A modified bentonite wastewater treatment agent and its application

Abstract

The present invention discloses a modified bentonite wastewater treatment agent and its application. The modified bentonite wastewater treatment agent of the present invention uses inexpensive calcium-based bentonite as the original soil, and is prepared by successively carrying out sodium modification, dry lithium modification, microwave treatment, and composite modification with a polymer. It has a good adsorption effect on perchlorate ions and can achieve a very high removal rate of perchlorate ions in wastewater in a short time. In the preparation of the modified bentonite wastewater treatment agent of the present invention, the raw materials used are cheap, the cost is low, the process is simple, it is easy to produce in batches and the production efficiency is high, which is convenient for use in industrial production. The modified bentonite prepared by the present invention does not have the problem of secondary pollution and is an environmentally friendly and efficient wastewater treatment agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a modified bentonite wastewater treatment agent and its application. Background Art

[0002] Perchlorate is a potentially toxic persistent pollutant, and its proportion in natural soil is very low. The ClO in water 4 - mainly comes from the dissolution of solid perchlorate and potassium salt, etc. Perchlorate is a non-volatile substance with high water solubility, and most soil minerals have little adsorption effect on it. Therefore, it has strong fluidity in water and will continuously diffuse into a larger water area, thus polluting drinking water on a large scale. In addition, ClO 4 - has relatively high kinetic stability. Only under the action of external energy or a catalyst can its chlorine atom be reduced from the +7 valence state to other lower valence states, and the process often takes decades or more. Therefore, perchlorate is a persistent harmful pollutant.

[0003] Currently, the commonly used methods for treating wastewater containing perchlorate include chemical / electrochemical advanced reduction, phytoremediation, microbial degradation, activated carbon adsorption method, etc. Among them, the chemical / electrochemical advanced reduction method can completely remove perchlorate without secondary pollution, but its application conditions are harsh, the cost is high, and the efficiency is low; the phytoremediation method can also completely degrade perchlorate, but its absorption is slow, the operation cycle is long, the system operation is unstable, the efficiency is low, and the treatment of the absorbed plants is also a problem. In the microbial degradation method, although the microorganisms capable of degrading perchlorate are widely sourced in nature, the microorganisms capable of degrading perchlorate need to be enriched and regulated first before they can be widely applied to pollution treatment projects. In the activated carbon adsorption method, the adsorption capacity of raw activated carbon for perchlorate is limited, and it needs to be modified to improve its adsorption ability to make it practical. However, this will increase its cost, also affect the absorption of other pollutants, and the amount of activated carbon used is large, so the application cost is very high. Moreover, secondary treatment of the perchlorate adsorbed on the activated carbon needs to be considered, and the introduction of modified substances will cause secondary pollution to the water body.

[0004] Bentonite is a natural mineral structure silicate mineral clay with a very low price and rich reserves in Guangxi. It has characteristics such as a large specific surface area and cation exchange capacity, and is often used in environmental governance. Since the adsorption of perchlorate ions by natural bentonite itself is very limited, it needs to be modified.

[0005] Xiao Ou et al. modified bentonite with cetyltrimethylammonium chloride in the article "Study on the Ion Exchange Performance of CTAC-Modified Bentonite for Adsorbing and Removing Perchlorate in Water" (Acta Scientiae Circumstantiae, 2013, 33(2), 415-423). For perchlorate with a concentration of 1 mmol / L, the maximum adsorption capacity of this modified bentonite for perchlorate was 0.42 mmol / g, and the adsorption equilibrium time was 6 h. Luo W. et al. used cetylpyridinium chloride to modify dispersed montmorillonite (dMt / HDPy) in the article "Influence of the pre-dispersion of montmorillonite on organic modification and the adsorption of perchlorate and methyl red anions" (Applied Clay Science, 2018). Its maximum adsorption capacity for perchlorate was approximately 0.58 mmol / g, and the equilibrium time > 130 min. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a modified bentonite wastewater treatment agent and its application. The modified bentonite wastewater treatment agent of the present invention is synthesized from inexpensive raw materials by a simple process with low cost and high efficiency, is easy to produce in batches and convenient to use in industrial production, has a good adsorption effect on perchlorate ions, and can achieve a very high removal rate of perchlorate ions in wastewater in a short time.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A modified bentonite wastewater treatment agent is prepared by the following steps:

[0009] (1) Prepare a suspension of calcium-based bentonite with a pulp concentration of 1-5% in water, stir it evenly at 50-70 °C, add Na 2 CO 3 , continue to stir for 60-120 minutes, then age for 1-3 h. After centrifugally washing the suspension multiple times, dry the solid and grind it to -200 mesh to obtain sodium-based bentonite; the weight of the solid Na 2 CO 3 is 3-5% of the weight of the calcium-based bentonite;

[0010] (2) Place the sodium-based bentonite and anhydrous lithium chloride in a high-speed grinder and stir for 1-5 min to obtain lithiated bentonite; wherein, the weight of the anhydrous lithium chloride is 1-5% of the weight of the sodium-based bentonite;

[0011] (3) Microwave treat the lithiated bentonite for 5 - 15 min to obtain activated bentonite; wherein, the microwave power is 200 - 1200 W;

[0012] (4) Prepare the activated bentonite into a suspension with a pulp concentration of 3 - 5% with water, stir it evenly at 50 - 70°C, add poly(diallyldimethylammonium chloride) thereto, and then stir for 2 - 6 h at 50 - 70°C, cool and centrifuge to obtain a solid, which is dried at 85 - 105°C and ground and sieved to obtain modified bentonite; wherein, the weight of the poly(diallyldimethylammonium chloride) is 30 - 100% of the weight of the activated bentonite.

[0013] In a preferred technical solution, in step (1), the pulp concentration in the suspension is 5%.

[0014] In a preferred technical solution, in step (1), the 2 CO 3 weight is 5% of the weight of the calcium-based bentonite.

[0015] In a preferred technical solution, in step (2), the rotation speed of the high-speed grinder is 25000 r / min and the stirring time is 2 min.

[0016] In a preferred technical solution, in step (3), the power of the microwave treatment is 800 W and the time of the microwave treatment is 10 min.

[0017] In a preferred technical solution, in step (4), the pulp concentration in the suspension is 5%.

