while reducing their dosage. The synergistic effect of organic titanium salts and composite inorganic salts forms colloidal particles that complex particulate matter in concrete wastewater, forming larger agglomerates for sedimentation, effectively removing impurities. Modified chitosan and branched polyethyleneimine undergo in-situ polymerization on the surfaces of graphene-supported mesoporous titanium dioxide, organic titanium salts, and composite inorganic salts, forming a core-shell structured inorganic-organic phase flocculant. Through the synergistic effect of organic phase gel, inorganic phase colloid, and high specific surface area filler, it effectively complexes impurities in concrete wastewater, enhancing its recycling value.

[0035] 3. By modifying polyethyleneimine with chlorohexane and epoxy silane, hydrophobic silane molecules are introduced into the branches of polyethyleneimine, giving the resulting polyethyleneimine a certain degree of negative charge, which can adsorb positively charged impurities. At the same time, the increased branching degree increases steric hindrance, improves the dispersibility of polyethyleneimine, slows down the flocculation and sedimentation rate of the flocculant, and allows the slow-release flocculant to work for a longer period of time. Branched polyethyleneimine has good reactivity. By undergoing in-situ polymerization with modified chitosan on the surface of the inorganic phase for secondary coating, the slow-release performance can be further improved, the working time of the slow-release flocculant can be extended, and the water purification performance of the slow-release flocculant can be improved. Detailed Implementation

[0036] This application discloses a process for recycling wastewater from commercial concrete production. Unless otherwise specified, all raw materials used in this application are commercially available. The following detailed description, in conjunction with embodiments, further illustrates this application:

[0037] Raw material specifications: Tetrabutyl titanate (CAS No.: 5593-70-4), graphene oxide (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), titanium tetrachloride (CAS No.: 7550-45-0), dodecylmethyl dihydroxyethyl ammonium bromide (CAS No.: 57122-49-3), carboxymethyl chitosan (CAS No.: 83512-85-0), polyquaternium-7 (CAS No.: 26590-05-6), polyethyleneimine (CAS No.: 9002-98) -6), with a molecular weight of 20,000, chlorohexane (CAS No.: 544-10-5), epoxy silane 3-(2,3-epoxypropoxy)propyltrimethoxysilane (CAS No.: 2530-83-8), crosslinking agent glutaraldehyde (CAS No.: 111-30-8), chitosan (CAS No.: 9012-76-4), polyquaternium-6 (CAS No.: 26062-79-3), methyltriethoxysilane (CAS No.: 2031-67-6).

[0038] Example 1

[0039] Preparation of graphene-supported mesoporous titanium dioxide

[0040] 10 kg of tetrabutyl titanate, 12 kg of anhydrous ethanol, and 5 kg of graphene oxide were mixed and dispersed to obtain a suspension. 24 L of 1 mol / L nitric acid aqueous solution was added under stirring at 800 rpm over 30 min to obtain a reaction solution. After standing for 4 h, the pH of the reaction solution was adjusted to 7, and the temperature was raised to 100 °C for 4 h. After cooling to below 30 °C, the solution was washed three times by centrifugation with deionized water and anhydrous ethanol, and then dried in an oven at 80 °C to obtain graphene-supported mesoporous titanium dioxide.

[0041] Preparation of organotitanium salts

[0042] 6.8 kg of titanium tetrachloride and 13.2 kg of dodecylmethyldihydroxyethylammonium bromide were mixed and dispersed in 40 L of dichloromethane and stirred at 200 rpm for 12 h. The solvent was removed by rotary evaporation to obtain an organotitanium salt.

[0043] Preparation of modified chitosan

[0044] 39.06 kg of carboxymethyl chitosan and 10.94 kg of polyquaternium-7 were mixed and dispersed in 100 L of deionized water. After stirring at 200 rpm for 1 h, an initiator aqueous solution containing 0.5 kg of potassium persulfate was added dropwise over 30 min. The reaction was continued for 2 h with stirring. Acetone was added to precipitate the mixture, and the precipitate was dried in an oven at 60 °C to obtain modified chitosan.

[0045] Preparation of branched polyethyleneimine

[0046] 38.1 kg of polyethyleneimine was dispersed in 100 L of methanol to obtain a polyethyleneimine dispersion. 2.38 kg of chlorohexane, 9.52 kg of epoxysilane and 4 kg of tetrabutylammonium bromide were added to the polyethyleneimine dispersion. The mixture was stirred at 500 rpm in an 80 °C water bath until the solution viscosity increased. Then, 200 L of 1 mol / L sodium hydroxide aqueous solution was added, and the mixture was stirred at 500 rpm in an 80 °C water bath for 6 h. The solvent was removed by rotary evaporation to obtain branched polyethyleneimine.

