A water purification agent with post-adjusted basicity, its preparation method and application

Abstract

This invention relates to a water purification agent with post-adjusted basicity, its preparation method, and its application, belonging to the field of water purification agent technology. The invention provides a method for preparing a water purification agent with post-adjusted basicity, the specific steps of which are: adding a regulator to a water purification agent to obtain a water purification agent with post-adjusted basicity; wherein the water purification agent is an iron salt solution, specifically FeCl3 solution, and the regulator is aluminum citrate solution; or the water purification agent is an aluminum salt solution, and the regulator is at least one of an organic acid and dilute hydrochloric acid. This invention, through the method of post-adjusting basicity, changes the basicity of the water purification agent system, thereby improving the utilization rate of the water purification agent. The prepared water purification agent with post-adjusted basicity ensures water quality treatment effect and stability, and reduces the dosage, thereby reducing the cost of the reagent. In high-alkalinity water bodies, the hydrolysis rate decreases by 50%, and the reagent utilization rate increases to 88%.

Description

Technical Field

[0001] This invention relates to the field of water purification agent technology, specifically to a water purification agent with post-adjusted basicity, its preparation method, and its application. Background Technology

[0002] Currently, existing polyaluminum chloride (PAC) is generally produced by reacting aluminum hydroxide or bauxite with hydrochloric acid solution (synthetic hydrochloric acid or by-product hydrochloric acid) under certain temperature and pressure to obtain an aluminum chloride solution. Then, calcium aluminate powder is added to adjust the basicity and initiate a polymerization reaction to generate PAC. Basicity is a characterization of the degree of polymerization of PAC; generally, the higher the basicity, the higher the degree of polymerization of PAC, resulting in stronger adsorption capacity during water treatment. When treating low-temperature, low-turbidity water, high-basicity PAC is more effective and requires less dosage, thus reducing operating costs and achieving better effluent quality (lower turbidity).

[0003] Calcium aluminate powder is used to adjust the basicity of polyaluminum chloride (PAC). The maximum basicity of PAC should not exceed 80%; otherwise, the reaction solution will be difficult to filter, and the water-insoluble content in the product will fail to meet national standards. Currently, many high-basicity (90%) products on the market are produced using so-called slurry spray drying or drum drying methods, resulting in products with high impurity content, particularly water-insoluble content, which fails to meet national standards.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a water purification agent with post-adjusted basicity, its preparation method, and its application. This invention, through a post-adjustment method, alters the basicity of the water purification agent system, thereby improving the agent's utilization rate. The resulting post-adjusted basicity water purification agent ensures water treatment effectiveness and stability while reducing dosage and thus lowering reagent costs. In high-alkalinity water (total alkalinity > 300 mg / L CaCO3), the hydrolysis rate decreases by 50%, and the reagent utilization rate increases to 88%.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: The first objective of this invention is to provide a method for preparing a water purification agent with post-adjusted basicity, the specific steps of which are: adding a regulator to the water purification agent to obtain a water purification agent with post-adjusted basicity; The water purification agent is an iron salt solution, specifically an FeCl3 solution, and the regulator is an aluminum citrate solution; Alternatively, the water purifier may be an aluminum salt solution, and the regulator may be at least one of an organic acid or dilute hydrochloric acid.

[0007] The beneficial effects of this invention are as follows: By adjusting the basicity of the water treatment agent system, the basicity of the water treatment agent system is changed, thereby improving the utilization rate of the water treatment agent. The resulting water treatment agent with adjusted basicity ensures the water quality treatment effect and stability, and reduces the dosage, thus reducing the cost of the agent. In high-alkalinity water (total alkalinity > 300 mg / L CaCO3), the hydrolysis rate decreases by 50%, and the agent utilization rate increases to 88%.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the aluminum content in the aluminum citrate solution is 8%~12% by mass, and the iron content in the FeCl3 solution is 10%~14% by mass; the mass ratio of the FeCl3 solution to the aluminum citrate solution is 1:2~4.

[0010] Furthermore, the aluminum citrate solution contains 10% aluminum by mass, the FeCl3 solution contains 12% iron by mass, and the mass ratio of the FeCl3 solution to the aluminum citrate solution is 1:3.

[0011] The beneficial effect of adopting the above-mentioned further scheme is that citric acid acts as a "molecular bridge" to simultaneously complex Al. 3+ with Fe 3+ This forms an Al-Fe-Citrate ternary complex, whose hydrolysis energy barrier is 2.3 times higher than that of a single aluminum salt. Citrate complexes with Al... 3+ Inhibiting hydroxyl bridging, thereby delaying hydrolysis; Fe 3+ It provides charge neutralization compensation, enhancing flocculation efficiency.

