CN112694136B - Synthetic method of polymeric ferric sulfate and polymeric ferric sulfate - Google Patents

Abstract

The application relates to the field of flocculant preparation, in particular to a synthetic method of polymeric ferric sulfate and the polymeric ferric sulfate. The synthetic method of the polymeric ferric sulfate comprises the four steps of acidizing ferrous sulfate aqueous solution, oxidizing by sodium nitrite and air, adding an organic framework and a cosolvent for further reaction, and carrying out post-treatment to obtain the polymeric ferric sulfate. The polymeric ferric sulfate prepared by the technical scheme is beneficial to greatly improving the water purification capacity of the polymeric ferric sulfate and has better application prospect.

Description

Synthetic method of polymeric ferric sulfate and polymeric ferric sulfate

Technical Field

The application relates to the field of flocculant preparation, in particular to a synthetic method of polymeric ferric sulfate and the polymeric ferric sulfate.

Background

Polyferric sulfate is a commonly used flocculant, generally obtained by oxidation of ferrous ions to ferric. The polymeric ferric sulfate has a good flocculation effect, the flocculation principle of the polymeric ferric sulfate is still discussed at present, and the main flow mechanism of the polymeric ferric sulfate is the DLVO theory, namely, the addition of a flocculating agent is beneficial to shortening the distance between particles in a water body, so that the total potential energy is mainly the attractive potential energy of van der Waals force, and the electrostatic repulsion potential energy between middle distances is reduced, thereby the particles in the system are agglomerated, and the flocculation purpose is achieved.

Although the polyferric sulfate has a good flocculation effect, the polyferric sulfate has a poor adsorption effect on impurities existing in wastewater in a non-colloidal form, the treated wastewater often has a high COD value, and the wastewater treatment effect needs to be further improved.

Disclosure of Invention

In order to improve the wastewater treatment effect of the polymeric ferric sulfate and reduce various impurities contained in wastewater treated by the polymeric ferric sulfate, the application provides a synthetic method of the polymeric ferric sulfate and the polymeric ferric sulfate.

In a first aspect, the present application provides a method for synthesizing polymeric ferric sulfate, which specifically adopts the following technical scheme: a method for synthesizing polymeric ferric sulfate comprises the following steps:

s1, adding sulfuric acid into the ferrous sulfate aqueous solution for acidification to obtain a first mixed solution;

s2, adding sodium nitrite into the first mixed solution, controlling the temperature to be 70-80 ℃, introducing oxygen or air, and reacting for 150-200 min to obtain a second mixed solution;

s3, adding an organic framework and a cosolvent into the second mixed solution, wherein the amount of the added substances of the organic framework is less than the sum of the amounts of the substances of ferric ions and ferrous ions contained in the second mixed solution; controlling the temperature to be 30-55 ℃, and fully reacting to obtain a third mixed solution;

s4, carrying out post-treatment on the third mixed solution, and separating to obtain polymeric ferric sulfate;

the organic framework molecule comprises more than two coordination groups, the coordination groups are at least one of carboxyl, hydroxyl, phenolic hydroxyl, methylamino, pyridine nitrogen, pyrazine nitrogen and cyano, and the interval between coordination atoms in any two coordination groups comprises at least two carbon atoms;

the cosolvent is an organic solvent miscible with water.

In the technical scheme, organic framework molecules are further added in the process of synthesizing the polymeric ferric sulfate. In the present application, an organic framework molecule is a small organic molecule having multiple coordination groups, where the multiple coordination groups can coordinate with iron ions, and since iron ions have a hexagonal coordination structure, the system can form a certain metal center-organic ligand system with a regular octahedral structure in the system when iron ions coordinate. Because the organic framework has a plurality of coordination groups, the organic framework can be coordinated with a plurality of iron ions in the coordination process to form a frame structure, and the frame structure can generate a certain adsorption effect in the wastewater, so that the polymeric ferric sulfate prepared in the application can realize a better removal effect on part of small molecules which are not easy to settle in the wastewater.

