Thallium removal agent suite for water treatment and water treatment method

Abstract

The invention provides a thallium removal agent suite for water treatment and a water treatment method, the thallium removal agent suite comprises 15-30% by mass of a sodium hypochlorite solution, 3-10% by mass of a potassium ferrate solution, a pH regulator, a coagulant and a flocculant. The water treatment method comprises the following steps: regulating the pH value of the wastewater to 10.5-11.5 at normal temperature by using a pH regulator; adding a sodium hypochlorite solution into the wastewater and stirring; adding a potassium ferrate solution into the wastewater and stirring; adjusting the pH value of the wastewater to 8.5-9.5 at normal temperature by using a pH regulator; and finally adding a coagulant and a flocculant into the wastewater. In the technological process, sodium hypochlorite and potassium ferrate are adopted for oxidation treatment on the wastewater under the alkaline condition, on one hand, Tl < + > in the wastewater can be effectively oxidized into Tl < 3 + >, on the other hand, other pollutants in the wastewater are oxidized, and on the other hand, the dosage of chemicals is reduced, and the adding cost of the chemicals is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and relates to a thallium removal agent kit for water treatment and a water treatment method. Background Art

[0002] Sintering and desulfurization are inevitable processes in steel production, and sintering wastewater and desulfurization wastewater contain a large number of pollutants, such as heavy metal ions, nitrides, sulfides, etc. Among them, thallium is a typical heavy metal pollutant. If it is directly discharged, it will cause potential harm to the environment and human health. Therefore, the discharge of thallium-containing wastewater in the steel industry needs to be effectively controlled.

[0003] In order to effectively control and direct the thallium pollution in the steel industry wastewater, the government departments of my country have promulgated a series of relevant laws and regulations. For example, the "Industrial Wastewater Thallium Pollutant Emission Standard" (DB43 / 968-2014) issued by Hunan Province stipulates that the emission limit of thallium pollutants in industrial wastewater involving heavy metal thallium is 0.005mg / L; for another example, the "Industrial Wastewater Thallium Pollutant Emission Standard" (DB44 / 1989-2017) issued by Guangdong Province stipulates that the emission limit of total thallium is: 0.005mg / L for existing enterprises and 0.002mg / L for newly built enterprises. / L, the special emission limit is 0.001mg / L; for example, Jiangsu Province has clarified the emission standard DB32 / 3431-2018 for thallium pollutants in steel industry wastewater, which stipulates that the emission limit of thallium pollutants in steel industry wastewater at the wastewater discharge outlet of workshops or production facilities is 0.002mg / L ((direct emission and indirect emission). With the attention paid to thallium pollutants and the further implementation of ultra-low emission standards, in 2020, the Ministry of Ecology and Environment added an emission limit for total thallium in the Amendment to the "Steel Industry Wastewater Discharge Standard" (Draft for Comments), requiring it to be 0.05mg / L.

[0004] The thallium removal process in industrial wastewater mainly adopts the method of adding reagents and coagulation and precipitation. The type of reagents has an impact on the process of water treatment, and the price difference of different reagents is large. In the past, when complex high-salt wastewater was treated for thallium removal, inorganic sulfur reagents such as sodium sulfide were usually used to capture and precipitate thallium. This method has the advantage of low cost. However, sodium sulfide has a peculiar smell, which leads to low work efficiency and high labor cost during manual dosing, and impurities such as suspended matter in wastewater cannot be removed. In addition, when using inorganic sulfur reagents to remove thallium, if slaked lime is used as a pH regulator, there is a problem of excessive mud volume in the entire treatment process. If a liquid pH regulator is used to adjust the pH, there is a problem that the thallium content of the effluent cannot be guaranteed to meet the standard. In this regard, a slaked lime-enhanced sodium sulfide coagulation technology is proposed in the prior art. Although it can ensure a stable thallium removal efficiency, it is difficult to collaboratively remove pollutants such as ammonia nitrogen and COD in the water body.

[0005] In view of this, it is necessary to propose a new thallium removal agent formula and process. Summary of the invention

[0006] The object of the present invention is to provide a thallium removal agent kit for water treatment and a water treatment method, so as to effectively remove thallium ions in wastewater while also removing pollutants such as ammonia nitrogen and COD simultaneously.

