A controlled-release polyferric sulfate water treatment agent and its preparation method

Abstract

The present invention discloses a controlled-release type polymeric ferric sulfate water treatment agent and its preparation method, belonging to the technical field of water treatment functional materials. The water treatment agent consists of polymeric ferric sulfate, an iron ion color indicator, a gel matrix, a cross-linking calcium agent, amino diatomaceous earth, a pore-forming agent and an inert filler. The preparation method includes: first preparing a network gel, then preparing soft materials, and finally obtaining the product through pill-making and drying. The present invention realizes the slow release and controllability of polymeric ferric sulfate, and the color indicator can directly reflect the consumption state of polymeric ferric sulfate, facilitating storage, transportation, dosing and recovery.

Description

Technical Field

[0001] This invention belongs to the field of water treatment functional materials technology, specifically relating to a controlled-release polyferric sulfate water treatment agent and its preparation method. Background Technology

[0002] In the process of industrialization, the discharge of water pollutants is characterized by large quantities and wide distribution, and wastewater pollution problems are becoming increasingly serious. In the field of water pollution control, chemical coagulation is the core treatment unit. Polyferric sulfate (PFS), as a highly efficient and economical inorganic polymeric flocculant, has significant advantages in removing heavy metal ions from water. It mainly removes colloids, suspended solids, and phosphorus through a hydrolysis-flocculation mechanism, while also having a co-precipitation effect on some heavy metals. It has a high hydrolysis rate, produces dense flocs, and settles quickly. It has been used in municipal sewage and industrial wastewater treatment for over thirty years, currently holding approximately 35% market share in the municipal sector, primarily for wastewater with high suspended solids and high phosphorus content. However, currently available PFS is mainly in liquid or solid powder form, and in practical applications, it still has the following inherent defects that restrict further improvement in its treatment effect and cannot meet the development needs of intelligent and precise water treatment:

[0003] 1. The release of active ingredients is uncontrollable, the dosing accuracy is low, and it is easy to cause waste of reagents or secondary pollution.

[0004] Conventional liquid or powdered PFS hydrolyzes rapidly after addition, and the release of its active ingredients is instantaneous and uncontrollable. This means that in actual water treatment processes, if the dosage is insufficient, pollutants will not be completely removed; if the dosage is excessive, not only will treatment costs increase, but unutilized iron ions may also remain in the water, increasing the color of the effluent and potentially causing secondary pollution.

[0005] 2. The product has a single form, which leads to inconvenience in storage, transportation and use.

[0006] Liquid PFS is highly corrosive, requires sophisticated storage and transportation equipment, and poses a risk of leakage; traditional solid PFS is prone to moisture absorption and clumping, affecting the accuracy of metering and ease of use. Neither of these existing forms is conducive to achieving precise, automated dosing and remote management of the reagents.

[0007] 3. The processing lacks intuitive status feedback and monitoring methods.

[0008] In existing technologies, operators cannot visually determine the real-time reaction status, remaining reagent levels, or treatment progress after reagent addition. This relies entirely on subsequent offline water quality monitoring, which suffers from feedback lag and makes it difficult to achieve real-time optimization and precise control of the treatment process.

[0009] 4. It has limited functionality and its ability to synergistically purify complex pollution systems.

[0010] Traditional PFS (Potentially Filtrated Foaming) mainly relies on charge neutralization and flocculation bridging, but its targeted adsorption capacity for dissolved organic matter and some characteristic pollutants is limited. Faced with increasingly complex industrial wastewater compositions, there is an urgent need to develop composite water treatment materials that combine flocculation and adsorption functions to improve overall purification efficiency.

[0011] Patent CN120483268A discloses a technology that enables the resource-based preparation of polyferric sulfate waste residue, but it still has significant drawbacks: it only provides traditional liquid or solid powder products, without controlled-release design, and the effective components are released instantaneously after addition, which can easily lead to waste of reagents or secondary pollution from iron ion residue; moreover, its function is limited, relying only on flocculation, and its ability to remove dissolved organic matter and trace heavy metals in complex wastewater is limited; at the same time, it does not have process monitoring methods, and its storage, transportation and addition are inconvenient, which cannot meet the needs of precise and intelligent water treatment.

