A device system and method for resourceful treatment of photovoltaic fluorine-containing mixed acid wastewater

Abstract

The application provides a resource treatment device system and method for photovoltaic fluorine-containing mixed acid wastewater. The resource treatment device system comprises a pretreatment unit, an acid-resistant nanofiltration unit, an adsorption fluorine removal unit and a membrane distillation concentration unit which are sequentially connected. The acid-resistant nanofiltration unit is internally provided with a hydrofluoric acid-resistant nanofiltration membrane. The adsorption fluorine removal unit is internally provided with an adsorption material. The adsorption material comprises lanthanum-zirconium bimetallic doped composite metal oxide or zirconium-based metal organic framework material. The membrane distillation concentration unit is internally provided with a hydrophobic microporous membrane. The application solves the systematic contradiction between "acid neutralization loss" and "fluorine recovery" by constructing a new technology system of "neutralization-free and acid retention", and realizes the double efficient resource recovery of acid and fluorine from the source.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment and resource recovery technology, and relates to a resource-based treatment method for fluoride-containing mixed acid wastewater, specifically to a resource-based treatment device system and method for photovoltaic fluoride-containing mixed acid wastewater. Background Technology

[0002] The photovoltaic industry generates large amounts of acidic wastewater during processes such as silicon wafer cutting, texturing, and etching. Typical characteristics of this type of wastewater include the presence of various acids such as hydrofluoric acid, hydrochloric acid, and nitric acid, as well as silicon powder, cutting fluid, surfactants, and trace amounts of heavy metal ions (such as Cu). 2+ Pb 2+ Hydrofluoric acid wastewater typically has a pH of 2-4 and a fluoride ion concentration as high as 1000-5000 mg / L. It is characterized by strong corrosiveness, high salinity, and large fluctuations in water quality. The corrosive damage to treatment equipment caused by hydrofluoric acid far exceeds that caused by conventional hydrochloric acid wastewater, making it the core technical challenge in treating this type of wastewater.

[0003] Current technologies for treating this type of wastewater mainly have the following problems: First, chemical precipitation (such as adding lime or calcium chloride) converts fluoride ions into calcium fluoride precipitate. This method is simple to operate, but it has significant drawbacks: on the one hand, chemical precipitation of fluoride-containing wastewater produces a large amount of fluoride-containing sludge, of which calcium fluoride accounts for only more than 40%, making it difficult to achieve effective utilization of fluoride resources; on the other hand, precipitation cannot recover acid resources, and the treatment process requires a large amount of reagents, resulting in high overall operating costs.

[0004] Secondly, while membrane separation technology has been applied in the field of waste acid recovery, conventional polyamide reverse osmosis membranes and nanofiltration membranes are highly susceptible to membrane material degradation and desalination layer peeling in acidic environments containing hydrofluoric acid, leading to rapid membrane element failure (usually within days to weeks). Existing acid-resistant nanofiltration membranes are mostly designed for hydrochloric acid or sulfuric acid systems, and their long-term tolerance to hydrofluoric acid remains insufficient.

[0005] Third, although induced crystallization precipitation methods (such as the CrystPFB+SepPFB combined process, i.e., the combined process of crystallization granulation fluidized bed + high-efficiency solid-liquid separation fluidized bed) can recover calcium fluoride, the fluoride concentration in the treated effluent is still as high as 20~30mg / L, and the fluoride recovery efficiency is only 45%~63%, which cannot meet the increasingly stringent emission standards and cannot achieve acid recovery.

[0006] Fourth, CN 121758014A discloses a process and system for recovering perfluoride from photovoltaic cell production wastewater. The technical route is as follows: pretreatment → ultrafiltration → nanofiltration → nanofiltration permeate enters a neutralization and adjustment tank, where it is neutralized with some dilute acid water to a pH of 5-8. Then, it passes through a two-stage RO membrane to intercept fluoride, obtaining a concentrated sodium fluoride solution. Finally, it reacts with lime solution and calcium chloride solution in a fluoride recovery crystallization reactor to produce calcium fluoride crystals. Although this technical route achieves fluoride recovery (claiming up to 99%), it has the following significant drawbacks: (1) After the nanofiltration product water is neutralized, the mixed acid resources (HCl, HF, HNO3) are completely destroyed, and the acid is neutralized into salt, making it impossible to realize the resource recovery of acid and causing a large waste of acid resources; (2) The neutralization process requires a large amount of alkali solution, which significantly increases operating costs and reagent consumption; (3) The two-stage RO membrane has extremely high requirements for the corrosion resistance of the membrane when intercepting fluorides, and it is difficult to guarantee the long-term stability of operation. (4) The process is essentially aimed at achieving the goal of "fluoride removal and emission compliance", and acid recovery is not taken into consideration in the design.

[0007] Therefore, there is an urgent need to develop a photovoltaic fluoride-containing wastewater treatment system and method that can solve the problem of strong corrosion of membrane modules by hydrofluoric acid wastewater and simultaneously achieve efficient recovery of mixed acid resources, fluorine resources and water resources, shifting from "end-of-pipe treatment" to "resource recovery". Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a resource-based treatment device system and method for photovoltaic fluoride-containing mixed acid wastewater. This invention constructs a novel "neutralization-acid retention" technical system, resolving the irreconcilable systemic contradiction between "acid neutralization loss" and "fluoride recovery," thus achieving efficient dual resource recovery of both acid and fluoride at the source.

[0009] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater, the resource-based treatment device system comprising a pretreatment unit, an acid-resistant nanofiltration unit, an adsorption defluorination unit, and a membrane distillation concentration unit connected in sequence. The acid-resistant nanofiltration unit is equipped with a hydrofluoric acid-resistant nanofiltration membrane. The adsorption and defluorination unit is internally equipped with an adsorption material; the adsorption material includes lanthanum-zirconium bimetallic doped composite metal oxide or zirconium-based metal-organic framework material. The membrane distillation concentration unit is equipped with a hydrophobic microporous membrane.

