A new magnetic composite coagulant and application thereof

Abstract

The present application relates to a kind of new magnetic composite coagulant, by the following preparation method is obtained, (1), the preparation of polymeric ferric phosphate sulfate:98% concentrated sulfuric acid is added dropwise to saturated hydrated ferric nitrate solution, then the prepared saturated Na2HPO4 solution and saturated NaHCO3 solution are added dropwise in turn, to obtain polymeric ferric phosphate sulfate;(2), the preparation of modified polymeric ferric phosphate sulfate: first silane coupling agent KH550 or KH570 is hydrolyzed 1 hour, then the hydrolyzed silane coupling agent KH550 is added dropwise into three-necked flask in step (1), to obtain modified polymeric ferric phosphate sulfate;(3), chitosan, Fe3O4 and modified polymeric ferric phosphate sulfate are dissolved in dilute acetic acid solution, slowly add cerium sulfate, react 2-6h to obtain new magnetic composite coagulant.Composite magnetic flocculant has the performance of realizing oil-water-floc separation quickly and efficiently.

Description

Technical Field

[0001] This invention relates to the field of oily wastewater treatment agents, and in particular to a novel magnetic composite coagulant. Background Technology

[0002] Currently, most low-carbon oil well extraction technologies involve chemical flooding in tertiary oil recovery. Polymer flooding produces produced fluids containing large amounts of polymers, which are highly viscous and difficult to degrade, making treatment very troublesome. Ternary flooding uses surfactants, alkalis, and polymers; the surfactants in the produced fluid reduce the interfacial tension of the oil droplets, forming emulsion-like droplets that are even more difficult to separate.

[0003] Oily wastewater after dewatering typically contains surfactants. The polar groups of these surfactants contact the aqueous phase, while the non-polar groups contact the oil phase, forming O / W type emulsified oil droplets. Single coagulants adsorb these emulsified oil droplets through charge neutralization, causing them to settle as impurities. This not only generates large amounts of oily sludge but also wastes petroleum resources. Traditional demulsifiers, primarily used for crude oil dehydration, are not ideal for treating oily wastewater. Conventional single cationic or nonionic demulsifiers are sensitive to the oil phase and are greatly affected by water quality fluctuations, leading to unstable treatment results. Current combined use of flocculants and demulsifiers still relies on physical mixing, without forming chemical bonds between the agents, resulting in poor chemical compatibility and the risk of functional conflicts. Strict requirements on the order of addition can lead to reduced demulsification efficiency due to flocs encapsulating oil droplets. The flocculant can encapsulate incompletely broken emulsified oil droplets, forming a more complex "oil-floc" complex. Furthermore, compatibility issues exist between agents; some cationic flocculants and anionic demulsifiers may neutralize each other, forming precipitates that affect flocculation and demulsification. Moreover, traditional flocculation technologies produce loose and fragile flocs, leading to secondary suspension. These flocs need to be separated from the water through natural settling, filtration, flotation, or centrifugation, increasing economic and environmental pressures. In addition, current flocculation technologies for treating oily wastewater produce flocs containing large amounts of oil. This oil encapsulates the floc particles, reducing sludge permeability and resulting in low efficiency of mechanical dewatering (such as filter press and centrifugation). Improper disposal (such as stockpiling or landfilling) can lead to the release of oil again, causing secondary pollution. Summary of the Invention

[0004] In view of the problems existing in the above-mentioned background technology, this invention is proposed. This invention covalently branches PPFS onto chitosan with long molecular chains and loads it onto magnetic Fe3O4 with a large specific surface area, achieving chemical assembly of the composite flocculant. PPFS is distributed on the chitosan chains, increasing the active sites and positive charge density, reducing its self-aggregation tendency, and improving stability. Simultaneously, flocculation and demulsification are synergistically integrated, possessing both charge neutralization and interfacial activity. It undergoes saponification with oil droplets, disrupting the interfacial film of emulsified oil droplets, promoting oil droplet aggregation, reducing petroleum resource waste, and adsorbing suspended solids. The composite flocculant reduces reagent conflict, simplifies the dosing process, and reduces sludge production. Its branched structure facilitates the formation of a network of magnetic flocs, which can settle rapidly under an external magnetic field and capture more suspended solids during the settling process, thereby reducing reagent usage. The composite flocculant innovates flocculation technology, combining resource recovery principles and achieving a balance between economic efficiency and environmental protection.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A novel magnetic composite coagulant is obtained by the following preparation method, which includes the following steps:

[0007] (1) Preparation of polyferric phosphate sulfate (PPFS): 98% concentrated sulfuric acid is added dropwise to a saturated solution of hydrated ferric nitrate, saturated ferric sulfate, or saturated ferric chloride, wherein [SO4] 2- ]:[Fe] T The molar ratio is 1:1 to 1.5:1. Then, the prepared saturated Na₂HPO₄ solution and saturated NaHCO₃ solution are added dropwise sequentially, where OH⁻... - Fe 3+ The molar ratio is 0.3:1 to 0.6:1, the reaction temperature is controlled at 25 to 45℃, and the reaction time is controlled at 30 to 90 min; thus, polyferric phosphate sulfate is obtained.

[0008] (2) Preparation of modified polyferric phosphate: First, hydrolyze the silane coupling agent KH550 or KH570 for 1 hour, and then add the hydrolyzed silane coupling agent KH550 or KH570 dropwise to the three-necked flask in step (1), and react at 50℃~60℃ for 10 hours to obtain modified polyferric phosphate; wherein the silane coupling agent accounts for 0.01%-1% of the mass fraction of polyferric phosphate.

[0009] (3) Chitosan, Fe3O4 and modified polyferric phosphate sulfate are dissolved in dilute acetic acid (2wt%) solution, wherein the mass ratio of chitosan, Fe3O4 and modified polyferric phosphate sulfate is (0.1~3):(0.1~1):1, and the mass ratio of chitosan to dilute acetic acid is 1:0.2~1:1. Nitrogen gas is introduced and cerium sulfate is slowly added at 20~40℃. The mass percentage of cerium sulfate in the whole reaction system is 0.01%~0.1%. The reaction is stirred at 40℃ for 2~6h to obtain a new type of magnetic composite coagulant.

[0010] The chitosan has a degree of deacetylation (DD) of 75%-85%, a medium molecular weight (Mw) of 50-200 kDa, and is one or a mixture of several industrial-grade chitosan powders.

[0011] The novel magnetic composite coagulant is applied to the treatment of oily wastewater in a combined treatment plant after oil removal. This novel nano-magnetic composite coagulant is a water pollution control agent.

[0012] In the aforementioned technical solutions, chitosan possesses both demulsifying and flocculating functions, exhibiting both hydrophilic and lipophilic groups. The lipophilic groups can adsorb surfactants at the interface of emulsified oil droplets through hydrophobic association, promoting oil droplet aggregation by reducing interfacial tension. However, chitosan has a low density, limiting its solubility in water. Polyferric phosphate sulfate (PPFS) is a highly polymerized flocculant with excellent positive charge density, enabling better charge neutralization, but it lacks demulsifying properties. Nano-ferric oxide (Fe3O4), due to its large specific surface area, magnetic properties, and recyclability, is often used as a carrier, producing magnetic flocs that simplify flocculation processes and improve flocculation speed. However, current reagent synthesis focuses only on individual flocculation, demulsification, or separation speed issues. To date, there are no reports on composite magnetic flocculants that simultaneously achieve rapid oil-water-floc separation.

[0013] The beneficial effects of this invention are as follows: This application prepares a stable functional composite flocculant by grafting PPFS onto the long chain of chitosan via copolymerization and then loading it onto magnetic iron oxide (Fe3O4). In this method, the amino and hydroxyl groups on the surface of chitosan (CS) first undergo a condensation reaction with the -COOH and -OH groups of Fe3O4. Then, the KH-570 organically modified PPFS acquires double bonds and -OH groups, participating in the reaction as an active reactive monomer. PPFS reacts with the -NH2 or -OH groups of CS through acylation, achieving chemical assembly between the agents and improving the stability and synergistic functionality of the composite flocculant. The chitosan on PPFS adsorbs emulsified oil droplets, while the hydrolyzed iron salts undergo a saponification reaction with the emulsified oil, disrupting the interfacial film of the emulsified oil droplets and promoting droplet aggregation. This solves the problem of self-polymerization of chitosan and PPFS and increases the active sites and positive charge density. Furthermore, the introduction of magnetic materials can make the flocs more compact, saving floc settling time. The magnetic flocs are also more tightly connected, allowing them to adsorb more impurity particles during settling, thus improving turbidity removal and demulsification effects. This reduces costs and environmental impact by decreasing the dosage of chemicals and simplifying the floc treatment process. The composite magnetic flocculant exhibits rapid and efficient oil-water-floc separation performance. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is the infrared spectrum of the flocculant of the present invention.