Because in this application, the polyferric sulfate of conventional form and the iron coordination molecule that combines organic skeleton coexist, it is better to gather and sink the effect, and the COD value in the waste water after handling is also lower. In addition, although the solubility of the organic framework iron coordination molecule is reduced due to the existence of the organic framework, the iron ion has six orbitals for coordination, so the rest orbitals can be coordinated with hydroxyl. In this application, the coordinating groups on the organic framework molecules selected for use are monodentate ligands, generally speaking, because of steric hindrance effect, the ligand of 2 ~ 4 organic framework molecules can only be coordinated on the iron ion, so the ligand whole can have certain electric charge, it can disperse in water comparatively evenly, in the water purification process, then can be at the effect of general polyferric sulfate coagulation, be difficult for remaining in water.

In addition, in general, residual ferrous ions in the polyferric sulfate can not play a role of coagulation and pollute water quality, but when the technical scheme is adopted, the organic framework is very easy to coordinate with the ferrous ions, so the generated ferrous ions basically can not remain in the treated wastewater, the requirement on the oxidation degree of the polyferric sulfate is not high, and meanwhile, the coordination of the organic framework and the ferrous ions can also form a framework structure, so the ferrous ions which are not completely reacted can be fully utilized, and the quality of the polyferric sulfate is further improved.

Because the organic framework molecules basically have poor solubility, the addition of the cosolvent is helpful for better dispersing the organic framework molecules, so that the coordination process of the organic framework and iron ions can be smoothly carried out.

By adopting the technical scheme, the prepared polymeric ferric sulfate has a good sedimentation effect, can well remove various impurities in water, improves the clarity of the obtained water, reduces the COD value in the treated wastewater, and has a good application prospect.

Optionally, the organic framework comprises an aromatic system, and the aromatic system comprises one of a benzene ring, a biphenyl-like structure, an acene-like aromatic structure, a quinoline-like structure, and a polypyridyl structure.

In the technical scheme, the aromatic groups are adopted to connect the coordination groups, so that the aromatic groups have high integral rigidity and are not easy to deform, different coordination groups on one organic framework molecule are ensured to be respectively coordinated with different iron ions, a framework structure is favorably formed, and the coagulation capacity and the adsorption capacity of the polymeric ferric sulfate are further improved.

Optionally, the coordinating group is a carboxyl group or a phenolic hydroxyl group directly attached to the aromatic system.

Carboxyl and phenolic hydroxyl have good coordination effect on iron ions, and the coordination bond formed by the carboxyl and phenolic hydroxyl and the iron ions is strong, so that the iron ions are not easy to hydrolyze, the residue of the iron ions in a water body is reduced, and the quality of the treated wastewater is improved.

Optionally, the aromatic system of the organic framework is connected with a branched chain, wherein the branched chain is 3-6 carbon alkyl or 3-6 carbon alkoxy.

The alkyl chain or the alkoxy chain with a certain length is arranged on the aromatic system, so that on one hand, the whole electron cloud density of the aromatic system is improved, the coordination group can give an electron pair more easily and coordinate with iron ions, and on the other hand, the phenomenon of pi-pi stacking of the aromatic system is reduced, a frame structure can be formed better, and the water purifying capacity and the impurity removing capacity of the prepared polymeric ferric sulfate are further improved. Meanwhile, the branched chain on the aromatic ring is beneficial to improving the integral lipophilicity of the framework structure, has a good adsorption effect on part of lipophilic impurities in a system, and further improves the coagulation performance of the polyferric sulfate. In addition, the structure is also beneficial to reducing the moisture absorption and deliquescence property of the polymeric ferric sulfate and improving the storage time of the polymeric ferric sulfate.

Optionally, the ratio of the organic framework to the amount of the added ferrous sulfate is (0.05-0.1): 1.