[0010] The present invention describes a mixed acid wastewater containing fluoride used in photovoltaic applications, comprising hydrochloric acid, nitric acid, and hydrofluoric acid; and the fluoride in the mixed acid wastewater contains F... - The concentration is 1000~5000 mg / L, for example, it can be 1000 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L or 5000 mg / L, but is not limited to the listed values. Other values ​​within the range that are not listed are also applicable.

[0011] Preferably, the pH value of the fluoride-containing mixed acid wastewater is 2 to 4, for example, it can be 2, 2.4, 2.8, 3.2, 3.6 or 4, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0012] In this invention, an acid-resistant nanofiltration membrane capable of long-term stable operation in a hydrofluoric acid-containing environment is used to achieve efficient separation of monovalent acid and heavy metal ions. This fundamentally resolves the technical contradiction between "acid retention" and "fluoride removal," ensuring the complete preservation of the acid's recovery value. Subsequently, without neutralization, the nanofiltration permeate is selectively captured by adsorbent materials under natural low-acidity conditions (pH=2~4), simultaneously recovering calcium fluoride. This method overcomes the industry's technical prejudice that "fluoride-containing wastewater must be neutralized first." Then, a membrane distillation technology driven by low-grade waste heat is used to achieve high concentration of dilute acid, and the simultaneously generated high-purity condensate (conductivity <30μS / cm) is reused for backwashing and flushing at the system's front end, forming an "energy-material" dual closed-loop integrated system. This significantly reduces system energy consumption and fresh water consumption, achieving triple resource recovery of acid, fluoride, and water. The device system provided by this invention solves the irreconcilable systemic contradiction between "acid neutralization loss" and "fluorine recovery" in the prior art, and realizes efficient dual resource recovery of acid and fluorine from the source.

[0013] As a preferred embodiment of the present invention, the pretreatment unit includes a purification device and an ultrafiltration device connected together.

[0014] Preferably, the impurity removal device includes a bar screen and / or a sedimentation tank.

[0015] Preferably, the impurity removal device includes a bar screen and a sedimentation tank connected in sequence; the bar screen is used to intercept large suspended solids and silica powder particles in the wastewater, and the sedimentation tank is used to remove settleable colloidal substances and particulate matter in the wastewater.

[0016] Preferably, the ultrafiltration device includes an ultrafiltration membrane module.

[0017] Preferably, the ultrafiltration membrane module includes a polyvinylidene fluoride ultrafiltration membrane module.

[0018] The impurity removal device described in this invention is used to remove large suspended solids, silicon powder particles, and colloidal substances from photovoltaic fluorine-containing mixed acid wastewater.

[0019] As a preferred embodiment of the present invention, the inlet of the acid-resistant nanofiltration unit is connected to the product water outlet of the ultrafiltration device.

[0020] Preferably, the hydrofluoric acid resistant nanofiltration membrane comprises a modified polypiperazine amide composite membrane or a polytetrafluoroethylene modified composite nanofiltration membrane.

[0021] Preferably, the pore size of the hydrofluoric acid resistant nanofiltration membrane is 0.5~2nm, for example, it can be 0.5nm, 0.8nm, 1.1nm, 1.4nm, 1.7nm or 2nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the recovery rate of the hydrofluoric acid resistant nanofiltration membrane is 65-75%, for example, it can be 65%, 67%, 69%, 71%, 73% or 75%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] It is worth noting that the modification method of the modified polypiperazine amide composite membrane is low-temperature plasma modification. The specific process includes: using a specific gas (at least one of oxygen, nitrogen or argon) to generate low-temperature plasma at a specific power and frequency to bombard and modify the surface of the polypiperazine amide composite membrane. Furthermore, the modification effect of the low-temperature plasma modification is as follows: it introduces polar groups (such as -OH, -COOH, -NH2, etc.) on the membrane surface, which improves hydrophilicity and antifouling ability, while also improving the acid resistance of the membrane.

[0024] In addition, the polytetrafluoroethylene modified composite nanofiltration membrane was prepared using the preparation method provided in CN119607895A.

[0025] Under normal temperature conditions, after continuous operation for 90 days in a strongly acidic environment containing HF concentrations of 1000~5000 mg / L, the hydrofluoric acid resistant nanofiltration membrane of the present invention exhibits a desalination rate of no more than 5% of the initial value for a 2000 ppm Na2SO4 solution; this unit is used to selectively permeate monovalent acids (HCl, HF, HNO3) and retain divalent and higher heavy metal ions (retention rate ≥98%).

[0026] As a preferred embodiment of the present invention, the inlet of the adsorption and defluorination unit is connected to the permeate port of the acid-resistant nanofiltration unit.

[0027] Preferably, the adsorption and defluorination unit is a three-column series adsorption device, including an online adsorption column, an offline regeneration column, and a standby column that operate alternately.

[0028] Preferably, the adsorbent material is loaded inside the online adsorption column.

[0029] Preferably, the particle size of the lanthanum-zirconium bimetallic doped composite metal oxide is 0.5~1mm, for example, it can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the static saturated adsorption capacity of the lanthanum-zirconium bimetallic doped composite metal oxide is 20~25 mg / g, for example, it can be 20 mg / g, 21 mg / g, 22 mg / g, 23 mg / g, 24 mg / g or 25 mg / g, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] In this invention, the lanthanum-zirconium bimetallic doped composite metal oxide is prepared using the preparation method disclosed in CN121651623A; Preferably, the particle size of the zirconium-based metal-organic framework material is 0.5~2mm, for example, it can be 0.5mm, 0.8mm, 1.1mm, 1.4mm, 1.7mm or 2mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] It is worth noting that the preparation method of the zirconium-based metal-organic framework material (Zr-MOF) includes any one of the following: room temperature synthesis, hydrothermal / solvothermal synthesis, solvent-free synthesis, or supercritical CO2 continuous flow reactor method. This invention does not limit the specific preparation method of the Zr-MOF, as long as the obtained Zr-MOF exhibits high selective adsorption capacity for fluoride ions (static saturated adsorption capacity ≥ 20 mg / g).