[0016] Figure 2 This is a residual turbidity spectrum of oily wastewater under different dosages of the flocculant of this invention.

[0017] Figure 3 This is a demulsification rate curve of oily wastewater under different dosages of the flocculant of this invention.

[0018] Figure 4 The image shows the microstructure of non-magnetic flocs in PPFS.

[0019] Figure 5 Microscopic morphology of PPFS-chitosan-Fe3O4 magnetic flocs. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Example 1:

[0022] 1. Preparation of polyferric phosphate sulfate: 138g of Fe(NO3)3·9H2O was dissolved in 100g of water in a three-necked flask. 45g of 98% concentrated sulfuric acid was added dropwise until all ferrous ions were oxidized to ferric ions. The mixture was stirred and reacted at 35℃ for 30 minutes. 13mL of saturated sodium dihydrogen phosphate solution and 18mL of saturated sodium bicarbonate solution were slowly added dropwise to the three-necked flask to obtain polyferric phosphate sulfate.

[0023] 2. Preparation of modified polyferric phosphate sulfate: In a separate beaker, 50 mL of KH-570 was hydrolyzed at room temperature for 1 hour. KH-570 was then added dropwise to the three-necked flask containing polyferric phosphate sulfate (PPFS) from step 1, and the mixture was heated to 50°C for aging reaction for 10 hours. Modified polyferric phosphate sulfate was obtained.

[0024] 3. Dissolve 5g chitosan, 100g modified polyferric phosphate sulfate, and 0.01g Fe3O4 in 0.1g dilute acetic acid solution by stirring under nitrogen at 40℃. Then slowly add 0.04g cerium sulfate and stir at 40℃ for 2 hours. After the reaction is complete, wash with acetone and ethanol to remove unreacted substances. The yellow powder obtained by drying at 50℃ is the composite flocculant PPFS-chitosan-Fe3O4. The infrared spectrum of the composite flocculant PPFS-chitosan-Fe3O4 is shown below. Figure 1 As shown, PPFS at 1384cm -1 1193cm -1 and 834cm -1 At this location, characteristic absorption peaks corresponding to the stretching vibrations of Fe-O-Fe, P=O, and HSO4- appeared, respectively. In the infrared spectrum of chitosan CS, characteristic absorption peaks corresponding to the stretching vibrations of Fe-O-Fe, P=O, and HSO4- appeared at 1655 cm⁻¹. -1 and 1599cm -1 Characteristic peaks of C=O and NH were detected at 2933 cm⁻¹, further confirming the polyamine branched structure of chitosan CS. Both chitosan CS and Fe₃O₄ showed characteristic peaks at 2933 cm⁻¹. -1 and 2871cm -1 Asymmetric stretching vibration peaks of CH were detected at 615 cm⁻¹, which were attributed to the terminal methyl group [-CH₃] and the methylene group [-CH₂-], respectively. Furthermore, Fe₃O₄ showed a peak at 615 cm⁻¹. -1 The characteristic absorption peaks of Fe-O appeared at [location missing]. The ternary composite coagulant PPFS-chitosan-Fe3O4 exhibited Fe-O-Fe, Fe-O, P=O, and HSO4 absorption peaks. - Characteristic peaks of chitosan CS, PPFS, and PPFS-chitosan-Fe3O4 are observed at approximately 3500 cm⁻¹. -1 A characteristic peak caused by the -OH vibration appeared at the location. Analysis indicates that the flocculant PPFS-chitosan-Fe3O4 was successfully prepared.

[0025] 30-90 ppm of flocculant was added to 500 ml of oily wastewater, and the mixture was stirred at 200 rpm for 1 min. After settling for 30 min, the supernatant was collected for turbidity and Zeta potential analysis, and the flocs were analyzed using SEM. The parameters of untreated and flocculant-treated oily wastewater are compared below: The changes in residual turbidity of the oily wastewater are shown in [reference needed]. Figure 2 The changes in demulsification rate are shown in Table 1. Figure 3 The microstructure of the non-magnetic flocs is shown in Table 2. Figure 4 The microstructure of PPFS-chitosan-Fe3O4 magnetic flocs is shown in the figure. Figure 5 .

