A method for improving efficiency and reducing consumption by compounding phosphorus removal composite nanomaterials

Abstract

The present invention discloses a method for improving efficiency and reducing consumption by compounding phosphorus removal composite nanomaterials, which belongs to the field of water treatment technology. The method determines the volume ratio of the loading material by the ratio of organic phosphorus and orthophosphate in water, and the ratio of phosphorus adsorption of lanthanide materials and iron-based materials, and has good pertinence for different types of wastewater containing different phosphorus concentrations; the method scientifically utilizes the differences in kinetics, thermodynamics and adsorption capacity of deep phosphorus removal between lanthanide composite nanomaterials and iron-based composite nanomaterials, and adopts a compounding method to fully utilize the high adsorption capacity and La-P specific reaction of lanthanide materials, as well as the rapid adsorption kinetics and Fe-P specific reaction of iron-based materials, which can greatly improve the utilization rate of the two materials and the depth of effluent phosphorus removal, reduce the regeneration frequency and regeneration agent consumption, and achieve efficiency improvement and consumption reduction of deep phosphorus removal by adsorption.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and more specifically relates to a method for improving efficiency and reducing consumption by compounding and using phosphorus removal composite nanomaterials. Background Art

[0002] Lanthanum, a rare earth element, is abundant in soil and environmentally friendly. As a strategic resource, my country boasts abundant rare earth mineral deposits, laying a solid foundation for its industrial application. Lanthanum has a large coordination number and a strong affinity for phosphate, demonstrating efficient phosphate removal even at trace levels. Lanthanum's specific adsorption of phosphorus forms a lanthanum-phosphate complex. Lanthanum phosphate has a pKsp of 26.15 in aqueous solution, significantly lower than that of other metal phosphates. Numerous reports have been published on the preparation of lanthanum-loaded or modified materials. For example, in "Application of Phoslock(TM), an innovative phosphorus binding clay, to two Western Australian waterways: preliminary findings," published in Hydrobiologia, Vol. 494, 2003, CISRO in Australia developed Phoslock, a lanthanum-modified bentonite that can be used to immobilize and detoxify phosphorus in lakes. Another study, "Green synthesis of a novel hybrid sorbent of zeolite / lanthanum hydroxide and its application in the removal and recovery of phosphate from water," published in Journal of Colloid Interface and Science, Vol. 423, 2014, reported that a lanthanum-loaded zeolite composite material can achieve deep phosphorus removal and possesses high phosphorus adsorption capacity, but material regeneration is difficult. Iron, one of the most abundant elements in the Earth's crust, is also widely used in the deep treatment of wastewater. Iron-based materials also exhibit a certain degree of selectivity for phosphates, forming internal coordination complexes with phosphates and some organic phosphorus species, thereby achieving high-speed, selective phosphorus removal. For example, the resin-based iron-loaded composite nanomaterial developed in "Selective removal of phosphorus from wastewater combined with its recovery as a solid-phase fertilizer" published in "Water Research" Volume 45 in 2011 has good phosphorus removal ability. Although the adsorption capacity is lower than that of lanthanide materials, it still has a good phosphorus removal depth and faster adsorption kinetics.