[0033] As a preferred embodiment of the present invention, the inlet of the membrane distillation concentration unit is connected to the product water outlet of the adsorption defluorination unit.

[0034] Preferably, the hydrophobic microporous membrane is made of polytetrafluoroethylene or polyvinylidene fluoride.

[0035] Preferably, the pore size of the hydrophobic microporous membrane is 0.1~0.45μm, for example, it can be 0.1μm, 0.2μm, 0.3μm, 0.4μm or 0.45μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the membrane flux of the hydrophobic microporous membrane is 10~12 LMH, for example, it can be 10 LMH, 10.4 LMH, 10.8 LMH, 11.2 LMH, 11.6 LMH or 12 LMH, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the condensate outlet of the membrane distillation concentration unit is connected to the backwash water tank.

[0038] Preferably, the backwash tank has two outlets, one of which is connected to the inlet of the acid-resistant nanofiltration unit, and the other outlet is connected to the inlet of the ultrafiltration device.

[0039] As a preferred embodiment of the present invention, the resource recovery processing device further includes a deep desorption unit, an online fluoride ion detection device, and a PLC controller.

[0040] Preferably, the inlet of the deep desorption unit is connected to the concentrate outlet of the membrane distillation concentration unit.

[0041] Preferably, the deep desorption unit includes a desorption / absorption tower.

[0042] Preferably, the online fluoride ion detection device is installed at the permeate port of the acid-resistant nanofiltration unit and the product water port of the adsorption and defluorination unit.

[0043] Preferably, the PLC controller is used to control the regeneration cycle and influent flow rate of the adsorption defluorination unit based on feedback of fluoride ion concentration.

[0044] Secondly, the present invention provides a resource-based treatment method for photovoltaic fluorine-containing mixed acid wastewater, wherein the resource-based treatment method is carried out using the resource-based treatment device system provided in the first aspect.

[0045] As a preferred embodiment of the present invention, the resource recovery method includes the following steps: (1) The fluoride-containing mixed acid wastewater is pretreated and then separated by nanofiltration to obtain a nanofiltration permeate with a pH value of 2 to 4. (2) The nanofiltration permeate is subjected to deep defluorination treatment and membrane distillation concentration treatment in sequence to obtain condensate and concentrated acid solution.

[0046] In this invention, the deep defluorination treatment in step (2) specifically includes an adsorption stage, a regeneration stage, a calcium fluoride generation stage, and solid-liquid separation and discharge. More specifically, the adsorption stage includes: fluoride-containing mixed acid wastewater (pH 2-4) passes through an adsorption column, where fluoride ions are captured by the adsorption material, and the effluent fluoride ion concentration is ≤5mg / L; the regeneration stage includes: after the adsorption material is saturated, the water intake is stopped, and an alkaline solution is introduced into the adsorption column to wash off the adsorbed fluoride ions, forming a regenerated wastewater containing a high concentration of fluoride ions; the calcium fluoride generation stage includes: the regenerated wastewater is discharged from the adsorption column and sent to an independent reaction tank or sedimentation tank, where a calcium salt solution is added to cause a precipitation reaction; the solid-liquid separation and discharge includes: after the reaction is completed, the mixed liquid containing CaF2 precipitate enters a sedimentation tank or filter press for solid-liquid separation, the supernatant can be returned to the system or discharged externally, and the bottom calcium fluoride filter cake has a moisture content of ≤80%, which is recycled and transported as a by-product.

[0047] As a preferred embodiment of the present invention, the pretreatment includes a purification process and an ultrafiltration process performed sequentially.

[0048] Preferably, the separation pressure of the nanofiltration separation process is 0.8~1.2MPa, for example, it can be 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa or 1.2MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, the separation temperature of the nanofiltration separation process is 20~30℃, for example, it can be 20℃, 22℃, 24℃, 26℃, 28℃ or 30℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the residence time for the deep defluorination treatment is 30-40 minutes, for example, 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes or 40 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the deep defluorination treatment further includes sequentially regenerating the adsorbent material with alkaline solution and performing a precipitation reaction after the adsorption material has become saturated.

[0052] Preferably, the concentration of the alkali solution used for alkali regeneration is 2 to 5 wt%, for example, it can be 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] Preferably, the alkaline solution comprises a sodium hydroxide solution.

[0054] Preferably, the precipitant used in the precipitation reaction includes a calcium salt, and the calcium salt includes calcium chloride.

[0055] In this invention, the fluoride ion concentration in the mixed acid solution obtained after the deep defluorination treatment is less than 50% of the first-level discharge standard limit of the national "Integrated Wastewater Discharge Standard" (GB 8978-1996), i.e., ≤5 mg / L. For example, it can be 5 mg / L, 4.9 mg / L, 4.8 mg / L, 4.7 mg / L, 4.6 mg / L, or 4.5 mg / L, etc., but is not limited to the listed values. Other values ​​not listed within the range are also applicable. The purity of the CaF2 precipitate obtained by the precipitation reaction is ≥97%. For example, it can be 97%, 97.2%, 97.4%, 97.6%, 97.8%, or 98%, etc., but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0056] In addition, the present invention realizes the regeneration cycle and influent flow rate of deep defluorination treatment through an online fluoride ion detection device and a PLC controller.

