Polymeric ferric chloride and its production process and application

Abstract

The application discloses polymeric ferric chloride and a production process and application thereof, and preparation of the polymeric ferric chloride comprises the following steps: S1, mixing waste acid with iron oxide scale, adjusting acidity, heating and refluxing, and cooling to obtain a mixture; S2, adding an oxidizing agent and a stabilizer into the mixture, and continuously heating and reacting to obtain the polymeric ferric chloride; the stabilizer is a chitosan-desferrioxamine complex; the polymeric ferric chloride is prepared by using a catalytic oxidation method, the chitosan-desferrioxamine complex stabilizer is used to chelate Fe, the stability of the polymeric ferric chloride is improved, the hydrolysis of Fe is inhibited, and the process is beneficial to improving the total iron content in the polymeric ferric chloride and improving the flocculation effect of the polymeric ferric chloride in sewage treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to sewage treatment technical field, especially to a kind of polymeric ferric chloride and its production process and application. BACKGROUND

[0002] Polymeric ferric chloride English abbreviation PFC, molecular formula can be expressed as [Fe2(OH) n Cl 6-n ]m, wherein n, m are molar number, it is a kind of inorganic polymer new coagulant, belongs to iron salt, with good flocculation effect, its flocculation mechanism is to provide polymeric ferric hydroxyl ion in water, realizes flocculation settlement by adsorbing suspended particles.Flocculant (coagulant, water purifying agent) is the most important component in industrial water treatment agent, its role is to make colloidal particles in water unstable and form flocculation body, so as to be separated from water to achieve the purpose of water purification.In the existing inorganic coagulant used, polymeric ferric chloride has the most superior coagulation performance, it has strong electric neutralization and adsorption bridge capacity, significantly improves the coagulation effect, not only has safety and no biological toxicity, but also has the characteristics of fast flocculation body formation, large structure of alum flower, dense, less dosage, fast settlement, sludge dewatering, the water treated has no color residue, no harmful aluminum ion residue.Especially for the treatment of low temperature, low turbidity wastewater has more advantages, especially suitable for winter water treatment in the north cold region.It is suitable for the pH value range (pH 4-11, optimum pH 6-9), and no other coagulant needs to be added.In the treatment of domestic water, industrial water, municipal sewage, industrial wastewater and oil sewage, it has the ability of turbidity removal, oil removal, deodorization, decolorization, COD and BOD reduction.Compared with the same dosage, the water purification effect is better than that of polymeric ferric sulfate, polymeric aluminum chloride and other inorganic polymer flocculants.

[0003] In recent years, domestic and foreign are researching and developing liquid polymeric ferric chloride, the process routes used are basically divided into two kinds of process routes.One is alkalization method, and the other is catalytic oxidation method.The former is to use ferric chloride as raw material, adjust to a certain alkalization degree in the presence of sodium carbonate, then add stabilizer to obtain product: the latter uses ferrous chloride liquid and hydrochloric acid as raw material, reacts under the action of different strong oxidizing agents such as nitrite, chlorate, concentrated nitric acid, hydrogen peroxide and oxygen.

[0004] When the above methods exist, the effective content (total iron content) of product is not high, and the polymeric ferric chloride has strong hydrolysis tendency and poor storage stability. SUMMARY

[0005] Therefore, the present application provides a kind of polymeric ferric chloride and its production process and application, to solve the problem of low total iron content and poor stability in polymeric ferric chloride.

[0006] To achieve the above technical purposes, the following technical solutions are adopted in the present application.

[0007] In a first aspect, the present application provides a production process of polymeric ferric chloride, comprising the following steps:

[0008] S1. mixing waste acid with mill scale, adjusting the acidity, heating and refluxing, and cooling to obtain a mixture;

[0009] S2. adding an oxidizing agent and a stabilizer to the mixture and continuing to heat and react to obtain polymeric ferric chloride; the stabilizer is a chitosan-desferrioxamine complex.