[0003] For many years, our research group has been dedicated to the application-based research and engineering application technology development of composite nanomaterials for phosphorus removal. For example, our Nanjing University graduation thesis, "Applied Fundamentals of Deep Phosphorus Removal and Recovery from Wastewater Based on Nanocomposites," disclosed a D201-based nanohydrated lanthanum oxide material, its preparation method, and its application in phosphorus adsorption. Related research was also published in "Enhanced phosphate removal by nanosized hydrated La(III) oxide confined in cross-linked polystyrene networks" (Environmental Science & Technology, Vol. 50, 2016). The lanthanum-loaded composite nanomaterial reported in the paper exhibited high phosphorus adsorption capacity, high phosphorus selectivity, and excellent separation and regeneration performance, showing promising application prospects. The research team also reported an iron-loaded composite nanomaterial in "Development of polymer-based nanosized hydrated ferric oxides (HFOs) for enhanced phosphate removal from waste effluents" (Water Research, Vol. 92, 2009), which demonstrated excellent deep phosphorus removal and regeneration performance and also showed promising application prospects. Compared to lanthanum-loaded composite nanomaterials and iron-loaded composite nanomaterials, lanthanide-based materials exhibit greater adsorption capacity, approximately 2-5 times that of iron-based materials, and greater selectivity, approximately twice that of iron-based materials. However, lanthanide-based materials exhibit slower kinetics, achieving deep phosphorus removal primarily through crystallization. In the presence of competing ions, the adsorption rate is an order of magnitude lower than that of iron-based materials. Furthermore, iron-based materials can also remove some organophosphates. Under the same regeneration conditions, iron-based materials are easier to desorb and regenerate than lanthanide-based materials.

[0004] The preparation and application methods for iron-based and lanthanide-based composite nanomaterials for phosphorus removal developed by our research group have been granted Chinese invention patents. These methods have been successfully mass-produced and applied in engineering applications at rates of 30-1000 tons per day, demonstrating strong technical validation. However, numerous challenges remain in their application. For example, the working capacity (2 mg / g) of iron-based materials in practical applications is far lower than their maximum adsorption capacity (15 mg / g). Lanthanide-based materials require lower flow rates to achieve deep phosphorus removal efficiency consistent with laboratory results, resulting in slow mass transfer and reaction processes within the column, making them difficult to apply efficiently under high-volume, high-flow conditions. Lanthanide-based materials are also relatively expensive, requiring high investment costs and challenging to regenerate. This is primarily due to the fact that existing deep phosphorus removal methods often utilize only a single material, failing to effectively leverage the unique characteristics of diverse deep phosphorus removal composite nanomaterials. Therefore, there is an urgent need to develop novel deep phosphorus removal technologies based on composite nanomaterials to improve phosphorus removal efficiency while reducing costs and consumption. Summary of the Invention

[0005] In response to the problems of high consumption, insufficient efficiency and difficulty in large-scale application and promotion of existing deep phosphorus removal technologies using single composite nanomaterials, the present invention provides a method for improving efficiency and reducing consumption by compounding phosphorus removal composite nanomaterials. In this method, lanthanum-loaded composite nanomaterials and iron-loaded composite nanomaterials are placed in adsorption columns in series, respectively. The volume ratio of the loaded materials is determined by the ratio of organic phosphorus and orthophosphate in water and the ratio of the phosphorus adsorption amount of lanthanide materials and iron-based materials. This can significantly improve the working capacity and utilization rate of the two materials, while also improving the phosphorus removal depth, reducing the regeneration frequency, and reducing the consumption of regeneration agents.

[0006] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0007] A method for improving efficiency and reducing consumption by compounding and using phosphorus removal composite nanomaterials, comprising the following steps:

[0008] 1) First, determine the concentrations of inorganic orthophosphate and total phosphorus in water, and calculate the mass ratio of inorganic orthophosphate to total phosphorus, recorded as A;

[0009] 2) Calculate the phosphorus removal adsorption capacity of the lanthanide composite nanomaterial (hydrated lanthanum oxide nanoparticles loaded in a cross-linked polystyrene mesh) and the iron composite nanomaterial (ferrihydrite nanoparticles loaded in a cross-linked polystyrene mesh), and calculate the adsorption capacity ratio of the lanthanide material to the iron material, denoted as B;

[0010] 3) multiplying the A obtained in step 1) by a weight value of 0.2, and multiplying the B obtained in step 2) by a weight value of 0.8, and adding the final values ​​to obtain a ratio which is the filling volume ratio of the lanthanide composite nanomaterial and the iron composite nanomaterial;

[0011] 4) The lanthanide composite nanomaterials and the iron composite nanomaterials are loaded into two adsorption columns connected in series. The lanthanide material should be loaded in front of the iron material, while the iron material adsorption column can be connected in parallel with two columns, one for backup and one for use.

