Composite metal dicyandiamide formaldehyde cationic flocculant as well as preparation method and application thereof

Abstract

The invention discloses a composite metal dicyandiamide formaldehyde cationic flocculant as well as a preparation method and application thereof. Dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and aluminum polychlorid are taken and added into a reactor provided with a condensation return pipe and a thermometer; adding dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 mass of ammonium chloride, opening condensate water, starting to stir, heating to 30-60 DEG C, carrying out heat preservation reaction for 5-20 minutes, and adding the rest 1 / 2 mass of ammonium chloride; the temperature is set to be 50-90 DEG C, heat preservation reaction is conducted for 1-4 h, and then a product is naturally cooled; and adding polyaluminum chloride into the naturally cooled product, setting the temperature to 50-90 DEG C, keeping the temperature to react for 1-4 hours, stopping heating, and naturally cooling the product to obtain the composite metal dicyandiamide formaldehyde cationic flocculant, which has the effects of net capturing, bridging and complexing sedimentation due to a large amount of floccules generated by hydrolysis, and realizes removal of colored substances on printing and dyeing wastewater.

Description

Technical Field

[0001] The present application relates to the technical field of decolorization treatment of printing and dyeing wastewater, and in particular to a composite metal dicyandiamide formaldehyde cationic flocculant and a preparation method and application thereof. Background Art

[0002] For a long time, the process of industrialization has been accelerating, and the consumption of water resources has been increasing day by day. At the same time, industrial wastewater has become the main source of wastewater discharge. Among them, printing and dyeing wastewater, as one of the sources of environmental pollution, has caused many hazards. The waste liquid has a large amount of water, complex composition and deep color, large pH value changes, and is difficult to biodegrade. Therefore, printing and dyeing wastewater has become one of the major environmental problems that need to be solved urgently.

[0003] At present, a variety of treatment methods have been developed for different printing and dyeing wastewaters, including adsorption, chemical oxidation, biological, flocculation and sedimentation. Among them, the flocculation and sedimentation method has the advantages of high decolorization efficiency and simple operation. In actual wastewater treatment, the decolorization flocculants with good decolorization effect on difficult-to-treat printing and dyeing wastewater are mainly organic polymers, such as polyacrylamide, dicyandiamide formaldehyde polymer, polydimethyldiallyl ammonium chloride, etc. Compared with other polymers, dicyandiamide formaldehyde polymer is a cationic polymer that can provide a large amount of positive charge. The guanamine structure in its polymer molecules reacts with printing and dyeing molecules, and further aggregates through electrostatic action and the formation of intermolecular hydrogen bonds through bridging, netting and other coagulation actions to precipitate and remove colored substances in printing and dyeing wastewater, and has good decolorization performance for printing and dyeing wastewater. However, due to the high price of dicyandiamide, the cost of decolorization flocculants is relatively high, which is difficult for most manufacturers to accept. Polyaluminium chloride is a water purification material, an inorganic polymer coagulant, low in price, and has a high degree of electrical neutralization and bridging effect on colloids and particles in water, and can remove micro-toxic substances and heavy metal ions, but its decolorization effect on printing and dyeing wastewater is not obvious when used alone. Therefore, the development of green, environmentally friendly, economical and efficient composite metal dicyandiamide formaldehyde cationic decolorization flocculant plays an important role in solving the problem of printing and dyeing wastewater pollution.

