Preparation method and application of polysulfuric acid ferric chloride flocculant

Abstract

The invention discloses a preparation method and application of a polyferric sulfate flocculant, and relates to the technical field of industrial waste liquid recycling and sewage treatment. A sulfuric acid replacement method is combined with a negative pressure evaporation method to recover hydrochloric acid in waste liquid, the ratio of chloride ions to sulfate radicals is regulated and controlled, an alkalizer is added into evaporation mother liquor to be heated and dissolved, then oxidizing gas is introduced for oxidation, and red brown liquid, namely the flocculating agent, is prepared after hydrolytic polymerization. The raw materials are wide in source and low in price and cost, special complex operation is not needed in the preparation process, and the preparation method is suitable for industrial production; the prepared polyferric sulfate chloride is applied to phosphorus-containing sewage treatment, and the treatment efficiency is extremely high.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method and application of a polymeric ferric sulfate coagulant, and particularly relates to the technical field of industrial waste liquid resource utilization and sewage treatment. BACKGROUND

[0002] A large amount of strong acid waste liquid containing iron and iron-containing waste residue (more than 25 million tons) are produced in the process of chemical acid etching of cold rolled galvanized and color coated in the metal products industry, which has the characteristics of high iron and high acid content (Fe 2+ : about 50-150 g / L, HCl: about 5%-15%). If it is directly discharged without treatment, its strong acidity will seriously corrode the pipeline equipment, cause soil acidification, groundwater pollution and water eutrophication, and the heavy metal ions in the waste liquid may also be enriched through the food chain, threatening human health. The traditional treatment method (such as alkali neutralization method) not only needs to consume a large amount of alkali agent, which is costly, but also causes waste of resources, and safe disposal and resource utilization are important technical problems faced by the steel industry.

[0003] It can be resourcefully utilized based on the main components of the pickling waste liquid. For example, hydrochloric acid in the waste liquid can be recovered by diffusion dialysis, electrodialysis, negative pressure evaporation and other processes, iron red (Fe2O3) or crystalline ferrous chloride (FeCl2) can be recovered by precipitation method, but there are problems of low added value, high energy consumption and the like. In recent years, based on the recovery of hydrochloric acid from hydrochloric acid pickling waste liquid, the synthesis of iron-based flocculants (such as polymeric ferric chloride) has become a research hotspot, but the problem of poor stability of polymeric ferric chloride under high salt base needs to be solved.

[0004] By introducing sulfate (SO4 2- ) and chloride ion (Cl ⁻ ) coordination, the stability and adaptability of the polymer can be significantly improved under the condition of reducing acidity. Cl ⁻ and SO4 2- as coordination anions, combine with trivalent iron ions (Fe 3+ ) to form polymers of different structures. Cl ⁻ tends to form smaller polymers (such as dimers or oligomers), SO4 2- is a double-charged anion, and the bridging effect with Fe 3+ is strong, which easily forms a macromolecular network structure, enhances the charge neutralization and adsorption bridging capacity of the flocculant, but excessive crosslinking will reduce the solubility and dispersibility of the polymer, and too high SO4 2- ratio will cause the surface negative charge of the polymer to be too strong, resulting in electrostatic repulsion with negatively charged pollutant particles, which in turn reduces the flocculation efficiency. The ratio of the two directly affects the molecular weight and morphology of the polymer, and further affects the flocculation performance and settling speed of the product. Therefore, developing a new preparation process of polymeric ferric sulfate coagulant has important significance for efficient resource utilization of pickling waste liquid. SUMMARY

[0005] To solve or partially solve the problems of high cost, high pollution, low efficiency and performance defects of the flocculant in the traditional pickling waste liquid treatment method, the purpose of the present application is to provide a preparation method of polymeric ferric sulfate chlorination flocculant, which specifically comprises the following steps: (1) Add concentrated sulfuric acid to the pickling waste liquid at a volume ratio of (5-11.6):100 of concentrated sulfuric acid to filtered pickling waste liquid, carry out waste liquid replacement reaction, adjust the vacuum degree, and then evaporate and recover hydrochloric acid in the pickling waste liquid to obtain an evaporation mother liquor. To prevent crystals from precipitating in the mother liquor, water is added to the mother liquor. The molar ratio of Cl - to SO4 2- is 1.5-4.5.