[0012] Patent CN11984141A discloses a technology that improves coagulation efficiency through a combination of "modified chitosan + PFS", but it still has significant limitations: it is a simple powder / liquid compound, and the instantaneous release of PFS leads to low dosing accuracy; there is no process monitoring method, resulting in delayed control; and in cases where the hardware testing facilities for wastewater treatment capacity are poorly configured or the operators lack sufficient skill, the dosage is difficult to control, and the agent cannot be recycled.

[0013] The aforementioned problems are even more pronounced in remote areas and grassroots wastewater treatment plants where testing facilities are limited and operators have limited expertise. Liquid PFS is highly corrosive, and storage and transportation conditions in remote areas are limited, making leakage a common occurrence. Solid PFS is prone to moisture absorption and clumping, and the lack of precise metering equipment at grassroots sites further exacerbates dosage errors. In scenarios with insufficient testing facilities, operators often choose to overdose to "ensure treatment effectiveness," resulting in significant waste of reagents. Unreacted iron ions also remain in the water, leading to increased effluent color and secondary pollution. If the dosage is insufficient, pollutants are not completely removed. Existing PFS is completely dispersed in the water after addition, and even if overdosed, it cannot be recovered and must be discharged with the effluent or disposed of by sedimentation. Over the long term, the cost of reagents places a significant burden on grassroots sites.

[0014] The aforementioned shortcomings of existing technologies collectively point to an urgent need for a polyferric sulfate water treatment agent that is morphologically stable, easy to use, can provide process indication signals, has controllable release characteristics, and can release polyferric sulfate with residues that can be salvaged and reused. Summary of the Invention

[0015] To address the problems of uncontrollable drug release, lack of state indication, and inconvenient storage, transportation, and dosing of existing polyferric sulfate water treatment agents and their compounding technologies, especially in remote areas and grassroots areas where testing facilities and professional operators are scarce, which can easily lead to drug waste, secondary pollution, and operational safety hazards, this invention provides a controllable release, self-indicating, and easy-to-use solid microsphere dosage form and its preparation method.

[0016] Through experimental comparison and selection of various controlled-release and inhibited-release materials, and by combining different quality control properties of the materials with preparation parameters, the problem was effectively solved. This resulted in the preparation of a polyferric sulfate water treatment agent that can be supplied to remote areas and grassroots communities with weak infrastructure. The agent is stable during transportation and storage, can provide indicator signals during use, has minimal harm from overdosing, and can be salvaged and reused.

[0017] This invention is achieved through the following means:

[0018] This invention provides a controlled-release polyferric sulfate water treatment agent, which is a network gel microsphere. Its sustained-release performance originates from a dense ternary network framework synergistically constructed from aminodiatomite, a gel matrix containing carboxylic acid groups, and a cross-linking calcium agent.

[0019] This invention provides a controlled-release polyferric sulfate water treatment agent, which is a network gel microsphere, and is composed of the following components by mass percentage based on the total mass of the water treatment agent:

[0020] Polyferric sulfate 25-40%

[0021] Iron ion colorimetric indicator 0.1-0.5%

[0022] Gel matrix 15-25%

[0023] Cross-linked calcium agent 5-10%

[0024] Amino-containing diatomaceous earth with an amino density of 0.8-2.0 mmol / g, 10-20%

[0025] 5-10% pore-forming agent

[0026] Inert filler is added to bring the total to 100%.

[0027] During the screening and optimization of numerous sustained-release and inhibited-release materials, the inventors discovered that the core structure of this invention—the network gel framework—exhibits relatively optimal density and stability. This framework is synergistically constructed from aminodiatomaceous earth with an amino density of 0.8–2.0 mmol / g, a gel matrix containing carboxylic acid groups, and a water-soluble calcium salt (crosslinking calcium agent) through the following specific stepwise process:

[0028] First, aminodiatomaceous earth and a gel matrix containing carboxylic acid groups are subjected to high shear treatment in purified water to achieve full and homogeneous pre-dispersion and penetration of the two.

[0029] Subsequently, calcium salts were added under specific viscosity conditions. Calcium ions reacted with carboxyl groups in the gel matrix in a typical ionic crosslinking reaction, forming a unique structure.