[0004] Based on the above problems, the synthesis of composite metal dicyandiamide formaldehyde cationic decolorizing flocculant by chemically compounding inorganic flocculant polyaluminum chloride into dicyandiamide formaldehyde polymer provides a new possibility for solving the problem of printing and dyeing wastewater pollution. However, related research is still relatively rare. To this end, the present application provides a composite metal dicyandiamide formaldehyde cationic decolorizing flocculant, a preparation method and application thereof. First, an intermediate is synthesized by dehydration polycondensation reaction using dicyandiamide, formaldehyde, ammonium chloride and the like as raw materials, and then the composite metal dicyandiamide formaldehyde cationic decolorizing flocculant is synthesized by chemical compounding with polyaluminium chloride. The effects of the preparation method (material molar ratio, reaction temperature, reaction time, etc.) of the composite metal dicyandiamide formaldehyde cationic decolorizing flocculant and the conditions for decolorizing application (decolorizing time, dosage of decolorizing flocculant, etc.) on the decolorization application of printing and dyeing wastewater are systematically studied. The study shows that the prepared composite metal dicyandiamide formaldehyde cationic decolorizing flocculant can provide a large amount of cations to neutralize and destabilize the negative charge carried by the dye molecule, which can make up for the shortcomings of the two acting alone, can improve the decolorizing performance, reduce the amount of organic decolorizing flocculant used, and reduce the processing cost. It has good economic value, has far-reaching significance for the sustainable development of society, and has broad application prospects. Summary of the invention

[0005] Technical issues solved:

[0006] The technical problem to be solved by the present application is that the printing and dyeing wastewater has a large discharge, deep chromaticity, large pH value changes, and is difficult to biodegrade. Not only is the composition complex and the chemical oxygen demand content high, which causes great harm, but also the development of modern dyes and the progress of printing and dyeing processing technology have greatly improved the printing and dyeing structure and stability. It is difficult to degrade efficiently and quickly by biological treatment. Adding a decolorizing flocculant to destabilize and remove it is a simple and efficient method. When treating actual printing and dyeing wastewater, due to the high price of dicyandiamide, the cost of the decolorizing flocculant is relatively high, and the inorganic flocculant polyaluminum chloride is not obvious when used alone for the decolorization effect of printing and dyeing wastewater. Based on the deficiencies of the prior art, the present application provides a composite metal dicyandiamide formaldehyde cationic flocculant. Coagulant and its preparation method and application, firstly use dicyandiamide, formaldehyde, ammonium chloride and other raw materials to synthesize intermediates through dehydration polycondensation reaction, and then synthesize composite metal dicyandiamide formaldehyde cationic decolorization flocculant with polyaluminium chloride chemical compound, systematically study the preparation method of composite metal dicyandiamide formaldehyde cationic decolorization flocculant (material molar ratio, reaction temperature, reaction time, etc.) and decolorization application conditions (decolorization time, decolorization flocculant dosage, etc.) on the decolorization application of printing and dyeing wastewater, the prepared composite metal dicyandiamide formaldehyde cationic decolorization flocculant can make up for the defects of each used alone, as a decolorization flocculant for printing and dyeing wastewater, it not only has the ability to efficiently remove the color of printing and dyeing wastewater, but also reduces the cost of wastewater treatment. In addition, the realization of printing and dyeing wastewater treatment provides technical support for the decolorization treatment of printing and dyeing wastewater, and has far-reaching significance in ecological environment protection and human health.

[0007] Technical solution:

[0008] Composite metal dicyandiamide formaldehyde cationic flocculant, its molecular structure is as follows:

[0009]

[0010] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0011] The first step: according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1: (0.5-4): (0.25-2): (0.1-2): (0.1-4): (0.1-1): (0.5-2): (0.6-0.9), take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride, in a reactor equipped with a condensation reflux tube and a thermometer, add dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 of the mass of ammonium chloride, open the condensation water and stir to mix;

[0012] Step 2: Heat to 30-60°C, keep warm for 5-20 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0013] Step 3: Set the temperature to 50-90°C, keep the reaction for 1-4 hours, and then cool the product naturally;

[0014] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 50-90°C, keep the reaction for 1-4 hours, stop heating, and naturally cool to obtain a composite metal dicyandiamide formaldehyde cationic flocculant.

[0015] As a preferred technical solution of the present application: the molar concentration of the dicyandiamide is 0.5 to 2 mol / L.