In the technical scheme, the proportion of an easily hydrolyzed system and an difficultly hydrolyzed system formed by iron ions in the polymeric ferric sulfate system is moderate, and the polymeric ferric sulfate system has better coagulation and water purification effects in the actual use process.

Optionally, in step S3, the reaction time is 3-5 h.

In the technical scheme, the coordination reaction can be basically and completely carried out within 3-5 h of reaction time, and continuous reaction can cause the co-solvent molecules in the system to extrude and occupy hydroxyl coordination and sulfate ion coordination in the polymeric ferric sulfate, so that the dispersibility of the prepared polymeric ferric sulfate in water is poor, and the coagulation capacity is greatly reduced. If co-solvents which do not have coordination ability and are partially miscible with water are used, such co-solvents will either have lower solubility in water (e.g. ethyl acetate) or better boiling point (e.g. DMF) leading to more difficult reaction and work-up. Therefore, the cosolvent with certain coordination capacity (such as alcohols like ethanol and methanol, or acetic acid) is selected, and the good effect is achieved.

Optionally, step S4 specifically includes the following steps:

s4-1, concentrating the third mixed solution obtained in the step S3 to 20-30% of the initial volume of the third mixed solution, and cooling to normal temperature to obtain a concentrated solution;

s4-2, filtering the concentrated solution obtained in the step S4-1, and keeping filter residues;

s4-3, drying the filter residue obtained in the step S4-2.

In the technical scheme, the solubility of the polymeric ferric sulfate in the solution can be reduced through concentration and cooling, the polymeric ferric sulfate is filtered after being separated out, and the polymeric ferric sulfate is dried to obtain the granular polymeric ferric sulfate, so that the process is simple, and the yield is high. If the content of iron ions in the filtrate is high, the iron ions can be recycled by adjusting the pH value and the like, so that the method has a good economic effect.

Optionally, in step S4-2, after filtering, the filter residue is washed with a certain amount of acetone, ethyl ether or ethyl acetate.

In the process, the filter residue is cleaned by acetone, ether or ethyl acetate, the solvent is volatile and has good fat solubility, which is beneficial to eluting partial organic frameworks remained in the filter residue, and meanwhile, the solvent is easy to volatilize and remove in the drying process, can occupy the position where water is remained in a frame system, and further improves the drying degree.

Optionally, the step S4 further includes the following steps after the step S4-3:

and S4-4, adding diatomite which accounts for 5-10% of the total mass of the dried filter residues into the dried filter residues.

On one hand, the diatomite has better adsorbability, and the sedimentation effect of the polymeric ferric sulfate can be further improved by mixing the diatomite with the polymeric ferric sulfate. Meanwhile, the diatomite can well inhibit the deliquescence of the polyferric sulfate and improve the storage time of the polyferric sulfate.

In a second aspect, the present application provides a polyferric sulfate, which specifically adopts the following technical scheme:

polymeric ferric sulfate is prepared by the polymeric ferric sulfate synthesis method.

The polymeric ferric sulfate prepared by the technical scheme can remove organic impurities in wastewater after the wastewater is treated, is favorable for reducing the COD value after the wastewater treatment, and has a good flocculation effect.

To sum up, the technical scheme adopted in the application at least comprises the following beneficial effects:

1. in the application, an organic framework is added in the process of synthesizing the polymeric ferric sulfate to form a metal-organic coordination structure of the organic framework-iron ions and form a frame system, and the polymeric ferric sulfate has the coagulation effect and the capability of removing organic impurities in wastewater through the adsorption effect of the frame system, so that the polymeric ferric sulfate has a better water purification effect.

2. In the further arrangement of the application, the coordination groups are connected through an aromatic system, and the impurity removal capability of the polymeric ferric sulfate is further improved by utilizing the rigid structure of the aromatic groups.

3. In a further arrangement of the application, the alkyl chain or the alkoxy chain with a certain length is arranged on the aromatic system, so that the lipophilicity of the polymeric ferric sulfate is improved, and the coagulation performance of the polymeric ferric sulfate is further improved.