[0057] As a preferred embodiment of the present invention, the hot-side temperature of the membrane distillation concentration process is 70~90℃, for example, it can be 70℃, 74℃, 78℃, 82℃, 86℃ or 90℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0058] Preferably, the cold-side temperature of the membrane distillation concentration process is 20~30℃, for example, it can be 20℃, 22℃, 24℃, 26℃, 28℃ or 30℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] Preferably, the vacuum degree of the membrane distillation concentration process is -50 to -80 kPa, for example, it can be -50 kPa, -55 kPa, -60 kPa, -65 kPa, -70 kPa, -75 kPa or -80 kPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] Preferably, the conductivity of the condensate is <30μS / cm, for example, it can be 30μS / cm, 29μS / cm, 28μS / cm, 27μS / cm, 26μS / cm or 25μS / cm, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] The heat source used in the membrane distillation concentration process described in this invention is low-grade waste heat or residual heat from the factory; the condensate is 100% recycled to the ultrafiltration device and the acid-resistant nanofiltration unit, so that the daily fresh water replenishment of the entire device system is reduced by no less than 80% of the average daily water consumption of similar wastewater treatment systems, and the comprehensive water resource recycling rate is ≥95%.

[0062] Preferably, the processing method further includes concentrating the concentrated acid solution to obtain industrial hydrochloric acid.

[0063] Preferably, the concentration of the industrial hydrochloric acid is 31-36%, for example, it can be 31%, 32%, 33%, 34%, 35% or 36%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In this invention, the concentration process includes feeding the concentrated acid solution into a desorption / absorption tower, adding calcium chloride or using a pressure difference method to obtain industrial hydrochloric acid.

[0065] The industrial hydrochloric acid described in this invention is an industrial-grade mixed acid containing nitric acid, rather than pure hydrochloric acid; this mixed acid can be used in downstream processes that are sensitive to nitrate radicals (this mixed acid can be directly used in other processes in the plant, such as metal pickling, pH adjustment, etc.), or for further separation and purification.

[0066] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0067] Compared with the prior art, the present invention has the following beneficial effects: The method provided by this invention breaks through the technical bias of "acid neutralization loss", achieving a total acid recovery rate of ≥90%, a water resource reuse rate of ≥95%, and producing high-purity calcium fluoride (≥97%) and 31%~36% industrial hydrochloric acid as by-products. The overall operating cost is reduced by 30%~40% compared with traditional processes, providing a systematic solution for the triple resource recovery of acid, fluoride and water from photovoltaic fluorine-containing mixed acid wastewater. Attached Figure Description

[0068] Figure 1 A schematic diagram of the structure of a resource-based treatment device system for photovoltaic fluorine-containing mixed acid wastewater provided in a specific embodiment of the present invention; Among them, 1 is the pretreatment unit, 2 is the acid-resistant nanofiltration unit, 3 is the adsorption defluorination unit, 4 is the membrane distillation concentration unit, 5 is the deep desorption unit, 6 is the online fluoride ion detection device, 7 is the PLC controller, 8 is the backwash water tank, 1-1 is the impurity removal device, and 1-2 is the ultrafiltration device. Detailed Implementation

[0069] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0070] In one specific embodiment, the present invention provides a resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater, such as... Figure 1 As shown, the resource recovery system includes a pretreatment unit 1, an acid-resistant nanofiltration unit 2, an adsorption defluorination unit 3, and a membrane distillation concentration unit 4, which are connected in sequence. The acid-resistant nanofiltration unit 2 is equipped with a hydrofluoric acid-resistant nanofiltration membrane. The adsorption and defluorination unit 3 is internally provided with an adsorption material; the adsorption material includes lanthanum-zirconium bimetallic doped composite metal oxide or zirconium-based metal-organic framework material. The membrane distillation concentration unit 4 is equipped with a hydrophobic microporous membrane.

[0071] The pretreatment unit 1 includes a cleansing device 1-1 and an ultrafiltration device 1-2 connected together; the cleansing device 1-1 includes a grid interception device and / or a sedimentation tank; the ultrafiltration device 1-2 includes an ultrafiltration membrane module; the ultrafiltration membrane module includes a polyvinylidene fluoride ultrafiltration membrane module.

[0072] The inlet of the acid-resistant nanofiltration unit 2 is connected to the product water outlet of the ultrafiltration device 1-2; the hydrofluoric acid-resistant nanofiltration membrane includes a modified polypiperazine amide composite membrane or a polytetrafluoroethylene modified composite nanofiltration membrane; the pore size of the hydrofluoric acid-resistant nanofiltration membrane is 0.5~2nm; the recovery rate of the hydrofluoric acid-resistant nanofiltration membrane is 65~75%.

[0073] The inlet of the adsorption and defluorination unit 3 is connected to the permeate port of the acid-resistant nanofiltration unit 2; the adsorption and defluorination unit 3 is a three-column series adsorption device, including an online adsorption column, an offline regeneration column, and a standby column that operate alternately; the adsorbent material is loaded in the online adsorption column; the particle size of the lanthanum-zirconium bimetallic doped composite metal oxide is 0.5~1mm; the static saturated adsorption capacity of the lanthanum-zirconium bimetallic doped composite metal oxide is 20~25mg / g; the particle size of the zirconium-based metal-organic framework material is 0.5~2mm.

[0074] The inlet of the membrane distillation concentration unit 4 is connected to the product water outlet of the adsorption defluorination unit; the hydrophobic microporous membrane is made of polytetrafluoroethylene or polyvinylidene fluoride; the pore size of the hydrophobic microporous membrane is 0.1~0.45μm; the membrane flux of the hydrophobic microporous membrane is 10~12LMH; the condensate outlet of the membrane distillation concentration unit 4 is connected to the backwash water tank 8; the backwash water tank 8 has two outlets, one of which is connected to the inlet of the acid-resistant nanofiltration unit, and the other outlet is connected to the inlet of the ultrafiltration device.