[0016] The present application also discloses the application of a composite metal dicyandiamide formaldehyde cationic flocculant in decolorizing printing and dyeing wastewater, wherein the dosage of the composite metal dicyandiamide formaldehyde cationic flocculant is 10 to 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the initial pH value of the printing and dyeing wastewater is 1 to 14; the decolorization application is firstly rapid stirring at a speed of 150 to 400 r / min for a stirring time of 3 to 10 minutes, and then slow stirring at a speed of 20 to 60 r / min for a stirring time of 10 to 20 minutes.

[0017] As a preferred technical solution of the present application: the synthesis reaction mechanism of the composite metal dicyandiamide formaldehyde cationic flocculant is:

[0018] S1, ammonium chloride and formaldehyde produce hydrochloric acid through a reversible reaction;

[0019] S2, the dicyandiamide molecule absorbs hydrogen ions and undergoes an isomerization reaction under heating conditions, transforming from a diamide structure to a cyanoguanidine structure with a positive charge, and the dicyandiamide molecule continuously consumes hydrogen ions to promote the reaction of ammonium chloride and formaldehyde to proceed to the right;

[0020] S3, multiple dicyandiamide molecules can be connected to form hydroxymethyl derivatives through the imine bond generated by the addition reaction between the cyano group and its own amine group;

[0021] S4, a dehydration condensation reaction between two molecules of hydroxymethyl and hydroxymethyl or between hydroxymethyl and amine groups generated by the reaction with formaldehyde generates a macromolecule, namely, a dicyandiamide formaldehyde cationic decolorizing flocculant;

[0022] S5, C=O of the dicyandiamide formaldehyde cationic decolorizing flocculant and -OH of polyaluminium chloride can interact with each other by forming hydrogen bonds, thus obtaining a composite metal dicyandiamide formaldehyde cationic flocculant.

[0023] As a preferred technical solution of the present application: the reaction formula in S1 is: 4NH4Cl+6CHOH→(CH2)6N4+4HCl+6H2O

[0024] (CH2)6N4+HCl→(CH2)6N4·HCl

[0025]

[0026] As a preferred technical solution of the present application: the reaction formula in S2 is:

[0027]

[0028] As a preferred technical solution of the present application: the reaction formula in S3 is:

[0029]

[0030] As a preferred technical solution of the present application: the reaction formula in S4 is:

[0031]

[0032] As a preferred technical solution of the present application: the reaction formula in S5 is:

[0033]

[0034] The technical principle of the present application is: the composite metal dicyandiamide formaldehyde cationic flocculant of the present invention is firstly prepared by using dicyandiamide, formaldehyde and ammonium chloride as raw materials to synthesize an intermediate through a dehydration polycondensation reaction, and then chemically compounded with polyaluminium chloride to synthesize the composite metal dicyandiamide formaldehyde cationic flocculant. The influence of the preparation method (material molar ratio, reaction temperature and reaction time) and the conditions for decolorization application (decolorization time and dosage of decolorization flocculant) of the composite metal dicyandiamide formaldehyde cationic flocculant on the decolorization application of printing and dyeing wastewater is systematically studied. The prepared composite metal dicyandiamide formaldehyde cationic flocculant can make up for the defects of each of them being used alone. As a decolorization flocculant for printing and dyeing wastewater, it not only has the ability to efficiently remove the chromaticity of printing and dyeing wastewater, but also reduces the cost of wastewater treatment.

[0035] Beneficial effects:

[0036] The composite metal dicyandiamide formaldehyde cationic flocculant and its preparation method and application described in this application adopt the above technical scheme compared with the prior art, and have the following technical effects:

[0037] 1. The dicyandiamide formaldehyde polymer in the composite metal dicyandiamide formaldehyde cationic flocculant is synthesized through dehydration polycondensation reaction, which can provide a large amount of cations to neutralize the negative charge on the dye molecules and make them unstable. At the same time, due to the hydrolysis, a large amount of floccules are generated, which has the functions of netting, bridging and complexing sedimentation, thereby achieving the removal of colored substances in printing and dyeing wastewater;