[0010] Preferably, the preparation method of the chitosan-desferrioxamine complex is as follows: desferrioxamine powder is dissolved in a phosphate buffer solution to obtain a desferrioxamine solution; the desferrioxamine solution is added to a chitosan solution to perform a coupling reaction to obtain the chitosan-desferrioxamine complex.

[0011] Preferably, the pH value of the chitosan solution is 8.5-9.0.

[0012] Preferably, in step S1, the pH value is ≥5.0%, and preferably ≥10.0%.

[0013] Preferably, in step S1, the heating and refluxing temperature is 60-80℃, and the heating and refluxing time is 2-4h.

[0014] Preferably, in step S2, the continued heating temperature is 100℃, and the continued heating time is 30-40min.

[0015] Preferably, the mill scale includes red mill scale and black mill scale.

[0016] Preferably, the mass ratio of the stabilizer to iron in the mill scale is 0.05-0.10:1.

[0017] In a second aspect, the present application provides a polymeric ferric chloride.

[0018] In a third aspect, the present application provides an application of the polymeric ferric chloride in treating contaminated water.

[0019] The present application has the following beneficial effects: the present application uses a catalytic oxidation method to prepare polymeric ferric chloride, and uses a chitosan-desferrioxamine complex stabilizer to chelate Fe to improve the stability of the polymeric ferric chloride, inhibit the hydrolysis of Fe when not in use, and the process of the present application is beneficial to improving the total iron content of the polymeric ferric chloride and the flocculation effect of the polymeric ferric chloride in treating sewage. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0021] The present application provides a production process of polymeric ferric chloride, comprising the following steps:

[0022] S1. mixing waste acid with iron oxide scale, adjusting the acidity, heating and refluxing, and cooling to obtain a mixture;

[0023] S2. adding an oxidizing agent and a stabilizer to the mixture, and continuing to heat and react to obtain polymeric ferric chloride; the stabilizer is a chitosan-desferrioxamine complex.

[0024] In the process of preparing polymeric ferric chloride by oxidation method, the stabilizer chitosan-desferrioxamine is added. Chitosan is a linear molecule, which contains reactive groups -NH and -OH in the molecular chain. In an acidic solution, it can form a cationic polyelectrolyte with high charge density. In addition, the linear molecular chain contains multiple hydroxyl groups and amino groups, which enable it to have a certain chelating and enrichment effect on metal ions. Compared with pure desferrioxamine molecules and pure chitosan nanomaterials, chitosan and desferrioxamine have a synergistic effect in complexing iron ions. The chitosan-desferrioxamine composite nanoparticles in the chitosan-desferrioxamine composite nanosuspension exhibit stronger iron ion complexing ability. Chitosan and desferrioxamine are both easy to react with polymeric ferric chloride solution. On the other hand, the chitosan-desferrioxamine composite nanoparticles have the characteristic of pH-responsive release. When polymeric ferric chloride is used, the sewage is mostly in an acidic environment. Desferrioxamine molecules can be uniformly released in an acidic environment. The chelating and stabilizing effect of the chitosan-desferrioxamine complex is weakened, which is conducive to the layer-by-layer hydrolysis of polymeric ferric chloride for flocculation of pollutants. At the same time, chitosan also has a flocculating effect, which cooperates with polymeric ferric chloride to improve the sewage treatment capacity. During the addition of the oxidizing agent, the trivalent iron ions generated by oxidation are chelated by the stabilizer, avoiding the massive aggregation and precipitation of colloidal iron hydroxide. Therefore, the degree of polymerization is easy to control. After the reaction is completed, cooling is immediately performed to terminate the re-polymerization of polymeric ferric chloride, achieving stable storage.