[0030] Importantly, the specific step sequence described above (pre-dispersion followed by ionic cross-linking) is crucial for obtaining the desired framework structure. Experimental data (see Comparative Example 2 in the instruction manual) clearly show that simply blending all components significantly degrades the mechanical strength and sustained-release properties of the resulting product.

[0031] Therefore, the three-dimensional network gel skeleton constructed by the process of this invention has its density, stability and swelling behavior regulated, thereby effectively encapsulating polyferric sulfate and colorimetric indicators, and achieving long-term and stable control of their release rate.

[0032] The amino diatomite can be prepared by mature modification methods such as acid washing activation, silanization (e.g. using APTES) and elution purification of commercially available diatomite, with its amino density controlled at 0.8-2.0 mmol / g.

[0033] Furthermore, the iron ion colorimetric indicator is selected from one or more of phenanthrene, o-phenanthroline, chromazine S, and sulfosalicylic acid, with phenanthrene being the most preferred.

[0034] Furthermore, the gel matrix is ​​one or more of sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, highly substituted hydroxycellulose, and sodium alginate, and sodium carboxymethyl cellulose accounts for 50wt%-100wt% of the total gel matrix. Sodium carboxymethyl cellulose is the most preferred.

[0035] Furthermore, the pore-forming agent is polyethylene glycol 4000, polyethylene glycol 6000, cross-linked polyvinylpyrrolidone K15, or cross-linked polyvinylpyrrolidone K30, with polyethylene glycol 6000 being the most preferred.

[0036] Furthermore, the cross-linking calcium agent is calcium chloride, calcium nitrate, calcium lactate, or calcium gluconate, with calcium chloride being the most preferred.

[0037] Furthermore, the inert filler is dextrin, starch, or microcrystalline cellulose, preferably microcrystalline cellulose.

[0038] On the other hand, the present invention also provides a method for preparing the controlled-release polyferric sulfate water treatment agent, wherein the steps are as follows:

[0039] a. Preparation of network gel:

[0040] A network gel was prepared by mixing aminodiatomaceous earth with a basis density of 0.8–2.0 mmol / g, gel matrix, cross-linking calcium agent and purified water, and then subjecting the mixture to high shear treatment.

[0041] b. Preparation of soft materials:

[0042] Iron ion colorimetric indicator, polyferric sulfate, and pore-forming agent are dispersed in purified water and added to the network gel at a shear rate of 500-1000 rpm. The mixture is stirred for 10-20 min, and then an inert filler is added. The mixture is stirred at 300-500 rpm for 5-10 min to obtain a semi-solid soft material.

[0043] In the preparation of soft materials, the preferred shearing speed is 700-900 rpm, and the preferred stirring time is 12-18 minutes; the most preferred method is to mix and stir at a shearing speed of 800 rpm for 15 minutes.

[0044] The preferred stirring speed after adding the inert filler is 350-450 rpm, and the preferred stirring time is 6-9 minutes; the most preferred speed is 400 rpm for 8 minutes.

[0045] c. Making pills:

[0046] The soft material in b is granulated by centrifugation or rotary pelletizing, and dried under reduced pressure at 50-80℃. The drying temperature is preferably 60-75℃, and most preferably 65℃. The vacuum degree of the vacuum drying oven is controlled from -0.08 MPa to -0.1 MPa to obtain micro pellets with a particle size of 3-8 mm.

[0047] Iron ion colorimetric indicator, polyferric sulfate, and inert filler are blended with the network gel according to step b of the present invention, so that the indicator and polyferric sulfate are uniformly dispersed and embedded in the three-dimensional network; the pore-forming agent is embedded in the network in the form of solid micro-regions, and is dissolved or swollen and removed during the subsequent drying process at 50–80°C to form interconnected micropores, which are used to regulate the water medium permeation and polyferric sulfate release rate; the inert filler is distributed in the gaps between the gel skeleton, which improves the mechanical strength of the microspheres and reduces the breakage rate in water, thereby facilitating recovery.

[0048] On the other hand, the present invention also provides a method for preparing a network gel of a controlled-release polyferric sulfate water treatment agent, the method comprising the following steps:

[0049] a. Mix amino diatomaceous earth with an amino density of 0.8-2.0 mmol / g, a gel matrix containing carboxylic acid groups, and purified water to obtain a dispersion with a solid content of 5-15%; the solid content of the dispersion is preferably 8-12%; the most preferred is 10%.