[0007] To achieve the above-mentioned purpose, the present invention provides a thallium removal reagent kit for water treatment, comprising: sodium hypochlorite solution, potassium ferrate solution, pH regulator, coagulant and flocculant;

[0008] Calculated in mass percentage, the concentration of the sodium hypochlorite solution is 15% to 30%, and the concentration of the potassium ferrate solution is 3% to 10%.

[0009] Optionally, the coagulant is a polyaluminium chloride solution, and the mass percentage of the polyaluminium chloride solution is 30%.

[0010] Optionally, the coagulant is polyferric sulfate.

[0011] Optionally, the flocculant is a polyacrylamide solution, and the mass percentage of the polyacrylamide solution is 1‰ to 3‰.

[0012] Optionally, the pH adjuster includes a first pH adjuster and a second pH adjuster, the first pH adjuster includes an alkaline compound, and the second pH adjuster includes an acidic compound.

[0013] To achieve the above object, the present invention also provides a water treatment method, comprising:

[0014] Step S1, using a pH regulator to adjust the pH of the wastewater so that the pH of the wastewater at room temperature is 10.5-11.5;

[0015] Step S2, adding sodium hypochlorite solution to the wastewater treated in step S1 and stirring, wherein the mass percentage of the sodium hypochlorite solution is 15% to 30%;

[0016] Step S3, adding potassium ferrate solution to the wastewater treated in step S2 and stirring, wherein the mass percentage of the potassium ferrate solution is 3% to 10%;

[0017] Step S4, using a pH regulator to adjust the pH of the wastewater treated in step S3 so that the pH of the wastewater at room temperature is 8.5 to 9.5;

[0018] Step S5, adding coagulant and flocculant to the wastewater treated in step S4.

[0019] Optionally, the step S1, the step S2, the step S3, the step S4, and the step S5 are performed in different containers.

[0020] Optionally, the pH of the wastewater adjusted in step S1 at room temperature is 11, and the pH of the wastewater adjusted in step S4 at room temperature is 9.

[0021] Optionally, the stirring speed in step S2 is 300 rpm to 500 rpm, and the reaction time is 15 min to 20 min; the stirring speed in step S3 is 300 rpm to 500 rpm, and the reaction time is 20 min to 25 min.

[0022] Optionally, assuming that the thallium content in the wastewater is 1500 μg / L and the volume of the wastewater is 1 L, the volume of the sodium hypochlorite solution added in step S2 is 30 mL to 60 mL, and the volume of the potassium ferrate solution added in step S3 is 10 mL to 18 mL.

[0023] Compared with the prior art, the thallium removal reagent kit and water treatment method for water treatment of the present invention have the following advantages:

[0024] The aforementioned thallium removal reagent kit for water treatment includes sodium hypochlorite solution, potassium ferrate solution, pH regulator, coagulant, and flocculant, wherein the mass percentage of sodium hypochlorite solution is 15% to 30%, and the mass percentage of potassium ferrate solution is 3% to 10%. The process of using the thallium removal reagent kit to perform a water treatment process is as follows: first, use a pH regulator to adjust the pH of the wastewater so that the pH of the wastewater at room temperature is 10.5 to 11.5; then add sodium hypochlorite solution to the wastewater and stir; then add potassium ferrate solution to the wastewater and stir; then use a pH regulator to adjust the pH of the wastewater so that the pH of the wastewater at room temperature is 8.5 to 9.5; finally, add a coagulant and a flocculant to the wastewater. In this process flow, sodium hypochlorite and potassium ferrate are used to oxidize the wastewater under alkaline conditions. On the one hand, this method can effectively remove Tl in the wastewater. + Oxidized to Tl 3+ On the one hand, it also oxidizes other pollutants in the wastewater, and on the other hand, it reduces the dosage of chemicals and reduces the cost of chemical addition. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] In addition, each embodiment of the following description has one or more technical features, but this does not mean that the user of the present invention must implement all the technical features in any embodiment at the same time, or can only implement part or all of the technical features in different embodiments separately. In other words, under the premise that implementation is possible, those skilled in the art can selectively implement part or all of the technical features in any embodiment according to the disclosure of the present invention and according to the design specifications or implementation requirements, or selectively implement a combination of part or all of the technical features in multiple embodiments, thereby increasing the flexibility of the implementation of the present invention.