[0018] In a preferred technical solution, in step (4), the weight ratio of the poly(diallyldimethylammonium chloride) to the activated bentonite is 1:1.

[0019] In a preferred technical solution, in step (4), the viscosity of the poly(diallyldimethylammonium chloride) is 600 - 900 cP.

[0020] In a preferred technical solution, in step (4), the grinding and sieving is grinding through a 200-mesh sieve.

[0021] In a preferred technical solution, in step (4), the temperature of the water bath is 70°C and the stirring time is 4 h.

[0022] In a preferred technical solution, in step (4), the rotation speed of the centrifugation is 5000 rpm and the time is 10 min.

[0023] In a preferred technical solution, in step (4), the drying is carried out at 105°C.

[0024] In addition, the present invention also provides an application of the above-mentioned modified bentonite wastewater treatment agent in removing perchlorate ions from wastewater.

[0025] In some specific examples of the present invention, the application of the modified bentonite wastewater treatment agent in removing perchlorate ions from wastewater includes the following steps:

[0026] Adding the above-mentioned modified bentonite wastewater treatment agent to the wastewater containing perchlorate ions, and oscillating and treating the wastewater at 25-70°C; then, performing solid-liquid separation on the treated wastewater.

[0027] The results show that: taking the simulated wastewater containing perchlorate ions as the treatment object, and using the above-mentioned modified bentonite wastewater treatment agent to treat the simulated wastewater containing perchlorate ions, good effects have been achieved. For example, when using the above-mentioned modified bentonite wastewater treatment agent to treat the wastewater containing perchlorate ions with an initial concentration of 1 mg / L, when the dosage of the modified bentonite wastewater treatment agent is 1 g / mL of wastewater, adsorption equilibrium can be reached after oscillating at room temperature for 10 min, the removal rate of perchlorate is 68.66%, and the adsorption capacity is 0.69 mmol / g.

[0028] In the present invention, the room temperature generally refers to 10-40°C.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] (1) The modified bentonite wastewater treatment agent prepared by the present invention has a good adsorption effect on perchlorate ions and a high removal rate of perchlorate ions in wastewater. This effect is significantly better than the prior art. For example: CTAC-modified bentonite (0.43 mmol / g, adsorption equilibrium time is 6 h, Xiao Ou, Study on the Adsorption Performance of Modified Bentonite on Perchlorate in Water, South China University of Technology, 2013); Another example is cetylpyridinium chloride-modified dispersed montmorillonite (dMt / HDPy) (0.58 mmol / g, equilibrium time > 130 min, Luo W., et al., 2018); Another example is HDTMA-modified sodium mica (0.35 mmol / g, (Xie et al., 2010); Another example is MCM-41 (0.27 mmol / g, Komarneni et al., 2010); Another example is CTAB-modified granular activated carbon (0.04 mmol / g, Yoon et al., 2009).

[0031] (2) The present invention uses inexpensive calcium-based bentonite as the raw soil, and successively adopts sodium modification, dry lithium modification, microwave activation, and PDDA organic modification to prepare a modified bentonite wastewater treatment agent. The raw materials are cheap, the cost is low, the process is simple, it is easy to mass-produce, and the production efficiency is high, which is convenient for use in industrial production.

[0032] (3) The modified bentonite prepared by the present invention has no problem of secondary pollution and is an environmentally friendly and highly efficient adsorbent. Description of the Drawings

[0033] Figure 1 The XRD patterns of calcium-based bentonite, sodium-based bentonite, lithium-modified bentonite, activated bentonite, and modified bentonite in Example 1 of the present invention are given.

[0034] Figure 2 The FTIR patterns of calcium-based bentonite, sodium-based bentonite, lithium-modified bentonite, activated bentonite, and modified bentonite in Example 1 of the present invention are given.

[0035] Figure 3 The adsorption capacity and removal rate of perchlorate ions by the modified bentonite at different times in Example 4 of the present invention are given.

[0036] Figure 4 The adsorption capacity and removal rate of perchlorate ions by the modified bentonite at different dosages in Example 5 of the present invention are given.

[0037] Figure 5 The adsorption capacity and removal rate of perchlorate ions by the modified bentonite at different initial concentrations of perchlorate ions in Example 6 of the present invention are given.

[0038] Figure 6 The adsorption capacity and removal rate of perchlorate ions by the modified bentonite at different temperatures in Example 7 of the present invention are given. Detailed Embodiments

[0039] In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and do not represent or limit the scope of the patent protection of the present invention. The scope of protection of the present invention is subject to the claims.

[0040] In the following embodiments, the reagents or instruments not indicating the manufacturer can be all conventional products that can be purchased through the market. For example, calcium-based bentonite (Ca-Mt) from a certain mining area in Inner Mongolia is used as the raw material in the embodiments of the present invention, with a montmorillonite content of >95%, a cation exchange capacity of 0.71 mmol / g, a colloid value of 4.53 mL / g, a swelling capacity of 5.10 mL / g, a zeta potential of -25.90 mV, d 001The value is 1.48 nm.

[0041] In the present invention, the cation exchange capacity (CEC), colloid value, and swelling capacity are used to characterize the hydration performance of bentonite, and the specific description is as follows.

[0042] Cation exchange capacity (CEC)

[0043] The cation exchange capacity of bentonite is determined by the ammonium chloride-ethanol method. The specific method is as follows: Use 0.5 mol / L ammonium chloride-50% ethanol as the exchange solution to exchange the exchangeable cations contained in bentonite; after the exchange, use 95% ethanol to wash away the excess ammonium chloride adhering to the surface of bentonite; then add calcium chloride-formaldehyde solution, and calcium chloride can displace the exchanged NH 4 + ; Then it condenses with formaldehyde to produce hydrochloric acid, and titrate with 0.1 mol / L sodium hydroxide standard solution to determine the cation exchange capacity of bentonite.

[0044] Cation exchange capacity calculation formula: CEC = C × V × 100

[0045] In the formula: CEC is the cation exchange capacity, mmol / 100 g; C is the concentration of the NaOH standard solution, mol / L; V is the volume of the consumed NaOH standard solution, mL.