[0047] Preparation of slow-release flocculants

[0048] 3 kg of graphene-supported mesoporous titanium dioxide was dispersed in 50 L of deionized water and sonicated for 30 min to obtain a graphene dispersion. 8 kg of organic titanium salt and 6 kg of composite inorganic salt were added to the graphene dispersion. The mass ratio of aluminum sulfate, ferric chloride, and calcium carbonate in the composite inorganic salt was 1:1:1. The mixture was stirred at 200 rpm for 2 h to obtain a mixed dispersion. 20 kg of modified chitosan and 15 kg of branched polyethyleneimine were mixed and dispersed in 50 L of deionized water to obtain an organic phase solution. 10 kg of crosslinking agent was dissolved in 20 L of deionized water to obtain a crosslinking agent solution. The organic phase solution and crosslinking agent solution were added to the mixed dispersion over 2 h, while stirring at 500 rpm to obtain a slow-release flocculant solution. Acetone was added to precipitate the product, which was then dried in an oven at 60 °C to obtain the slow-release flocculant.

[0049] Preparation of regenerated wastewater

[0050] (1) Collect the wastewater from the production of commercial concrete, perform preliminary sedimentation to remove large particulate impurities, and obtain primary treated wastewater.

[0051] (2) Pass the primary treated wastewater into a filtration device to further remove small particulate impurities and obtain secondary treated wastewater;

[0052] (3) Add slow-release flocculant to the secondary wastewater and oscillate it with 20KHz ultrasound for 24h to allow the slow-release flocculant to react with the mud components. Then, precipitate the secondary wastewater again after the reaction. After separating the precipitate, obtain tertiary wastewater. Dry the precipitate and crush it to obtain recycled concrete filler.

[0053] (4) After the tertiary wastewater is oxidized with ozone, carbon dioxide is passed through to adjust the pH to neutral to obtain regenerated wastewater.

[0054] Example 2

[0055] Preparation of graphene-supported mesoporous titanium dioxide

[0056] 10 kg of tetrabutyl titanate, 12 kg of anhydrous ethanol, and 5 kg of graphene oxide were mixed and dispersed to obtain a suspension. 24 L of 1 mol / L nitric acid aqueous solution was added under stirring at 800 rpm over 30 min to obtain a reaction solution. After standing for 4 h, the pH of the reaction solution was adjusted to 7, and the temperature was raised to 100 °C for 4 h. After cooling to below 30 °C, the solution was washed three times by centrifugation with deionized water and anhydrous ethanol, and then dried in an oven at 80 °C to obtain graphene-supported mesoporous titanium dioxide.

[0057] Preparation of organotitanium salts

[0058] 6.8 kg of titanium tetrachloride and 13.2 kg of dodecylmethyldihydroxyethylammonium bromide were mixed and dispersed in 40 L of dichloromethane and stirred at 200 rpm for 12 h. The solvent was removed by rotary evaporation to obtain an organotitanium salt.

[0059] Preparation of modified chitosan

[0060] 34.25 kg of carboxymethyl chitosan and 15.75 kg of polyquaternium-7 were mixed and dispersed in 100 L of deionized water. After stirring at 200 rpm for 1 h, an initiator aqueous solution containing 0.5 kg of potassium persulfate was added dropwise over 30 min. The reaction was continued for 2 h with stirring. Acetone was added to precipitate the mixture, and the precipitate was dried in an oven at 60 °C to obtain modified chitosan.

[0061] Preparation of branched polyethyleneimine

[0062] 41.38 kg of polyethyleneimine was dispersed in 100 L of methanol to obtain a polyethyleneimine dispersion. 1.72 kg of chlorohexane, 6.9 kg of epoxysilane, and 4 kg of tetrabutylammonium bromide were added to the polyethyleneimine dispersion. The mixture was stirred at 500 rpm in an 80 °C water bath until the solution viscosity increased. Then, 200 L of 1 mol / L sodium hydroxide aqueous solution was added, and the mixture was stirred at 500 rpm in an 80 °C water bath for 6 h. The solvent was removed by rotary evaporation to obtain branched polyethyleneimine.