[0038] 2. The composite metal dicyandiamide formaldehyde cationic flocculant prepared by chemical composite synthesis with polyaluminium chloride can make up for the shortcomings of using each separately, not only can it improve the decolorization performance of printing and dyeing wastewater, but also can reduce the dosage of organic decolorization flocculant and reduce the treatment cost, and has good economic value;

[0039] 3. The composite metal dicyandiamide formaldehyde cationic flocculant prepared by the present invention has good decolorization effect, moderate viscosity, is easily soluble in water, has good flocculation effect when the dosage is small, and has broad application prospects;

[0040] 4. The prepared composite metal dicyandiamide formaldehyde cationic flocculant uses dicyandiamide, formaldehyde, polyaluminium chloride and the like as raw materials. In the dehydration and condensation synthesis process, all the raw materials input generate dicyandiamide formaldehyde polymers, without any emission of waste gas, waste water, waste residue and the like. It is a relatively advanced green chemical synthesis process with the advantages of easy availability of raw materials, low price, simple operation, mild reaction and short production cycle, and is fully suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-1 in printing and dyeing wastewater in Example 1 of the present application;

[0042] Figure 2 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-2 in printing and dyeing wastewater in Example 2 of the present application;

[0043] Figure 3 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-3 in printing and dyeing wastewater in Example 3 of the present application;

[0044] Figure 4 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-4 in printing and dyeing wastewater in Example 4 of the present application;

[0045] Figure 5 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-5 in printing and dyeing wastewater in Example 5 of the present application;

[0046] Figure 6 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-6 in printing and dyeing wastewater in Example 6 of the present application;

[0047] Figure 7 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-7 in printing and dyeing wastewater in Example 7 of the present application;

[0048] Figure 8 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-8 in printing and dyeing wastewater in Example 8 of the present application;

[0049] Fig. 9 This is a graph showing the decolorization performance of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-9 in printing and dyeing wastewater in Example 9 of the present application;

[0050] Fig.10 This is an infrared spectrum analysis diagram of the composite metal dicyandiamide formaldehyde cationic flocculant in Examples 1 to 9 of the present application;

[0051] Fig.11 This is an infrared spectrum analysis diagram of flocs after decolorization treatment of the composite metal dicyandiamide formaldehyde cationic flocculant in printing and dyeing wastewater in Examples 1 to 9 of the present application. DETAILED DESCRIPTION

[0052] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0053] Embodiment 1:

[0054] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0055] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:2:1:0.67:1.67:0.5:1.07:0.8, add 1.50 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride to a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0056] Step 2: Heat to 50°C, keep warm for 18 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0057] Step 3: Set the temperature to 70°C, keep the reaction for 2 hours, and then cool the product naturally;

[0058] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 70°C, keep the reaction for 2 hours, stop heating, and cool the product naturally to obtain a composite metal dicyandiamide formaldehyde cationic flocculant, named DFCF-1.

[0059] Add printing and dyeing wastewater with a pH value of 6 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-1 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization application is to first quickly stir at a speed of 250 r / min for 6 minutes, and then slowly stir at a speed of 50 r / min for 14 minutes.

[0060] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-1 decolorization in printing and dyeing wastewater was obtained, as shown in Figure 1 As shown in the figure, it can be seen that DFCF-1 has excellent decolorization performance. When the dosage of DFCF-1 is 100 mg / L, the decolorization rate can reach 93.28%.

[0061] Example 2

[0062] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0063] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:1.33:0.67:0.67:0.67:0.33:1.07:0.6, add 0.75 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 of the mass of ammonium chloride into a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0064] Step 2: Heat to 60°C, keep warm for 20 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0065] Step 3: Set the temperature to 70°C, keep the reaction for 2 hours, and then cool the product naturally;

[0066] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 70°C, keep the reaction for 2 hours, stop heating, and naturally cool the product to obtain a composite metal dicyandiamide formaldehyde cationic flocculant, named DFCF-2.

[0067] Add printing and dyeing wastewater with a pH value of 2 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-2 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization application is to first quickly stir at a speed of 200 r / min for 4 minutes, and then slowly stir at a speed of 30 r / min for 12 minutes.