Detailed Description

The present application is further described in detail in connection with the following examples.

For the polymeric ferric sulfate prepared in the following examples and preparation examples, evaluation was performed by the following dimensions.

Selecting sewage generated by a certain textile factory A, determining to obtain the sewage with a COD value of 144mg/mL and an SS value of 42mg/mL, adding the polyferric sulfate prepared in the following examples or purchasing the obtained polyferric sulfate into the sewage in an amount of 1g/L, stirring at 200rpm at room temperature for 1h, standing for 25min, taking supernatant, and determining the change conditions of the COD value and the SS value of the sewage before and after the polyferric sulfate is added.

Example 1, a polymeric ferric sulphate, was synthesized by the following procedure.

S1, dissolving 55.6g (0.2mol) of ferrous sulfate heptahydrate in 30mL of water, slowly dropwise adding 2mL of sulfuric acid with the mass fraction of 40%, heating to 50 ℃, and stirring uniformly to obtain a first mixed solution;

s2, continuously heating the first mixed solution to 70 ℃, adding 0.4g of sodium nitrite at one time, introducing air, and keeping stirring and reacting for 150min to obtain a second mixed solution;

s3, cooling the second mixed solution to 55 ℃, adding an organic framework and a cosolvent into the second mixed solution, wherein the organic framework is terephthalic acid, the addition amount of the terephthalic acid is 3.32g (0.02mol), the cosolvent is ethanol, the addition amount of the cosolvent is 10mL, and after the organic framework and the cosolvent are added, continuously stirring and reacting for 3 hours to obtain a third mixed solution;

s4, post-treating the third mixed solution, and specifically comprises the following steps:

s4-1, heating and concentrating the third mixed solution to 20% of the initial volume of the third mixed solution, and cooling to normal temperature to obtain a concentrated solution;

s4-2, carrying out suction filtration on the concentrated solution, and keeping filter residues;

s4-3, and drying the filter residue in the comparison step S4-3 in a vacuum drying oven at the temperature of 50 ℃ for 24 hours.

Examples 2 to 14, a polymeric ferric sulfate, were different from example 1 in that the organic skeleton was replaced with the substances shown in table 1 in the same amount of substances.

Meanwhile, the following comparative examples were selected for comparison.

Comparative example 1: the resulting polymeric ferric sulfate was purchased from Biotechnology (Shanghai) Inc.

Table 1, examples 1 to 14 lists the structural formulae of the organic frameworks

The results of sewage treatment for examples 1 to 14 and comparative example 1 are shown in Table 2.

Table 2, results of treating wastewater in examples 1 to 14 and comparative example 1

In the above experimental data, it can be seen that, compared with the polymeric ferric sulfate obtained in comparative example 1, the polymeric ferric sulfate used in the present application can realize a lower COD value and a lower SS value after sewage treatment, which proves that examples 1 to 14 have better water purification capability than comparative example 1. In examples 1 to 14, examples 1, 2, 4, 5, 6, 9, and 11, on the one hand, the organic skeleton employs a connection structure mainly based on an aromatic system, which has a relatively good rigid structure, and on the other hand, the organic skeleton employs a carboxyl group or a phenolic hydroxyl group as a coordinating group, which has a relatively strong coordinating effect, and at the same time, the stability and the holding degree of the framework structure formed after coordination are improved, so that the water purification effect of the polyferric sulfate is further enhanced compared with other examples.

Further, the organic skeleton selected in example 1 of examples 1 to 14, terephthalic acid, was less expensive, and the derivative thereof was also less expensive, so the organic skeleton selected in example 1 was improved on the side chain of the naphthalene ring, and the following examples were further provided.

Examples 15 to 20, a polymeric ferric sulfate, were different from example 1 in that the organic frameworks were replaced with the same amount of the substance as shown in Table 3.

Table 3, organic skeleton structure in examples 15 to 20

The polymeric ferric sulfate prepared in the above examples was subjected to a sewage treatment experiment, and the results are shown in table 4.