[0075] The resource recovery treatment device also includes a deep desorption unit 5, an online fluoride ion detection device 6, and a PLC controller 7; the inlet of the deep desorption unit 5 is connected to the concentrate outlet of the membrane distillation concentration unit 4; the online fluoride ion detection device 6 is located at the permeate outlet of the acid-resistant nanofiltration unit 2 and the product water outlet of the adsorption defluorination unit 3; the PLC controller 7 is used to control the regeneration cycle and influent flow rate of the adsorption defluorination unit based on the fluoride ion concentration feedback.

[0076] In another specific embodiment, the present invention provides a method for the resource-based treatment of photovoltaic fluoride-containing mixed acid wastewater using the above-described resource-based treatment device system, the resource-based treatment method comprising the following steps: (1) The fluoride-containing mixed acid wastewater is pretreated and then separated by nanofiltration to obtain a nanofiltration permeate with a pH value of 2 to 4. The pretreatment includes sequential impurity removal and ultrafiltration; the nanofiltration separation process has a separation pressure of 0.8~1.2 MPa and a separation temperature of 20~30℃. (2) The nanofiltration permeate is subjected to deep defluorination treatment and membrane distillation concentration treatment in sequence to obtain condensate and concentrated acid solution; The deep defluorination treatment also includes sequentially regenerating the adsorbent material after it has become saturated with alkali and performing a precipitation reaction; the concentration of the alkali used for alkali regeneration is 2-5 wt%; the precipitant used for the precipitation reaction includes calcium salts; The hot-side temperature of the membrane distillation concentration process is 70~90℃, and the cold-side temperature is 20~30℃; the vacuum degree of the membrane distillation concentration process is -50~-80kPa. The conductivity of the condensate is <30 μS / cm; (3) The concentration of the acid solution in step (2) is concentrated to obtain industrial hydrochloric acid with a concentration of 31-36%.

[0077] The following examples and comparative examples used fluoride-containing mixed acid wastewater treated from silicon wafer cutting and cleaning wastewater from a photovoltaic company. The water quality parameters were: pH=2.3, F... - Concentration 3200 mg / L, Cl - The concentration is 1800 mg / L, NO3 - The concentration was 600 mg / L, the COD content was 800 mg / L, the SS was 150 mg / L, and the Cu content was... 2+ The concentration is 12 mg / L, Pb 2+ The concentration was 8 mg / L. Treatment scale: 187.5 m² 3 / h (4500m) 3 / d) Example 1 This embodiment provides a resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater, such as... Figure 1 As shown, the resource recovery system includes a pretreatment unit 1, an acid-resistant nanofiltration unit 2, an adsorption defluorination unit 3, and a membrane distillation concentration unit 4, which are connected in sequence. The acid-resistant nanofiltration unit 2 is equipped with a hydrofluoric acid-resistant nanofiltration membrane. The adsorption and defluorination unit 3 is internally provided with an adsorption material; the adsorption material is a lanthanum-zirconium bimetallic doped composite metal oxide. The membrane distillation concentration unit 4 is equipped with a hydrophobic microporous membrane.

[0078] The pretreatment unit 1 includes a cleansing device 1-1 and an ultrafiltration device 1-2 connected together; the cleansing device 1-1 consists of a grid interception device and a sedimentation tank connected in sequence; the ultrafiltration device 1-2 includes an ultrafiltration membrane module; the ultrafiltration membrane module is a PVDF membrane module with a pore size of 0.03μm; the gap of the grid interception device is 2mm.

[0079] The inlet of the acid-resistant nanofiltration unit 2 is connected to the product water outlet of the ultrafiltration device 1-2; the hydrofluoric acid-resistant nanofiltration membrane is a low-temperature modified polypiperazine amide composite membrane; the pore size of the hydrofluoric acid-resistant nanofiltration membrane is 1.2 nm; the recovery rate of the hydrofluoric acid-resistant nanofiltration membrane is 70%.

[0080] The inlet of the adsorption and defluorination unit 3 is connected to the permeate port of the acid-resistant nanofiltration unit 2; the adsorption and defluorination unit 3 is a three-column series adsorption device, including an online adsorption column, an offline regeneration column, and a standby column that operate alternately; the adsorbent material is loaded in the online adsorption column; the particle size of the lanthanum-zirconium bimetallic doped composite metal oxide is 0.5~0.8mm; the packing height is 1.5m; and the static saturated adsorption capacity of the lanthanum-zirconium bimetallic doped composite metal oxide is 22mg / g.

[0081] The inlet of the membrane distillation concentration unit 4 is connected to the product water outlet of the adsorption defluorination unit; the hydrophobic microporous membrane is made of PTFE hollow fiber membrane with a membrane area of ​​20m². 2 The hydrophobic microporous membrane has a pore size of 0.2 μm and a membrane flux of 11 LMH. The condensate outlet of the membrane distillation concentration unit 4 is connected to the backwash water tank 8. The backwash water tank 8 has two outlets, one of which is connected to the inlet of the acid-resistant nanofiltration unit and the other of which is connected to the inlet of the ultrafiltration device.

[0082] The resource recovery treatment device also includes a deep desorption unit 5, an online fluoride ion detection device 6, and a PLC controller 7; the inlet of the deep desorption unit 5 is connected to the concentrate outlet of the membrane distillation concentration unit 4; the online fluoride ion detection device 6 is located at the permeate outlet of the acid-resistant nanofiltration unit 2 and the product water outlet of the adsorption defluorination unit 3; the PLC controller 7 is used to control the regeneration cycle and influent flow rate of the adsorption defluorination unit based on the fluoride ion concentration feedback.