[0012] 5) When the total phosphorus concentration of the influent is higher than 1 mg / L, a filling ratio with more lanthanide materials and less iron materials should be adopted. When the total phosphorus concentration of the influent is lower than 1 mg / L, a filling ratio with less lanthanide materials and more iron materials should be adopted.

[0013] 6) After the influent is filtered through the sand filter, it should first pass through the lanthanide material adsorption column and then through the iron material adsorption column to achieve deep phosphorus removal;

[0014] 7) Generally speaking, iron-based materials will penetrate before lanthanide materials and need to be regenerated. Two iron-based material adsorption columns can be connected in parallel to achieve one backup and one use. When regeneration is required, NaOH-NaCl binary solution can be used for mixed regeneration, and the regenerated water can be washed and reused.

[0015] Preferably, the ratio of orthophosphate to organic phosphorus in step 1) should be multiplied by a weight value of 0.8.

[0016] Preferably, the ratio of the adsorption capacity of the lanthanide material to the adsorption capacity of the iron material in step 2) should be multiplied by 0.2.

[0017] Preferably, in step 3), the volume ratio of the lanthanide material to the iron material should be the sum of 0.8×A and 0.2×B.

[0018] Preferably, in step 4), the lanthanide material and the iron material should be loaded into two adsorption columns connected in series, respectively.

[0019] Preferably, the adsorption column loaded with the iron-based material in step 4) can be connected in parallel with two columns, one for backup and the other for use.

[0020] Preferably, the lanthanide material in step 4) is loaded before the iron material.

[0021] Preferably, when the total phosphorus content of the influent in step 5) is 1 mg / L or more (including 1 mg / L), a volume distribution method of materials with more lanthanum and less iron should be adopted.

[0022] Preferably, when the total phosphorus content of the influent in step 5) is below 1 mg / L, a volume distribution method of materials with less lanthanum and more iron should be adopted.

[0023] Preferably, in step 6), the phosphorus-containing wastewater influent should first pass through a lanthanide material adsorption column and then pass through an iron material adsorption column.

[0024] Preferably, the regeneration agent in step 7) can be a NaOH-NaCl binary solution.

[0025] Preferably, in step 7), the adsorption column equipped with the iron-loaded material may be regenerated first, and the adsorption column equipped with the lanthanum-loaded material may be regenerated when appropriate.

[0026] Preferably, during the regeneration process in step 7), the system can be continuously operated.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Aiming at the problems of high consumption, low efficiency and difficulty in large-scale application and promotion of existing deep phosphorus removal technology using single composite nanomaterials, we focused on exploring the technical characteristics of two relatively mature composite nanomaterials for phosphorus removal, which can give full play to the characteristics of large adsorption capacity and high selectivity of lanthanum-loaded composite nanomaterials, and the characteristics of fast adsorption rate and ability to remove some organic phosphorus of iron-loaded composite nanomaterials ( Figure 3 , 4). This method determines the volume ratio of the loading materials by the ratio of organic phosphorus and orthophosphate in water, and the ratio of phosphorus adsorption of lanthanide materials and iron-based materials, and has good pertinence for different types of wastewater containing different phosphorus concentrations. For example, the proportion of orthophosphate in the wastewater in Example 1 is 0.8, compared with the orthophosphate proportion of 0.5 in the wastewater in Example 2, after calculation, more iron-based materials should be used to more effectively remove the phosphorus-containing wastewater in Example 2 containing more organic phosphorus, and the removal efficiency is improved by ~15%. In addition, the present invention adopts a weight distribution method to determine the dosage ratio of lanthanide materials and iron-based materials, which can reflect the important relationship between the adsorption capacity of the material and the phosphorus form in the wastewater, and can more accurately realize the functional distribution of lanthanum-loaded materials and iron-loaded materials, thereby effectively improving the deep phosphorus removal effect.