[0050] b. Place the dispersion in a sealed pressure shearing vessel equipped with online viscosity monitoring, controlling the vacuum level of the chamber at 0.04-0.08 MPa and the shearing speed at 1500-3000 rpm. The vacuum level for high shearing is preferably 0.05-0.07 MPa; most preferably 0.06 MPa. The high shearing speed is preferably 2000-2800 rpm; most preferably 2500 rpm.

[0051] c. When the apparent viscosity of the system reaches 5000-10000 mPa·s, immediately stop shearing, preferably when the apparent viscosity reaches 6000-9000 mPa·s, and most preferably when the viscosity reaches 8000 mPa·s, add the crosslinking calcium agent. The crosslinking process temperature is controlled at 25-40℃, preferably 28-35℃, and most preferably 30℃. The cavity vacuum degree is controlled at 0.04-0.08 MPa, preferably 0.05-0.07 MPa, and most preferably 0.06 MPa. The shearing speed is 100-300 rpm, preferably 150-250 rpm, and most preferably 200 rpm. Continue shearing for 5-30 seconds, preferably 10-20 seconds, and most preferably 15 seconds.

[0052] d. Break the vacuum, collect the contents, and you will get the network gel.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] 1. The formulation and preparation process provided by this invention ensure the uniformity and reproducibility of the network gel structure, enabling stable release of the water treatment agent. The entire process is mild and suitable for large-scale production.

[0055] 2. On the one hand, the synergistic effect of the network gel framework and aminodiatomite achieves a dual controlled-release mechanism of physical barrier and adsorption-based slow release, significantly extending the effective action time and avoiding the problems caused by instantaneous high-concentration release. Furthermore, aminodiatomite itself can synergistically adsorb pollutants, improving purification efficiency. On the other hand, the embedded iron ion colorimetric indicator provides operators with an intuitive "depletion warning" signal, reducing reliance on professional testing equipment and facilitating precise dosing. This reduces waste and secondary pollution risks caused by blind overdosing at the source.

[0056] 3. The water treatment agent is a solid gel pellet with stable morphology, which overcomes the corrosion and leakage risks of liquid products and the moisture absorption and clumping problems of powder products. It is convenient for safe storage, transportation and convenient addition in remote areas or grassroots sites with poor hardware conditions, and significantly improves the good applicability, safety and comprehensive economic benefits of polyferric sulfate. Detailed Implementation

[0057] The following description illustrates exemplary embodiments of the present invention, including various details to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions, operations, and structures are omitted in the following description.

[0058] Unless otherwise defined, the technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. While similar or identical methods and materials may be applied in experimental or practical applications, the present invention describes materials and methods hereinafter. In case of conflict, the definitions included herein shall prevail.

[0059] Diatomaceous earth pretreatment:

[0060] Acid washing and activation: Take commercially available diatomaceous earth and stir it with 1 mol / L hydrochloric acid at 70℃ for 2 hours → wash with water until neutral → dry at 80℃;

[0061] Silanization: The dry soil was dispersed in ethanol-water (8:2), and 3-aminopropyltrimethoxysilane (APTES, the amount of which is 15wt%-25wt% of the diatomaceous earth) was added. The mixture was then refluxed at 70℃ for 4 hours.

[0062] Elution and purification: Wash with ethanol → dry under vacuum at 80℃ to obtain the product.

[0063] Aminodiatomaceous earths with different amino densities can be obtained by using different amounts of 3-aminopropyltrimethoxysilane, and the amino density can be determined by hydrochloric acid-ethanol titration.

[0064] Example 1

[0065] 1. Raw material formula (based on 100g of finished product)

[0066]

[0067] 2. Preparation method:

[0068] (1) Preparation of network gel

[0069] a. Weigh out aminodiatomaceous earth and sodium carboxymethyl cellulose, add purified water, and stir to initially disperse them, thus preparing a dispersion with a solid content of 10%.

[0070] b. Transfer the above dispersion into a sealed pressure shearing tank with online viscosity monitoring, set the vacuum degree inside the tank to 0.06 MPa, start high-speed shearing, control the rotation speed to 2500 rpm, and the system temperature to 30℃.

