Flocculating agent compounding method suitable for high temperature and high pH value

Abstract

The invention relates to a compounding method of a flocculant adapting to high temperature and high pH value. The compounding method comprises the following steps: adding biochar into a sodium silicate solution, keeping the pH value of the solution to be 3-5, polymerizing to generate polysilicic acid containing biochar, adding aluminum chloride, keeping the pH value of the solution to be 8-10, stirring and reacting for 2 hours, and drying to obtain the composite flocculant for high temperature and high pH value. The use environment of the flocculant in the prior art is mostly acidic, flocculation effect reduction and failure are easy to occur under the alkaline condition, and the flocculant suitable for alkaline and high-temperature use conditions is prepared aiming at the two conditions that the use temperature of the flocculant in the prior art is mostly 5-20 DEG C and the stability of the flocculant becomes poor under the condition that the temperature exceeds 25 DEG C; the preparation method is simple, low in cost and suitable for being self-made in basic water plants.

Description

Technical Field

[0001] The invention relates to the field of flocculant production, in particular to a flocculant compounding method adaptable to high temperature and high pH value. Background Art

[0002] The research project on the influence of raw water pH on the aluminum index of factory water and control measures aims to improve the existing flocculant components, adapt to the changes of raw water high temperature and high pH index, and ensure that the excess aluminum in the factory water is controlled within the range of drinking water hygiene standards. The main components of existing flocculants are polyacrylamide with different polymerization degrees and different ionic degrees, which are divided into anionic, cationic, and modified zwitterionic types. In practical applications, the type of flocculant needs to be selected according to the actual situation of the water body to be treated. The sources of the main components of flocculants are inorganic and organic. Among them, inorganic salts include iron salts, aluminum salts, polyaluminum chloride, etc., which are rapidly hydrolyzed in water and release multivalent metal ions, and form colloids with other ions and particles in water to achieve the purpose of flocculation. The present invention uses existing flocculants for compounding, and combines the use method to ensure that it is suitable for the changes of raw water high temperature and high pH index, and ensure that the excess aluminum in the factory water is controlled within the range of drinking water hygiene standards. 。 Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention provides a flocculant compounding method that is adaptable to high temperature and high pH value. The present invention optimizes the water treatment performance under high temperature and high pH environment, while reducing the use of chemical agents and reducing environmental impact.

[0004] To achieve the above objectives, the present invention is implemented through the following technical scheme: a method for compounding a flocculant that adapts to high temperature and high pH value, comprising the following steps: adding biochar to a sodium silicate solution, maintaining the solution pH at 3-5, polymerizing to generate polymerized silicate containing biochar, adding aluminum chloride, maintaining the solution pH at 8-10, stirring the reaction for 2 hours, and drying to obtain a composite flocculant for high temperature and high pH.

[0005] Moreover, the weight ratio of sodium silicate to biochar is 1:0.3.

[0006] Moreover, the molar ratio of sodium silicate:aluminum chloride or aluminum hydroxide is 1:1.

[0007] Moreover, the biochar is magnetic biochar.

[0008] Furthermore, the addition of phosphoric acid maintains the solution pH at 3-5.

[0009] The present invention provides the following beneficial effects:

[0010] 1. The use environment of flocculants in the prior art is mostly acidic. Under alkaline conditions, the flocculation effect is easily reduced and failure occurs. With regard to temperature, the use temperature of flocculants in the prior art is mostly 5-20°C. When the temperature exceeds 25°C, the stability of the flocculant deteriorates. In view of the above two situations, the present invention prepares a flocculant suitable for alkaline and high temperature conditions. The preparation method is simple, the cost is low, and it is suitable for self-production by grassroots water plants.

[0011] 2. The present invention increases or reduces the residual Al by adding activated carbon. The present invention helps water supply companies establish a water quality early warning mechanism by summarizing the pH change pattern of the source water of the South-to-North Water Diversion Project and the corresponding change pattern of the residual aluminum in the factory water.

[0012] 3. According to the water treatment process conditions of the local water supply enterprise, the present invention proposes effective control measures for excess aluminum in factory water under high pH raw water conditions, so as to save project investment as much as possible, reasonably control operating costs, and ensure safe and high-quality water supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Working for the six-in-one mixing instrument.

[0014] Figure 2 Let stand for 30 minutes before adding the reagent.