[0083] This embodiment also provides a method for the resource-based treatment of photovoltaic fluoride-containing mixed acid wastewater using the above-mentioned resource-based treatment device system, the resource-based treatment method comprising the following steps: (1) The fluoride-containing mixed acid wastewater was subjected to pretreatment and nanofiltration separation treatment in sequence to obtain nanofiltration permeate with a pH value of 2.3; The pretreatment includes sequential impurity removal and ultrafiltration. The ultrafiltration process is carried out at a pressure of 0.1 MPa and a temperature of 25°C; the turbidity of the pretreated wastewater is 0.8 NTU and the COD is reduced to 420 mg / L. The separation pressure of the nanofiltration separation process is 1.0 MPa; the separation temperature of the nanofiltration separation process is 25°C. F in nanofiltration permeate - The concentration was 2850 mg / L, the Cl concentration was 1720 mg / L, and the NO3 concentration was... - The concentration is 580 mg / L, Cu 2+ Pb 2+ Not detected. After 90 days of continuous operation, the hydrofluoric acid-resistant nanofiltration membrane showed a 3.2% decrease in desalination rate for 2000 ppm Na2SO4 and an 8% decrease in membrane flux. This demonstrates that the hydrofluoric acid-resistant nanofiltration membrane described in this embodiment has significant durability advantages in HF-containing environments. (2) The nanofiltration permeate is subjected to deep defluorination treatment and membrane distillation concentration treatment in sequence to obtain condensate and concentrated acid solution; The empty bed contact time for the defluorination treatment is 30 minutes, and the effluent F... - The concentration was 4.2 mg / L; The deep defluorination treatment also includes sequentially regenerating the adsorbent material after it has become saturated with alkali and performing a precipitation reaction; the concentration of the alkali solution (NaOH solution) used for alkali regeneration is 3 wt%; the precipitant used for the precipitation reaction is calcium chloride; and calcium fluoride with a purity of 97.2% is obtained after the precipitation reaction. The hot-side temperature of the membrane distillation concentration process is 80°C, and the cold-side temperature is 25°C; the vacuum degree of the membrane distillation concentration process is -65 kPa. The conductivity of the condensate is 18 μS / cm; the concentrated acid solution contains 18.2% HCl, 2.8% HF, and 6.5% HNO3. (3) The concentration of the acid solution in step (2) is concentrated to obtain industrial hydrochloric acid with a concentration of 31.5%.

[0084] Using the device system and resource recovery method provided in this embodiment, it can be seen that: the total acid recovery rate is 90.2%, the water resource reuse rate is 96.5%, and the calcium fluoride recovery rate is 97.8%; Furthermore, the method provided in this embodiment further demonstrates the synergistic effect of each unit in the device system: the overall performance of the device system provided in this embodiment is far higher than the sum of the performance of each unit. The performance indicators of each unit operating individually differ significantly from those of the integrated system: the desalination rate of the nanofiltration membrane fluctuates by 3% to 5% when operating alone, while the desalination rate remains stable above 98% after synergy with other units in this system; the pH range of the adsorption unit when operating alone is 5 to 8, while its adsorption capacity still reaches 22 mg / g under low acidity conditions of pH=2 to 4 after synergy with this system; the electricity consumption per ton of water for the membrane distillation unit when operating alone is approximately 15 kWh, while after synergy with the front-end nanofiltration and adsorption units, due to the significant optimization of the influent water quality (heavy metal ions are retained, fluoride ions are removed), the membrane distillation operating life is extended by 2 times, and because it can be driven by low-grade waste heat from the plant, the operating cost per ton of water is reduced by approximately 30% compared to conventional membrane distillation.

[0085] Example 2 This embodiment provides a resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater, such as... Figure 1 As shown, the resource recovery system includes a pretreatment unit 1, an acid-resistant nanofiltration unit 2, an adsorption defluorination unit 3, and a membrane distillation concentration unit 4, which are connected in sequence. The acid-resistant nanofiltration unit 2 is equipped with a hydrofluoric acid-resistant nanofiltration membrane. The adsorption and defluorination unit 3 is internally provided with an adsorption material; the adsorption material is a zirconium-based metal-organic framework material. The membrane distillation concentration unit 4 is equipped with a hydrophobic microporous membrane.

[0086] The pretreatment unit 1 includes a dirt removal device 1-1 and an ultrafiltration device 1-2 connected together; the dirt removal device 1-1 is a grid interception device and a sedimentation tank connected in sequence; the ultrafiltration device 1-2 includes an ultrafiltration membrane module; the ultrafiltration membrane module is a polyvinylidene fluoride ultrafiltration membrane module.

[0087] The inlet of the acid-resistant nanofiltration unit 2 is connected to the product water outlet of the ultrafiltration device 1-2; the hydrofluoric acid-resistant nanofiltration membrane is a polytetrafluoroethylene modified composite nanofiltration membrane; the pore size of the hydrofluoric acid-resistant nanofiltration membrane is 1.5 nm; the recovery rate of the hydrofluoric acid-resistant nanofiltration membrane is 65%.

[0088] The inlet of the adsorption and defluorination unit 3 is connected to the permeate port of the acid-resistant nanofiltration unit 2; the adsorption and defluorination unit 3 is a three-column series adsorption device, including an online adsorption column, an offline regeneration column and a standby column that operate alternately; the adsorbent material is loaded in the online adsorption column; the particle size of the zirconium-based metal-organic framework material is 0.5~1mm and the filling height is 1.8m.