[0071] c. Continuously shear and monitor the apparent viscosity of the system. When the viscosity reaches 8000 mPa·s, immediately stop the high-speed shearing. Quickly add calcium chloride, then adjust the shearing speed to 200 rpm, and continue shearing for 15 seconds while maintaining a vacuum of 0.06 MPa and a temperature of 30°C.

[0072] d. Turn off shearing, break the vacuum, and collect the resulting homogeneous, viscous gel, which is the network gel.

[0073] (2) Preparation of soft material

[0074] a. Weigh out phenanthroxazine, polyferric sulfate, and polyethylene glycol 6000, add an appropriate amount of purified water (to make polyferric sulfate 30wt%), and stir thoroughly to disperse.

[0075] b. Slowly add the above dispersion to all the network gel prepared in step (1) at a shear rate of 800 rpm. After the addition is complete, maintain a speed of 800 rpm and continue stirring for 15 minutes to allow the active ingredients to be fully embedded in the gel network.

[0076] c. Add microcrystalline cellulose to the above mixture. Adjust the stirring speed to 400 rpm and continue stirring for 8 minutes to obtain a semi-solid soft material with uniform moisture content and good plasticity.

[0077] (3) Pelletizing and drying

[0078] a. The obtained soft material is put into a centrifugal granulator, and wet microspheres are prepared by controlling the centrifugal disc speed at 150 rpm.

[0079] b. Transfer the wet microspheres to a vacuum drying oven, control the vacuum level to -0.1 MPa, and dry them at 70°C under reduced pressure until the moisture content is below 5.0%.

[0080] c. After drying, the microspheres are sieved through a standard sieve, and microspheres with a particle size of 4-6 mm are selected to obtain the controlled-release polyferric sulfate water treatment agent product of the present invention.

[0081] Example 2

[0082] 1. Raw material formula (based on 100g of finished product)

[0083]

[0084] 2. Preparation process:

[0085] Same as Example 1.

[0086] Example 3

[0087] 1. Raw material formula (based on 100g of finished product)

[0088]

[0089] 2. Preparation method:

[0090] Same as Example 1.

[0091] Example 4

[0092] 1. Raw material formula (based on 100g of finished product)

[0093]

[0094] 2. Preparation process:

[0095] Same formulation as in Example 1.

[0096] Example 5

[0097] 1. Raw material formula (based on 100g of finished product)

[0098] Same as Example 1.

[0099] 2. Preparation method

[0100] (1) Preparation of network gel

[0101] a. Weigh out aminodiatomaceous earth and sodium carboxymethyl cellulose, add purified water, and stir to initially disperse them, thus preparing a dispersion with a solid content of 10%.

[0102] b. Transfer the above dispersion into a sealed pressure shearing tank for shearing. The system temperature is 30°C, the vacuum degree of the vacuum tank is controlled at 0.04MPa, and the high shearing speed is 1500rpm.

[0103] c. Continuously shear and monitor the apparent viscosity of the system. When the viscosity reaches 5000 mPa·s, immediately stop the high-speed shearing. Quickly add calcium chloride, then adjust the shearing speed to 100 rpm, and continue shearing for 5 seconds while maintaining a vacuum of 0.04 MPa and a temperature of 30°C.

[0104] d. Turn off shearing, break the vacuum, and collect the resulting homogeneous, viscous gel, which is the network gel.

[0105] (2) Preparation of soft material

[0106] a. Weigh out phenanthroxazine, polyferric sulfate, and polyethylene glycol 6000, add an appropriate amount of purified water (to make polyferric sulfate 30wt%), and stir thoroughly to disperse.

[0107] b. Slowly add the above dispersion to all the network gel prepared in step (1) at a shear rate of 500 rpm. After the addition is complete, maintain a speed of 500 rpm and continue stirring for 10 minutes to allow the active ingredients to be fully embedded in the gel network.

[0108] c. Add microcrystalline cellulose to the above mixture. Adjust the stirring speed to 300 rpm and continue stirring for 5 minutes to obtain a semi-solid soft material with uniform moisture content and good plasticity.

[0109] (3) Pelletizing and drying

[0110] a. The obtained soft material is put into a centrifugal granulator, and wet microspheres are prepared by controlling the centrifugal disc speed at 150 rpm.