[0012] Furthermore, the aluminum citrate solution is prepared by reacting sodium citrate solution with aluminum sulfate solution.

[0013] Furthermore, the molar ratio of sodium citrate in the sodium citrate solution to aluminum sulfate in the aluminum sulfate solution is 1:1.2~1.3.

[0014] Furthermore, the molar ratio of sodium citrate in the sodium citrate solution to aluminum sulfate in the aluminum sulfate solution is 1:1.2.

[0015] Furthermore, after adding the regulator, an alkaline solution needs to be added dropwise to adjust the basicity of the water purification agent.

[0016] Furthermore, the basicity of the water purification agent with adjusted basicity is 58%~62%.

[0017] Furthermore, the alkaline solution is an alkali metal hydroxide solution with a molar concentration of 1.0 mol / L to 1.5 mol / L.

[0018] Furthermore, the molar concentration of the alkaline solution is 1.25 mol / L.

[0019] Furthermore, the alkaline solution is preferably a sodium hydroxide solution or a potassium hydroxide solution.

[0020] Furthermore, when the regulator is at least one of organic acid and dilute hydrochloric acid, after the regulator is added, the pH of the water purification agent with adjusted basicity is 2.5~4.5 and the basicity is 5%~50%.

[0021] The beneficial effect of adopting the above-mentioned further solutions is that the acidic environment inhibits OH-. - Pre-reaction with metal ions ensures the retention of active components.

[0022] A second objective of this invention is to provide a water purification agent with post-adjusted basicity.

[0023] The beneficial effects of this invention are: the prepared water purification agent with adjusted basicity ensures water treatment effect and stability, and reduces the dosage, thereby reducing the cost of the agent. In high-alkalinity water (total alkalinity > 300 mg / L CaCO3), the hydrolysis rate decreases by 50%, and the agent utilization rate increases to 88%.

[0024] The third objective of this invention is the application of a post-adjusted basicity water purification agent, which is used in the treatment of produced water from high-alkalinity oilfields.

[0025] The beneficial effects of this invention are: the water purification agent of this invention reduces the hydrolysis rate by 50% in high alkalinity water (total alkalinity > 300 mg / L CaCO3) and increases the agent utilization rate to 88% (compared to ≤ 75% by traditional methods). Attached Figure Description

[0026] Figure 1 The Zeta potential bar chart and electrophoretic mobility charts of the water purification agents of Example 1 and Comparative Example 2 of this invention are shown. Figure 2 This is a Zeta potential distribution diagram of the water purification agents of Example 1 and Comparative Example 2 of the present invention. Detailed Implementation

[0027] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] Example 1: Preparation of a water purification agent with post-adjusted basicity (1) Sodium citrate solution and aluminum sulfate solution are mixed and reacted. The molar ratio of sodium citrate in sodium citrate solution to aluminum sulfate in aluminum sulfate solution is 1:1.2, yielding Al. 3+ A 10% (w / w) aluminum citrate solution; (2) Add Fe to aluminum citrate solution 3+ A 12% FeCl3 solution was prepared to achieve a 3:1 mass ratio of aluminum citrate to FeCl3. Then, 5% NaOH solution was added dropwise to adjust the basicity to 60%, resulting in a water purification agent with post-adjusted basicity.

[0029] Example 2: Preparation of a water purification agent with adjusted basicity (Part 2) Take industrial-grade PAC with a basicity of 70% and an Al2O3 content of 28%, add 0.8wt% citric acid solution, and stir until pH=3.8 and basicity 20% to obtain a water purification agent with adjusted basicity.

[0030] Example 3: Preparation of a water purification agent with post-adjusted basicity (Part 3) (1) Sodium citrate solution and aluminum sulfate solution are mixed and reacted. The molar ratio of sodium citrate in sodium citrate solution to aluminum sulfate in aluminum sulfate solution is 1:1.3, yielding Al. 3+ A 12% (w / w) aluminum citrate solution; (2) Add Fe to aluminum citrate solution 3+ A 10% FeCl3 solution was prepared to achieve a 2:1 mass ratio of aluminum citrate to FeCl3. Then, 5% NaOH solution was added dropwise to adjust the basicity to 58%, resulting in a water purification agent with adjusted basicity.