[0046] Colloid value

[0047] The colloid value of bentonite refers to the gel volume condensed by a unit weight of bentonite when magnesium oxide is added to the bentonite suspension. The specific method is as follows: Weigh 1.00 g of the dried bentonite sample and add it to a 100 mL stoppered graduated cylinder with 90 mL of distilled water. After shaking and dispersing for 5 min, add 0.20 g of light magnesium oxide, make up the volume to the 100 mL graduation line with distilled water, shake well for another 2 min, and let it stand for 24 h. Read the scale value at the gel interface, which is the gel volume, and calculate the colloid value of the unit weight of bentonite (gel volume / 1 g), with the unit of mL / g.

[0048] Swelling capacity

[0049] The swelling capacity refers to the volume after the expansion of bentonite in a certain dilute hydrochloric acid solution, and it is one of the technical indicators for identifying the type of bentonite ore and evaluating the weight of bentonite. The measurement steps are as follows: Weigh 1.00 g of the bentonite sample and place it in a 100 mL stoppered graduated cylinder containing 75 mL of water. After shaking well for 3 min, add 25 mL of 1 mol / L hydrochloric acid, shake well for another 2 min, and let it stand for 24 h. Read the scale value at the gel interface, and calculate the swelling capacity of the unit weight of bentonite (gel volume / 1 g) accordingly, with the unit of mL / g.

[0050] Loading amount

[0051] The loading amount refers to the loading amount of poly(diallyldimethylammonium chloride) (PDDA) on the modified bentonite (target product) determined by the high-temperature calcination method. The determination steps are as follows: Take a certain amount of bentonite and modified bentonite samples respectively, dry them at 85 °C for 24 h to remove the adsorbed water on the sample surface, then place them in a high-temperature box furnace and calcine at 500 °C for 4 h. After natural cooling, quickly take out the samples from the furnace, and weigh the weights of the calcined bentonite and PDDA-modified bentonite samples respectively. The loading amount of the polyelectrolyte PDDA on the modified bentonite is shown by the following formula: L = (1 - m a0 m bt / m at m b0 ) × 1000

[0052] In the formula, L is the loading amount of PDDA on the modified bentonite, mg / g; m a0 and m at are the weights of the activated bentonite (RC-Mt) before and after calcination, g; m b0 and m bt are the weights of the modified bentonite (PDDA / RC-Mt) before and after calcination, g.

[0053] Preparation of the modified bentonite wastewater treatment agent in Example 1

[0054] (1) Weigh 40.0 g of calcium-based bentonite (Ca-Mt), place it in a 1-L glass beaker, add ultrapure water to prepare a suspension with a pulp concentration of 5%; and put it into a water bath stirrer. Under the condition that the water temperature of the water bath is 70 °C, stir electrically for 15 min. After the suspension is evenly dispersed, add 2.0 g of solid Na 2 CO 3 (analytical pure), continue to stir for 90 minutes, then age in air for 2 h. After centrifugally washing the suspension three times, dry the solid and grind it to -200 mesh to obtain sodium-based bentonite (Na-Mt).

[0055] (2) Weigh 40.0 g of sodium-based bentonite (Na-Mt) and 2.0 g of anhydrous lithium chloride, place them in a high-speed crusher, and stir at a speed of 25000 r / min for 2 min to obtain lithiated bentonite (Li-Mt).

[0056] (3) Transfer the lithiated bentonite (Li-Mt) into a microwave instrument, and perform microwave treatment at 800 W for 10 min to obtain activated bentonite (RC-Mt).

[0057] (4) Weigh 40.0 g of the above-mentioned activated bentonite (RC-Mt) and place it in a 1L beaker, add ultrapure water to prepare a suspension with a slurry concentration of 5%; put it in a water bath, stir it with an electric stirrer for 15 minutes at a water temperature of 70°C to make the suspension fully dispersed; add 40.0 g of polydiallyldimethylammonium chloride (PDDA, viscosity of 600-900 cP) to the above suspension, stir it in a constant temperature water bath at 70°C for 4 hours, and then centrifuge it. Put the obtained solid product into a drying oven, thoroughly dry it at 105°C, crush it, grind it and pass it through a 200-mesh sieve to obtain modified bentonite (denoted as PDDA / RC-Mt).

[0058] The hydration properties of sodium bentonite (Na-Mt), lithium bentonite (Li-Mt) and activated bentonite (RC-Mt) were measured and compared with calcium bentonite (Ca-Mt). The results are shown in Table 1.

[0059] Table 1 Hydration properties of bentonite

[0060]

[0061] As can be seen from Table 1, compared with calcium-based bentonite, after sodium reaction, the colloid valence, expansion capacity and cation exchange capacity (CEC) increased significantly; compared with sodium-based bentonite, after lithium reaction, the colloid valence and cation exchange capacity (CEC) increased significantly, and the expansion capacity decreased slightly; compared with lithium bentonite, after microwave activation, the expansion capacity increased slightly, while the cation exchange capacity (CEC) and colloid valence decreased.

[0062] At the same time, X-ray diffraction and infrared spectroscopy tests were performed on sodium bentonite (Na-Mt), lithium bentonite (Li-Mt), activated bentonite (RC-Mt) and modified bentonite (PDDA / RC-Mt), and compared with calcium bentonite (Ca-Mt). The corresponding XRD and FTIR spectra are shown in Figure 2. Figure 1 and Figure 2 shown.

[0063] from Figure 1 It can be seen that the interlayer spacing of calcium-based bentonite (Ca-Mt) is 1.48nm, the interlayer spacing of sodium-based bentonite (Na-Mt) is 1.26nm, the interlayer spacing of lithium-based bentonite (Li-Mt) is 1.17nm, the interlayer spacing of activated bentonite (RC-Mt) is 1.23nm, and the interlayer spacing of modified bentonite (PDDA / RC-Mt) is 1.30nm. The interlayer spacing of the modified bentonite is significantly increased compared with the interlayer spacing of the activated bentonite (RC-Mt) before modification, indicating that PDDA is successfully intercalated between the bentonite layers.

[0064] at the same time, Figure 1In it, the peak intensity ratio of the d001 characteristic peak of lithium-bentonite (Li-Mt) is lower than that of sodium-based bentonite (Na-Mt), and the peak shape is also slightly wider, indicating that lithium ions replace sodium and enter the interlayer during the lithiumation process. The peak intensity of the d001 characteristic peak of the modified bentonite (PDDA / RC-Mt) is lower than that of the activated bentonite (RC-Mt), and the peak shape is also slightly wider, indicating that PDDA enters the interlayer of bentonite, resulting in a decrease in crystal crystallinity.

