A method for treating tunnel construction wastewater using modified kaolin

Abstract

The invention discloses a method for treating tunnel construction wastewater by using modified kaolin, comprising the following steps: 1. preparing modified kaolin: taking kaolin and adding it to a polytetrafluoroethylene liner, adding a mixed solution of isopropanol and ethanol thereto, stirring to mix the kaolin and the solvent, and then putting it into an oven for hydrothermal reaction, and after the hydrothermal reaction, centrifugally washing the modified kaolin to obtain modified kaolin; 2. treating tunnel construction wastewater: adding ferric chloride to the tunnel construction wastewater and stirring, adjusting the pH of the tunnel construction wastewater to 7.0-8.5, and then adding polyaluminium ferrosilicate to the tunnel construction wastewater and stirring for flocculation and sedimentation, adding modified kaolin after stirring, stirring for a period of time to form a flocculent body and settle it. The invention solves the problem of quickly, safely and efficiently reducing the pH of alkaline wastewater, removing organic matter in the water body, and quickly settling solid suspended matter in the water body.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction wastewater treatment, and in particular relates to a method for treating tunnel construction wastewater by utilizing modified kaolin. Background Art

[0002] The pH of tunnel construction wastewater is usually around 12, containing some organic matter and some insoluble solids. Therefore, how to quickly, safely and efficiently lower the pH of alkaline wastewater, remove organic matter in the water, and quickly settle suspended solids in the water is a difficult problem in the current alkaline wastewater treatment process.

[0003] The existing technology uses strong acid to adjust the pH of alkaline wastewater, which poses a safety hazard in transportation; the commonly used chlorine oxidation is dangerous for treating micro-polluted organic matter; and the use of PAM for flocculation will cleave the carcinogen acrylamide. Therefore, it is very important to develop a good material to reduce the pH of alkaline wastewater, remove organic matter in the water, and quickly settle suspended matter in the water. Summary of the invention

[0004] The object of the present invention is to provide a method for treating tunnel construction wastewater using modified kaolin, so as to solve the problems existing in the existing tunnel construction wastewater treatment mentioned in the background technology.

[0005] To achieve the above object, the present invention provides a method for treating tunnel construction wastewater using modified kaolin, comprising the following steps:

[0006] Step 1, preparing modified kaolin: first take kaolin and add it into a polytetrafluoroethylene liner, and add a mixed solution of isopropanol and ethanol thereto, wherein the volume ratio of isopropanol to ethanol is 2-10:1, stir to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal reaction, the hydrothermal temperature is controlled at 140-200°C, after the hydrothermal reaction is completed, the modified kaolin is centrifuged and washed to obtain modified kaolin;

[0007] Step 2, treating tunnel construction wastewater: first add ferric chloride to the tunnel construction wastewater and stir, adjust the pH of the tunnel construction wastewater to 7.0~8.5, then add polyaluminum ferrosilicate to the tunnel construction wastewater and stir for flocculation and sedimentation, after stirring, add the prepared modified kaolin, the addition amount of modified kaolin is 0.5~1.5g / L, and stir for a period of time to form floccules and settle.

[0008] In a specific embodiment, the method for treating tunnel construction wastewater using modified kaolin also includes step 3, recovering the kaolin: filtering and washing the settled flocs, and washing them with a dilute acid solution to remove hydroxides in the precipitate, and then heating to 95-100°C and keeping warm for more than 30 minutes to remove organic matter adsorbed by the modified kaolin, thereby recovering the modified kaolin.

[0009] In a specific embodiment, in step 3, heating is performed by microwave heating.

[0010] In a specific embodiment, in step 1, the hydrothermal time for the hydrothermal reaction is controlled to be 12 to 24 hours.

[0011] In a specific embodiment, in step 1, at least 6 L of a mixed solution of isopropanol and ethanol is required for every 1 kg of kaolin.