[0068] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-2 decolorization in printing and dyeing wastewater was obtained, as shown in Figure 2 As shown; it can be seen from the figure that DFCF-2 has excellent decolorization performance. When the dosage of DFCF-2 is 100 mg / L, the decolorization rate can reach 100%.

[0069] Example 3

[0070] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0071] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:2:1:0.75:1.5:0.5:1.2:0.7, add 1.00 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride to a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0072] Step 2: Heat to 30°C, keep warm for 5 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0073] Step 3: Set the temperature to 80°C, keep the reaction for 2 hours, and then cool the product naturally;

[0074] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 80°C, keep the reaction for 2 hours, stop heating, and naturally cool the product to obtain a composite metal dicyandiamide formaldehyde cationic flocculant, named DFCF-3.

[0075] Add printing and dyeing wastewater with a pH value of 4 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-3 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization application is to first quickly stir at a speed of 200 r / min for 5 minutes, and then slowly stir at a speed of 40 r / min for 13 minutes.

[0076] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-3 decolorizing in printing and dyeing wastewater was obtained, as shown in Figure 3 As shown in the figure, it can be seen that DFCF-3 has excellent decolorization performance. When the dosage of DFCF-3 is 100 mg / L, the decolorization rate can reach 95.39%.

[0077] Example 4

[0078] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0079] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:1:0.5:0.2:0.2:0.2:1:0.5, add 0.50 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride into a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0080] Step 2: Heat to 40°C, keep warm for 12 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0081] Step 3: Set the temperature to 60°C, keep the reaction for 1 hour, and then cool the product naturally;

[0082] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 60°C, keep the reaction warm for 1 hour, stop heating, and cool the product naturally to obtain a composite metal dicyandiamide formaldehyde cationic flocculant, named DFCF-4.

[0083] Add printing and dyeing wastewater with a pH value of 1 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-4 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization application is to first quickly stir at a speed of 150 r / min for 3 minutes, and then slowly stir at a speed of 20 r / min for 10 minutes.

[0084] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-4 decolorization in printing and dyeing wastewater was obtained, as shown in Figure 4 As shown in the figure, it can be seen that DFCF-4 has excellent decolorization performance. When the dosage of DFCF-4 is 100 mg / L, the decolorization rate can reach 97.28%.

[0085] Example 5

[0086] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0087] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride at a molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:2:1:1:2:0.5:1:0.9, add 2.00 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 of the mass of ammonium chloride into a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0088] Step 2: Heat to 35°C, keep warm for 10 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0089] Step 3: Set the temperature to 90°C, keep the reaction for 3 hours, and then cool the product naturally;

[0090] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 90°C, keep the reaction warm for 3 hours, stop heating, and naturally cool the product to obtain a composite metal dicyandiamide formaldehyde cationic flocculant, named DFCF-5.

[0091] Add printing and dyeing wastewater with a pH value of 7 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-5 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization process is firstly rapid stirring at a speed of 300 r / min for 7 minutes, and then slow stirring at a speed of 60 r / min for 15 minutes.

[0092] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-5 decolorizing in printing and dyeing wastewater was obtained, as shown in Figure 5 As shown in the figure, it can be seen that DFCF-5 has excellent decolorization performance. When the dosage of DFCF-5 is 100 mg / L, the decolorization rate can reach 92.77%.

[0093] Example 6

[0094] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0095] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride in a molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:2:1:0.5:0.1:0.25:0.5:0.9, add 1.00 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 of the mass of ammonium chloride into a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0096] Step 2: Heat to 45°C, keep warm for 17 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0097] Step 3: Set the temperature to 70°C, keep the reaction for 4 hours, and then cool the product naturally;

[0098] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 70°C, keep the reaction warm for 4 hours, stop heating, and naturally cool the product to obtain a composite metal dicyandiamide formaldehyde cationic flocculant named DFCF-6.