[0111] b. Transfer the wet microspheres to a vacuum drying oven, control the vacuum level to -0.08 MPa, and dry at 50°C until the moisture content is below 5.0%.

[0112] c. After drying, the microspheres are sieved through a standard sieve, and microspheres with a particle size of 4-6 mm are selected to obtain the controlled-release polyferric sulfate water treatment agent product of the present invention.

[0113] Comparative Example 1

[0114] 1. Raw material formula (based on 100g of finished product)

[0115] The formula does not contain sodium carboxymethyl cellulose, as detailed below:

[0116]

[0117] 2. Preparation method

[0118] Same as Example 1.

[0119] Comparative Example 2

[0120] The preparation process of the network-free gel is as follows:

[0121] 1. Raw material formula (based on 100g of finished product)

[0122] Same as Example 1.

[0123] 2. Preparation method

[0124] (1) Preparation of soft material

[0125] Aminodiatomite, sodium carboxymethyl cellulose, calcium chloride, phenanthrene, polyferric sulfate, and polyethylene glycol 6000 were weighed and placed in a high-efficiency wet granulator. The agitator was turned on at 300 rpm and dry-mixed for 10 minutes. Then, purified water accounting for 15% of the total material weight was added, and the agitator was kept at 300 rpm for wet mixing for 3 minutes, resulting in a semi-solid soft material with uniform moisture content and good plasticity.

[0126] (2) Pelletizing and drying

[0127] The pelleting and drying processes are the same as in Example 1 (3).

[0128] Experimental Example 1: Friability of Water Treatment Agent Microspheres and Stability in Simulated Environment

[0129] Friability determination:

[0130] Instrument: Friability tester, Shanghai Huanghai Instrument, CJY-300E.

[0131] Method: Take the microsphere sample to be tested (about 10g), place it on a 2mm sieve frame, blow off the surface powder, and accurately weigh the total weight W0.

[0132] Spread the sample evenly inside the drum of the friability tester, add 10 glass beads with a diameter of 0.5 cm, and cover.

[0133] Set the rotation speed to 25 rpm and run for 100 revolutions. Remove the microspheres and place them on a 2mm sieve frame. Blow off the surface powder and accurately weigh the total weight W1.

[0134] Friability = (W0 - W1) / W0 × 100%.

[0135] Simulated environmental stability (recovery rate) determination:

[0136] Accurately weigh 10.00g of intact microparticles (denoted as W0), place them in a beaker containing 1000mL of purified water, and continuously stir using an electronic stirrer. Adjust the stirrer blades so that they do not directly contact the microparticles, set the speed to 100rpm to simulate a moderate water flow, and continue stirring for 6 hours. Then, collect the intact particles through a 2mm sieve and dry them at 60℃ under reduced pressure until constant weight (W1).

[0137] Recovery rate = W1 / W0 × 100%.

[0138] Iron ion concentration determination:

[0139] The solution after 6 hours in the simulated environment was taken, and the iron ion concentration C1 was determined by the o-phenanthroline spectrophotometric method GB / T 3049-2006 "General Method for Determination of Iron Content in Industrial Chemical Products".

[0140] Take 10g of microspheres from the same batch, grind them, digest them in a nitric acid-perchloric acid system, bring the volume to a final volume, and determine the total iron ion concentration C2.

[0141] Iron ion release rate = C1 / C2 × 100%.

[0142] Experimental results:

[0143]

[0144] Regarding mechanical strength: the friability of the products in Examples 1-5 of this invention is all below 3%, which is far lower than that of the comparative products (Comparative Example 1: 9.8%; Comparative Example 2: 18.5%). This directly proves that the microspheres of this invention provide excellent cohesive strength and can meet the requirements for storage and transportation.

[0145] Regarding structural stability and controlled release capability: After simulated water flushing (100 rpm, 6 h), the product of this invention still maintains high structural integrity (recovery rate >65%), and the iron ion release rate (18%-35%) is significantly lower than that of the comparative example (>65%). The specific formulation and process of this invention achieve the dual objectives of resisting physical breakage and inhibiting rapid loss of active ingredients. Furthermore, the release rate results of Examples 2 and 3 show that the higher the polyferric sulfate loading, the higher the release, indicating that this invention has good controlled release capability for different loadings, and the release rate can be adjusted within a certain range through formulation.