[0012] In a specific embodiment, in step 1, the stirring time is 30 minutes; in step 2, after adding ferric chloride, stirring is carried out at a stirring speed of 300 r / min for 10 minutes, after adding polyaluminum ferrosilicate, stirring is carried out for 10 minutes, and after adding modified kaolin, stirring is carried out at a stirring speed of 300 r / min for 30 minutes.

[0013] In a specific embodiment, in step 2, the amount of polyaluminium ferric silicate added is 0.05-0.15 g / L.

[0014] In a specific embodiment, in step 1, the volume ratio of isopropanol to ethanol is 4-6:1.

[0015] In a specific embodiment, in step 1, the hydrothermal temperature is controlled to be 160-190°C.

[0016] In a specific embodiment, in step 2, the amount of modified kaolin added is 0.8-1.2 g / L.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The invention solves the problem of rapidly, safely and efficiently reducing the pH value of alkaline wastewater, removing organic matter in the water body, and rapidly settling suspended solids in the water body.

[0019] The present invention avoids the problem of using strong acid to adjust the pH of alkaline wastewater, which may cause potential safety hazards in transportation; it also avoids the danger of commonly used chlorine oxidation in treating micro-polluted organic matter; and it also avoids the risk of using PAM in flocculation to crack carcinogen acrylamide.

[0020] The present invention is used to treat alkaline tunnel construction wastewater, which can not only adjust the pH, remove organic matter in the water body, and accelerate the sedimentation of suspended particles, but also avoid the use of strong acids, strong oxidants (such as Cl2, etc.) and PAM, and can achieve the integration of adjusting pH - removing organic matter - accelerating particle sedimentation, and reduce costs, reduce the generation of pollutants, and can also achieve the recycling of modified kaolin, providing a new solution for the treatment of alkaline wastewater.

[0021] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention is further described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0023] Figure 1 is a sedimentation curve diagram of suspended particles after adding the modified kaolin in Example 1 of the present invention and a sedimentation curve diagram of suspended particles without adding the modified kaolin;

[0024] Figure 2 is a scanning electron microscope image of the modified kaolin in one embodiment of the present invention. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] A method for treating tunnel construction wastewater using modified kaolin of the present invention comprises the following steps:

[0027] Step 1, preparing modified kaolin: first take kaolin and add it into a polytetrafluoroethylene liner, and add a mixed solution of isopropanol and ethanol thereto, wherein the volume ratio of isopropanol to ethanol is 2-10:1, stir to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal reaction, the hydrothermal temperature is controlled at 140-200°C, after the hydrothermal reaction is completed, the modified kaolin is centrifuged and washed to obtain modified kaolin;

[0028] Step 2, treating tunnel construction wastewater: first add ferric chloride to the tunnel construction wastewater and stir, adjust the pH of the tunnel construction wastewater to 7.0~8.5, then add polyaluminum ferrosilicate to the tunnel construction wastewater and stir for flocculation and sedimentation, after stirring, add the prepared modified kaolin, the addition amount of modified kaolin is 0.5~1.5g / L, and stir for a period of time to form floccules and settle.

[0029] The method for treating tunnel construction wastewater using modified kaolin also includes step 3, recovering the kaolin: filtering and washing the settled flocs, and washing them with a dilute acid solution to remove hydroxides in the precipitate, and then heating them to 95-100° C. and keeping them warm for more than 30 minutes to remove organic matter adsorbed by the modified kaolin, thereby recovering the modified kaolin.

[0030] In the step 3, heating is performed by microwave heating.

[0031] In the step 1, the hydrothermal time of the hydrothermal reaction is controlled to be 12 to 24 hours. In the step 1, at least 6L of a mixed solution of isopropanol and ethanol is required for every 1kg of kaolin. In the step 1, the stirring time is 30 minutes; in the step 2, after adding ferric chloride, stirring is carried out at a stirring speed of 300r / min for 10 minutes, after adding polyaluminium ferrosilicate, stirring is carried out for 10 minutes, and after adding modified kaolin, stirring is carried out at a stirring speed of 300r / min for 30 minutes.

[0032] In step 2, the amount of polyaluminium ferrosilicate added is 0.05-0.15 g / L.

