Coagulant for industrial wastewater treatment and preparation method thereof

Abstract

The invention discloses a coagulant for industrial wastewater treatment and a preparation method thereof, and belongs to the technical field of water treatment.The coagulant comprises a main flocculant and an auxiliary flocculant, the main flocculant is polyferric sulfate and / or polyaluminum chloride, and the auxiliary flocculant is organic modified diatomite; the organic modified diatomite is prepared by condensing aminated diatomite and a carboxylation modifier; the aminated diatomite is diatomite treated by an aminated silane coupling agent. The auxiliary flocculant not only has a porous characteristic, active functional groups on the surface can adsorb metal cations, and the auxiliary flocculant can be integrally used as a crystal nucleus to promote growth and aggregation of other precipitates (such as ferric hydroxide, aluminum hydroxide and the like) on the surface, so that the precipitation process is accelerated, the removal efficiency of pollutants in wastewater is improved, and the wastewater treatment effect is improved. The effect of enhancing coagulation is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a coagulant for industrial wastewater treatment and a preparation method thereof. Background Art

[0002] With the rapid development of the electronic information industry, the demand and output of printed circuit boards (PCBs) have increased significantly. The quality of wastewater and waste liquid from different processes in the printed circuit board industry is different. The waste liquid mainly includes: etching waste liquid, electroplating waste liquid, developing waste liquid and film removal waste liquid. Since the wastewater of printed circuit boards has many production nodes and complex components, it contains heavy metal pollutants, difficult-to-degrade high-concentration organic pollutants, and complexed heavy metal ions. This type of wastewater must be treated to meet the standards before it can be discharged into the water body. At present, for this type of wastewater with relatively complex water quality, the treatment processes include coagulation and precipitation, oxidation-reduction method and biological method, etc. Among them, coagulation and precipitation, as a traditional process, is widely used due to its easy operation, low cost and good treatment effect. The coagulation reaction can effectively remove colloidal particles in the wastewater, and can also form insoluble precipitates with organic matter dissolved in the water phase. Commonly used coagulants include inorganic coagulants and organic coagulants. Among them, inorganic coagulants are mainly FeCl3, Al2(SO4)3 and their polymers. Organic coagulants include cationic polymer coagulants, amphoteric organic polymer coagulants, anionic polymer coagulants and non-ionic coagulants. Therefore, the selection and use of coagulants will greatly affect the treatment effect of wastewater.

[0003] Etching waste liquid includes acidic etching waste liquid and alkaline etching waste liquid, which correspond to acidic etching and alkaline etching processes respectively. The main component of the waste liquid is copper ammonia complex. Taking ammonia-ammonium chloride-copper ammonia etching solution as an example, there is a large amount of [Cu(NH3)4] 2+ Complex ions, also contain ammonium ions (NH4 + ) and chloride ions (Cl-). The pH value of alkaline etching waste liquid is relatively high, generally around 8-10, and the copper content is also high. It is one of the waste liquids that circuit board companies need to focus on treating.

[0004] Acidic copper waste liquid (Cu 2+ >500mg / L, in addition to copper, it also contains HCl, NH4Cl, NaCl, etc.), waste liquid containing copper-ammine complex produced by alkaline etching (mainly in the form of [Cu(NH3)4]Cl2), and wastewater mainly includes: electroplating wastewater, wastewater containing copper-EDTA complex produced by oil removal pretreatment in each process and chemical copper deposition process, cleaning water of chemical copper plating, etc. Since printed circuit board wastewater entering the water body will cause extensive and serious harm to the ecological environment and humans, the research on printed circuit board wastewater treatment technology is becoming increasingly important.