[0063] Preparation of slow-release flocculants

[0064] 5 kg of graphene-supported mesoporous titanium dioxide was dispersed in 50 L of deionized water and sonicated for 30 min to obtain a graphene dispersion. 10 kg of organic titanium salt and 8 kg of composite inorganic salt were added to the graphene dispersion. The mass ratio of aluminum sulfate, ferric chloride, and calcium carbonate in the composite inorganic salt was 1:1:1. The mixture was stirred at 200 rpm for 2 h to obtain a mixed dispersion. 30 kg of modified chitosan and 25 kg of branched polyethyleneimine were mixed and dispersed in 50 L of deionized water to obtain an organic phase solution. 15 kg of crosslinking agent was dissolved in 20 L of deionized water to obtain a crosslinking agent solution. The organic phase solution and crosslinking agent solution were added to the mixed dispersion over 2 h. The mixture was stirred at 500 rpm during the addition to obtain a slow-release flocculant solution. Acetone was added to precipitate the product, which was then dried in an oven at 60 °C to obtain the slow-release flocculant.

[0065] Preparation of regenerated wastewater

[0066] (1) Collect the wastewater from the production of commercial concrete, perform preliminary sedimentation to remove large particulate impurities, and obtain primary treated wastewater.

[0067] (2) Pass the primary treated wastewater into a filtration device to further remove small particulate impurities and obtain secondary treated wastewater;

[0068] (3) Add slow-release flocculant to the secondary wastewater and oscillate it with 20KHz ultrasound for 24h to allow the slow-release flocculant to react with the mud components. Then, precipitate the secondary wastewater again after the reaction. After separating the precipitate, obtain tertiary wastewater. Dry the precipitate and crush it to obtain recycled concrete filler.

[0069] (4) After the tertiary wastewater is oxidized with ozone, carbon dioxide is passed through to adjust the pH to neutral to obtain regenerated wastewater.

[0070] Example 3

[0071] Preparation of graphene-supported mesoporous titanium dioxide

[0072] 10 kg of tetrabutyl titanate, 12 kg of anhydrous ethanol, and 5 kg of graphene oxide were mixed and dispersed to obtain a suspension. 24 L of 1 mol / L nitric acid aqueous solution was added under stirring at 800 rpm over 30 min to obtain a reaction solution. After standing for 4 h, the pH of the reaction solution was adjusted to 7, and the temperature was raised to 100 °C for 4 h. After cooling to below 30 °C, the solution was washed three times by centrifugation with deionized water and anhydrous ethanol, and then dried in an oven at 80 °C to obtain graphene-supported mesoporous titanium dioxide.

[0073] Preparation of organotitanium salts

[0074] 6.8 kg of titanium tetrachloride and 13.2 kg of dodecylmethyldihydroxyethylammonium bromide were mixed and dispersed in 40 L of dichloromethane and stirred at 200 rpm for 12 h. The solvent was removed by rotary evaporation to obtain an organotitanium salt.

[0075] Preparation of modified chitosan

[0076] 36.5 kg of carboxymethyl chitosan and 13.5 kg of polyquaternium-7 were mixed and dispersed in 100 L of deionized water. After stirring at 200 rpm for 1 h, an initiator aqueous solution containing 0.5 kg of potassium persulfate was added dropwise over 30 min. The stirring was continued for 2 h. Acetone was added to precipitate the mixture, and the precipitate was dried in an oven at 60 °C to obtain modified chitosan.

[0077] Preparation of branched polyethyleneimine

[0078] 40 kg of polyethyleneimine was dispersed in 100 L of methanol to obtain a polyethyleneimine dispersion. 2 kg of chlorohexane, 8 kg of epoxysilane and 4 kg of tetrabutylammonium bromide were added to the polyethyleneimine dispersion. The mixture was stirred at 500 rpm in an 80 °C water bath until the solution viscosity increased. Then, 200 L of 1 mol / L sodium hydroxide aqueous solution was added, and the mixture was stirred at 500 rpm in an 80 °C water bath for 6 h. The solvent was removed by rotary evaporation to obtain branched polyethyleneimine.

[0079] Preparation of slow-release flocculants

[0080] 4 kg of graphene-supported mesoporous titanium dioxide was dispersed in 50 L of deionized water and sonicated for 30 min to obtain a graphene dispersion. 9 kg of organic titanium salt and 7 kg of composite inorganic salt (aluminum sulfate, ferric chloride, and calcium carbonate in a mass ratio of 1:1:1) were added to the graphene dispersion and stirred at 200 rpm for 2 h to obtain a mixed dispersion. 25 kg of modified chitosan and 20 kg of branched polyethyleneimine were mixed and dispersed in 50 L of deionized water to obtain an organic phase solution. 12.5 kg of crosslinking agent was dissolved in 20 L of deionized water to obtain a crosslinking agent solution. The organic phase solution and crosslinking agent solution were added to the mixed dispersion over 2 h, with stirring at 500 rpm during the addition to obtain a slow-release flocculant solution. Acetone was added to precipitate the product, which was then dried in an oven at 60 °C to obtain the slow-release flocculant.