Table 4, results of treating wastewater in examples 15 to 20

Numbering	COD value after treatment (mg/mL)	SS value after treatment (mg/mL)
			Example 15	29.6	7.5
Example 16	29.2	7.4
			Example 17	27.7	6.9
Example 18	27.1	7.0
			Example 19	34.0	8.1
Example 20	27.2	7.0

In examples 15 to 20, the alkoxy group or the alkyl group connected to the side chain of the benzene ring can be compared with example 1 by means of friedel-crafts acylation, friedel-crafts alkylation, post-halogenation suzuki reaction, etc., and it is found that the water purification ability of the polymeric ferric sulfate can be improved by introducing the alkyl group or the alkoxy group having no active group at the end into the side chain of the benzene ring. However, if a group having a hydroxyl group at the terminal is introduced, the overall water-purifying ability is not significantly affected. Compared with the introduction of one carbon chain, the introduction of two carbon chains has no obvious change in water purification capacity.

In the above examples, example 17, which is a simpler preparation, was selected, and the preparation process of the polyferric sulfate was further adjusted to obtain the following examples.

Example 21, a polymeric ferric sulfate, was different from example 17 in that the reaction temperature was 75 ℃ and the reaction time was 180min in step S2.

Example 22, a polymeric ferric sulfate, was different from example 17 in that the reaction temperature was 80 ℃ and the reaction time was 200min in step S2.

Examples 23 to 25, which are polyferric sulfate, differ from example 17 in that the amounts of the organic skeleton-containing substance added in step S3 were 0.05mol, 0.1mol, and 0.3mol, respectively.

Examples 26 to 29, which are different from example 17 in that the reaction time was 2 hours, 4 hours, 5 hours, and 6 hours in this order in step S3, were polymeric ferric sulfate.

Examples 30 to 32, a polyferric sulfate, were different from example 17 in that in step S3, acetonitrile, methanol and isopropanol were used as the co-solvents.

Example 33, a polymeric ferric sulfate, was different from example 17 in that the third mixed solution was concentrated to 30% of the initial volume by heating in step S4-1.

Example 34, a polymeric ferric sulfate, differs from example 17 in that the residue is filtered, washed with acetone in step S4-2, and then subjected to step S4-3.

Example 35, a polymeric ferric sulfate, differs from example 17 in that the residue is filtered and washed with ether in step S4-2, and then the process proceeds to step S4-3.

Example 36, a polymeric ferric sulfate, differs from example 17 in that the residue is filtered, washed with ethyl acetate in step S4-2, and then subjected to step S4-3.

Example 37, a polymeric ferric sulfate, different from example 34, further comprising the following steps after step S4-3:

and S4-4, adding diatomite accounting for 5% of the total mass of the dried filter residues into the dried green plants.

Example 38, a polymeric ferric sulphate, differs from example 37 in that the amount of diatomaceous earth added is 10% of the total mass of the filter residue.

In examples 37 and 38, diatomaceous earth was purchased from Biotechnology engineering (Shanghai) Inc.

Meanwhile, the following comparative examples were set.

Comparative example 2, a polymeric ferric sulfate, differs from example 1 in that step S3 is not included, and step S2 is directly proceeded to step S4 after the reaction is completed.

Comparative example 3, a polymeric ferric sulfate, differs from example 1 in that no organic framework is added in step S3.

Comparative example 4, a polymeric ferric sulfate, differs from example 1 in that no co-solvent is added in step S3.

The results of the sewage treatment experiments for examples 21 to 38 and comparative examples 2 to 4 are shown in Table 5.