[0006] (2) Heat the evaporation mother liquor obtained in step (1), add an alkali agent and dissolve it to obtain an acid iron solution.

[0007] (3) Pass the acid iron solution obtained in step (2) into an oxidizing gas to carry out oxidation and obtain an oxidation solution.

[0008] (4) Carry out maturation reaction on the oxidation solution obtained in step (3) to obtain a polymeric ferric sulfate chlorination flocculant.

[0009] Preferably, in step (1), the pickling waste liquid is a hydrochloric acid pickling waste liquid in the metal product industry, and the main components are hydrochloric acid and ferrous ions.

[0010] Preferably, in step (1), the adjustment condition of the vacuum degree is that the pressure is adjusted to 0.075 MPa by a vacuum pump.

[0011] Preferably, in step (1), the condition for evaporating and recovering hydrochloric acid in the pickling waste liquid is that the hydrochloric acid is recovered at 64°C by a rotary evaporator, and the recovery time is 35 min.

[0012] Preferably, in step (2), the heating condition of the evaporation mother liquor is water bath heating, and the alkali agent is iron oxide, and the addition amount is 10-50 g / L, which is dissolved by stirring at 100°C.

[0013] Preferably, in step (3), the oxidizing gas is oxygen, ozone or chlorine, and the ozone addition amount is 1-5 g / L.

[0014] Preferably, in step (4), the maturation reaction condition is that the maturation temperature is 30-70°C, and the reaction time is 30 min.

[0015] Another purpose of the present application is to use the polymeric ferric sulfate chlorination flocculant prepared by the above preparation method to treat phosphorus-containing waste sewage.

[0016] Mechanism of the present application: The metal product industry hydrochloric acid pickling waste liquid mainly contains hydrochloric acid and ferrous ions, and by using the high boiling point characteristics of sulfuric acid, the replacement with hydrochloric acid can occur under negative pressure and low temperature conditions, and the evaporated hydrochloric acid can be condensed and recovered; iron oxide is added to the solution after replacement of sulfuric acid, to consume excess free acid and adjust the total iron content, and an oxidizing agent is added to oxidize Fe 2+ in the solution to Fe 3+ , and the hydrolysis of Fe 3+ generates a hydroxyl bridged polynuclear complex, and Cl - and SO4 2- participate in coordination together, Cl⁻ tends to form smaller aggregates (such as dimers or oligomers), SO4 2- is a double-charged anion, and has a strong bridging effect with Fe 3+ , and is easy to form a macromolecular network structure, thereby enhancing the charge neutralization and adsorption bridging capacity of the flocculant; the solution is aged at a certain temperature to promote the growth of the polymer chain, thereby forming a red-brown polymeric ferric chloride sulfate liquid with a certain degree of polymerization; the hydrolysis product has a positive charge, and can capture negatively charged pollutants (such as phosphate, chromate and dichromate, etc.) through electrostatic adsorption, and settle down with the flocculent, thereby achieving the purpose of removing pollutants.

[0017] Advantages of the present application: (1) The preparation method of the present application has a wide source of raw materials, low price, low cost, simple process, and does not require complex operation, is suitable for large-scale industrial production, and has a broad market application prospect.

[0018] (2) In the process of preparing the polymeric ferric chloride sulfate flocculant, the sulfuric acid displacement method is combined with the negative pressure evaporation method to recover the hydrochloric acid in the waste liquid, and the acid recycling is realized.

[0019] (3) In the process of preparing the polymeric ferric chloride sulfate flocculant, the evaporation mother liquor is used to prepare the polymeric ferric chloride sulfate flocculant, and the full component recovery and utilization of waste acid is realized.

[0020] (4) The present application uses the metal product industry hydrochloric acid pickling waste liquid to prepare the polymeric ferric chloride sulfate flocculant, SO4 2- coordinates to inhibit the excessive hydrolysis of Fe 3+ , avoids the generation of iron hydroxide (Fe(OH)3) precipitate in storage, and further improves the stability of the flocculant.

[0021] (5) By accurately controlling the Cl - / SO4 2- ratio, the polymeric ferric chloride sulfate flocculant can be applied to various complex water qualities, and has a wide application scenario.

[0022] (6) The polymeric ferric chloride flocculant is prepared by taking the hydrochloric acid pickling waste liquid in the metal product industry as raw material, and is applied to the phosphorus-containing sewage treatment, realizes the "waste treatment with waste" and the resource utilization of waste, accords with the energy saving and environmental protection concept, provides a new idea for solving the waste acid pollution problem.