[0031] Example 4: Preparation of a water purification agent with post-adjusted basicity (Part 4) (1) Sodium citrate solution and aluminum sulfate solution are mixed and reacted. The molar ratio of sodium citrate in sodium citrate solution to aluminum sulfate in aluminum sulfate solution is 1:1.2, yielding Al. 3+ A 10% (w / w) aluminum citrate solution; (2) Add Fe to aluminum citrate solution 3+ A 10% FeCl3 solution was prepared to achieve a 4:1 mass ratio of aluminum citrate to FeCl3. Then, 5% NaOH solution was added dropwise to adjust the basicity to 62%, resulting in a water purification agent with post-adjusted basicity.

[0032] Example 5: Preparation of a water purification agent with adjusted basicity (Part 5) Take industrial-grade PAC with a basicity of 70% and an Al2O3 content of 28%, add 0.8wt% dilute hydrochloric acid solution, and stir until pH=2.5 and basicity 8% to obtain a water purification agent with adjusted basicity.

[0033] Example 6: Preparation of a water purification agent with post-adjusted basicity (Part 6) Take industrial-grade PAC with a basicity of 70% and an Al2O3 content of 28%, add 0.8wt% organic acid solution, and stir until pH=4.5 and basicity 50% to obtain a water purification agent with adjusted basicity.

[0034] Comparative Example 1: Preparation of a water purification agent with adjusted basicity The only difference between this comparative example and Example 1 is that the molar ratio of sodium citrate to aluminum sulfate in step (1) is 1:1, while the other conditions and steps are the same as in Example 1.

[0035] Comparative Example 2: Preparation of a water purification agent with adjusted basicity The only difference between this comparative example and Example 1 is that FeCl3 solution was not added in step (2), while the other conditions and steps are the same as in Example 1.

[0036] Comparative Example 3: Preparation of a water purification agent with adjusted basicity The only difference between this comparative example and Example 1 is that in step (2), the basicity is first adjusted to 60% by adding 5% NaOH solution dropwise, and then Fe is added to the aluminum citrate solution. 3+ A water purification agent with adjusted basicity was obtained by preparing a 12% FeCl3 solution with an aluminum citrate:FeCl3 mass ratio of 3:1.

[0037] Comparative Example 4: Preparation of a water purification agent with post-adjusted basicity The only difference between this comparative example and Example 2 is that the citric acid solution is replaced with a hydrochloric acid solution of the same concentration; all other conditions and steps are the same as in Example 2.

[0038] Comparative Example 5: Preparation of a water purification agent with adjusted basicity The only difference between this comparative example and Example 2 is that the pH was adjusted to 4.8; all other conditions and steps were the same as in Example 2.

[0039] Performance testing: 1. Structural characterization The water purification agent prepared in Example 1 was freeze-dried to obtain a Fe-Al-citric acid solid complex. The structure of the Fe-Al-citric acid solid complex was characterized as follows: To obtain the Fe-Al-citric acid solid complex powder for solid characterization, the liquid water purification agent prepared in Example 1 was freeze-dried. The specific steps are as follows: (1) Pre-freezing treatment: The water purification agent of Example 1 was placed in an ultra-low temperature freezer at -80℃ and rapidly frozen for 4 hours until it formed a completely solid state; (2) Freeze drying: cold trap temperature: -55℃, vacuum degree: <10 Pa, heat up to -25℃ and hold for 24 hours, purpose: sublime to remove most of the free water; then desorb and dry, slowly heat up to 25℃ and hold for 12 hours to completely remove the bound water to obtain a loose and porous light yellow to yellowish brown solid powder, which is stored in a desiccator for later use.

[0040] a. Zeta potential test The testing instrument was a Malvern nanoparticle size and Zeta potential analyzer (Malvern Zetasizer Nano ZS series). The specific testing steps are as follows: The water purification agent with post-adjusted basicity prepared in Example 1 and the water purification agent with post-adjusted basicity prepared in Comparative Example 1 were diluted with produced water from the Shengli Oilfield to be treated (or a NaCl solution simulating its ionic strength) to ensure that the sample conductivity was within the optimal measurement range of the instrument (usually 1-20 mS / cm) and that the concentration was appropriate to avoid multiple scattering. Concentration requirements: It is recommended that the dilution factor be such that the concentration of the effective component (Al+Fe) of the water purification agent is 10-50 mg / L. Equilibration treatment: The diluted sample was placed in a constant temperature water bath at 25℃ for at least 10 minutes to equilibrate. Test parameters were set as follows: temperature 25.0 ± 0.1℃; equilibration time 60 seconds; measurement mode was set to automatic mode (the instrument automatically determines the voltage and the number of measurements). Each sample was measured 3-5 times consecutively, and the average value was taken. The instrument software automatically calculates and reports the Zeta potential (mV) and electrophoretic mobility based on the Smoluchowski or Hückel model (selected according to particle size and medium conditions), as shown in the following figures. Figure 1 , Figure 2 As shown.