[0065] From Figure 2 It can be found that in the infrared spectrum of the modified bentonite (PDDA / RC-Mt), symmetric and asymmetric stretching vibration characteristic absorption peaks of the carbon-hydrogen bond C-H appear at 2856 cm -1 and 2945 cm -1 respectively, indicating that PDDA is successfully loaded on the bentonite. The characteristic peak 3446 cm -1 corresponding to the interlayer bound water hydroxyl group has significantly lower intensity, which also indicates that PDDA enters the interlayer of bentonite.

[0066] In addition, the zeta potentials of the bentonites obtained at different stages were also measured and compared with those of calcium-based bentonite (Ca-Mt). It was found that the zeta potentials of calcium-based bentonite (Ca-Mt), sodium-based bentonite (Na-Mt), lithium-bentonite (Li-Mt), activated bentonite (RC-Mt), and modified bentonite (PDDA / RC-Mt) were -25.90, -33.66, -31.50, -30.57, and 49.30 mV, respectively. That is, before PDDA modification, the zeta potentials of each bentonite were negative; after PDDA modification, the zeta potential of the modified bentonite turned positive. This shows that after PDDA modification of the activated bentonite (RC-Mt), not only does PDDA enter the interlayer of bentonite, but also a large amount of PDDA is loaded on the surface of the bentonite. The PDDA loaded on the surface of the bentonite + neutralizes the electronegativity on the surface of the bentonite and makes the zeta potential turn positive, thus providing positive charge electrostatic attraction adsorption sites that can adsorb anionic pollutants.

[0067] The loading amount of the prepared modified bentonite (PDDA / RC-Mt) was measured, and it was found that the loading amount of PDDA in the above-mentioned modified bentonite (PDDA / RC-Mt) was 433.43 mg / g.

[0068] Preparation of the modified bentonite wastewater treatment agent in Example 2

[0069] (1) Weigh 40.0 g of calcium bentonite (Ca-Mt) and place it in a 1 L glass beaker. Add ultrapure water to prepare a suspension with a slurry concentration of 5%. Place the suspension in a water bath stirring pot and stir it with an electric stirrer for 15 min at a water temperature of 70°C. After the suspension is evenly dispersed, add 2.0 g of solid Na 2 CO 3 (analytical grade), continue stirring for 90 minutes, and then age in air for 2 hours. After the suspension is centrifuged and washed three times, the solid is dried and ground to -200 mesh to obtain sodium bentonite (Na-Mt).

[0070] (2) Weigh 40.0 g of sodium bentonite (Na-Mt) and 0.4 g of anhydrous lithium chloride and place them in a high-speed pulverizer. Stir them at a speed of 25,000 r / min for 2 min to obtain lithiated bentonite (Li-Mt).

[0071] (3) The lithiated bentonite (Li-Mt) was transferred into a microwave apparatus and microwaved at 800 W for 10 min to obtain activated bentonite (RC-Mt).

[0072] (4) Weigh 40.0 g of activated bentonite (RC-Mt) and place it in a 1 L beaker, add ultrapure water to prepare a suspension with a slurry concentration of 5%; place it in a water bath, stir it with an electric stirrer for 15 minutes at a water temperature of 70°C to make the suspension fully dispersed; add 40.0 g of polydiallyldimethylammonium chloride (PDDA, viscosity of 600-900 cP) to the above suspension, stir it in a constant temperature water bath at 70°C for 4 hours, and then centrifuge it. Put the obtained solid product into a drying oven, thoroughly dry it at 105°C, crush it, grind it and pass it through a 200-mesh sieve to obtain modified bentonite (denoted as PDDA / RC-Mt).

[0073] The hydration properties of the lithium bentonite (Li-Mt) and activated bentonite (RC-Mt) obtained above were measured and compared with calcium-based bentonite (Ca-Mt) and sodium-based bentonite (Na-Mt). The results are shown in Table 2.

[0074] Table 2 Hydration properties of bentonite

[0075]

[0076] It can be found in Table 2 that compared with calcium-based bentonite, after sodium reaction, the colloid valence, expansion capacity and cation exchange capacity (CEC) all increased significantly; compared with sodium-based bentonite, after lithium reaction, the colloid valence and cation exchange capacity (CEC) all increased significantly, and the expansion capacity decreased; compared with lithium bentonite, after microwave activation, the cation exchange capacity (CEC) and colloid valence decreased, and the expansion capacity increased significantly.

[0077] Meanwhile, X-ray diffraction and infrared spectroscopy tests were carried out on lithium bentonite (Li-Mt), activated bentonite (RC-Mt), and modified bentonite (PDDA / RC-Mt). The results showed that the interlayer spacing of lithium bentonite (Li-Mt) was 1.19 nm, that of activated bentonite (RC-Mt) was 1.24 nm, and that of modified bentonite (PDDA / RC-Mt) was 1.43 nm. Similarly, the interlayer spacing of the modified bentonite increased significantly compared with that of the activated bentonite (RC-Mt) before modification, indicating that PDDA was successfully intercalated into the interlayer of bentonite.

[0078] Meanwhile, in the infrared spectrum of the modified bentonite (PDDA / RC-Mt), characteristic absorption peaks of symmetric and asymmetric stretching vibrations of the carbon-hydrogen bond C-H appeared at 2856 cm -1 and 2945 cm -1 respectively, indicating that PDDA was successfully loaded on the bentonite. The characteristic peak at 3446 cm -1 corresponding to the hydroxyl group of the interlayer bound water was significantly lower in intensity, which also indicated that PDDA had entered the interlayer of bentonite.

[0079] In addition, the zeta potentials of the bentonites obtained at different stages were also measured, and it was found that the zeta potentials of lithium bentonite (Li-Mt), activated bentonite (RC-Mt), and modified bentonite (PDDA / RC-Mt) were -30.94, -33.61, and 41.74 mV respectively. That is, before PDDA modification, the zeta potentials of each bentonite were negative; after PDDA modification, the zeta potential of the modified bentonite turned positive. This shows that after PDDA modification of the activated bentonite (RC-Mt), not only did PDDA enter the interlayer of bentonite, but also a large amount of PDDA was loaded on the surface of the bentonite. The PDDA loaded on the surface of the bentonite + neutralized the electronegativity on the surface of the bentonite and made the zeta potential turn positive, thus providing positive charge electrostatic attraction adsorption sites that can adsorb anionic pollutants.