[0025] The acid used in the present application is waste acid. In the steel processing industry, hydrochloric acid solution is often used to clean the surface of steel parts to remove rust. During pickling, the hydrochloric acid in the hydrochloric acid solution is continuously consumed, and the divalent iron ions in the hydrochloric acid solution are also continuously increased with the consumption of the hydrochloric acid. When the hydrochloric acid solution no longer has a cleaning effect on the steel, the resulting washing waste liquid is the pickling waste liquid. The composition of the pickling waste liquid mainly includes water, ferrous chloride, hydrogen chloride and a small amount of impurities. The content varies with the pickling process, operating temperature, steel variety and specification, and is generally 10-20% ferrous chloride and 3-10% hydrogen chloride. The pickling waste liquid cannot be directly discharged due to its high acid and salt content. If it is neutralized and discharged, a large amount of alkali is needed, and a large amount of high-concentration salt-containing wastewater is generated. The use of waste acid in the present application not only utilizes waste resources, but also helps to produce polymeric ferric chloride without excess impurities and reduces environmental pollution. The ferrous ions in the iron-containing waste acid can oxidize and reduce the heavy metal ions in the hydrochloric acid solution without fluorine to form precipitates, thereby effectively removing the heavy metal ions in the hydrochloric acid solution without fluorine.

[0026] In the present scheme, the preparation method of the chitosan-deferoxamine complex is as follows: deferoxamine powder is dissolved in a phosphate buffer to obtain a deferoxamine solution; the deferoxamine solution is added to a chitosan solution to perform a coupling reaction, and the chitosan-deferoxamine complex is obtained.

[0027] The pH value of the chitosan solution is 8.5-9.0.

[0028] In step S1, the acidity is ≥5.0%, preferably ≥10.0%.

[0029] In step S1, the temperature of heating reflux is 60-80℃, and the time of heating reflux is 2-4h.

[0030] In step S2, the temperature of continued heating is 100℃, and the time of continued heating is 30-40min.

[0031] Under the above limitations of acidity and heating conditions, the obtained polymeric ferric chloride meets the requirements of HG / T 4672-2014 "Water Treatment Agent Polymeric Ferric Chloride", and the iron yield is high.

[0032] The oxide scale includes red oxide scale and black oxide scale. The main component of the red oxide scale is Fe2O3, and the main component of the black oxide scale is Fe3O4. The amount of the oxidizing agent increases with the increase of the proportion of ferrous ions in the oxide scale.

[0033] The mass ratio of the stabilizer to iron in the oxide scale is 0.05-0.10:1.

[0034] In a second aspect, the present application provides a polymeric ferric chloride.

[0035] In a third aspect, the application provides a use of the polymeric ferric chloride in treating contaminated water.

[0036] The present application is further illustrated by the following specific examples.

[0037] Preparation of raw materials

[0038] Chitosan-deferoxamine complex: 10 g of commercially available deferoxamine powder was dissolved in 100 ml of phosphate solution with pH 7.4 to obtain a deferoxamine solution; 10 g of chitosan was dissolved in 100 ml of 1% acetic acid solution, and the pH was adjusted to 8.5-9.0 using 1 mol / L sodium hydroxide to obtain a chitosan solution; the deferoxamine solution was added to the chitosan solution, and the mixture was stirred at 4°C overnight to obtain a chitosan-deferoxamine complex solution with a solid content of 0.1 g / ml.

[0039] Examples 1-9

[0040] A production process of polymeric ferric chloride, comprising the following steps:

[0041] S1. Mixing waste acid (total iron content 1.07%, acidity (calculated as HCl) 2.3%) with iron oxide scale (total iron content 73.21%), adjusting the acidity to ≥5.0%, preferably ≥10.0%, heating to reflux at 60-80°C for 2-4 h and cooling to below 50°C to obtain a mixture;

[0042] S2. Adding 0.5% sodium chlorate solution and prepared chitosan-deferoxamine complex solution to the mixture, continuing to heat to micro-boiling (100°C) for reaction, cooling, filtering, transferring to a sample bottle for aging to obtain polymeric ferric chloride; the mass ratio of chitosan-deferoxamine complex to iron in the iron oxide scale is 0.1:1.