[0041] Depend on Figure 1 , Figure 2 It can be seen that: the average zeta potential of the water purification agent with adjusted basicity in Example 1 is +35.8mV, while that of aluminum citrate alone is +28.1mV), Fe 3+ Enhances charge neutralization capacity.

[0042] b. Coagulation effect evaluation (beaker test): Based on the industry standard "Evaluation Method for Coagulation Performance of Water Treatment Agents", the hydrolysis rate is determined (for high-alkalinity water bodies). The rate of pH change of the solution over time after dosing is monitored, and the hydrolysis rate is compared relative to the initial dpH / dt value. The agent utilization rate is determined using the residual aluminum determination method. The water purification agent with post-adjusted basicity in Example 1 showed a 50% decrease in hydrolysis rate and an increase in agent utilization rate to 88% in high-alkalinity water (total alkalinity > 300 mg / L CaCO3).

[0043] 2. Oilfield produced water treatment Produced water from a block of Shengli Oilfield was treated with the post-basicity-adjusting water purification agents of Example 1 and Comparative Example 1. The characteristics of the produced water were: oil content 152 mg / L, total alkalinity 420 mg / L (calculated as CaCO3), and suspended solids 280 mg / L. 80 mg / L of the water purification agent prepared in Example 1 and 100 mg / L of the post-basicity-adjusting water purification agent of Comparative Example 1 were added to the produced water, respectively. The temperature was kept constant at 25±1℃, and the stirring program was 200 rpm / 2 min + 40 rpm / 15 min. After standing for 30 min, samples were taken, and the time for complete hydrolysis in both groups was recorded. The oil removal rate, SS removal rate, and sludge amount of each group after complete hydrolysis were also measured. Each experiment was repeated in triplicate, and the RSD was <5%.

[0044] (1) Determination of complete hydrolysis time: The Ferron time-by-time complexation colorimetric method was used; the time corresponding to the change rate of active aluminum concentration < 5% at three consecutive time points is the complete hydrolysis time. (2) The oil removal rate was detected by infrared spectrophotometry (SY / T 0530-2011), and the calculation formula is as follows: oil removal rate (%) = (oil content in raw water - oil content after treatment) / oil content in raw water × 100%; where the oil content in raw water is 152 mg / L; (3) The gravimetric method (GB / T 11901-1989) was used to test the removal rate of suspended solids. The calculation formula is as follows: SS removal rate (%) = (SS concentration in raw water - SS concentration after treatment) / SS concentration in raw water × 100%, where the SS concentration in raw water is 280 mg / L. (4) The sludge quantity was tested. First, the volume was measured using the graduated cylinder sedimentation method, and the mass was measured using the drying and weighing method. The calculation formula is as follows: Dry sludge quantity (mg / L) = (sludge mass - container mass) × 10 6 (water sample volume), the results are shown in Table 1: Table 1. Performance test results of water purification agents in each embodiment and comparative example. From Table 1, we can obtain: (1) In high-alkalinity water (total alkalinity > 300 mg / L CaCO3), Example 1 showed a 14.5% increase in oil removal rate, a 13.8% increase in SS removal rate, a 167% increase in hydrolysis time, and a -43% reduction in sludge volume compared to Comparative Example 1, which used a post-adjusted basicity water purifier. Example 1 achieved a better removal rate and less sludge volume at a lower dosage due to the citric acid complexation that delayed hydrolysis. The reasons for the sludge reduction were: ① reduced dosage; ② inhibition of excessive aluminum hydroxide precipitation, resulting in denser flocs. Through the above tests and calculations, the advantages of the post-adjusted basicity water purifier in slow-release synergistic effect and sludge reduction can be quantitatively verified.

[0045] (2) The proportion of sodium citrate in Comparative Example 1 was relatively increased, compared with Al 3+ The complexation is stronger and more stable, leading to excessive inhibition of the subsequent hydrolysis process. When treating high-alkalinity water, floc formation will be abnormally slow, the coagulation and destabilization effect will be poor, resulting in a significantly lower COD and suspended solids removal rate than in Example 1. This proves that a 1:1.2 ratio is the optimal balance between "slow release" and "effective flocculation".