[0005] The patent application with publication number CN118754276A discloses a coagulant for treating sewage and a preparation method thereof, the preparation method comprising two steps: preparation of S1 coagulant reaction solution and preparation of S2 coagulant. The secondary coagulant is an inorganic-organic composite coagulant generated by mixing titanium chloride, magnesium chloride and methacryloyloxyethyl trimethylammonium chloride (DMC) in a certain proportion and reacting at low temperature. This coagulant has high flocculation and decontamination ability and stable properties, and can be used in sewage with different pH and different temperatures. However, the vacuum rotary evaporation and freeze-drying process in the application are complicated to operate, the freeze-drying temperature is -50°C to 70°C, and the freeze-drying time is 10-12h, which not only requires high-specification freeze-drying equipment, but also a long freeze-drying time, which reduces production efficiency. Summary of the invention

[0006] The object of the present invention is to provide a coagulant for industrial wastewater treatment and a preparation method thereof, so as to solve the problem of poor removal effect of metal ions in industrial wastewater.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A coagulant for industrial wastewater treatment comprises a main flocculant and an auxiliary flocculant, wherein the main flocculant is polyferric sulfate and / or polyaluminium chloride, and the auxiliary flocculant is organically modified diatomaceous earth; the organically modified diatomaceous earth is prepared by condensing amino diatomaceous earth with a carboxyl modifier; the amino diatomaceous earth is diatomaceous earth treated with an amino silane coupling agent.

[0009] Furthermore, the mass ratio of the polyferric sulfate, polyaluminium chloride and organic modified diatomite is 0-100:0-100:0.2-1. The mixed use of polyferric sulfate and polyaluminium chloride can broaden the application scope of the coagulant, and the floc structure formed is more compact and stable. The sedimentation rate of such flocs is faster than that of flocs formed when a single flocculant is used. The charges on the surface of the particles can be better neutralized, so that the mutual attraction between the particles is enhanced.

[0010] Furthermore, the aminosilane coupling agent is at least one of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and 3-aminopropyltrimethoxysilane.

[0011] Furthermore, the carboxyl modifier is citric acid, ethylenediaminetetraacetic acid or a hyperbranched polymer containing a terminal carboxyl group. A hyperbranched polymer containing a terminal carboxyl group, such as trimethylolpropane, is used as the central core, and citric acid is used as a comonomer, and a hyperbranched polymer of the terminal carboxyl group type is obtained by esterification reaction according to a molar ratio of 1:3. The hyperbranched structure has good dispersibility, and its unique three-dimensional structure can also adsorb metal ions or other pollutants to achieve a flocculation effect.

[0012] A method for preparing a coagulant for industrial wastewater treatment comprises the following steps:

[0013] Further, the organic modified diatomaceous earth is prepared by the following steps:

[0014] The first step is to mix diatomite and water, stir and disperse to obtain a diatomite suspension, add an aminosilane coupling agent to the diatomite suspension, heat and stir under weak acid conditions to obtain an amino diatomite dispersion; add a carboxyl modifier to the above amino diatomite dispersion to undergo a condensation reaction to obtain an organically modified diatomite; during the treatment of diatomite, the aminosilane coupling agent undergoes dehydration condensation with Si-OH on the surface of the diatomite to form S iOS i, and introduces amino groups on the surface of the diatomite to facilitate subsequent reaction with carboxyl groups;

[0015] A carboxyl modifier is added to the above-mentioned amination diatomite dispersion to undergo condensation reaction to obtain organically modified diatomite; the amino terminal exposed on the outer surface of the amination diatomite undergoes condensation with the COOH group in the structure of the carboxyl modifier to prepare organically modified diatomite.

[0016] Furthermore, the mass ratio of diatomaceous earth, aminosilane coupling agent and carboxyl modifier is 15-20g: 0.12-0.15g: 0.03g-0.5g.

[0017] Furthermore, in the first step, the aminosilane coupling agent is dispersed with a 50% by volume ethanol aqueous solution and then added; and the carboxylation modifier is dispersed with a 50% by volume ethanol aqueous solution and then added.

[0018] Furthermore, the weakly acidic pH value ranges from 4 to 6; and the heating and stirring temperature is 70 to 80°C.