[0027] The purpose of the present invention is to provide a thallium removal agent kit for water treatment and a water treatment method, so as to remove pollutants such as ammonia nitrogen and COD while removing thallium, reduce the dosage of the agent, and save the cost of adding the agent.

[0028] The thallium removal reagent kit for water treatment comprises sodium hypochlorite solution, potassium ferrate solution, pH regulator, coagulant and flocculant. In terms of mass percentage, the concentration of the sodium hypochlorite solution is 15% to 30%, and the concentration of the potassium ferrate solution is 3% to 10%.

[0029] When the above-mentioned thallium removal agent is used to treat thallium-containing wastewater, under the condition that the wastewater is alkaline, sodium hypochlorite solution and potassium ferrate solution are used to remove reducing substances such as Tl in the wastewater. + , ammonia nitrogen, COD, etc. are oxidized, and then the oxidation products are adsorbed and precipitated with the action of coagulants and flocculants to remove Tl + , ammonia nitrogen, COD and other pollutants. The use of the thallium removal reagent kit for water treatment provided by the embodiment of the present invention to treat thallium-containing wastewater has the following advantages: (1) it can simultaneously remove pollutants such as metallic thallium, ammonia nitrogen, COD and the like; (2) it can reduce the dosage of potassium ferrate, thereby saving the reagent cost. In addition, the specific water treatment method will be described in detail later.

[0030] It should be noted that the mass percentage of the sodium hypochlorite solution used in the embodiment of the present invention is within the range of 15% to 30% because a sodium hypochlorite solution with a mass percentage higher than 30% is prone to cause safety accidents, and a sodium hypochlorite solution with a mass percentage lower than 15% has a poor oxidation effect. The mass percentage of potassium ferrate is within the range of 3% to 10% because, on the one hand, the dissolution rate of potassium ferrate is considered, and on the other hand, the oxidation effect of potassium ferrate is considered.

[0031] Optionally, the pH regulator includes a first pH regulator and a second pH regulator, wherein the first pH regulator includes an alkaline compound and the second pH regulator includes an acidic compound. More specifically, the first pH regulator includes but is not limited to at least one of slaked lime and sodium hydroxide, and the second pH regulator includes but is not limited to a hydrochloric acid solution. Thus, a suitable pH regulator can be selected as needed to adjust the acidity and alkalinity of the wastewater.

[0032] Alternatively, the coagulant may be a conventional coagulant, such as a polyaluminium chloride solution. Alternatively, the coagulant may also be polyferric sulfate.

[0033] Optionally, the flocculant may be a conventional flocculant, such as a polyacrylamide solution.

[0034] The process of treating thallium-containing wastewater using the thallium removal reagent kit is as follows, including:

[0035] Step S1, using the pH regulator to adjust the pH of the wastewater so that the pH value of the wastewater at room temperature is 10.5-11.5.

[0036] Step S2, adding 15% to 30% by mass of sodium hypochlorite solution to the wastewater treated in step S1 and stirring.

[0037] Step S3, adding 3% to 10% by mass of potassium ferrate solution to the wastewater treated in step S2 and stirring.

[0038] Step S4, using the pH regulator to adjust the pH of the wastewater treated in step S3 so that the pH of the wastewater at room temperature is 8.5-9.5.

[0039] Step S5, adding coagulant and flocculant to the wastewater treated in step S4.

[0040] The normal temperature refers to 20°C to 30°C.

[0041] By performing step S1, the wastewater is placed in an alkaline condition.

[0042] By performing step S2, sodium hypochlorite can be used to oxidize under alkaline conditions to oxidize ammonia nitrogen and COD in the wastewater, and also partially remove Tl + Oxidized to Tl 3+ .

[0043] By performing step S3, potassium ferrate can be oxidized under alkaline conditions to remove Tl + Oxidized to Tl 3+ .