[0081] Preparation of regenerated wastewater

[0082] (1) Collect the wastewater from the production of commercial concrete, perform preliminary sedimentation to remove large particulate impurities, and obtain primary treated wastewater.

[0083] (2) Pass the primary treated wastewater into a filtration device to further remove small particulate impurities and obtain secondary treated wastewater;

[0084] (3) Add slow-release flocculant to the secondary wastewater and oscillate it with 20KHz ultrasound for 24h to allow the slow-release flocculant to react with the mud components. Then, precipitate the secondary wastewater again after the reaction. After separating the precipitate, obtain tertiary wastewater. Dry the precipitate and crush it to obtain recycled concrete filler.

[0085] (4) After the tertiary wastewater is oxidized with ozone, carbon dioxide is passed through to adjust the pH to neutral to obtain regenerated wastewater.

[0086] Example 4

[0087] Example 4 is based on Example 3. The only difference between Example 4 and Example 3 is that in Example 4, the graphene-supported mesoporous titanium dioxide is replaced with a mixture of graphene oxide and mesoporous titanium dioxide in a mass ratio of 1:1.

[0088] Example 5

[0089] Example 5 is based on Example 3. The only difference between Example 5 and Example 3 is that the organic titanium salt is replaced with titanium tetrachloride in Example 5.

[0090] Example 6

[0091] Example 6 is based on Example 3. The only difference between Example 6 and Example 3 is that in Example 6, the composite inorganic salt is replaced with a mixture of aluminum sulfate and ferric chloride in a mass ratio of 1:1.

[0092] Example 7

[0093] Example 7 is based on Example 3. The only difference between Example 7 and Example 3 is that the complex inorganic salt is replaced with calcium carbonate in Example 7.

[0094] Example 8

[0095] Example 8 is based on Example 3. The only difference between Example 8 and Example 3 is that the amount of carboxymethyl chitosan used in Example 8 is 43.48 kg and the amount of polyquaternium-7 used is 6.52 kg.

[0096] Example 9

[0097] Example 9 is based on Example 3. The only difference between Example 9 and Example 3 is that the amount of carboxymethyl chitosan used in Example 9 is 31.25 kg and the amount of polyquaternium-7 used is 18.75 kg.

[0098] Example 10

[0099] Example 10 is based on Example 3. The only difference between Example 10 and Example 3 is that carboxymethyl chitosan is replaced with chitosan in Example 10.

[0100] Example 11

[0101] Example 11 is based on Example 3. The only difference between Example 11 and Example 3 is that in Example 11, polyquaternium-7 is replaced with polyquaternium-6.

[0102] Example 12

[0103] Example 12 is based on Example 3. The only difference between Example 12 and Example 3 is that in Example 12, the amount of polyethyleneimine is 35.29 kg, the amount of chlorohexane is 2.94 kg, and the amount of epoxysilane is 11.77 kg.

[0104] Example 13

[0105] Example 13 is based on Example 3. The only difference between Example 13 and Example 3 is that in Example 13, the amount of polyethyleneimine is 42.42 kg, the amount of chlorohexane is 1.52 kg, and the amount of epoxysilane is 6.06 kg.

[0106] Example 14

[0107] Example 14 is based on Example 3. The only difference between Example 14 and Example 3 is that in Example 14, epoxysilane is replaced with methyltriethoxysilane.

[0108] Comparative Example 1

[0109] Comparative Example 1 is based on Example 3. The only difference between Comparative Example 1 and Example 3 is that the slow-release flocculant in Comparative Example 1 is replaced with a mixture of cationic polyacrylamide and polyaluminum chloride in a mass ratio of 1:1.

[0110] Performance testing

[0111] The standards GB8978-1996 Integrated Wastewater Discharge Standard, GB / T19923-2024 Water Quality Standard for Industrial Water Used in Urban Wastewater Reuse, and JGJ63-2006 Standard for Water Used in Concrete were selected as the standards to test the pH value, insoluble matter, soluble matter, chloride ion, sulfate ion and alkali content of the reclaimed wastewater. Each sample was tested three times, and the average value was taken after measurement. The results are recorded in Table 1.