[0080] The loading amount test was carried out on the modified bentonite (PDDA / RC-Mt) prepared in this example, and it was found that the loading amount of PDDA in the above-mentioned modified bentonite (PDDA / RC-Mt) was 474.31 mg / g.

[0081] Preparation of Modified Bentonite Wastewater Treatment Agent in Example 3

[0082] (1) Weigh 40.0 g of calcium-based bentonite (Ca-Mt) and place it in a 1-L glass beaker. Add ultrapure water to prepare a suspension with a pulp concentration of 5%. Put it into a water bath magnetic stirrer and stir it electrically for 15 min at a water bath temperature of 70 °C. After the suspension is evenly dispersed, add 2.0 g of solid Na 2 CO 3 (analytical grade), continue stirring for 90 min, and then age it in air for 2 h. Centrifuge and wash the suspension three times, dry the solid, and grind it to -200 mesh to obtain sodium-based bentonite (Na-Mt).

[0083] (2) Weigh 40.0 g of sodium-based bentonite (Na-Mt) and 1.2 g of anhydrous lithium chloride and place them in a high-speed grinder. Stir at a speed of 25000 r / min for 2 min to obtain lithiumated bentonite (Li-Mt).

[0084] (3) Transfer the lithiumated bentonite (Li-Mt) into a microwave instrument and perform microwave treatment at 800 W for 10 min to obtain activated bentonite (RC-Mt).

[0085] (4) Weigh 40.0 g of activated bentonite (RC-Mt) and place it in a 1-L beaker. Add ultrapure water to prepare a suspension with a pulp concentration of 5%. Put it into a water bath and stir it electrically for 15 min at a water bath temperature of 70 °C to fully disperse the suspension evenly. Add 40.0 g of poly(diallyldimethylammonium chloride) (PDDA, viscosity 600 - 900 cP) to the above suspension and stir it in a 70 °C constant temperature water bath for 4 h, then centrifuge and separate. Put the obtained solid product into an oven and thoroughly dry it at 105 °C, then crush, grind, and pass through a 200-mesh sieve to obtain modified bentonite (denoted as PDDA / RC-Mt).

[0086] Measure the hydration properties of the obtained lithiumated bentonite (Li-Mt) and activated bentonite (RC-Mt), and compare them with calcium-based bentonite (Ca-Mt) and sodium-based bentonite (Na-Mt). The results are shown in Table 3.

[0087] Table 3 Hydration properties of bentonite

[0088]

[0089] It can be found from Table 3 that compared with calcium-based bentonite, after sodiumation reaction, the colloid value, swelling capacity, and cation exchange capacity (CEC) all increase significantly; compared with sodium-based bentonite, after lithiation reaction, the colloid value and cation exchange capacity (CEC) both increase significantly, and the swelling capacity slightly decreases; compared with lithiated bentonite, after microwave activation, the cation exchange capacity (CEC) and colloid value both decrease, and the swelling capacity increases.

[0090] Meanwhile, X-ray diffraction and infrared spectroscopy tests were carried out on calcium-based bentonite (Ca-Mt), sodium-based bentonite (Na-Mt), lithium bentonite (Li-Mt), activated bentonite (RC-Mt), and modified bentonite (PDDA / RC-Mt). It was found that the interlayer spacing of lithium bentonite (Li-Mt) was 1.17 nm, the interlayer spacing of activated bentonite (RC-Mt) was 1.22 nm, and the interlayer spacing of modified bentonite (PDDA / RC-Mt) was 1.35 nm. The interlayer spacing of the modified bentonite increased significantly compared with that of the activated bentonite (RC-Mt) before modification, indicating that PDDA was successfully intercalated into the interlayer of bentonite.

[0091] Meanwhile, in the infrared spectrum of the modified bentonite (PDDA / RC-Mt), symmetric and asymmetric stretching vibration characteristic absorption peaks of the carbon-hydrogen bond C-H appeared at 2856 cm -1 and 2945 cm -1 respectively, indicating that PDDA was successfully loaded on the bentonite. The characteristic peak 3446 cm -1 corresponding to the interlayer bound water hydroxyl group had significantly lower intensity, also indicating that PDDA entered the interlayer of bentonite.

[0092] In addition, the zeta potentials of the original soil and the bentonite obtained at different stages were also measured, and it was found that the zeta potentials of lithium bentonite (Li-Mt), activated bentonite (RC-Mt), and modified bentonite (PDDA / RC-Mt) were -34.83, -35.06, and 50.86 mV respectively. That is, before PDDA modification, the zeta potentials of each bentonite were negative; after PDDA modification, the zeta potential of the modified bentonite turned positive. This shows that after PDDA modification of the activated bentonite (RC-Mt), not only did PDDA enter the interlayer of bentonite, but also a large amount of PDDA was loaded on the surface of bentonite. The PDDA loaded on the surface of bentonite + , neutralized the electronegativity on the surface of bentonite and made the zeta potential turn positive, thus providing positive charge electrostatic attraction adsorption sites, which can adsorb anionic pollutants.

[0093] The loading amount test was carried out on the modified bentonite (PDDA / RC-Mt) prepared in this example, and it was found that the loading amount of PDDA in the above-mentioned modified bentonite (PDDA / RC-Mt) was 459.01 mg / g.

[0094] Comparative Example 1

[0095] (1) Weigh 40.0 g of calcium-based bentonite (Ca-Mt) and place it in a 1-L glass beaker. Add ultrapure water to prepare a suspension with a pulp concentration of 5%. Then put it into a water bath stirrer. Under the condition that the water temperature of the water bath is 70 °C, stir it electrically for 15 min. After the suspension is evenly dispersed, add 2.0 g of solid Na 2 CO 3 (analytical grade), continue stirring for 90 minutes, and then age it in the air for 2 h. After centrifugally washing the suspension three times, dry the solid and grind it to -200 mesh to obtain sodium-based bentonite (Na-Mt).