[0046] (3) The water purification agent obtained in Comparative Example 2 lacks Fe 3+ The "instantaneous charge neutralization compensation" results in a significantly lower zeta potential compared to the product of Example 1 (potentially below +30mV). When treating negatively charged colloidal systems (such as oily wastewater), the initial destabilization capacity is insufficient, requiring higher dosages to achieve the same effect. Furthermore, the floc structure is loose, sludge settling properties deteriorate, and sludge volume increases. This directly demonstrates the effectiveness of Fe... 3+ It plays a key role in enhancing charge neutralization capacity, reducing chemical consumption and sludge volume.

[0047] (4) In Comparative Example 3, increasing the basicity first will cause Al 3+ Pre-hydrolysis forms a partially hydroxyaluminum polymer. Fe is then added at this point. 3+ The two substances are difficult to combine uniformly at the molecular level, which may lead to local precipitation or the formation of heterogeneous polymers. Product stability decreases (due to increased precipitation), and coagulation performance fluctuates greatly. In high-alkalinity water, the reproducibility of its slow-release effect and water treatment effect will be inferior to Example 1. This demonstrates that the process sequence of "compounding first, then adjusting alkali" is crucial for forming a stable, uniform, and efficient Al / Fe / citric acid composite system.

[0048] (5) In Comparative Example 4, hydrochloric acid only provides H+. + While it acts as an acidifier, it has absolutely no complexing ability. The resulting product is merely a more acidic form of ordinary PAC. When treating highly alkaline water, its hydrolysis rate is extremely fast, and the floc formation time will be similar to that of ordinary PAC (approximately 8 minutes), failing to achieve the "extended to 17 minutes" slow-release effect described in Example 2. Its COD removal rate will drop back to a level comparable to that of ordinary PAC (approximately 76%). This strongly demonstrates that the unique complexing effect of citrate is the fundamental reason for the performance improvement (slow release, enhanced efficiency), rather than simply pH adjustment.

[0049] (6) In Comparative Example 5, the amount of citric acid added was insufficient, which affected the Al content in PAC. 3+The complexation modification effect is insufficient. The product's sustained-release performance is only slightly improved (floc formation time may only be extended to 10-12 minutes), and the improvement effect on COD removal rate is limited (may only reach 80-82%). This indicates that pH=3.8 (corresponding to a specific amount of citric acid) is a key point to achieve the best complexation modification effect; if the acidity is too low (insufficient addition), the effect will be reduced.

[0050] In summary, this invention improves the utilization rate of water purification agents by adjusting the basicity of the water purification agent system. The resulting water purification agent with adjusted basicity ensures water treatment effect and stability, and reduces the dosage, thereby lowering the cost of the agent.

[0051] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a water purifying agent for post-adjustment of base, characterized by, The specific steps are as follows: Add a regulator to the water purification agent to obtain a water purification agent with adjusted basicity; The water purification agent is an iron salt solution, specifically an FeCl3 solution, and the regulator is an aluminum citrate solution; Alternatively, the water purification agent may be an aluminum salt solution, and the regulator may be at least one of an organic acid or dilute hydrochloric acid; The aluminum citrate solution contains 8% to 12% aluminum by mass, and the FeCl3 solution contains 10% to 14% iron by mass; the mass ratio of the FeCl3 solution to the aluminum citrate solution is 1:2 to 4. After adding the regulator, an alkaline solution also needs to be added dropwise to adjust the basicity of the water purification agent; The basicity of the water purification agent after adjusting the basicity is 58%~62%; When the regulator is at least one of organic acid and dilute hydrochloric acid, after the regulator is added, the pH of the water purification agent with adjusted basicity is 2.5~4.5 and the basicity is 5%~50%.

2. The method of claim 1, wherein the water purifying agent is prepared by adding the base to the water and then adding the acid to the water. When the water purification agent is FeCl3 solution and the regulator is aluminum citrate solution, the aluminum citrate solution is prepared by reacting sodium citrate solution with aluminum sulfate solution.

3. The method of claim 2, wherein the water purifying agent is prepared by adding the base to the water purifying agent of claim 1. The molar ratio of sodium citrate in the sodium citrate solution to aluminum sulfate in the aluminum sulfate solution is 1:1.2~1.

3.

4. A water purifying agent for post-adjusting the base degree, characterized by Prepared by the preparation method according to any one of claims 1 to 3; The aforementioned post-adjusted basicity water purification agent is used in the treatment of produced water from high-alkalinity oilfields.

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