[0023] (7) The polymeric ferric chloride flocculant prepared by the method is applied to the phosphorus-containing sewage treatment, and when the polymeric ferric chloride flocculant is 10 ppm, the total phosphorus (TP) removal rate is extremely high, the process is simple, the overall investment is saved, and the operation cost is reduced.

[0024] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below in combination with specific examples, but the protection scope of the present application is not limited to the content.

[0026] Example 1 A preparation method of a polymeric ferric chloride flocculant, and the specific steps are as follows: (1) The concentrated sulfuric acid is added to the pickling waste liquid according to the volume ratio of the concentrated sulfuric acid to the filtered pickling waste liquid of 11.6:100, a waste liquid displacement reaction is carried out, the vacuum degree is adjusted to 0.075 MPa, then the hydrochloric acid in the pickling waste liquid is evaporated and recovered by using a rotary evaporator at 64 DEG C, the evaporation time is set to 35 min, the evaporation mother liquor is obtained, distilled water is added to the evaporation mother liquor to restore the volume to 100 mL, at this time, the Cl - / SO4 2- Molar ratio is 1.5.

[0027] (2) The iron oxide is added to the evaporation mother liquor, the iron oxide is added in an amount of 30 g / L, and the acid-iron solution is obtained after being dissolved at 100 DEG C.

[0028] (3) The ozone is introduced into the acid-iron solution, the ozone is added in an amount of 3 g / L, and the oxidation solution is obtained.

[0029] (4) The obtained oxidation solution is reacted at 50 DEG C for 30 min, and the polymeric ferric chloride flocculant is obtained.

[0030] Example 2 A preparation method of a polymeric ferric chloride flocculant, and the specific steps are as follows: (1) according to the proportion of concentrated sulfuric acid and the volume ratio of the filtered pickling waste liquid of 11.6:100, concentrated sulfuric acid is added to the pickling waste liquid, the waste liquid replacement reaction is carried out, the vacuum degree is adjusted to 0.075 MPa, then the hydrochloric acid in the pickling waste liquid is evaporated and recovered by using a rotary evaporator at 64 DEG C, the evaporation time is set to 35 min, the evaporation mother liquor is obtained, distilled water is added to the evaporation mother liquor to restore the volume to 100 mL, at this time, the Cl - / SO4 2- molar ratio is 1.5.

[0031] (2) iron oxide is added to the evaporation mother liquor, the amount of iron oxide added is 50 g / L, after dissolution at 100 DEG C, an acid iron solution is obtained.

[0032] (3) ozone is introduced into the acid iron solution, the ozone dosage is 5 g / L, and an oxidation solution is obtained.

[0033] (4) the obtained oxidation solution is reacted at 70 DEG C for 30 min, and a polymeric ferric chloride flocculant is obtained.

[0034] Example 3 A preparation method of a polymeric ferric chloride flocculant, the specific steps are as follows: (1) according to the proportion of concentrated sulfuric acid and the volume ratio of the filtered pickling waste liquid of 1:20, concentrated sulfuric acid is added to the pickling waste liquid, the waste liquid replacement reaction is carried out, the vacuum degree is adjusted to 0.075 MPa, then the hydrochloric acid in the pickling waste liquid is evaporated and recovered by using a rotary evaporator at 64 DEG C, the evaporation time is set to 35 min, the evaporation mother liquor is obtained, distilled water is added to the evaporation mother liquor to restore the volume to 100 mL, at this time, the Cl - / SO4 2- molar ratio is 4.5.

[0035] (2) iron oxide is added to the evaporation mother liquor, the amount of iron oxide added is 30 g / L, after dissolution at 100 DEG C, an acid iron solution is obtained.

[0036] (3) ozone is introduced into the acid iron solution, the ozone dosage is 3 g / L, and an oxidation solution is obtained.

[0037] (4) the obtained oxidation solution is reacted at 50 DEG C for 30 min, and a polymeric ferric chloride flocculant is obtained.