[0096] (2) Weigh 40.0 g of sodium-based bentonite (Na-Mt) and place it in a 1-L beaker. Add ultrapure water to prepare a suspension with a pulp concentration of 1%. Then put it into a water bath. Under the condition that the water temperature of the water bath is 70 °C, stir it electrically for 15 min to make the suspension fully and evenly dispersed;

[0097] (3) Add 40.0 g of poly(diallyldimethylammonium chloride) (PDDA, viscosity 600 - 900 cP) to the above suspension. Stir it under a 70 °C constant temperature water bath for 4 h, then centrifuge and separate. Put the obtained solid product into a drying oven and thoroughly dry it at 105 °C. Then crush, grind and pass through a 200-mesh sieve to obtain modified bentonite (denoted as PDDA-Mt).

[0098] After testing, the interlayer spacing of this modified bentonite (PDDA-Mt) is 1.48 nm, the zeta potential is 42.11 mV, and the loading amount of PDDA is 171.86 mg / g.

[0099] Comparative Example 2

[0100] (1) Weigh 40.0 g of calcium-based bentonite (Ca-Mt) and place it in a 1-L glass beaker. Add ultrapure water to prepare a suspension with a pulp concentration of 5%. Then put it into a water bath stirrer. Under the condition that the water temperature of the water bath is 70 °C, stir it electrically for 15 min. After the suspension is evenly dispersed, add 2.0 g of solid Na 2 CO 3 (analytical grade), continue stirring for 90 minutes, and then age it in the air for 2 h. After centrifugally washing the suspension three times, dry the solid and grind it to -200 mesh to obtain sodium-based bentonite (Na-Mt).

[0101] (2) Dissolve 2 g of lithium chloride in water, add 40.0 g of sodium-based bentonite (Na-Mt), and add ultrapure water to prepare a suspension with a pulp concentration of 5% (the weight of sodium-based bentonite accounts for 5% of the weight of the suspension). Stir for 2 h under the condition that the water bath temperature is 70 °C, then centrifuge and discard the supernatant. Add deionized water and repeat centrifugal washing three times. Dry the washed solid at 105 °C, grind it through a -200 mesh sieve for standby, and the obtained sample is denoted as lithium-modified bentonite (Li-Mt).

[0102] (3) Transfer the lithium-modified bentonite (Li-Mt) into a microwave instrument and microwave-treat it at 800 W for 10 min to obtain activated bentonite (RC-Mt).

[0103] (4) Weigh 40.0 g of activated bentonite (RC-Mt) and place it in a 1 L beaker, add ultrapure water to prepare a suspension with a pulp concentration of 5%; and put it into a water bath pot. Under the condition that the water bath temperature is 70 °C, stir electrically for 15 min to fully disperse and homogenize the suspension; add 40.0 g of polydiallyldimethylammonium chloride (PDDA, viscosity 600 - 900 cP) to the above suspension, stir for 4 h under a 70 °C constant temperature water bath, then centrifuge. Put the obtained solid product into a drying oven, thoroughly dry it at 105 °C, crush, grind it and pass through a 200 mesh sieve to obtain modified bentonite (denoted as PDDA / RC-Mt).

[0104] Measure the hydration properties of the obtained lithium-modified bentonite (Li-Mt) and activated bentonite (RC-Mt), and compare them with calcium-based bentonite (Ca-Mt) and sodium-based bentonite (Na-Mt). The results are shown in Table 4.

[0105] Table 4 Hydration properties of bentonite

[0106]

[0107] Test the loading amount of the modified bentonite (PDDA / RC-Mt) prepared in this comparative example and find that: in the above-mentioned modified bentonite (PDDA / RC-Mt), the loading amount of PDDA is 332.08 mg / g.

[0108] Comparative Example 3

[0109] (1) Place 40.0 g of calcium-based bentonite (Ca-Mt) and 2 g of anhydrous lithium chloride in a high-speed crusher, stir at a high speed of 25000 r / min for 2 min, and obtain lithium-modified bentonite (Li-Mt).

[0110] (2) Transfer the lithium-modified bentonite (Li-Mt) into a microwave instrument and microwave-treat it at 800 W for 10 min to obtain activated bentonite (RC-Mt).

[0111] (3) Take 40.0 g of the above-activated bentonite (RC-Mt) and place it in a 1-L beaker. Add ultrapure water to prepare a suspension with a pulp concentration of 5%. Then put it in a water bath. Under the condition that the water temperature of the water bath is 70 °C, stir it electrically for 15 min to fully disperse and homogenize the suspension. Add 40.0 g of poly(diallyldimethylammonium chloride) (PDDA, viscosity 600 - 900 cP) to the above suspension. After stirring for 4 h under a constant water bath at 70 °C, perform centrifugal separation. Put the obtained solid product into a drying oven and thoroughly dry it at 105 °C. Then crush, grind, and pass through a 200-mesh sieve to obtain modified bentonite (denoted as PDDA / RC-Mt).

[0112] Measure the hydration properties of the obtained lithium bentonite (Li-Mt) and activated bentonite (RC-Mt), and compare them with calcium bentonite (Ca-Mt). The results are shown in Table 5.

[0113] Table 5 Hydration properties of bentonite

[0114]

[0115] Perform a loading test on the modified bentonite (PDDA / RC-Mt) prepared in this comparative example and find that: in the above modified bentonite (PDDA / RC-Mt), the loading of PDDA is 132.12 mg / g.

[0116] Comparative Example 4

[0117] (1) Place 40.0 g of calcium bentonite (Ca-Mt) and 2 g of anhydrous lithium chloride in a high-speed grinder. Stir at a speed of 25000 r / min for 2 min to obtain lithium bentonite (Li-Mt).

[0118] (2) Transfer the lithium bentonite (Li-Mt) to a microwave instrument and perform microwave treatment at 800 W for 10 min to obtain activated bentonite (RC-Mt).