[0044] By executing step S4, the alkalinity of the wastewater is weakened, and then executing step S5, the coagulant and flocculant can effectively adsorb the oxidation products obtained by the reaction of steps S2 and S3, and finally coagulate and precipitate, so that the effluent meets the requirements.

[0045] It can be understood that the step S1 uses the first pH regulator to adjust the pH of the wastewater, and preferably adjusts the pH of the wastewater to 11 at room temperature. The step S4 uses the second pH regulator to adjust the pH of the wastewater, and preferably adjusts the pH of the wastewater to 9 at room temperature.

[0046] Further, each step in the water treatment process is performed in a different container. Specifically in the embodiment of the present invention, step S1 is performed in a regulating tank, step S2 is performed in a first reaction tank, step S3 is performed in a second reaction tank, step S4 is performed in an equalizing tank, and step S5 is performed in an inclined plate sedimentation tank.

[0047] Furthermore, the amount of the sodium hypochlorite solution added in step S2 and the amount of the potassium ferrate solution added in step S3 should be reasonable. Too much addition will cause waste, while too little addition will not fully oxidize ammonia nitrogen, COD, and Tl. + After repeated tests, it was determined that for 1L of sewage with a thallium content of 1500μg / L, the volume of the sodium hypochlorite solution added in step S2 is 30mL-60mL, and the volume of the potassium ferrate solution added in step S3 is 10mL-18mL.

[0048] In addition, in the step S2, the residence time of the wastewater in the first reaction tank is 15min to 20min, and the wastewater in the first reaction tank is preferably stirred by a first mechanical stirring device at a stirring speed of 300rpm to 500rpm. In the step S3, the residence time of the wastewater in the second reaction tank is 20min to 25min, and the wastewater in the second reaction tank is preferably stirred by a second mechanical stirring device at a stirring speed of 300rpm to 500rpm.

[0049] In step S5, the coagulant and the flocculant are added in conventional amounts. In addition, when polyaluminium chloride solution is used as the coagulant, the mass percentage of the polyaluminium chloride solution can be 30%. The mass percentage of the polyacrylamide solution used as the flocculant can be 1‰ to 3‰.

[0050] In order to make the objects, advantages and features of the present invention more clear, the present invention is further described in detail below in conjunction with several specific embodiments.

[0051] <Example 1>

[0052] The treatment object of this embodiment is the desulfurization wastewater of a power plant, the water output of the power plant is about 12t / d. At room temperature, the pH of the desulfurization wastewater is about 6.2, the thallium content is 340μg / L, and the ammonia nitrogen content is 162mg / L.

[0053] The Environmental Protection Bureau in the area where the power plant is located requires that the thallium content of the treated effluent be controlled below 5μg / L, and the ammonia nitrogen content of the effluent be controlled below 30mg / L.

[0054] Water treatment process:

[0055] Step S1, discharge the wastewater into the regulating tank, and use sodium hydroxide aqueous solution to adjust the pH of the wastewater to about 11.5 at room temperature.

[0056] Step S2: the wastewater treated in step S1 is heated to 2 m 3 / h flow rate into the first reaction tank, and make the mass percentage of 20% sodium hypochlorite solution according to 0.0142m 3 / h flow into the first reaction tank, and the first mechanical stirring device is controlled to operate at a speed of 300rpm. In this step, the residence time of the wastewater in the first reaction tank is 18min, that is, the reaction time in this step is 18min.

[0057] Step S3: the wastewater treated in step S2 is heated to 2 m 3 / h flow rate into the second reaction tank, and the mass percentage of 5% potassium ferrate solution at 0.008m 3 / h flow into the second reaction tank, and the second mechanical stirring device is controlled to operate at a speed of 350rpm. In this step, the residence time of the wastewater in the second reaction tank is 20min, that is, the reaction time of this step is 20min.

[0058] Step S4: the wastewater treated in step S3 is heated to 2 m 3 / h flow rate into the equalization tank, and high-quality hydrochloric acid is used to adjust the pH of the wastewater to about 9 at room temperature.