[0019] Furthermore, the diatomite is pre-treated with alkaline activation before use, and the alkaline activation treatment step includes the following steps: adding the diatomite to an alkaline reagent, heating it at 70-80°C for 20-30min, taking it out, filtering it, and drying it. Diatomite is a porous siliceous mineral formed by the accumulation of ancient diatom remains. Its main component is SiO2, and there are a large number of orderly arranged micropores on the outer wall of diatoms. This characteristic gives diatomite the characteristics of large specific surface area and strong adsorption capacity. After alkaline activation, the impurities in the internal pores of the diatomite are dissolved, which can further expand the micropores on the outer wall of the diatomite and improve the adsorption effect.

[0020] Furthermore, the alkaline reagent is a sodium hydroxide solution with a pH value of 12 and a potassium hydroxide solution with a pH value of 12.

[0021] Beneficial effects of the present invention:

[0022] The coagulant in the present invention includes a main flocculant and an auxiliary flocculant, wherein polyferric sulfate and / or polyaluminium chloride are the main flocculants, and the auxiliary flocculant is an organic modified diatomite. The organic modified diatomite is prepared by condensing amino diatomite with a carboxyl modifier; the amino diatomite is diatomite treated with an amino silane coupling agent, and the organic modified diatomite can be used as an auxiliary flocculant to effectively treat metal ions in wastewater, and the alkalinity consumption is low, which is more suitable for coagulation treatment of wastewater containing metal ions under alkaline conditions. The auxiliary flocculant in the present invention not only has a porous characteristic, but also the active functional groups on the surface can adsorb metal cations, and the auxiliary flocculant as a whole can also be used as a crystal nucleus to promote the growth and aggregation of other precipitates (such as iron hydroxide, aluminum hydroxide, etc.) on its surface, thereby accelerating the precipitation process, improving the removal efficiency of pollutants in wastewater, and playing an effect of strengthening coagulation. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Obviously, the following descriptions are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in the field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0025] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter described in the claims.

[0026] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0027] A coagulant for industrial wastewater treatment comprises organic modified diatomaceous earth, polyferric sulfate and / or polyaluminium chloride; the modified diatomaceous earth is prepared by condensing amino diatomaceous earth with a carboxyl modifier; the amino diatomaceous earth is diatomaceous earth treated with an amino silane coupling agent.

[0028] Example 1

[0029] This embodiment provides a method for preparing a coagulant for industrial wastewater treatment, comprising the following steps:

[0030] The first step is to prepare organic modified diatomaceous earth:

[0031] 15 g of diatomaceous earth and 100 mL of water were mixed and stirred to obtain a diatomaceous earth suspension. A mixture of 0.12 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension. The pH value of the system was adjusted to 5, and the mixture was stirred at 70° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0032] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.03 g of the carboxylation modifier (citric acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0033] The second step is to use the prepared organic modified diatomite as an auxiliary flocculant and the main flocculant as polyferric sulfate and / or polyaluminium chloride, and mix them in proportion to obtain a coagulant for industrial wastewater treatment. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organic modified diatomite (OD) is 0-100:0-100:0.2-1.

[0034] Take PCB complex wastewater (copper content 214.29 mg / L, pH <3, wastewater from this batch is selected in both the embodiment and the comparative example), adjust the initial pH to 9, add the prepared coagulant, and record the effluent copper content and effluent pH value. The results are shown in Table 1 below:

[0035] Table 1

[0036]

[0037] The mixed use of PFS and PAC can broaden the application scope of coagulants. The hydrolysis reaction of PFS can still proceed in an acidic environment. Under alkaline conditions, the hydrolysis product will form a precipitate, causing PFS to lose its coagulation effect. At the same time, the hydrogen ions generated during the hydrolysis process will dissolve the precipitated copper hydroxide (copper comes from wastewater). According to the test results recorded in Table 1, a single PFS will result in a relatively low pH value of the effluent. The floc structure formed by the mixture of PFS and PAC is more compact and stable. The sedimentation rate of this floc is faster than that formed when a single flocculant is used. This is because the mixed agent can better neutralize the charge on the surface of the particles and enhance the mutual attraction between the particles. The compact floc settles faster in water, which is conducive to shortening the sedimentation time of water treatment and improving the treatment efficiency. After PFS and PAC are mixed, the amount of the main coagulant can be reduced, thereby reducing costs. With the increase in the amount of organically modified diatomaceous earth, the copper content of the effluent tends to be stable. The addition of organically modified diatomaceous earth provides condensation nuclei for the coagulant reaction and can also play a role in strengthening the coagulation effect.