[0033] Preferably, in step 1, the volume ratio of isopropanol to ethanol is 4-6:1. Preferably, in step 1, the hydrothermal temperature is controlled to be 160-190°C. Preferably, in step 2, the amount of modified kaolin added is 0.8-1.2 g / L.

[0034] Example 1

[0035] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 5:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 180°C and a reaction time of 18h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0036] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.2g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 1g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0037] Recovery of kaolin. The settled floccules are filtered and washed with a dilute acid solution to remove hydroxides in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove adsorbed organic matter, thereby recovering the modified kaolin. Preferably, the modified kaolin is heated by microwave heating.

[0038] Comparative Example 1

[0039] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 5:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 120°C and a reaction time of 8h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0040] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.06g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 0.3g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0041] Recovery of kaolin. The settled floccules are filtered, washed, and washed with a dilute acid solution to remove the hydroxide in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove the adsorbed organic matter, thereby realizing the recovery of the modified kaolin.

[0042] The difference between Comparative Example 1 and Example 1 is that in the preparation process of modified kaolin, the hydrothermal condition is 120° C., the reaction time is 8 hours, and in the process of water flocculation, the added amount of modified kaolin is 0.3 g / L.

[0043] Example 2

[0044] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 2:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 180°C and a reaction time of 18h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0045] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.2g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 1g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0046] Recovery of kaolin. The settled floccules are filtered, washed, and washed with a dilute acid solution to remove the hydroxide in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove the adsorbed organic matter, thereby realizing the recovery of the modified kaolin.

[0047] The difference between Example 2 and Example 1 is that in the process of hydrothermal preparation of modified kaolin, the volume ratio of isopropanol to ethanol is 2:1.

[0048] Example 3

[0049] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 10:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 180°C and a reaction time of 18h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0050] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.2g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 1g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0051] Recovery of kaolin. The settled floccules are filtered, washed, and washed with a dilute acid solution to remove the hydroxide in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove the adsorbed organic matter, thereby realizing the recovery of the modified kaolin.

[0052] The difference between Example 3 and Example 1 is that in the process of hydrothermal preparation of modified kaolin, the volume ratio of isopropanol to ethanol is 10:1.

[0053] Example 4

[0054] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 5:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 140°C and a reaction time of 12h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0055] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.2g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 1g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0056] Recovery of kaolin. The settled floccules are filtered, washed, and washed with a dilute acid solution to remove the hydroxide in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove the adsorbed organic matter, thereby realizing the recovery of the modified kaolin.

[0057] The difference between Example 4 and Example 1 is that in the preparation process of modified kaolin, the hydrothermal temperature is 140° C. and the hydrothermal time is 12 h.

[0058] Example 5

[0059] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 5:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 200°C and a reaction time of 24h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0060] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.2g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 1g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0061] Recovery of kaolin. The settled floccules are filtered, washed, and washed with a dilute acid solution to remove the hydroxide in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove the adsorbed organic matter, thereby realizing the recovery of the modified kaolin.

[0062] The difference between Example 5 and Example 1 is that in the preparation process of modified kaolin, the hydrothermal temperature is 200° C. and the hydrothermal time is 24 h.

[0063] Example 6

[0064] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 5:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 180°C and a reaction time of 18h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0065] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.1g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 0.5g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0066] Recovery of kaolin. The settled floccules are filtered, washed, and washed with a dilute acid solution to remove the hydroxide in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove the adsorbed organic matter, thereby realizing the recovery of the modified kaolin.

[0067] The difference between Example 6 and Example 1 is that during the flocculation process of the water body, the amount of modified kaolin added is 0.5 g / L.

[0068] Example 7

[0069] Preparation of modified kaolin. Take 5g of kaolin and add it to the polytetrafluoroethylene liner, and add 30mL of a mixed solution of isopropanol and ethanol, wherein the volume ratio of isopropanol to ethanol is 5:1, and then stir for 30min to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal treatment at a temperature of 180°C and a reaction time of 18h. After the hydrothermal treatment, the modified kaolin is centrifuged and washed to obtain modified kaolin.