[0015] Figure 3 It is the average value of the residual aluminum concentration of S-1 three times.

[0016] Figure 4 It is the average value of the residual aluminum concentration of S-2 three times.

[0017] Figure 5 Let stand for 30 minutes before adding the reagent.

[0018] Figure 6 This is the relationship between the concentrations of S-1 and S-2 and the residual aluminum. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The embodiment of the present invention provides a method for compounding a flocculant that is adapted to high temperature and high pH value, comprising the following steps: adding biochar (straw-based) to a sodium silicate solution, adding phosphoric acid to maintain the solution pH at 3-5, generating polymerized silicate containing biochar after polymerization, adding aluminum chloride, maintaining the solution pH at 8-10, stirring the reaction for 2 hours, and drying to obtain a composite flocculant for high temperature and high pH value. The weight ratio of sodium silicate to biochar is 1:0.3-0.5, and the molar ratio of sodium silicate to aluminum chloride is 1:1-2.

[0021] Biochar (straw-based) is added to the sodium silicate solution, and phosphoric acid is added to maintain the solution pH 3-5. In this step, phosphoric acid modifies the pore size of the biochar on the one hand, and provides an acidic environment on the other hand to complete the polymerization of sodium silicate. When the sodium silicate is polymerized, it is partially polymerized in the space of the biochar. When aluminum is polymerized in the next step, the aluminum is loaded in the pore size of the biochar, so after adsorption, the residual leakage rate is low. Patent document CN113582312A also produces a flocculant containing biochar and polyaluminum silicate, but in the preparation process, it is completed separately as modified biochar, polysilicic acid solution and polyaluminum ferric chloride, and then mixed. There is an effect of reducing Al residue, and it can only complete adsorption, and its purpose is also to reduce COD.

[0022] How to use the composite flocculant: first dissolve it into a 10%-30% solution, then add water to dilute it to the concentration required by different users. Generally, 0.1-3.0kg (1-30ppm) of the agent is added for every 100 tons of turbid water. When the turbidity of the raw water is high, the dosage can be appropriately increased, and when the turbidity is low, the dosage can be appropriately reduced.

[0023] Example 1

[0024] A method for compounding a flocculant suitable for high temperature and high pH value, comprising the following steps: adding biochar (straw-based) to a sodium silicate solution, adding phosphoric acid to maintain the solution pH at 3-5, generating polymerized silicate containing biochar after polymerization, adding aluminum chloride or aluminum hydroxide, maintaining the solution pH at 8-10, stirring the reaction for 2 hours, and drying to obtain a composite flocculant for high temperature and high pH value. The weight ratio of sodium silicate to biochar is 1:0.3, and the molar ratio of sodium silicate to aluminum chloride or aluminum hydroxide is 1:1. It is designated as S-1 model.

[0025] Example 2

[0026] A flocculant compounding method adapted to high temperature and high pH value comprises the following steps: adding phosphoric acid to a sodium silicate solution to maintain the solution pH at 3-5, generating polymerized silicate containing biochar after polymerization, adding aluminum chloride, maintaining the solution pH at 8-10, stirring and reacting for 2 hours, and drying to obtain a composite flocculant for high temperature and high pH value. The weight ratio of sodium silicate to biochar is 1:0.3, and the molar ratio of sodium silicate to aluminum chloride or aluminum hydroxide is 1:1. It is recorded as S-2 model.

[0027] Example 3

[0028] A method for compounding a flocculant adapted to high temperature and high pH value, comprising the following steps: adding magnetic biochar (straw-based) to a sodium silicate solution, adding phosphoric acid to maintain the solution pH at 3-5, generating polymerized silicate containing biochar after polymerization, adding aluminum chloride, maintaining the solution pH at 8-10, stirring the reaction for 2 hours, and drying to obtain a composite flocculant for high temperature and high pH value. The weight ratio of sodium silicate to biochar is 1:0.3, and the molar ratio of sodium silicate to aluminum chloride or aluminum hydroxide is 1:1. The iron residue in Example 3 is reduced by 70% compared with the example, and Al remains the same.

[0029] The other models are commercially available flocculants and are subject to the manufacturer’s code.