[0112] Table 1. Test results of reclaimed wastewater quality

[0113]

[0114] As shown in Table 1, the pH value of Examples 1-3 is greater than 7.2, the insoluble content is less than 902 mg / L, the soluble content is less than 1160 mg / L, the chloride ion content is less than 342 g / L, the sulfate ion content is less than 308 mg / L, and the alkali content is less than 785 mg / L. This shows that the slow-release flocculant prepared in this application has good flocculation and water purification effects, and the regenerated wastewater obtained has high recycling value.

[0115] As shown in Table 1, the only difference between Example 4 and Example 3 is that in Example 4, the graphene-supported mesoporous titanium dioxide was replaced with a mixture of graphene oxide and mesoporous titanium dioxide in a mass ratio of 1:1. Compared with Example 3, the purity of the regenerated wastewater decreased in Example 4. This is because when the graphene-supported mesoporous titanium dioxide was replaced with a mixture of graphene oxide and mesoporous titanium dioxide, the two did not directly combine, resulting in a decrease in the synergistic effect of improving adsorption performance. At the same time, the dispersion performance of graphene oxide decreased, making it prone to aggregation, which in turn affected the performance of the slow-release flocculant, thus reducing the purity of the regenerated wastewater.

[0116] As shown in Table 1, the only difference between Example 5 and Example 3 is that the organic titanium salt was replaced with titanium tetrachloride in Example 5. Compared with Example 3, the purity of the regenerated wastewater decreased in Example 5. This is because titanium tetrachloride lacks the modification treatment of dodecylmethyldihydroxyethylammonium bromide and lacks quaternary ammonium salt groups, which reduces the adsorption effect on small molecule organic matter and thus affects the adsorption performance of the slow-release flocculant, resulting in a decrease in the purity of the regenerated wastewater.

[0117] As shown in Table 1, the only difference between Examples 6 and 7 and Example 3 is that in Example 6, the composite inorganic salt was replaced with a mixture of aluminum sulfate and ferric chloride in a mass ratio of 1:1, and in Example 7, the composite inorganic salt was replaced with calcium carbonate. Compared with Example 3, the purity of the regenerated wastewater decreased in Examples 6 and 7. This is because reducing the types of inorganic salts in the composite inorganic salt has a complexing and flocculating effect on different types of impurities. Reducing the types affects the synergistic effect of the composite inorganic salt, thus reducing the purity of the regenerated wastewater.

[0118] As shown in Table 1, the only difference between Examples 8 and 9 and Example 3 is that the mass ratio of carboxymethyl chitosan to polyquaternium-7 in Example 8 is 1:0.15, and the mass ratio of carboxymethyl chitosan to polyquaternium-7 in Example 9 is 1:0.6. Compared with Example 3, the purity of the regenerated wastewater in Examples 8 and 9 is lower. This is because the mass ratio of carboxymethyl chitosan to polyquaternium-7 is not within the specified range. Too much or too little polyquaternium-7 will affect the reactivity and molecular chain structure of the modified chitosan, thereby affecting the flocculation performance and stability of the slow-release flocculant, thus reducing the purity of the regenerated wastewater.

[0119] As shown in Table 1, the only difference between Examples 10 and 11 and Example 3 is that carboxymethyl chitosan was replaced with chitosan in Example 10, and polyquaternium-7 was replaced with polyquaternium-6 in Example 11. Compared with Example 3, the purity of the regenerated wastewater decreased in Examples 10 and 11. This is because if carboxymethyl chitosan is replaced with chitosan, the reactivity and compatibility decrease; if polyquaternium-7 is replaced with polyquaternium-6, the introduction of acrylamide groups is lacking, resulting in a decrease in adsorption and flocculation performance, thus reducing the purity of the regenerated wastewater.

[0120] As shown in Table 1, the only difference between Examples 12 and 13 and Example 3 is that the mass ratio of polyethyleneimine, chlorohexane, and epoxysilane in Example 12 is 3:0.25:1, while the mass ratio of polyethyleneimine, chlorohexane, and epoxysilane in Example 13 is 7:0.25:1. Compared with Example 3, the purity of the regenerated wastewater in Examples 12 and 13 is lower. This is because the mass ratio of polyethyleneimine, chlorohexane, and epoxysilane is not within the specified range. The branching degree of polyethyleneimine is different. Too high or too low branching degree will affect the effective working time and slow-release performance of the slow-release flocculant in the wastewater, thus affecting the flocculation effect and resulting in a decrease in the purity of the regenerated wastewater.