[0099] Add printing and dyeing wastewater with a pH value of 8 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-6 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization application is to first quickly stir at a speed of 250 r / min for 8 minutes, and then slowly stir at a speed of 25 r / min for 16 minutes.

[0100] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-6 decolorization in printing and dyeing wastewater was obtained, as shown in Figure 6 As shown in the figure, it can be seen that DFCF-6 has excellent decolorization performance. When the dosage of DFCF-6 is 100 mg / L, the decolorization rate can reach 91.27%.

[0101] Example 7

[0102] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0103] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:2.67:0.67:0.67:0.67:0.5:1.07:0.6, add 0.75 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 of the mass of ammonium chloride into a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0104] Step 2: Heat to 55°C, keep warm for 19 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0105] Step 3: Set the temperature to 80°C, keep the reaction for 3 hours, and then cool the product naturally;

[0106] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 80°C, keep the reaction warm for 3 hours, stop heating, and naturally cool the product to obtain a composite metal dicyandiamide formaldehyde cationic flocculant named DFCF-7.

[0107] Add printing and dyeing wastewater with a pH value of 10 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-7 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization process is firstly rapid stirring at a speed of 300 r / min for 9 minutes, and then slow stirring at a speed of 55 r / min for 17 minutes.

[0108] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-7 decolorization in printing and dyeing wastewater was obtained, as shown in Figure 7 As shown in the figure, it can be seen that DFCF-7 has excellent decolorization performance. When the dosage of DFCF-7 is 100 mg / L, the decolorization rate can reach 98.87%.

[0109] Example 8

[0110] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0111] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:2:1:0.75:1.5:0.5:1.2:0.6, add 1.00 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride to a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0112] Step 2: Heat to 60°C, keep warm for 20 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0113] Step 3: Set the temperature to 70°C, keep the reaction for 2 hours, and then cool the product naturally;

[0114] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 70°C, keep the reaction for 2 hours, stop heating, and naturally cool the product to obtain a composite metal dicyandiamide formaldehyde cationic flocculant, named DFCF-8.

[0115] Add printing and dyeing wastewater with a pH value of 12 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-8 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization application is to first quickly stir at a speed of 350 r / min for 10 minutes, and then slowly stir at a speed of 45 r / min for 18 minutes.

[0116] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-8 decolorization in printing and dyeing wastewater was obtained, as shown in Figure 8 As shown in the figure, it can be seen that DFCF-8 has excellent decolorization performance. When the dosage of DFCF-8 is 100 mg / L, the decolorization rate can reach 96.32%.

[0117] Example 9

[0118] The preparation method of the composite metal dicyandiamide formaldehyde cationic flocculant specifically comprises the following steps:

[0119] Step 1: Take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1:1.33:1:0.67:1.67:0.5:1.07:0.6, add 1.50 mol of dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 of the mass of ammonium chloride into a reactor equipped with a condenser reflux tube and a thermometer, turn on the condensation water and start stirring to mix;

[0120] Step 2: Heat to 50°C, keep warm for 18 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride;

[0121] Step 3: Set the temperature to 60°C, keep the reaction for 3 hours, and then cool the product naturally;

[0122] Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 60°C, keep the reaction warm for 3 hours, stop heating, and cool the product naturally to obtain a composite metal dicyandiamide formaldehyde cationic flocculant named DFCF-9.

[0123] Add printing and dyeing wastewater with a pH value of 14 into a beaker and place it on a flocculation stirrer. The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant DFCF-9 is 10, 50, 100, 150, and 200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the decolorization application is to first quickly stir at a speed of 400 r / min for 7 minutes, and then slowly stir at a speed of 35 r / min for 20 minutes.

[0124] After settling for 30 minutes, the upper clear liquid was taken at 0 and 30 minutes to measure the absorbance of the decolorized water sample. The performance diagram of DFCF-9 decolorizing in printing and dyeing wastewater was obtained, as shown in Fig. 9 As shown in the figure, it can be seen that DFCF-9 has excellent decolorization performance. When the dosage of DFCF-9 is 100 mg / L, the decolorization rate can reach 99.02%.