[0030] The following is the adding effect experiment of the present invention:

[0031] Phase 1:

[0032] Take natural inlet water without adjusting the pH value, fix the dosage (the specific value needs to be determined from the production and operation data provided by the main business), add reagents from different manufacturers to 6 identical water samples respectively, coagulate, stir and let stand, then take the supernatant to measure the residual aluminum, turbidity and pH value.

[0033] According to the experimental results, 2-3 drugs are selected from the 6 drugs as the drugs for subsequent experiments. The number of experiments is adjusted according to the results.

[0034] Experimental drugs: S-1 drug, BJHQ drug, SDLJ drug, S-2 drug, HNSL drug, HNZY drug.

[0035] 1. Table 1. Raw water related parameters

[0036] Water collection time 9:15 temperature 31.2℃ pH 8.59 Turbidity 2.03NTU

[0037] Experimental procedures

[0038] ① Take 5g of each of the six polyaluminium chloride agents and add them to six 100ml volumetric flasks to make a 5% concentration stock solution for later use.

[0039] ② Take six identical water samples of 1000 ml each, add 0.1 ml of six reagents (water plant dosing concentration: 1000 ml water + 5 mg reagent) and conduct a beaker coagulation experiment;

[0040] ③Simulate the process of dosing stirring and folded plate flocculation and advection sedimentation, set the stirring program: 2min 400r / min; 3min 120r / min, 6min 60r / min; 12min 30r / min; let it stand for 20min, take the supernatant to measure turbidity, residual aluminum and pH value.

[0041] 3. Determination of residual aluminum

[0042] ① Prepare 7 50ml colorimetric tubes, and take 25ml of each of the above six water samples and distilled water as blank controls.

[0043] ② Add 1 drop of p-nitrophenol solution to each tube, mix well and add water until it turns light yellow, add nitric acid solution until the yellow color disappears and then add 2 more drops.

[0044] ③ Add 3 ml of chrome blue S solution, mix, add 1 ml of emulsifier OP solution, 2 ml of CPB solution, 3 ml of buffer solution, dilute to 50 ml with pure water, mix well and let stand for 30 minutes.

[0045] ④ The eight points (at least five) of the standard curve have been drawn, and the standard solution prepared once can be used for three months.

[0046] 5. Measure the absorbance at 620nm wavelength using a 2cm colorimetric tube and the reagent blank as a reference.

[0047] Note: The used colorimetric tube needs to be soaked in acid for more than one day, washed and dried before it can be used next time.

[0048] 4. Experimental results

[0049] Table 2. Phase I trial results

[0050]

[0051]

[0052] 5. Experimental conclusion

[0053] It can be seen that in the first test, the residual aluminum was ranked from small to large as 4<1<5<2<6<3, and the turbidity was ranked from small to large as 6<2<3<1<5<4. In the second test, the residual aluminum was ranked from small to large as 4<5<2<3<1=6, and the turbidity was ranked from small to large as 6=5<4<1<3<2. In the third test, the residual aluminum was ranked from small to large as 2<3<5<6<4<1, and the turbidity was ranked from small to large as 2<3<1<5<4<6. Considering the residual aluminum value first and combining with the comprehensive analysis of turbidity, S-1 and S-2 were selected as the subsequent medications in the second stage.

[0054] 1. Purpose of the experiment

[0055] By controlling the different gradients of raw water pH value, we found the most suitable pH range for the two reagents in the first phase of the test, and provided a basis for the water plant to determine what reagents to add in response to changes in raw water pH.

[0056] 2. Experimental Principle

[0057] For the two agents screened out in the first stage, each of them was used to configure the raw water with different pH gradients in the laboratory to simulate different incoming water qualities. The turbidity and residual aluminum value after coagulation were further analyzed through beaker coagulation experiments to determine the most suitable pH range for each agent to be added, further providing a basis for the water plant to select the type of agent to be added; the residual aluminum after coagulation was measured by the chrome azuro blue S spectrophotometry.

[0058] 3. Experimental Methods

[0059] 1. Go to the water intake of the flow regulating valve of Hengshui Fuyang Water Plant to take raw water samples.

[0060] Table 3. Raw water related parameters

[0061] Water collection time 09：30 temperature 32℃ pH 8.64 Turbidity 2.47NTU

[0062] 1. Prepare pH gradient solution (7.8, 8.0, 8.2, 8.4, 8.6, 8.8)

[0063] ① Use a volumetric flask to prepare 1 mol / L HCl and NaOH standard solutions respectively;

[0064] ② Take two 25L water buckets (each pH water sample in the second stage needs more than 3L) and adjust the pH with standard solution;

[0065] ③After adding an appropriate amount of standard solution, use a portable instrument to measure the pH. After each measurement, rinse the probe with distilled water and wipe it dry with filter paper.