[0029] (2) The present invention adopts a two-column series adsorption method, and the phosphorus-containing wastewater first passes through the lanthanum-loaded composite nanomaterial and then passes through the iron-loaded composite nanomaterial, which can give full play to the characteristics of the lanthanum-loaded composite nanomaterial with large adsorption capacity and high selectivity, and the iron-loaded composite nanomaterial with low adsorption capacity and high adsorption rate. The two columns operate independently and do not interfere with each other ( Figure 1 The iron-loaded adsorption column can also be connected in parallel with two columns, one for backup and one for use, to facilitate the continuous operation of the adsorption process ( Figure 2 ). The front lanthanide material can remove most of the total phosphorus in the rapid filtration process, while the rear iron material can ensure the deep treatment of the remaining total phosphorus, and can also achieve an increase in the utilization rate of the iron material, avoiding the problem of too fast penetration of the total phosphorus concentration in the effluent due to insufficient adsorption capacity. As shown in Example 3, under the same material bed volume conditions, the treatment depth and treatment capacity of the single lanthanide material and the single iron material are significantly lower than those of the lanthanide-iron material composite operation process ( Figure 5 ), and the combined operation phosphorus treatment depth can reach below the eutrophication limit of 0.02 mg / L.

[0030] (3) The distribution ratio of lanthanide materials and iron-based materials in the present invention is fixed, but the ratio of lanthanum to iron or iron to lanthanum can be adjusted according to the total phosphorus concentration. When the total phosphorus concentration is low, the total working capacity of the monolithic column adsorption system can be appropriately reduced, and the deep treatment of phosphorus can be guaranteed under the same bed volume conditions. When the total phosphorus concentration is high, the proportion of lanthanide materials can be appropriately increased to ensure sufficient working capacity of the overall adsorption system, thereby reducing the regeneration frequency, improving adsorption efficiency, and reducing power consumption.

[0031] (4) The present invention can operate in a manner that a single column of lanthanide material is connected in series with two columns of iron-based material, and the two columns of iron-based material are connected in parallel, with one column in standby and the other in use. Due to the large adsorption capacity of the lanthanide material, when the water output of the lanthanide material column reaches the breakthrough value, regeneration can be temporarily stopped. After the iron-based material column reaches the breakthrough value, the iron-based material is regenerated first. The above-mentioned operation mode can realize the continuous operation of the phosphorus removal system, avoiding the situation where the deep phosphorus removal system cannot operate due to regeneration. When the lanthanide material is regenerated, the iron-based material column can also be operated separately first, and then operated in series after the lanthanide material regeneration is completed.

[0032] (5) The method of the present invention can be formulated in a compounding manner for different application scenarios. Since the price of lanthanide materials is significantly higher than that of iron materials, compounding can effectively reduce the investment cost and operating power consumption of phosphorus removal by adsorption, which is conducive to the large-scale promotion and application of materials and technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Flow chart of the process used in the embodiment of the present invention;

[0034] Figure 2 This is a physical picture of the series column;

[0035] Figure 3 a is the adsorption isotherm diagram of iron-based composite nanomaterials;

[0036] Figure 3 b is the adsorption isotherm of lanthanide composite nanomaterials;

[0037] Figure 4 Comparison of the removal of organophosphates by iron-based and lanthanide-based materials at different sulfate concentrations

[0038] Figure 5 The fixed bed breakthrough curves for the removal of phosphorus-containing wastewater using lanthanide materials alone, iron materials alone, and a combination of lanthanide and iron materials in Example 3 (where the material volumes are the same) are shown. DETAILED DESCRIPTION

[0039] The present invention is further described below with reference to specific examples. The phosphorus solutions used for adsorption are a phosphorus stock solution prepared from potassium dihydrogen phosphate and a phosphorus stock solution of organophosphate HEDP. The materials used are ton-level mass-produced lanthanide composite nanomaterials and iron-based composite materials, with maximum adsorption capacities of 95.2 mg / g and 32.0 mg / g, respectively.