[0119] (3) Take 40.0 g of the above-activated bentonite (RC-Mt) and place it in a 1-L beaker. Add ultrapure water to prepare a suspension with a pulp concentration of 5%. Then put it in a water bath. Under the condition that the water temperature of the water bath is 70 °C, stir it electrically for 15 min. After the suspension is dispersed evenly, add 2.0 g of solid Na 2 CO 3(Analytical pure), continue stirring for 90 minutes, and then age in air for 2 h; then, add 40.0 g of polydiallyldimethylammonium chloride (PDDA, viscosity 600 - 900 cP) to the above suspension, stir at a constant water bath temperature of 70 °C for 4 h, then centrifuge, put the obtained solid product into a drying oven, thoroughly dry at 105 °C, crush and grind, and pass through a 200-mesh sieve to obtain modified bentonite (denoted as PDDA / RC-Mt).

[0120] The hydration properties of the obtained lithium bentonite (Li-Mt) and activated bentonite (RC-Mt) were measured and compared with calcium bentonite (Ca-Mt). The results are shown in Table 6.

[0121] Table 6 Hydration properties of bentonite

[0122]

[0123] The loading amount of the modified bentonite (PDDA / RC-Mt) prepared in this comparative example was tested and found that: in the above modified bentonite (PDDA / RC-Mt), the loading amount of PDDA was 210.08 mg / g.

[0124] II. Application of wastewater treatment agent in removing perchlorate ions from wastewater

[0125] Example 4

[0126] Take 0.05 g of the modified bentonite PDDA / RC-Mt obtained in Example 1 and place it in an iodine flask, then add 50 mL of a sodium perchlorate simulated wastewater solution with an initial concentration of 1 mmol / L, oscillate at a constant speed (160 rpm) with an oscillator at room temperature (25 ± 2 °C), and measure the remaining concentration of perchlorate in the solution at 0.1, 0.2, 0.5, 1, 2, 3, 5, 10, 30, 60, 120, 240, and 480 min respectively.

[0127] Use an ion meter to measure the perchlorate concentration in the filtrate, and calculate the removal rate and adsorption amount of perchlorate ions through the following formula:

[0128] E 0 =[(C 0 -C t ) / C 0 ×100%

[0129] Q=(C 0 -C t )×V / m

[0130] In the formula, E 0 is the removal rate of perchlorate ions by the bentonite adsorbent, unit: %; C 0$C_0$ is the perchlorate concentration in the solution before adsorption, unit: mmol / L; t $C_t$ is the perchlorate concentration in the solution at adsorption time $t$, unit: mmol / L; $Q$ is the adsorption capacity of bentonite adsorbent for perchlorate, unit: mmol / g; $V$ is the volume of the wastewater solution, unit: L; $m$ is the weight of the bentonite adsorbent, unit: g.

[0131] The changes in the adsorption capacity and removal rate of perchlorate in the simulated wastewater by the modified bentonite PDDA / RC-Mt at different times are as Figure 3 shown. From Figure 3 it can be seen that the adsorption rate of PDDA / RC-Mt for perchlorate is very fast, and the adsorption equilibrium can be reached in 10 min. The removal rate of perchlorate is 68.66%, and the adsorption capacity is 0.69 mmol / g. This result is significantly better than the records in the existing literature, not only with a larger adsorption capacity, higher adsorption efficiency, but also a faster adsorption rate. For example, the cetyltrimethylammonium chloride modified bentonite prepared in "Xiao Ou. Study on the Adsorption Performance of Modified Bentonite for Perchlorate in Water [D]. South China University of Technology, 2013" has a maximum adsorption capacity of only 0.43 mmol / g for perchlorate under similar experimental conditions, and the adsorption equilibrium time is 6 h; for another example, the maximum adsorption capacity of the cetylpyridinium chloride modified dispersed montmorillonite (dMt / HDPy) prepared in "Luo W., et al., Influence of the pre-dispersion of montmorillonite on organic modification and the adsorption of perchlorate and methyl red anions [J]. Applied Clay Science, 2018" for perchlorate is about 0.58 mmol / g, and the equilibrium time > 130 min.

[0132] Example 5

[0133] Take different dosages (0.005 g, 0.025 g, 0.05 g, 0.1 g, 0.15 g, 0.25 g) of the modified bentonite PDDA / RC-Mt prepared in Example 2 and place them in an iodine flask. Then add 50 mL of the sodium perchlorate simulated wastewater solution with an initial concentration of 1 mmol / L. At room temperature (25 ± 2 °C), use a shaker to oscillate at a constant speed (160 rpm) for 4 hours, and then use an ion meter to measure the remaining concentration of perchlorate in the solution. Calculate the perchlorate adsorption capacity and removal rate using the same method as in Example 4, and the results are as Figure 4 shown.

[0134] From Figure 4It can be seen that when the dosage of the modified bentonite PDDA / RC-Mt is 0.005 g, the adsorption capacity of perchlorate is the highest, reaching 2.42 mmol / g; when the dosage of the modified bentonite PDDA / RC-Mt is 0.25 g, the removal rate of perchlorate is the highest, reaching 77.82%.

[0135] Example 6

[0136] Take 0.05 g of the modified bentonite PDDA / RC-Mt prepared in Example 1 above and place it in an iodine flask. Then add 50 mL of sodium perchlorate simulated wastewater solution with initial concentrations of 0.1, 0.5, 1, 2, 3, and 5 mmol / L respectively. At room temperature (25 ± 2 °C), shake it with a shaker at a constant speed (160 rpm) for 4 hours, and then use an ion meter to measure the remaining concentration of perchlorate in the solution. Calculate the perchlorate adsorption capacity and removal rate using the same method as in Example 4, and the results are as Figure 5 shown.

[0137] As Figure 5 can be seen, the adsorption capacity and removal rate of the modified bentonite for perchlorate increase significantly with the increase of the initial concentration of perchlorate. When the perchlorate concentration reaches 5 mmol / L (i.e., 497.25 mg / L), the adsorption capacity of the modified bentonite for perchlorate is 2.70 mmol / g (i.e., 268.52 mg / g), indicating that this modified bentonite is also suitable for the treatment of high-concentration anion wastewater.

[0138] Example 7

[0139] Take 0.05 g of the modified bentonite PDDA / RC-Mt prepared in Example 1 above and place it in an iodine flask. Then add 50 mL of sodium perchlorate simulated wastewater solution with an initial concentration of 1 mmol / L. At 25 °C, 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C respectively, shake it with a shaker at a constant speed (160 rpm) for 4 hours, and then use an ion meter to measure the remaining concentration of perchlorate in the solution. Calculate the perchlorate adsorption capacity and removal rate using the same method as in Example 4, and the results are as Figure 6 shown.