[0059] Step S5: subjecting the wastewater treated in step S4 to a temperature of 2 m 3 / h flow into the inclined plate sedimentation tank, and add polyaluminium chloride solution and polyacrylamide solution into the wastewater. The mass percentage of the polyaluminium chloride solution used in this step is 30%, and the mass percentage of the polyacrylamide solution is 2‰.

[0060] After the above treatment, the thallium content in the power plant's effluent was stabilized at around 4μg / L, and the ammonia nitrogen content was between 23mg / L and 27mg / L, meeting the requirements of the local Environmental Protection Bureau.

[0061] <Example 2>

[0062] The treatment object of this embodiment is the sintering wastewater of a steel plant. The water output of the steel plant is about 18t / d. At room temperature, the pH of the sintering wastewater is about 1.2, the thallium content is 2740μg / L, and the COD content is 450mg / L~480mg / L.

[0063] The Environmental Protection Bureau in the area where the steel plant is located requires that the thallium content of the treated effluent be controlled below 5μg / L, and the COD content of the effluent be controlled below 200mg / L.

[0064] Water treatment process:

[0065] Step S1, discharge the wastewater into the regulating tank, and use sodium hydroxide aqueous solution to adjust the pH of the wastewater to about 10.5 at room temperature.

[0066] Step S2: subjecting the wastewater treated in step S1 to a temperature of 5 m 3 / h flow rate into the first reaction tank, and make the mass percentage of 15% sodium hypochlorite solution according to 0.512m 3 / h flow rate into the first reaction tank, and the first mechanical stirring device is controlled to operate at a speed of 400rpm. In this step, the residence time of the wastewater in the first reaction tank is 20min, that is, the reaction time in this step is 20min.

[0067] Step S3: subjecting the wastewater treated in step S2 to a temperature of 5 m 3 / h flow rate into the second reaction tank, and the mass percentage of 10% potassium ferrate solution at 0.140m 3 / h flow into the second reaction tank, and the second mechanical stirring device is controlled to operate at a speed of 350rpm. In this step, the residence time of potassium ferrate solution in the wastewater is 23min, that is, the reaction time of this step is 23min.

[0068] Step S4: subjecting the wastewater treated in step S3 to a temperature of 5 m 3 / h flow rate into the equalization tank, and high-quality hydrochloric acid is used to adjust the pH of the wastewater to about 8.5 at room temperature.

[0069] Step S5: subjecting the wastewater treated in step S4 to a temperature of 5 m 3 / h flow into the inclined plate sedimentation tank, and add polyaluminium chloride solution and polyacrylamide solution into the wastewater. The mass percentage of the polyaluminium chloride solution used in this step is 30%, and the mass percentage of the polyacrylamide solution is 1‰.

[0070] After the above treatment, the PH value of the effluent from the steel plant at room temperature fluctuates between 9-10, and the average thallium content is 21.4μg / L~3.5μg / L, and the COD content is 180mg / L~195mg / L, meeting the requirements of the local Environmental Protection Bureau.

[0071] <Example 3>

[0072] The treatment object is the sintering wastewater of a steel plant, which has a water storage capacity of 80t / d. At room temperature, the pH of the sintering wastewater is about 2.3, the thallium content is 4796μg / L, the ammonia nitrogen content is about 65mg / L, and the COD content is 130mg / L~150mg / L.

[0073] The local Environmental Protection Bureau requires that the thallium content of the steel plant's effluent should not be higher than 2μg / L, the ammonia nitrogen content should be lower than 20mg / L, and the COD content should be lower than 200mg / L.

[0074] Processing process:

[0075] Step S1, allowing the wastewater to enter the regulating tank, and using slaked lime solution to adjust the pH of the wastewater to about 11 at room temperature.

[0076] Step S2: the wastewater treated in step S1 is heated to 8 m 3 / h flow rate into the first reaction tank, and the mass percentage of 30% sodium hypochlorite solution at 1.525m 3 / h flow rate into the first reaction tank, and the first mechanical stirring device is operated at a speed of 500rpm. In this step, the residence time of the wastewater in the first reaction tank is 18min, so that the reaction time of this step is 18min.