[0066] 2. Conduct the coagulation beaker experiment

[0067] ① Take 1000ml of six pH water samples and add 0.1ml of the same agent (water plant dosing concentration: 1000ml water + 5mg agent)

[0068] ② Set the stirring program: 2 min 400r / min; 3 min 120r / min, 6 min 60r / min; 12 min 30r / min; let it stand for 20 min, take the supernatant to measure turbidity, residual aluminum and pH value. Perform 3 parallel tests to eliminate accidental errors.

[0069] 3. Determination of residual aluminum

[0070] IV. Experimental Results

[0071] Table 4. Phase II trial results

[0072]

[0073]

[0074]

[0075] Experimental experience: Record the volume of standard solution added when adjusting the pH to provide a reference for adjusting the pH in the next experiment.

[0076] Table 5. pH adjustment record

[0077] Target pH Add standard solution Final pH 7.8 0.50ml HCl 7.78 8.0 0.32 ml HCl 8.02 8.2 0.2 ml HCl 8.23 8.4 8.42 8.6 8.57 8.8 0.10mlNaOH 8.77

[0078] Experimental Conclusion

[0079] According to experimental data, the optimal pH value of S-1 is 7.8, and the optimal pH value of S-2 is 8.2. In the third stage, different amounts of reagents are added according to the current pH values.

[0080] Phase 3

[0081] 1. Experimental steps

[0082] 1. Go to the water intake of the flow regulating valve of Hengshui Fuyang Water Plant to take raw water samples.

[0083] Table 6. Raw water related parameters

[0084] Water collection time 9:36 temperature 34℃ pH 8.44 Turbidity 4.13NTU

[0085] 2. Six-joint stirring procedure:

[0086] Table 7. Six-way stirring program

[0087] Procedure Phase Time (min) Speed ​​(r / min) 1 2 400 2 3 120 3 6 60 4 12 30

[0088] 1. Add 0.4ml, 0.5ml, 0.6ml, 0.7ml, 0.8ml, 0.9ml of 5% Yulong (old) and Xianke reagents to a 1L coagulation cup for coagulation and let it settle for 20 minutes. Take the supernatant to measure turbidity, residual aluminum and pH value. Perform 3 parallel tests to eliminate accidental errors.

[0089] 2. Determination of residual aluminum

[0090] 1. Experimental Results

[0091] Table 8. Experimental record table of the third stage①

[0092]

[0093]

[0094] Table 9. Experimental record table of the third stage ②

[0095]

[0096]

[0097] 2. Experimental Conclusion

[0098] Considering the economy, the concentration of the agent is 5%, so the best dosage of S-1 is 5 mg / L when the raw water pH is 7.8. When the raw water pH is 8.2, the residual aluminum content is close when the S-2 dosage is 8 and 9 mg / L, and the residual aluminum content and turbidity of the former are lower than the latter, so the best dosage is 8 mg / L.

[0099] Summary: S-1 is effective and stable, suitable for use in water plants.

[0100] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flocculant compounding method adapted to high temperature and high pH value, characterized in that: The following steps are involved: Biochar is added to the sodium silicate solution to maintain the solution pH at 3-5, and polymerized to generate polysilicic acid containing biochar, and aluminum chloride is added to maintain the solution pH at 8-10, and the reaction is stirred for 2 hours, and dried to obtain a composite flocculant for high temperature and high pH.

2. The method for compounding a flocculant adapted to high temperature and high pH value according to claim 1, characterized in that: The weight ratio of sodium silicate to biochar is 1:0.

3.

3. The method for compounding a flocculant adapted to high temperature and high pH value according to claim 1, characterized in that: The molar ratio of sodium silicate:aluminum chloride or aluminum hydroxide is 1:

1.

4. The method for compounding a flocculant adapted to high temperature and high pH value according to claim 1, characterized in that: The biochar is magnetic biochar.

5. The method for compounding a flocculant adapted to high temperature and high pH value according to claim 1, characterized in that: The phosphoric acid was added to maintain the solution pH at 3-5.

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