[0040] Example 1

[0041] A method for improving efficiency and reducing consumption by compounding and using phosphorus removal composite nanomaterials, comprising the following steps:

[0042] 1) First, prepare phosphorus-containing wastewater and adjust the total phosphorus concentration to 3 mg / L, of which orthophosphate accounts for 80% and HEDP accounts for 20%. At the same time, 100 mg / L sulfate and 50 mg / L chloride ions are added as coexisting ions;

[0043] 2) The lanthanide composite nanomaterials and the iron composite nanomaterials were loaded into two glass adsorption columns, each 130 mm long and 12 mm in diameter, and connected in series via latex tubing. The volume ratio of the lanthanide material to the iron material was calculated to be 1.2:1, and the total volume was 10 ml.

[0044] 3) The phosphorus-containing simulated wastewater was introduced into the glass adsorption column through a peristaltic pump in the order of lanthanum first and iron second, and the flow rate was adjusted to 20 bed volumes / hour;

[0045] 4) Use an automatic collector to collect the effluent, and measure the total phosphorus concentration of the effluent at regular time intervals. The breakthrough point is set at 0.5 mg / L.

[0046] 5) A set of control experiments can be conducted simultaneously, in which the phosphorus-containing simulated wastewater of the same configuration is passed into a glass column of the same volume but containing only lanthanide materials at the same flow rate.

[0047] In this embodiment, the lanthanum-iron material composite column can process 4,800 bed volumes of water before the breakthrough point, while the lanthanide material alone can only process 4,000 bed volumes of water. In addition, the price of lanthanide material is about 80,000 yuan / ton, and the price of iron material is about 300 million yuan / ton. The investment cost of the lanthanum-iron composite method is significantly lower than that of using a single lanthanide material.

[0048] Example 2

[0049] A method for improving efficiency and reducing consumption by compounding and using phosphorus removal composite nanomaterials, comprising the following steps:

[0050] 1) First, prepare phosphorus-containing wastewater and adjust the total phosphorus concentration to 3 mg / L, of which orthophosphate accounts for 50% and HEDP accounts for 50%. At the same time, 100 mg / L sulfate and 50 mg / L chloride ions are added as coexisting ions;

[0051] 2) The lanthanide composite nanomaterials and the iron composite nanomaterials were loaded into two glass adsorption columns, each 130 mm long and 12 mm in diameter, and connected in series via latex tubing. The volume ratio of the lanthanide material to the iron material was calculated to be 1:1.1, and the total volume was 10 ml.

[0052] 3) The phosphorus-containing simulated wastewater was introduced into the glass adsorption column through a peristaltic pump in the order of lanthanum first and iron second, and the flow rate was adjusted to 20 bed volumes / hour;

[0053] 4) Use an automatic collector to collect the effluent, and measure the total phosphorus concentration of the effluent at regular time intervals. The breakthrough point is set at 0.5 mg / L.

[0054] 5) A set of control experiments can be conducted simultaneously, in which the phosphorus-containing simulated wastewater of the same configuration is passed into a glass column of the same volume but with a lanthanum-iron material ratio of 1.1:1 at the same flow rate.

[0055] In this embodiment, when the lanthanum-iron material compounding ratio is 1:1.1, the column can treat 4,500 bed volumes of water before the breakthrough point, while when the lanthanum-iron material ratio is 1.1:1, it can only treat 4,100 bed volumes of water. This is because when the proportion of organic phosphoric acid in the water increases, the proportion of iron-based materials needs to be increased to achieve more efficient deep phosphorus removal. In addition, the price of lanthanum-based materials is about 80,000 yuan / ton, and the price of iron-based materials is about 300 million yuan / ton. The investment cost of the lanthanum-iron compounding method is lower than that of using a single lanthanum-based material.