[0077] Step S3: the wastewater treated in step S2 is heated to 8 m 3 / h flow rate into the second reaction tank, and the mass percentage of 10% potassium ferrate solution at 0.455m 3 / h flow rate into the second reaction tank, and the second mechanical stirring device is operated at a speed of 450rpm. In this step, the residence time of the wastewater in the second reaction tank is 25min, so that the reaction time of this step is 25min.

[0078] Step S4: subjecting the wastewater treated in step S3 to 8 m 3 / h flow rate into the equalization tank, and hydrochloric acid is used to adjust the pH of the wastewater to about 9.5 at room temperature.

[0079] Step S5: subjecting the wastewater treated in step S4 to 8 m 3 / h flow into the inclined plate sedimentation tank, and add polyaluminium chloride solution and polyacrylamide solution into the inclined plate sedimentation tank. The mass percentage of the polyaluminium chloride solution used in this step is 30%, and the mass percentage of the polyacrylamide solution is 3‰.

[0080] After the above treatment, the PH value of the effluent from the steel plant at room temperature is maintained between 9-10, the average thallium content is 1.1μg / L~1.5ug / L, the average ammonia nitrogen content is 15mg / L~18mg / L, and the COD content is evaluated to be 180mg / L~195mg / L, which meets the local environmental protection requirements.

[0081] Although the present invention is disclosed as above, it is not limited thereto. Those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A thallium removal agent kit for water treatment, characterized in that: include: Sodium hypochlorite solution, potassium ferrate solution, pH regulator, coagulant and flocculant; Calculated in mass percentage, the concentration of the sodium hypochlorite solution is 15% to 30%, and the concentration of the potassium ferrate solution is 3% to 10%.

2. The thallium removal agent kit for water treatment according to claim 1, characterized in that: The coagulant is a polyaluminium chloride solution, and the mass percentage of the polyaluminium chloride solution is 30%.

3. The thallium removal agent kit for water treatment according to claim 1, characterized in that: The coagulant is polyferric sulfate.

4. The thallium removal agent kit for water treatment according to claim 1, characterized in that: The flocculant is a polyacrylamide solution, and the mass percentage of the polyacrylamide solution is 1‰ to 3‰.

5. The thallium removal agent kit for water treatment according to claim 1, characterized in that: The pH adjuster includes a first pH adjuster and a second pH adjuster, wherein the first pH adjuster includes an alkaline compound and the second pH adjuster includes an acidic compound.

6. A water treatment method, characterized in that: include: Step S1, using a pH regulator to adjust the pH of the wastewater so that the pH of the wastewater at room temperature is 10.5-11.5; Step S2, adding sodium hypochlorite solution to the wastewater treated in step S1 and stirring, wherein the mass percentage of the sodium hypochlorite solution is 15% to 30%; Step S3, adding potassium ferrate solution to the wastewater treated in step S2 and stirring, wherein the mass percentage of the potassium ferrate solution is 3% to 10%; Step S4, using a pH regulator to adjust the pH of the wastewater treated in step S3 so that the pH of the wastewater at room temperature is 8.5 to 9.5; Step S5, adding coagulant and flocculant to the wastewater treated in step S4.

7. The water treatment method according to claim 6, characterized in that: The step S1, the step S2, the step S3, the step S4 and the step S5 are performed in different containers.

8. The water treatment method according to claim 6 or 7, characterized in that: The pH of the wastewater adjusted in step S1 at room temperature is 11, and the pH of the wastewater adjusted in step S4 at room temperature is 9.

9. The water treatment method according to claim 6, characterized in that: The stirring speed in step S2 is 300 rpm to 500 rpm, and the reaction time is 15 min to 20 min; the stirring speed in step S3 is 300 rpm to 500 rpm, and the reaction time is 20 min to 25 min.

10. The water treatment method according to claim 6, characterized in that: Assuming that the thallium content in the wastewater is 1500 μg / L and the volume of the wastewater is 1 L, the volume of the sodium hypochlorite solution added in step S2 is 30 mL to 60 mL, and the volume of the potassium ferrate solution added in step S3 is 10 mL to 18 mL.