[0140] As Figure 6 can be seen, both the adsorption capacity and removal rate of the modified bentonite for perchlorate gradually increase with the increase of the adsorption temperature, indicating that the increase in temperature is beneficial to the progress of the adsorption reaction, and this reaction process may be a spontaneous endothermic reaction process.

[0141] Example 8

[0142] Mix perchlorate, nitrate, sulfate, and phosphate together to prepare a mixed solution. In this mixed solution, the concentrations of perchlorate, nitrate, sulfate, and phosphate are all 1 mmol / L.

[0143] Measure 50 mL of the mixed solution, and add 0.05 g of the modified bentonite PDDA / RC-Mt prepared in Example 1 above. Adsorb for 4 h at room temperature (around 25 °C), and then measure the remaining concentrations of perchlorate, nitrate, sulfate, and phosphate respectively. The adsorption amounts of the modified bentonite wastewater treatment agent (PDDA-modified soil) for perchlorate, nitrate, sulfate, and phosphate are 0.55, 0.11, 0.19, and 0.27 mmol / g respectively, and the removal rates are 54.90%, 11.17%, 19.29%, and 26.81% respectively. This shows that the modified bentonite wastewater treatment agent can also selectively adsorb perchlorate ions well in a solution with multiple anions coexisting, achieving good perchlorate ion removal effect.

[0144] Comparative Example 5

[0145] Take 0.05 g of the modified bentonite PDDA-Mt prepared in Comparative Example 1 and place it in an iodine flask. Then add 50 mL of a sodium perchlorate simulated wastewater solution with an initial concentration of 1 mmol / L, and oscillate at a constant speed (160 rpm) for 4 hours at room temperature (25 ± 2 °C) using an oscillator. Measure the remaining concentration of perchlorate in the solution with an ion meter. Calculate the perchlorate adsorption amount and removal rate using the same method as in Example 4, which are 0.462 mmol / g and 62.81% respectively.

[0146] Comparative Example 6

[0147] Take 0.05 g of the modified bentonite PDDA-Mt prepared in Comparative Example 2 and place it in an iodine flask. Then add 50 mL of a sodium perchlorate simulated wastewater solution with an initial concentration of 1 mmol / L, and oscillate at a constant speed (160 rpm) for 4 hours at room temperature (25 ± 2 °C) using an oscillator. Measure the remaining concentration of perchlorate in the solution with an ion meter. Calculate the perchlorate adsorption amount and removal rate using the same method as in Example 4, which are 0.54 mmol / g and 53.52% respectively.

[0148] Comparative Example 7

[0149] Take 0.05 g of the modified bentonite PDDA-Mt prepared in Comparative Example 3 and place it in an iodine flask. Then add 50 mL of a sodium perchlorate simulated wastewater solution with an initial concentration of 1 mmol / L to it, and shake it at a constant speed (160 rpm) with an oscillator for 4 hours at room temperature (25 ± 2 °C). Use an ion meter to measure the remaining concentration of perchlorate in the solution. Calculate the perchlorate adsorption capacity and removal rate using the same method as in Example 4, which are 0.36 mmol / g and 35.71%, respectively.

[0150] Comparative Example 8

[0151] Take 0.05 g of the modified bentonite PDDA-Mt prepared in Comparative Example 4 and place it in an iodine flask. Then add 50 mL of a sodium perchlorate simulated wastewater solution with an initial concentration of 1 mmol / L to it, and shake it at a constant speed (160 rpm) with an oscillator for 4 hours at room temperature (25 ± 2 °C). Use an ion meter to measure the remaining concentration of perchlorate in the solution. Calculate the perchlorate adsorption capacity and removal rate using the same method as in Example 4, which are 0.50 mmol / g and 50.03%, respectively.

[0152] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as specified, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A modified bentonite wastewater treatment agent is prepared by the following steps: (1) Prepare a suspension of calcium-based bentonite in water with a pulp concentration of 1-5%, stir it evenly at 50-70 °C, add Na 2 CO 3 , continue to stir for 60-120 minutes, then age for 1-3 h. After centrifugally washing the suspension multiple times, dry the solid and grind it to 200 mesh to obtain sodium-based bentonite; the weight of the solid Na 2 CO 3 is 3-5% of the weight of the calcium-based bentonite; (2) Place the sodium-based bentonite and anhydrous lithium chloride in a high-speed grinder and stir for 1 - 5 min to obtain lithiated bentonite; Among them, The weight of the anhydrous lithium chloride is 1 - 5% of the weight of the sodium-based bentonite; (3) Microwave-treat the lithiated bentonite for 5 - 15 min to obtain activated bentonite; among them, the microwave power is 200 - 1200 W; (4) Prepare the activated bentonite into a suspension with a pulp concentration of 3 - 5% with water. Stir at 50 - 70 °C until evenly dispersed. Add polydiallyldimethylammonium chloride thereto, and then stir at 50 - 70 °C for 2 - 6 h. After cooling and centrifugal separation, the obtained solid is dried at 85 - 105 °C and ground and sieved to obtain modified bentonite; among them, the weight of the polydiallyldimethylammonium chloride is 30 - 100% of the weight of the activated bentonite; The wastewater is wastewater containing perchlorate.

2. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (1), the pulp concentration in the suspension is 5%.

3. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (1), the weight of the Na 2 CO 3 is 5% of the weight of the calcium-based bentonite.

4. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (2), the rotation speed of the high-speed grinder is 25000 r / min and the stirring time is 2 min.

5. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (3), the power of the microwave treatment is 800 W and the time of the microwave treatment is 10 min.

6. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (4), the pulp concentration in the suspension is 5%.

7. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (4), the weight ratio of the polydiallyldimethylammonium chloride to the activated bentonite is 1:

1.

8. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (4), the viscosity of the polydiallyldimethylammonium chloride is 600 - 900 cP.

9. The modified bentonite wastewater treatment agent according to claim 1, characterized in that In step (4), the grinding and sieving is grinding through a 200-mesh sieve.

10. Application of the modified bentonite wastewater treatment agent according to any one of claims 1 - 9 in removing perchlorate ions from wastewater.

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