[0121] As shown in Table 1, the only difference between Example 14 and Example 3 is that epoxy silane was replaced with methyltriethoxy silane in Example 14. Compared with Example 3, the purity of the regenerated wastewater decreased in Example 14. This is because replacing epoxy silane with methyltriethoxy silane reduces the reactivity of methyltriethoxy silane and the degree of branching of branched polyethyleneimine, thereby reducing the dispersion performance and slow-release flocculation performance, affecting the working performance of the slow-release flocculant, and thus reducing the purity of the regenerated wastewater.

[0122] As shown in Table 1, the only difference between Comparative Example 1 and Example 3 is that the slow-release flocculant in Comparative Example 1 was replaced with a mixture of cationic polyacrylamide and polyaluminum chloride in a mass ratio of 1:1. Compared with Example 3, the purity of the regenerated wastewater in Comparative Example 1 decreased significantly. This is because replacing the slow-release flocculant with a mixture of inorganic and organic flocculants lacks modification treatment and slow-release flocculation design. The flocculant will act quickly and settle rapidly, making it difficult to exist in the water for a long time. Impurities in the wastewater cannot be removed sufficiently and effectively, resulting in a significant decrease in the purity of the regenerated wastewater.

[0123] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A process for the recycling of concrete production wastewater, characterized in that: It comprises the following steps: (1) Collecting commercial concrete production wastewater, carrying out preliminary sedimentation, removing large particle impurities, and obtaining first-stage treated wastewater; (2) Passing the first-stage treated wastewater into a filtering device to further remove small particle impurities, and obtaining second-stage treated wastewater; (3) Adding a slow-release flocculant into the second-stage treated wastewater, allowing the slow-release flocculant to react with the slurry components, re-sedimenting the reacted second-stage treated wastewater, separating the sediment, and obtaining third-stage treated wastewater, drying the sediment, crushing it, and obtaining recycled concrete filler; (4) Carrying out oxidation treatment on the third-stage treated wastewater with an oxidizing agent, adjusting the pH to neutral, and obtaining recycled wastewater; The preparation raw materials of the slow-release flocculant comprise the following components in mass fraction: graphene loaded mesoporous titanium dioxide 3-5 parts, organic titanium salt 8-10 parts, composite inorganic salt 6-8 parts, modified chitosan 20-30 parts, branched polyethyleneimine 15-25 parts, and crosslinking agent 10-15 parts; The composite inorganic salt comprises aluminum sulfate, ferric chloride, and calcium carbonate; The preparation raw materials of the modified chitosan comprise carboxymethyl chitosan and polyquaternary salt-7; The mass ratio of the carboxymethyl chitosan and the polyquaternary salt-7 is 1:(0.28-0.46); The preparation raw materials of the branched polyethyleneimine comprise polyethyleneimine, chlorohexane, and epoxy silane; The mass ratio of the polyethyleneimine, chlorohexane, and epoxy silane is (4-6):0.25:1; The slow-release flocculant is prepared by the following steps: The graphene loaded mesoporous titanium dioxide is dispersed into deionized water, and graphene dispersion liquid is obtained after ultrasonic treatment; the organic titanium salt and the composite inorganic salt are added into the graphene dispersion liquid, and mixed dispersion liquid is obtained after stirring; the modified chitosan and the branched polyethyleneimine are mixed and dispersed into deionized water to obtain organic phase solution; the crosslinking agent is dissolved in deionized water to obtain crosslinking agent solution; the organic phase solution and the crosslinking agent solution are added into the mixed dispersion liquid under stirring, and slow-release flocculant solution is obtained after reaction; acetone is added into the slow-release flocculant solution for precipitation to obtain the product, which is dried to obtain the slow-release flocculant.

2. A process for the recycling of concrete production wastewater according to claim 1, characterized in that: The graphene loaded mesoporous titanium dioxide is prepared by the following steps: Tetrabutyl titanate, anhydrous ethanol, and graphene oxide are mixed and dispersed to obtain a suspension, nitric acid aqueous solution is added under stirring to obtain a reaction liquid, the pH of the reaction liquid is adjusted to neutral after standing, and the reaction is carried out under heating, and the graphene loaded mesoporous titanium dioxide is obtained after cooling, washing, and drying.

3. A process for the recycling of concrete production wastewater according to claim 1, characterized in that: The preparation raw materials of the organic titanium salt comprise titanium tetrachloride and dodecylmethyl dihydroxyethyl ammonium bromide.

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