[0070] Treatment of alkaline tunnel construction wastewater. Take 200mL of wastewater sample with pH=12, first add 0.1g ferric chloride to the wastewater, that is, the addition amount of ferric chloride is 0.5g / L, and stir at a stirring rate of 300r / min for 10min to adjust the pH of the wastewater to 7, then add 0.02g polyaluminum ferric silicate to the wastewater, that is, the addition amount of polyaluminum ferric silicate is 0.1g / L, and stir for 10min to flocculate and settle the suspended particles and iron salt flocs in the water, and wait for the stirring to end. Add 0.3g modified kaolin to the above water body, that is, the addition amount of modified kaolin is 1.5g / L, and stir at a stirring rate of 300r / min for 30min to adsorb organic matter in the water body and accelerate the sedimentation of flocs.

[0071] Recovery of kaolin. The settled floccules are filtered, washed, and washed with a dilute acid solution to remove the hydroxide in the precipitate, and then the modified kaolin is heated to 100°C and kept warm for 30 minutes to remove the adsorbed organic matter, thereby realizing the recovery of the modified kaolin.

[0072] The difference between Example 7 and Example 1 is that during the flocculation process of the water body, the amount of modified kaolin added is 1.5 g / L.

[0073] Table 1 below is a comparison table of the removal effects of Examples 1 to 7 and Comparative Example 1 on the removal of organic matter in wastewater and the removal effects on suspended solids in water.

[0074] Table 1:

[0075]

[0076] Among them, TOC stands for total organic carbon, which uses the carbon content to express the total amount of organic matter in the water; COD stands for chemical oxygen demand, which uses a chemical method to measure the amount of reducing substances that need to be oxidized in the water sample; SS stands for suspended solids, which refers to solid matter suspended in the water.

[0077] It can be seen from Table 1 that the modified kaolin prepared under the conditions of Comparative Example 1 has a poorer effect on the removal of organic matter in water than that of Example 1. This may be because the temperature in the hydrothermal process when preparing the modified kaolin is low and the reaction time is short, so that isopropanol cannot completely enter the interlayer of kaolin and stably adsorb, resulting in a decrease in the adsorption effect of the modified kaolin on organic matter. In addition, the amount of modified kaolin added is too small, which reduces its carrier flocculation effect on suspended particles in the water, resulting in a higher SS content in the treated water.

[0078] It can be seen from Table 1 that the modified kaolin prepared under the conditions of Example 2 has a poorer adsorption capacity for organic matter than that of Example 1, indicating that when the amount of isopropanol added is too low, the loading amount of isopropanol on the modified kaolin is low, resulting in a weaker adsorption capacity for organic matter and a reduced removal effect of organic matter in water.

[0079] It can be seen from Table 1 that the modified kaolin prepared under the conditions of Example 3 has a worse adsorption effect on organic matter in water than that of Example 1, indicating that when the amount of isopropanol added is too high, the amount of ethanol added is correspondingly reduced. During the hydrothermal process, the reduction in the amount of ethanol added will make it difficult to open the channels between the kaolin layers, resulting in a decrease in the loading capacity of kaolin for isopropanol, thereby weakening the adsorption capacity of the modified kaolin for organic matter in water.

[0080] It can be seen from Table 1 that under the conditions of Example 4, the adsorption effect of modified kaolin on organic matter is weaker than that of Example 1. This may be because during the preparation of the modified kaolin, the hydrothermal temperature is low and the hydrothermal time is short, which cannot make isopropanol firmly adsorbed on the surface of kaolin, resulting in a decrease in the adsorption capacity of the prepared modified kaolin on organic matter.

[0081] It can be seen from Table 1 that the modified kaolin prepared under the conditions of Example 5 has a worse organic matter removal effect than that of Example 1, indicating that during the preparation of the modified kaolin, when the hydrothermal temperature is high and the hydrothermal time is long, isopropanol will enter the interlayer of kaolin, causing the isopropanol content on the surface of kaolin to decrease, resulting in poor adsorption of organic matter by the modified kaolin.