[0125] The composite metal dicyandiamide formaldehyde cationic flocculants prepared in Examples 1 to 9 were subjected to physical and chemical characterization to obtain their physical and chemical properties, as shown in Table 1. It can be seen from Table 1 that:

[0126] The composite metal dicyandiamide formaldehyde cationic flocculant prepared by the method has a stable solid content of 53.21-68.22%, a stable viscosity value of 1217.00-1503.00 mPa·s, a stable cationic value of 28.10-38.20%, a molecular weight of up to one million, and a stable viscosity of 3.00×10^ 6g / mol, and according to the relative molecular mass of its cationic chain segment, the average value of the number of repeating units of the composite metal dicyandiamide formaldehyde cationic flocculant n≈41600.

[0127] Table 1 Physicochemical properties of different dicyandiamide formaldehyde cationic decolorizing flocculants

[0128]

[0129] Among them, the method for determining the solid content of the product is to weigh m1 sample, dry it in an oven at 110°C for about 7h, take it out and cool it to room temperature, weigh it as m2, and the solid content is calculated by the formula S=m2 / m1×100%; use NDJ-8S type rotational viscometer to measure its shear viscosity at room temperature; the determination of cationic degree adopts colloid titration method, that is, weigh the decolorizing flocculant after drying and constant weight with weighing paper, the mass is m0 in a 250mL weighing bottle, add 100mL distilled water, stir until dissolved, adjust the pH, add toluidine blue indicator, and titrate with PVSK standard solution with a molar concentration of C1 until the solution changes from blue to red purple as the titration end point, the consumed volume is V1, V0 is the volume of the standard solution consumed when blank, and the cationic degree is calculated by the formula A =72C1×(V1-V0) / 1000m0×100% (72 is the relative molecular mass of the cationic chain segment); the product molecular weight determination method is to accurately weigh 0.05g of solid product, add a certain amount of water and 2mol / L sodium chloride solution to prepare a solution, fix the viscometer in a constant temperature water bath, leave it for 15min, take the prepared solution and inject it into the B ball along the clean viscometer tube wall, close one end of the tube, and draw air from the other end to slowly raise the solution level to a specified height, release the closed tube mouth in turn, let the solution fall naturally in the tube, use a stopwatch to accurately record the time when the liquid level drops, repeat the test 3 times, the average time is t, the difference between the 3 measured values ​​does not exceed 0.5s, then the molecular weight is calculated by the formula M=(η / 3.73×10000)^ (1 / 0.66) (η is obtained by looking up the table of t / t0).

[0130] The composite metal dicyandiamide formaldehyde cationic flocculant prepared in Examples 1 to 9 was subjected to infrared analysis. The infrared spectrum ( Fig.10 ) analysis, at 3259cm -1 Nearby are the characteristic absorption peaks of -OH, NH, and N-H2; 2175cm -1 H2N + =C absorption peak, H2N + =C has a positive charge and can neutralize the dye molecules; 1615cm -1 The peak at 1133 cm is the characteristic peak of C=O, indicating the presence of amide groups in the product; -1 The characteristic peak of -C-NH- is at 1046cm-1 The characteristic peak of -CH2-OH is shown at the bottom.

[0131] The flocs obtained after decolorization of the composite metal dicyandiamide formaldehyde cationic flocculant prepared in Examples 1 to 9 were subjected to infrared analysis. The infrared spectrum ( Fig.11 ) analysis, the flocculent precipitate was at 2175cm -1 H2N + =C absorption peak, proving that the flocculent precipitate contains decolorizing flocculant.