[0089] The inlet of the membrane distillation concentration unit 4 is connected to the product water outlet of the adsorption defluorination unit; the hydrophobic microporous membrane is made of polyvinylidene fluoride; the pore size of the hydrophobic microporous membrane is 0.25 μm; the membrane flux of the hydrophobic microporous membrane is 10 LMH; the condensate outlet of the membrane distillation concentration unit 4 is connected to the backwash water tank 8; the backwash water tank 8 has two outlets, one of which is connected to the inlet of the acid-resistant nanofiltration unit, and the other outlet is connected to the inlet of the ultrafiltration device.

[0090] The resource recovery treatment device also includes a deep desorption unit 5, an online fluoride ion detection device 6, and a PLC controller 7; the inlet of the deep desorption unit 5 is connected to the concentrate outlet of the membrane distillation concentration unit 4; the online fluoride ion detection device 6 is located at the permeate outlet of the acid-resistant nanofiltration unit 2 and the product water outlet of the adsorption defluorination unit 3; the PLC controller 7 is used to control the regeneration cycle and influent flow rate of the adsorption defluorination unit based on the fluoride ion concentration feedback.

[0091] This embodiment also provides a method for the resource-based treatment of photovoltaic fluoride-containing mixed acid wastewater using the above-mentioned resource-based treatment device system, the resource-based treatment method comprising the following steps: (1) The fluoride-containing mixed acid wastewater was subjected to pretreatment and nanofiltration separation treatment in sequence to obtain nanofiltration permeate with a pH value of 2.3; The pretreatment includes sequential impurity removal and ultrafiltration; the nanofiltration separation process has a separation pressure of 0.8 MPa and a separation temperature of 20°C. (2) The nanofiltration permeate is subjected to deep defluorination treatment and membrane distillation concentration treatment in sequence to obtain condensate and concentrated acid solution; The deep defluorination treatment also includes sequentially regenerating the adsorbent material after it has become saturated with alkaline solution and performing a precipitation reaction; the concentration of the NaOH solution used for alkaline regeneration is 2 wt%; the precipitant used for the precipitation reaction is calcium chloride; and calcium fluoride precipitate is obtained after the precipitation reaction. The hot-side temperature of the membrane distillation concentration process is 70°C, and the cold-side temperature is 20°C; the vacuum degree of the membrane distillation concentration process is -50 kPa. The conductivity of the condensate is 23 μS / cm; (3) The concentration of the acid solution in step (2) is concentrated to obtain industrial hydrochloric acid with a concentration of 32%.

[0092] Example 3 This embodiment provides a resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater, such as... Figure 1 As shown, the resource recovery system includes a pretreatment unit 1, an acid-resistant nanofiltration unit 2, an adsorption defluorination unit 3, and a membrane distillation concentration unit 4, which are connected in sequence. The acid-resistant nanofiltration unit 2 is equipped with a hydrofluoric acid-resistant nanofiltration membrane. The adsorption and defluorination unit 3 is internally provided with an adsorption material; the adsorption material includes lanthanum-zirconium bimetallic doped composite metal oxide or zirconium-based metal-organic framework material. The membrane distillation concentration unit 4 is equipped with a hydrophobic microporous membrane.

[0093] The pretreatment unit 1 includes a dirt removal device 1-1 and an ultrafiltration device 1-2 connected together; the dirt removal device 1-1 is a grid interception device and a sedimentation tank connected in sequence; the ultrafiltration device 1-2 includes an ultrafiltration membrane module; the ultrafiltration membrane module is a polyvinylidene fluoride ultrafiltration membrane module.

[0094] The inlet of the acid-resistant nanofiltration unit 2 is connected to the product water outlet of the ultrafiltration device 1-2; the hydrofluoric acid-resistant nanofiltration membrane is a low-temperature ion-modified polypiperazine amide composite membrane; the pore size of the hydrofluoric acid-resistant nanofiltration membrane is 2 nm; the recovery rate of the hydrofluoric acid-resistant nanofiltration membrane is 75%.

[0095] The inlet of the adsorption and defluorination unit 3 is connected to the permeate port of the acid-resistant nanofiltration unit 2; the adsorption and defluorination unit 3 is a three-column series adsorption device, including an online adsorption column, an offline regeneration column, and a standby column that operate alternately; the adsorbent material is loaded in the online adsorption column; the particle size of the lanthanum-zirconium bimetallic doped composite metal oxide is 0.5 mm, and the packing height is 1.6 m; the static saturated adsorption capacity of the lanthanum-zirconium bimetallic doped composite metal oxide is 25 mg / g.

[0096] The inlet of the membrane distillation concentration unit 4 is connected to the product water outlet of the adsorption defluorination unit; the hydrophobic microporous membrane is made of polyvinylidene fluoride; the pore size of the hydrophobic microporous membrane is 0.4 μm; the membrane flux of the hydrophobic microporous membrane is 12 LMH; the condensate outlet of the membrane distillation concentration unit 4 is connected to the backwash water tank 8; the backwash water tank 8 has two outlets, one of which is connected to the inlet of the acid-resistant nanofiltration unit, and the other outlet is connected to the inlet of the ultrafiltration device.

[0097] The resource recovery treatment device also includes a deep desorption unit 5, an online fluoride ion detection device 6, and a PLC controller 7; the inlet of the deep desorption unit 5 is connected to the concentrate outlet of the membrane distillation concentration unit 4; the online fluoride ion detection device 6 is located at the permeate outlet of the acid-resistant nanofiltration unit 2 and the product water outlet of the adsorption defluorination unit 3; the PLC controller 7 is used to control the regeneration cycle and influent flow rate of the adsorption defluorination unit based on the fluoride ion concentration feedback.