[0056] Example 3

[0057] A method for improving efficiency and reducing consumption by compounding and using phosphorus removal composite nanomaterials, comprising the following steps:

[0058] 1) First, obtain real biochemical tailwater from a sewage treatment plant. The total phosphorus concentration is approximately 2 mg / L, of which orthophosphate accounts for 88% and other types of phosphorus account for 12%. It contains coexisting ions such as nitrate, sulfate, and chloride. The conductivity is approximately 0.8 ms / μm, the pH is approximately 7, and the TOC concentration in the water is approximately 12 mg / L.

[0059] 2) The lanthanide composite nanomaterials and the iron composite nanomaterials were loaded into two glass adsorption columns, each 130 mm long and 12 mm in diameter, and connected in series via latex tubing. The volume ratio of the lanthanide material to the iron material was calculated to be 1.3:1, and the total volume was 10 ml.

[0060] 3) The phosphorus-containing simulated wastewater was introduced into the glass adsorption column through a peristaltic pump in the order of lanthanum first and iron second, and the flow rate was adjusted to 20 bed volumes / hour;

[0061] 4) Use an automatic collector to collect the effluent, and measure the total phosphorus concentration of the effluent at regular time intervals. The breakthrough point is set at 0.5 mg / L.

[0062] 5) Two groups of control experiments can be conducted simultaneously, in which the same configuration of phosphorus-containing simulated wastewater is passed into the glass column of the same volume but containing only lanthanide materials or iron materials at the same flow rate.

[0063] like Figure 5 As shown, the lanthanum-iron composite column in this embodiment can process 6,500 bed volumes of water before the breakthrough point, while the lanthanide material alone can only process about 5,100 bed volumes of water, and the iron material can only process about 1,000 bed volumes of water. In addition, the price of the lanthanide material is about 80,000 yuan / ton, and the price of the iron material is about 300 million yuan / ton. The investment cost of the lanthanum-iron composite method is significantly lower than that of using a single lanthanide material, and its efficiency is significantly higher than that of using an iron material alone.

Claims

1. A method for improving efficiency and reducing consumption by compounding phosphorus removal composite nanomaterials, characterized in that: The following steps are involved: 1) First, determine the concentrations of inorganic orthophosphate and total phosphorus in the water, and calculate the ratio of inorganic orthophosphate to total phosphorus, recorded as A; 2) Calculate the phosphorus removal adsorption capacity of the lanthanide composite nanomaterials and the iron composite nanomaterials, and calculate the adsorption capacity ratio of the lanthanide material to the iron material, which is recorded as B; 3) multiplying the A obtained in step 1) by a weight value of 0.2, and multiplying the B obtained in step 2) by a weight value of 0.8, and adding the final values ​​to obtain a ratio which is the filling volume ratio of the lanthanide composite nanomaterial and the iron composite nanomaterial; 4) The lanthanide composite nanomaterials and the iron composite nanomaterials are loaded into two adsorption columns connected in series. The lanthanide material should be loaded in front of the iron material, while the iron material adsorption column can be connected in parallel with two columns, one for backup and one for use. 5) When the total phosphorus concentration of the influent is higher than 1 mg / L, a filling ratio with more lanthanide materials and less iron materials should be adopted. When the total phosphorus concentration of the influent is lower than 1 mg / L, a filling ratio with less lanthanide materials and more iron materials should be adopted. 6) After the influent is filtered through sand filtration, it should first pass through the lanthanide material adsorption column and then through the iron material adsorption column to achieve deep phosphorus removal; 7) The iron-based material will penetrate before the lanthanide material and needs to be regenerated. Two iron-based material adsorption columns can be connected in parallel to achieve one backup and one use; when regeneration is required, NaOH-NaCl binary solution can be used for mixed regeneration, and the regenerated water can be washed and reused; the lanthanide composite nanomaterial is hydrated lanthanum oxide nanoparticles loaded in the cross-linked polystyrene mesh, and the iron-based composite nanomaterial is ferrihydrite nanoparticles loaded in the cross-linked polystyrene mesh.

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