[0038] Example 2

[0039] This embodiment provides a method for preparing a coagulant for industrial wastewater treatment, comprising the following steps:

[0040] The first step is to prepare organic modified diatomaceous earth:

[0041] 20 g of diatomaceous earth and 100 mL of water were mixed, and after stirring and dispersing, a diatomaceous earth suspension was obtained. A mixture of 0.15 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension, the pH value of the system was adjusted to 5, and the mixture was stirred at 70-80° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0042] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.5 g of the carboxylation modifier (citric acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 2 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0043] In the second step, the prepared organically modified diatomaceous earth is used as an auxiliary flocculant, and the main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organically modified diatomaceous earth (OD) is 40:40:0.5, and a coagulant for industrial wastewater treatment is obtained.

[0044] Example 3

[0045] This embodiment provides a method for preparing a coagulant for industrial wastewater treatment, comprising the following steps:

[0046] The first step is to prepare organic modified diatomaceous earth:

[0047] 15 g of diatomaceous earth and 100 mL of water were mixed and stirred to obtain a diatomaceous earth suspension. A mixture of 0.12 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension. The pH value of the system was adjusted to 5, and the mixture was stirred at 70° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0048] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.03 g of the carboxylation modifier (ethylenediaminetetraacetic acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0049] In the second step, the prepared organically modified diatomaceous earth is used as an auxiliary flocculant, and the main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organically modified diatomaceous earth (OD) is 40:40:0.5, and a coagulant for industrial wastewater treatment is obtained.

[0050] Example 4

[0051] This embodiment provides a method for preparing a coagulant for industrial wastewater treatment, comprising the following steps:

[0052] The first step is to prepare organic modified diatomaceous earth:

[0053] 20 g of diatomaceous earth and 100 mL of water were mixed, and after stirring and dispersing, a diatomaceous earth suspension was obtained. A mixture of 0.15 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension, the pH value of the system was adjusted to 5, and the mixture was stirred at 70-80° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0054] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.5 g of the carboxylation modifier (ethylenediaminetetraacetic acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 2 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0055] In the second step, the prepared organically modified diatomaceous earth is used as an auxiliary flocculant, and the main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organically modified diatomaceous earth (OD) is 40:40:0.5, and a coagulant for industrial wastewater treatment is obtained.

[0056] Example 5

[0057] A method for preparing a coagulant for industrial wastewater treatment comprises the following steps:

[0058] The first step is to prepare organic modified diatomaceous earth:

[0059] Add diatomaceous earth to a sodium hydroxide solution with a pH value of 12, heat at 80°C for 20 minutes, take it out, filter it, and dry it;

[0060] 15 g of the treated diatomaceous earth was mixed with 100 mL of water, and the mixture was dispersed by stirring to obtain a diatomaceous earth suspension. A mixture of 0.12 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension, the pH value of the system was adjusted to 5, and the mixture was stirred at 70° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0061] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.03 g of the carboxylation modifier (citric acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0062] In the second step, the prepared organically modified diatomaceous earth is used as an auxiliary flocculant, and the main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organically modified diatomaceous earth (OD) is 40:40:0.5, and a coagulant for industrial wastewater treatment is obtained.

[0063] Example 6

[0064] A method for preparing a coagulant for industrial wastewater treatment comprises the following steps:

[0065] The first step is to prepare organic modified diatomaceous earth:

[0066] Add diatomaceous earth to a sodium hydroxide solution with a pH value of 12, heat at 80°C for 20 minutes, take it out, filter it, and dry it;

[0067] 20 g of the treated diatomaceous earth was mixed with 100 mL of water, and the mixture was stirred and dispersed to obtain a diatomaceous earth suspension. A mixture of 0.15 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension, the pH value of the system was adjusted to 5, and the mixture was stirred at 70-80° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0068] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.5 g of the carboxylation modifier (citric acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 2 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0069] In the second step, the prepared organically modified diatomaceous earth is used as an auxiliary flocculant, and the main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organically modified diatomaceous earth (OD) is 40:40:0.5, and a coagulant for industrial wastewater treatment is obtained.