[0043] In Examples 1-9, the pH value, heating reflux time and temperature of step S1 are shown in Table 1, and the iron ion content in the polymeric ferric chloride is tested.

[0044] Table 1 Reaction condition settings of Examples 1-9

[0045]

[0046] Comparative Example 1

[0047] A production process of polymeric ferric chloride, other contents being the same as in Example 1, except that no stabilizer is used.

[0048] Comparative Example 2

[0049] A production process of polymeric ferric chloride, other contents are the same as example 1, the difference is that the stabilizer used is deferoxamine.

[0050] Comparative example 3

[0051] A production process of polymeric ferric chloride, other contents are the same as example 1, the difference is that the stabilizer used is chitosan.

[0052] Evaluation test

[0053] The content of ferric ion in the polymeric ferric chloride obtained in examples 1-9 and comparative examples 1-3 was tested, and the polymeric ferric chloride was observed for 60 days to evaluate the stability, and the results are shown in Table 2.

[0054] The polymeric ferric chloride obtained in examples 1-9 and comparative examples 1-3 was put into 500ml wastewater according to the dosage of 0.5%, and the COD removal rate was tested, and the results are shown in Table 2.

[0055] Table 2 test results

[0056]

[0057] The above results show that the polymeric ferric chloride obtained by the scheme has high stability, and deferoxamine and chitosan have the effect of synergistically improving the stability, under the limitation of the process conditions of the scheme, the content of ferric ion in the polymeric ferric chloride is higher, which shows that the yield is higher.

[0058] The application uses catalytic oxidation method to prepare polymeric ferric chloride, and uses chitosan-deferoxamine compound stabilizer to chelate Fe(III) to improve the stability of polymeric ferric chloride, inhibit the hydrolysis of Fe(III), and the process of the scheme is beneficial to the improvement of the total iron content in the polymeric ferric chloride and the flocculation effect of polymeric ferric chloride in treating wastewater.

[0059] The above is only the preferred specific embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application.

Claims

1. A process for the production of polymeric ferric chloride, characterized in that, The method comprises the following steps: S1. mixing waste acid with mill scale, adjusting acidity, heating and refluxing, and cooling to obtain a mixture; S2. adding an oxidizing agent and a stabilizer to the mixture, and continuing to heat and react to obtain the polymeric ferric chloride; the stabilizer is a chitosan-deferoxamine complex.

2. The process for producing polymeric ferric chloride according to claim 1, characterized in that, The chitosan-deferoxamine complex is prepared by the following method: deferoxamine powder is dissolved in a phosphate buffer to obtain a deferoxamine solution; the deferoxamine solution is added to a chitosan solution to perform a coupling reaction to obtain the chitosan-deferoxamine complex.

3. The process for producing polymeric ferric chloride according to claim 2, characterized in that, The pH value of the chitosan solution is 8.5-9.

0.

4. The process for producing polymeric ferric chloride according to claim 1, characterized by, In step S1, the acidity is ≥5.0%.

5. The process for producing polymeric ferric chloride according to claim 1, characterized in that, In step S1, the temperature for heating and refluxing is 60-80°C, and the time for heating and refluxing is 2-4h.

6. The process for producing polymeric ferric chloride according to claim 1, characterized in that, In step S2, the temperature for continuing to heat is 100°C, and the time for continuing to heat is 30-40min.

7. The process for producing polymeric ferric chloride according to claim 1, characterized by, The mill scale comprises red mill scale and black mill scale.

8. The process for producing polymeric ferric chloride according to claim 1, characterized by, The mass ratio of the stabilizer to iron in the mill scale is 0.05-0.10:

1.

9. The polymeric ferric chloride prepared by the production process according to any one of claims 1-8.

10. The polymeric ferric chloride according to claim 9 for treating contaminated water.

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