[0082] It can be seen from Table 1 that under the conditions of Example 6, when the amount of modified kaolin added is lower than that of Example 1, the flocculation and sedimentation effect of the modified kaolin on the water body is reduced. The amount of modified kaolin added is lower than that of Example 1, resulting in the floccules in the water body being unable to form a large number of floccules through the kaolin carrier during the sedimentation process, which reduces the sedimentation rate of the floccules in the water body.

[0083] It can be seen from Table 1 that under the conditions of Example 7, when the amount of modified kaolin added is more than that of Example 1, the flocculation effect will be reduced. This may be because when the amount of kaolin added is more than that of Example 1, the excess kaolin causes a large amount of colloids with mutually repulsive charges to be produced in the water body, which reduces the flocculation and sedimentation effect of the modified kaolin on the water body.

[0084] Effect of post-treatment of modified kaolin recovery:

[0085] The kaolin prepared in Example 1 was repeatedly treated and recovered according to the tunnel construction wastewater treatment method and modified kaolin recovery method in Example 1. The treatment effect is shown in Table 2 below:

[0086] Table 2:

[0087]

[0088] It can be seen from Table 2 that the modified kaolin was repeatedly treated and recycled, and its treatment effect did not decrease significantly after being recycled for 7 times. Therefore, the total number of times the modified kaolin was used should be controlled to no more than 7 times.

[0089] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for treating tunnel construction wastewater using modified kaolin, characterized in that: The following steps are involved: Step 1, preparing modified kaolin: first take kaolin and add it into a polytetrafluoroethylene liner, and add a mixed solution of isopropanol and ethanol thereto, wherein the volume ratio of isopropanol to ethanol is 4-6:1, stir to fully mix the kaolin and the solvent, and then put it into an oven for hydrothermal reaction, and the hydrothermal temperature is controlled at 160-190°C. After the hydrothermal reaction is completed, the modified kaolin is centrifuged and washed to obtain modified kaolin; Step 2, treating tunnel construction wastewater: first add ferric chloride to the tunnel construction wastewater and stir, adjust the pH of the tunnel construction wastewater to 7.0-8.5, then add polyaluminum ferrosilicate to the tunnel construction wastewater and stir for flocculation and sedimentation, after stirring, add the prepared modified kaolin, the addition amount of modified kaolin is 0.8-1.2 g / L, and stir for a period of time to form floccules and settle.

2. The method for treating tunnel construction wastewater using modified kaolin according to claim 1, characterized in that: The method for treating tunnel construction wastewater using modified kaolin also includes step 3, recovering the kaolin: filtering and washing the settled floccules, and washing them with a dilute acid solution to remove hydroxides in the precipitate, and then heating them to 95-100° C. and keeping them warm for more than 30 minutes to remove organic matter adsorbed by the modified kaolin, thereby recovering the modified kaolin.

3. The method for treating tunnel construction wastewater using modified kaolin according to claim 2, characterized in that: In the step 3, heating is performed by microwave heating.

4. The method for treating tunnel construction wastewater using modified kaolin according to claim 1, characterized in that: In the step 1, the hydrothermal time of the hydrothermal reaction is controlled to be 12 to 24 hours.

5. The method for treating tunnel construction wastewater using modified kaolin according to claim 1, characterized in that: In the step 1, at least 6 L of a mixed solution of isopropanol and ethanol is required for every 1 kg of kaolin.

6. The method for treating tunnel construction wastewater using modified kaolin according to claim 1, characterized in that: In the step 1, the stirring time is 30 minutes; in the step 2, after adding ferric chloride, stirring is carried out at a stirring speed of 300 r / min for 10 minutes, after adding polyaluminum ferrosilicate, stirring is carried out for 10 minutes, and after adding modified kaolin, stirring is carried out at a stirring speed of 300 r / min for 30 minutes.

7. The method for treating tunnel construction wastewater using modified kaolin according to claim 1, characterized in that: In the step 2, the amount of polyaluminium ferrosilicate added is 0.05 to 0.15 g / L.

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