[0070] Example 7

[0071] A method for preparing a coagulant for industrial wastewater treatment comprises the following steps:

[0072] The first step is to prepare organic modified diatomaceous earth:

[0073] Add diatomaceous earth to a sodium hydroxide solution with a pH value of 12, heat at 70°C for 30 minutes, take it out, filter it, and dry it;

[0074] 15 g of the treated diatomaceous earth was mixed with 100 mL of water, and the mixture was dispersed by stirring to obtain a diatomaceous earth suspension. A mixture of 0.12 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension, the pH value of the system was adjusted to 5, and the mixture was stirred at 70° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0075] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.03 g of the carboxylation modifier (ethylenediaminetetraacetic acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0076] In the second step, the prepared organically modified diatomaceous earth is used as an auxiliary flocculant, and the main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organically modified diatomaceous earth (OD) is 40:40:0.5, and a coagulant for industrial wastewater treatment is obtained.

[0077] Example 8

[0078] A method for preparing a coagulant for industrial wastewater treatment comprises the following steps:

[0079] The first step is to prepare organic modified diatomaceous earth:

[0080] Add diatomaceous earth to a sodium hydroxide solution with a pH value of 12, heat at 70°C for 30 minutes, take it out, filter it, and dry it;

[0081] 20 g of the treated diatomaceous earth was mixed with 100 mL of water, and the mixture was stirred and dispersed to obtain a diatomaceous earth suspension. A mixture of 0.15 g of γ-aminopropyltriethoxysilane and 10 mL of a 50% by volume ethanol solution was added to the diatomaceous earth suspension, the pH value of the system was adjusted to 5, and the mixture was stirred at 70-80° C. for 60 min to obtain an amino diatomaceous earth dispersion.

[0082] A carboxylation modifier was added to the above-mentioned amino diatomite dispersion. 0.5 g of the carboxylation modifier (ethylenediaminetetraacetic acid) was dispersed in 5 mL of 50% ethanol aqueous solution and then added. After the addition, the temperature was raised to 50° C. and stirred for 20 min. Then, the mixture was added to a stainless steel reactor with a polytetrafluoroethylene liner, heated to 120° C., and reacted for 2 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain an organically modified diatomite.

[0083] In the second step, the prepared organically modified diatomaceous earth is used as an auxiliary flocculant, and the main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organically modified diatomaceous earth (OD) is 40:40:0.5, and a coagulant for industrial wastewater treatment is obtained.

[0084] Comparative Example 1

[0085] This comparative example uses activated diatomaceous earth:

[0086] The diatomaceous earth was added into a sodium hydroxide solution with a pH value of 12, heated at 70° C. for 30 minutes, taken out, filtered, and dried to obtain activated diatomaceous earth.

[0087] The main flocculants are polyferric sulfate and polyaluminium chloride, and the mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organic modified diatomaceous earth (OD) is 40:40:0.5; the activated diatomaceous earth and the main flocculant are mixed to obtain a coagulant for industrial wastewater treatment.

[0088] Comparative Example 2

[0089] This comparative example uses activated diatomaceous earth:

[0090] The diatomaceous earth was added into a sodium hydroxide solution with a pH value of 12, heated at 70° C. for 30 minutes, taken out, filtered, and dried to obtain activated diatomaceous earth.

[0091] In this comparative example, the main flocculant is polyaluminium chloride, and the mass ratio of polyaluminium chloride (PAC) to organically modified diatomaceous earth (OD) is 100:0.5.

[0092] Comparative Example 3

[0093] In this comparative example, no auxiliary flocculant is added, and only the main flocculant is added. The main flocculants are polyferric sulfate and polyaluminium chloride. The mass ratio of polyferric sulfate (PFS), polyaluminium chloride (PAC) and organic modified diatomaceous earth (OD) is 40:40:0.5.