[0132] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Composite metal dicyandiamide formaldehyde cationic flocculant, its molecular structure is as follows:

2. A method for preparing the composite metal dicyandiamide formaldehyde cationic flocculant according to claim 1, characterized in that: The specific steps include: The first step: according to the molar ratio of dicyandiamide: formaldehyde: ammonium chloride: urea: melamine: acrylamide: hexamethylenetetramine: polyaluminium chloride = 1: (0.5-4): (0.25-2): (0.1-2): (0.1-4): (0.1-1): (0.5-2): (0.6-0.9), take dicyandiamide, formaldehyde, ammonium chloride, urea, melamine, acrylamide, hexamethylenetetramine and polyaluminium chloride, in a reactor equipped with a condensation reflux tube and a thermometer, add dicyandiamide, formaldehyde, urea, melamine, acrylamide, hexamethylenetetramine and 1 / 2 of the mass of ammonium chloride, open the condensation water and stir to mix; Step 2: Heat to 30-60°C, keep warm for 5-20 minutes, then add the remaining 1 / 2 of the mass of ammonium chloride; Step 3: Set the temperature to 50-90°C, keep the reaction for 1-4 hours, and then cool the product naturally; Step 4: Add polyaluminium chloride to the naturally cooled product, set the temperature to 50-90°C, keep the reaction for 1-4 hours, stop heating, and naturally cool to obtain a composite metal dicyandiamide formaldehyde cationic flocculant.

3. The method for preparing the composite metal dicyandiamide formaldehyde cationic flocculant according to claim 2, characterized in that: The molar concentration of the dicyandiamide is 0.5-2 mol / L.

4. An application of the composite metal dicyandiamide formaldehyde cationic flocculant according to claim 1 in decolorizing printing and dyeing wastewater, characterized in that: The dosage of the composite metal dicyandiamide formaldehyde cationic flocculant is 10-200 mg / L; the printing and dyeing wastewater includes production wastewater and washing wastewater; the initial pH value of the printing and dyeing wastewater is 1-14; the decolorization application is firstly rapid stirring at a speed of 150-400 r / min for 3-10 minutes, and then slow stirring at a speed of 20-60 r / min for 10-20 minutes.

5. The composite metal dicyandiamide formaldehyde cationic flocculant according to claim 1, characterized in that: The synthesis reaction mechanism of the composite metal dicyandiamide formaldehyde cationic flocculant is: S1, ammonium chloride and formaldehyde produce hydrochloric acid through a reversible reaction; S2, the dicyandiamide molecule absorbs hydrogen ions and undergoes an isomerization reaction under heating conditions, transforming from a diamide structure to a cyanoguanidine structure with a positive charge, and the dicyandiamide molecule continuously consumes hydrogen ions to promote the reaction of ammonium chloride and formaldehyde to proceed to the right; S3, multiple dicyandiamide molecules can be connected to form hydroxymethyl derivatives through the imine bond generated by the addition reaction between the cyano group and its own amine group; S4, a dehydration condensation reaction between two molecules of hydroxymethyl and hydroxymethyl or between hydroxymethyl and amine groups generated by the reaction with formaldehyde generates a macromolecule, namely, a dicyandiamide formaldehyde cationic decolorizing flocculant; S5, C=O of the dicyandiamide formaldehyde cationic decolorizing flocculant and -OH of polyaluminium chloride can interact with each other by forming hydrogen bonds, thus obtaining a composite metal dicyandiamide formaldehyde cationic flocculant.

6. The composite metal dicyandiamide formaldehyde cationic flocculant according to claim 5, characterized in that: The reaction formula in S1 is: 4NH4Cl+6CHOH→(CH2)6N4+4HCl+6H2O (CH2)6N4+HCl→(CH2)6N4·HCl 7. The composite metal dicyandiamide formaldehyde cationic flocculant according to claim 1, characterized in that: The reaction formula in S2 is:

8. The composite metal dicyandiamide formaldehyde cationic flocculant according to claim 1, characterized in that: The reaction formula in S3 is:

9. The composite metal dicyandiamide formaldehyde cationic flocculant according to claim 1, characterized in that: The reaction formula in S4 is:

10. The composite metal dicyandiamide formaldehyde cationic flocculant according to claim 1, characterized in that: The reaction formula in S5 is:

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