[0038] Example 4 A preparation method of a polymeric ferric chloride flocculant, the specific steps are as follows: (1) according to the proportion of concentrated sulfuric acid and the volume ratio of the filtered acid pickling waste liquid of 9.3:100, concentrated sulfuric acid is added to the acid pickling waste liquid, the displacement reaction of the waste liquid is carried out, the vacuum degree is adjusted to 0.075 MPa, then the hydrochloric acid in the acid pickling waste liquid is recovered by using a rotary evaporator at 64 DEG C, the evaporation time is set to 35 min, the evaporation mother liquor is obtained, distilled water is added to the evaporation mother liquor to restore the volume to 100 mL, at this time, the Cl - / SO4 2- molar ratio is 2.5.

[0039] (2) iron oxide is added to the evaporation mother liquor, the amount of iron oxide added is 10 g / L, after dissolving at 100 DEG C, the acid iron solution is obtained.

[0040] (3) ozone is introduced into the acid iron solution, the ozone dosage is 1 g / L, and the oxidation solution is obtained.

[0041] (4) the obtained oxidation solution is reacted at 30 DEG C for 30 min, and the polymeric ferric sulfate chloride flocculant is obtained.

[0042] The flocculants prepared in examples 1-4 of the present application are subjected to product quality inspection, and the test result data are shown in table 1.

[0043] In order to verify the removal effect of the flocculants of each example on total phosphorus, a solution with a total phosphorus concentration of 5 mg / L is prepared by using potassium dihydrogen phosphate to simulate phosphorus-containing wastewater, the pH of the wastewater is adjusted to 7, then the wastewater is evenly divided into 6 portions of 800 mL of water sample, and then the water sample is placed under the coagulation stirrer, the stirring parameters are set to fast stirring for 1 min, the speed is 200 r / min, slow stirring for 15 min, the speed is 70 r / min, the coagulation stirrer is started at the same time, different coagulants are added into the water sample, after stirring, the upper clear liquid is taken after standing and settling for 10 min, the content of TP is tested, the removal rate is calculated, and the removal effect is shown in table 1.

[0044] Table 1 flocculant product quality inspection table As can be seen from table 1, the flocculants obtained in examples 1-3 of the present application all meet the corresponding product quality standards, the treatment effect of the flocculants obtained in all examples on phosphorus-containing wastewater is obvious in a short time, and the flocculants have the characteristics of short reaction time, low dosage, high total phosphorus removal rate, etc.

[0045] From the above examples, it can be seen that the raw material used in the method of the present application is industrial waste liquid, the cost is low, and no special and complex operation is required in the preparation process, the process is simple, and it is suitable for industrial production.

[0046] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a polyferric sulfate chloride flocculant, characterized in that: The following steps are involved: (1) Add concentrated sulfuric acid to the pickling waste liquid at a volume ratio of (5-11.6):100 to the filtered pickling waste liquid, perform a waste liquid replacement reaction, adjust the vacuum degree, and then evaporate and recover the hydrochloric acid in the pickling waste liquid to obtain an evaporated mother liquor, add water to the evaporated mother liquor, and the molar ratio of chloride ion to sulfate in the mother liquor is 1.5-4.5; (2) heating the evaporated mother liquor obtained in step (1), adding an alkalizing agent and dissolving the alkalizing agent to obtain an acid iron solution; (3) introducing an oxidizing gas into the iron acid solution obtained in step (2) for oxidation to obtain an oxidized solution; (4) The oxidizing solution obtained in step (3) is subjected to a aging reaction to obtain a polyferric sulfate chloride flocculant.

2. The method for preparing the polyferric sulfate chloride flocculant according to claim 1, wherein: In step (1), the pickling waste liquid is hydrochloric acid pickling waste liquid from the metal products industry, and its main components are hydrochloric acid and ferrous ions.

3. The method for preparing the polyferric sulfate chloride flocculant according to claim 1, wherein: In step (2), the alkalizing agent is iron oxide, the addition amount is 10-50 g / L, and it is stirred and dissolved at 100°C.

4. The method for preparing the polyferric sulfate chloride flocculant according to claim 1, wherein: In step (3), the oxidizing gas is oxygen, ozone, or chlorine, and the dosage of the oxidizing gas is 1-5 g / L.

5. The method for preparing the polyferric sulfate chloride flocculant according to claim 1, wherein: In step (3), the aging reaction conditions are: reaction at 30-70°C for 30 minutes.

6. The polyferric sulfate chloride flocculant prepared by the method according to any one of claims 1 to 5.

7. Use of the polyferric sulfate chloride flocculant according to claim 8 in the treatment of phosphorus-containing wastewater.

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