Table 5, examples 21 to 35 and comparative examples 2 to 4 show the results of sewage treatment

As can be seen from the comparison of the experimental data, in the process adjustment, the reaction time of step S3 needs to be limited to 3-5 hours, otherwise, the water purification effect of the polyferric sulfate is adversely affected. Meanwhile, in the post-treatment process, the filter residue is cleaned by solvents such as acetone and ether, which is beneficial to eluting organic micromolecules contained in the filter residue and further improves the water purification effect of the polymeric ferric sulfate. Furthermore, the diatomite is added, which is beneficial to further improving the water purification effect of the polymeric ferric sulfate. In addition, the diatomite is added in long-term experiments, so that the deliquescence speed of the polyferric sulfate is reduced, and the polyferric sulfate is not easy to agglomerate and agglomerate during long-term storage.

In the above examples and comparative examples, the applicant selected example 34, in which the effect was better, performed further scale-up experiments, and performed measurements in the scaled-up amount of wastewater, in which 1kg of the polymeric ferric sulfate described in the present application was added per ton of wastewater in the order of 1 ton, and performed wastewater treatment experiments in a similar manner, and the results are shown in table 6.

Results of the iron polysulfate scale-up experiments in Table 6 and example 34

The experimental results prove that the polymeric ferric sulfate prepared by the method has a good application prospect in the actual industry.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims (9)

1. A method for synthesizing polymeric ferric sulfate is characterized by comprising the following steps:

s1, adding sulfuric acid into the ferrous sulfate aqueous solution for acidification to obtain a first mixed solution;

s2, adding sodium nitrite into the first mixed solution, controlling the temperature to be 70-80 ℃, introducing oxygen or air, and reacting for 150-200 min to obtain a second mixed solution;

s3, adding an organic framework and a cosolvent into the second mixed solution, wherein the amount of the added substances of the organic framework is less than the sum of the amounts of the substances of ferric ions and ferrous ions contained in the second mixed solution; controlling the temperature to be 30-55 ℃, and fully reacting to obtain a third mixed solution;

s4, carrying out post-treatment on the third mixed solution, and separating to obtain polymeric ferric sulfate;

the organic framework molecule comprises more than two coordination groups, the coordination groups are selected from at least one of carboxyl, hydroxyl, methylamino, pyridine nitrogen, pyrazine nitrogen and cyano, and the interval between coordination atoms in any two coordination groups comprises at least two carbon atoms;

the organic framework molecule also comprises an aromatic system, and the aromatic system comprises one of a benzene ring, a biphenyl-like structure, a acene aromatic hydrocarbon structure, a quinoline-like structure and a polypyridyl structure;

the cosolvent is an organic solvent miscible with water.

2. The method as claimed in claim 1, wherein the coordinating group is a carboxyl group or a phenolic hydroxyl group directly linked to the aromatic system.

3. The method of claim 1, wherein the aromatic system of the organic framework is connected with a branched chain, wherein the branched chain is a 3-6 carbon alkyl group or a 3-6 carbon alkoxy group.

4. The method for synthesizing polymeric ferric sulfate according to claim 1, wherein the ratio of the organic framework to the added ferrous sulfate is (0.05-0.1): 1.

5. The method for synthesizing polymeric ferric sulfate according to claim 4, wherein in step S3, the reaction time is 3-5 h.

6. The method for synthesizing polymeric ferric sulfate according to claim 1, wherein the step S4 specifically comprises the following steps:

s4-1, concentrating the third mixed solution obtained in the step S3 to 20-30% of the initial volume of the third mixed solution, and cooling to normal temperature to obtain a concentrated solution;

s4-2, filtering the concentrated solution obtained in the step S4-1, and keeping filter residues;

s4-3, drying the filter residue obtained in the step S4-2.

7. The method as claimed in claim 6, wherein in step S4-2, after filtering, the filter residue is washed with a certain amount of acetone, ethyl ether or ethyl acetate.

8. The method for synthesizing polymeric ferric sulfate of claim 7, wherein the step S4 further comprises the following steps after the step S4-3:

and S4-4, adding diatomite which accounts for 5-10% of the total mass of the dried filter residues into the dried filter residues.

9. Polyferric sulfate, characterized in that it is obtained by the process for the synthesis of polyferric sulfate according to any one of claims 1 to 8.