[0146] Experiments showed that as the iron ion release rate increased, the color of the microspheres tended to lighten.

[0147] The above test results are consistent with the design of this invention, which allows water treatment operators to determine whether iron ions have been completely released based on the color of the water treatment agent microspheres, and to decide whether to add new water treatment agent based on the improvement in water quality. When the water quality meets the standards, operators can use a grid / screen or a retrieval device such as a filter or filter bag to collect and recycle any unreleased water treatment agent at the outlet for reuse, thus saving costs.

Claims

1. A controlled-release polyferric sulfate water treatment agent, comprising network gel microspheres, characterized in that, Based on the total mass of the water treatment agent, it consists of the following components by mass percentage: Polyferric sulfate 25-40% Iron ion colorimetric indicator 0.1-0.5% Gel matrix 15-25% Cross-linked calcium agent 5-10% Amino-containing diatomaceous earth with an amino density of 0.8-2.0 mmol / g, 10-20% 5-10% pore-forming agent Inert filler is added to bring the total to 100%.

2. The polyferric sulfate water treatment agent according to claim 1, characterized in that, The iron ion colorimetric indicator is selected from one or more of phenanthrene, o-phenanthroline, chromazin S, and sulfosalicylic acid.

3. The polyferric sulfate water treatment agent according to claim 1, characterized in that, The gel matrix is ​​one or more of sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, highly substituted hydroxycellulose, and sodium alginate, and sodium carboxymethyl cellulose accounts for 50wt%-100wt% of the total gel matrix.

4. The polyferric sulfate water treatment agent according to claim 1, characterized in that, The cross-linking calcium agent is calcium chloride, calcium nitrate, calcium lactate, or calcium gluconate.

5. The polyferric sulfate water treatment agent according to claim 1, characterized in that, The pore-forming agents are polyethylene glycol 4000, polyethylene glycol 6000, cross-linked polyvinylpyrrolidone K15, and cross-linked polyvinylpyrrolidone K30.

6. The polyferric sulfate water treatment agent according to claim 1, characterized in that, The inert filler is dextrin, starch, or microcrystalline cellulose.

7. A method for preparing the controlled-release polyferric sulfate water treatment agent according to any one of claims 1-6, characterized in that, Includes the following steps: a. Preparation of network gel: A network gel was prepared by mixing amino-containing diatomaceous earth with an amino density of 0.8-2.0 mmol / g, a gel matrix, a cross-linking calcium agent, and purified water, and then subjecting the mixture to high shear treatment. b. Preparation of soft materials: Iron ion colorimetric indicator, polyferric sulfate, and pore-forming agent are dispersed in purified water and added to the network gel at a shear rate of 500-1000 rpm. The mixture is stirred for 10-20 min, and then an inert filler is added. The mixture is stirred at 300-500 rpm for 5-10 min to obtain a semi-solid soft material. c. Making pills: The soft material in b is granulated by centrifugation or rotary pelletizing, dried under reduced pressure at 50-80℃, and the vacuum degree of the vacuum drying oven is controlled from -0.08MPa to -0.1MPa until the moisture content is less than 5.0%, resulting in micro pellets with a particle size of 3-8mm.

8. The method for preparing the controlled-release polyferric sulfate water treatment agent according to claim 7, characterized in that, The preparation of the network gel includes the following steps: a. Mix amino diatomaceous earth with an amino density of 0.8-2.0 mmol / g, a gel matrix containing carboxylic acid groups, and purified water to obtain a dispersion with a solid content of 5-15%. b. Place the dispersion in a closed pressure shearing tank with online viscosity monitoring, and control the vacuum degree of the chamber to be 0.04-0.08 MPa and the shearing speed to be 1500-3000 rpm. c. When the apparent viscosity of the system reaches 5000-10000 mPa·s, stop shearing immediately, add crosslinking calcium agent, control the temperature of the crosslinking process at 25-40℃, control the vacuum degree of the cavity at 0.04-0.08Mpa, the shearing speed at 100-300rpm, and continue shearing for 5-30s. d. Break the vacuum, collect the contents, and you will get the network gel.

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