[0026] Table 1

[0027]

[0028] Table 2

[0029]

[0030] Compared with existing technologies:

[0031] 1. When the optimal dosage of PPFS-chitosan-Fe3O4 is 50 mg / L, the turbidity removal rate increases to 97.85%, and the demulsification rate reaches 72.5%. Compared with existing commercially available single PPFS inorganic polymeric coagulants, it effectively improves the disruption of emulsified oil and the adsorption of colloidal impurities. It disrupts the highly stable emulsified oil molecule film, exhibiting excellent coagulation effects on difficult-to-treat oily wastewater, and is more conducive to petroleum resource recovery.

[0032] 2. Fe3O4 acts as a carrier, coating branched CS (Chemical Solids). PPFS (Polypropylene Gas Fibers) are covalently bonded to the long CS chains, forming a multi-active-site network structure magnetic composite coagulant. The positive charge on the long chains of the magnetic composite coagulant not only increases the number of active sites but also prevents the entanglement of the long CS chains and the aggregation of the coagulant, giving the coagulant high adsorption activity and high stability. Charge neutralization reduces the electrostatic repulsion between oil droplets, compressing the negative electron layer of the droplets and reducing surface tension, leading to aggregation. Furthermore, the long chains of PPFS and CS increase the collision probability between the coagulant and emulsified oil droplets. After collision, a saponification reaction occurs, disrupting the emulsified oil film and promoting droplet aggregation. The branched structure facilitates adsorption and sweeping effects, forming large-volume network flocs that can efficiently capture emulsified oil droplets and other suspended solids in oily wastewater treatment. The magnetic flocs are tightly connected, enabling rapid oil-water-floc separation under an external magnetic field, reducing time and labor costs.

[0033] 3. The octopus-like structure of the composite flocculant PPFS-chitosan-Fe3O4 not only features long molecular chains but also a greater number of active sites distributed along these chains. High charge density increases the probability of collisions with impurities, effectively disrupting the stability of colloidal particles. The long organic molecular chains facilitate the formation of large and dense flocs. These large, magnetically networked flocs can sweep up more particles during sedimentation. Through chemical bonding, the composite coagulant combines strong charge neutralization, high adsorption bridging, and high-network sweeping effects, fully leveraging its synergistic advantages. The large and dense flocs shorten the floc settling time, which is of great significance for the efficient treatment of oily wastewater.

Claims

1. A novel magnetic composite coagulant, prepared by the following method, comprising the following steps: (1) Preparation of polyferric phosphate sulfate (PPFS): 98% concentrated sulfuric acid is added dropwise to a saturated solution of hydrated ferric nitrate, saturated ferric sulfate, or saturated ferric chloride, wherein [SO4] 2- ]:[Fe] T The molar ratio is 1:1 to 1.5:

1. Then, the prepared saturated Na₂HPO₄ solution and saturated NaHCO₃ solution are added dropwise sequentially, where OH⁻... - Fe 3+ The molar ratio is 0.3:1 to 0.6:1, the reaction temperature is controlled at 25 to 45℃, and the reaction time is controlled at 30 to 90 min; thus, polyferric phosphate sulfate is obtained. (2) Preparation of modified polyferric phosphate: First, the silane coupling agent KH570 was hydrolyzed for 1 hour, and then the hydrolyzed silane coupling agent KH570 was added dropwise to the three-necked flask in step (1). The reaction was carried out at 50℃~60℃ for 10 hours to obtain modified polyferric phosphate; wherein the silane coupling agent accounted for 0.01%-1% of the mass fraction of polyferric phosphate. (3) Chitosan, nano Fe3O4 and modified polyferric phosphate sulfate are dissolved in dilute acetic acid (2wt%) solution, wherein the mass ratio of chitosan, nano Fe3O4 and modified polyferric phosphate sulfate is (0.1~3):(0.1~1):1, and the mass ratio of chitosan to dilute acetic acid is 1:0.2~1:

1. Nitrogen gas is introduced and cerium sulfate is slowly added at 20~40℃. The mass percentage of cerium sulfate in the whole reaction system is 0.01%~0.1%. The reaction is stirred at 40℃ for 2~6h to obtain a new type of magnetic composite coagulant.

2. The novel magnetic composite coagulant according to claim 1, characterized in that, The chitosan is an industrial-grade chitosan powder with a degree of deacetylation of 75%-85% and a molecular weight of 50-200 kDa.

3. The application of the novel magnetic composite coagulant according to claim 1, wherein the novel magnetic composite coagulant is applied to the treatment of oily wastewater in a combined station after oil removal.

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