[0094] Performance tests were performed on Examples 2 to 8 and Comparative Examples 1 to 3, and the results are shown in Table 2:

[0095] Table 2

[0096]

[0097] Combining the test results of Table 1 and Table 2, it can be seen that the auxiliary flocculant prepared by the present invention has a good auxiliary flocculation effect, and can effectively treat metal ions (copper ions) in wastewater by coordinating with the main flocculant to treat wastewater. The silicon hydroxyl groups on the surface of the treated auxiliary flocculant (aminosilane coupling agent and carboxylation agent) are consumed, and the pH value of the solution decreases slowly during the coagulation process, reducing the alkalinity consumption. And after the carboxylation treatment, the adsorption performance of metal ions is also increased. The adsorption process is mainly ion exchange or electrostatic attraction, without the generation of additional hydrogen ions, and will not cause the pH to decrease. It is more suitable for coagulation treatment of wastewater containing metal ions under alkaline conditions.

[0098] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0099] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A coagulant for industrial wastewater treatment, characterized in that: The invention comprises a main flocculant and an auxiliary flocculant, wherein the main flocculant is polyferric sulfate and / or polyaluminium chloride, and the auxiliary flocculant is organic modified diatomaceous earth; the organic modified diatomaceous earth is prepared by condensing amino diatomaceous earth with a carboxyl modifier; the amino diatomaceous earth is diatomaceous earth treated with an amino silane coupling agent.

2. A coagulant for industrial wastewater treatment according to claim 1, characterized in that: The mass ratio of the polyferric sulfate, the polyaluminium chloride and the organic modified diatomaceous earth is 0-100:0-100:0.2-1.

3. A coagulant for industrial wastewater treatment according to claim 1, characterized in that: The aminosilane coupling agent is at least one of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane and 3-aminopropyltrimethoxysilane.

4. A coagulant for industrial wastewater treatment according to claim 1, characterized in that: The carboxyl modifier is at least one of citric acid, ethylenediaminetetraacetic acid and a hyperbranched polymer containing a terminal carboxyl group.

5. A method for preparing a coagulant for industrial wastewater treatment according to any one of claims 1 to 4, characterized in that: The steps include: The first step is to mix diatomaceous earth and water, stir and disperse to obtain a diatomaceous earth suspension, add an aminosilane coupling agent to the diatomaceous earth suspension, heat and stir under weak acid conditions to obtain an amino diatomaceous earth dispersion; add a carboxyl modifier to the above amino diatomaceous earth dispersion, and condense to obtain an organic modified diatomaceous earth; The second step is to use the prepared organic modified diatomaceous earth as an auxiliary flocculant and mix it with the main flocculant to obtain a coagulant for industrial wastewater treatment.

6. The method for preparing a coagulant for industrial wastewater treatment according to claim 5, characterized in that: The mass ratio of diatomite, aminosilane coupling agent and carboxyl modifier is 15-20g: 0.12-0.15g: 0.03g-0.5g.

7. The method for preparing a coagulant for industrial wastewater treatment according to claim 5, characterized in that: The aminosilane coupling agent described in the first step is dispersed in a 50% by volume ethanol aqueous solution and then added; The carboxyl modifier is dispersed in an ethanol aqueous solution with a volume fraction of 50% and then added.

8. The method for preparing a coagulant for industrial wastewater treatment according to claim 5, characterized in that: The weakly acidic pH range is 4-6; The heating and stirring temperature is 70-80℃.

9. The method for preparing a coagulant for industrial wastewater treatment according to claim 5, characterized in that: The diatomaceous earth is pre-treated with alkaline activation before use, and the alkaline activation treatment comprises the following steps: adding the diatomaceous earth into an alkaline reagent, heating for reaction, taking out, filtering, and drying.

10. The method for preparing a coagulant for industrial wastewater treatment according to claim 9, characterized in that: The alkaline reagent is a sodium hydroxide solution with a pH value of 12 and a potassium hydroxide solution with a pH value of 12.

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