[0098] This embodiment also provides a method for the resource-based treatment of photovoltaic fluoride-containing mixed acid wastewater using the above-mentioned resource-based treatment device system, the resource-based treatment method comprising the following steps: (1) The fluoride-containing mixed acid wastewater was subjected to pretreatment and nanofiltration separation treatment in sequence to obtain nanofiltration permeate with a pH value of 2.3; The pretreatment includes sequential impurity removal and ultrafiltration; the nanofiltration separation process has a separation pressure of 1.2 MPa and a separation temperature of 30°C. (2) The nanofiltration permeate is subjected to deep defluorination treatment and membrane distillation concentration treatment in sequence to obtain condensate and concentrated acid solution; The deep defluorination treatment also includes sequentially regenerating the adsorbent material after adsorption saturation with alkaline solution and performing a precipitation reaction; the concentration of the NaOH solution used for alkaline regeneration is 5 wt%; the precipitant used for the precipitation reaction is calcium chloride; and calcium fluoride precipitate is obtained after the precipitation reaction. The hot-side temperature of the membrane distillation concentration process is 90°C, and the cold-side temperature is 30°C; the vacuum degree of the membrane distillation concentration process is -80 kPa. The conductivity of the condensate is 20 μS / cm; (3) The concentration of the acid solution in step (2) is concentrated to obtain industrial hydrochloric acid with a concentration of 36%.

[0099] Example 4 This embodiment provides a resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater. The only difference between this resource-based treatment device system and Embodiment 1 is that: In this embodiment, the pore size of the hydrophobic microporous membrane is adjusted to 0.55 μm; the conductivity of the condensate obtained in this embodiment is 32 μS / cm.

[0100] Example 5 This embodiment provides a resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater. The only difference between this resource-based treatment device system and Embodiment 1 is that: In this embodiment, the backwash water tank is omitted, meaning the condensate return process is omitted.

[0101] Comparative Example 1 This comparative example provides a resource recovery treatment system for photovoltaic fluoride-containing mixed acid wastewater. The only difference between this resource recovery treatment system and Example 1 is that: This comparative example uses a commercially available conventional polyamide nanofiltration membrane instead of the hydrofluoric acid resistant nanofiltration membrane.

[0102] Comparative Example 2 This comparative example provides a resource recovery treatment system for photovoltaic fluoride-containing mixed acid wastewater. The only difference between this resource recovery treatment system and Example 1 is that: This comparative example modifies the hydrofluoric acid resistant nanofiltration membrane to the acid resistant nanofiltration membrane provided in Example 1 of CN112717712A.

[0103] Comprehensive analysis of the hydrofluoric acid-resistant nanofiltration membranes provided in Example 1 and Comparative Example 1 shows that after 60 days of operation, the desalination rate of the nanofiltration membrane provided in Comparative Example 1 decreased to 65%, the desalination rate of the nanofiltration membrane provided in Comparative Example 2 decreased to 87%, and the desalination rate of the nanofiltration membrane provided in Example 1 remained at 96.5%. After 90 days of operation, the desalination rate of the nanofiltration membrane provided in Comparative Example 2 decreased to 79%, and the desalination rate of the nanofiltration membrane provided in Example 1 remained at 95.2%. This further demonstrates that the nanofiltration membrane provided by the present invention has significant durability advantages in HF-containing environments.

[0104] Comparative Example 3 This comparative example provides a resource recovery treatment system for photovoltaic fluoride-containing mixed acid wastewater. The only difference between this resource recovery treatment system and Example 1 is that: This comparative example omits the inclusion of the adsorption and defluorination unit.

[0105] Compared to Example 1, this comparative example omits the adsorption defluorination unit. The nanofiltration permeate is directly distilled through membrane distillation. After 30 days of operation, the hydrophobicity of the hydrophobic microporous membrane decreases by 40%, the membrane flux decreases by 35%, and white scale appears on the membrane surface. This demonstrates that the adsorption defluorination unit is crucial for protecting the membrane distillation equipment and proves the synergistic necessity between low-pH adsorption defluorination and membrane distillation concentration.

[0106] Comparative Example 4 This comparative example provides a resource recovery treatment system for photovoltaic fluoride-containing mixed acid wastewater. The only difference between this resource recovery treatment system and Example 1 is that: This comparative example adds a pH adjustment unit after the acid-resistant nanofiltration unit and omits the adsorption defluorination unit and membrane distillation concentration unit.

[0107] This comparative example utilizes a pH adjustment unit to neutralize nanofiltration permeate to pH ≈ 9 with lime, resulting in the precipitation of mixed sludge (hazardous waste). The supernatant is then discharged after two-stage RO treatment. Results indicate that acid resources are completely lost; the calcium fluoride sludge is unsellable as a product due to mixed heavy metals, with a sludge disposal cost of 280,000 yuan / month; the comprehensive cost per ton of water is 62 yuan / m³. 3 (This invention costs approximately 37 yuan / m) 3 The water resource recycling rate is only about 70%.

[0108] Performance testing: The mixed acids obtained by the resource recovery methods provided in the above embodiments and comparative examples were analyzed, and the results are shown in Table 1: Table 1 Note: "—" indicates that the comparative example could not achieve this recovery (Comparative example 3 omitted the adsorption and defluorination unit, and could not obtain calcium fluoride product; Comparative example 4 used the neutralization precipitation method, and the acid resources were completely lost).

[0109] In summary, this invention solves the irreconcilable systemic contradiction between "acid neutralization loss" and "fluorine recovery" by constructing a novel "neutralization-acid retention" technical system, thereby achieving efficient dual resource recovery of acid and fluorine from the source.

[0110] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A resource-based treatment device system for photovoltaic fluoride-containing mixed acid wastewater, characterized in that, The resource recovery processing device system includes a pretreatment unit, an acid-resistant nanofiltration unit, an adsorption defluorination unit, and a membrane distillation concentration unit connected in sequence. The acid-resistant nanofiltration unit is equipped with a hydrofluoric acid-resistant nanofiltration membrane. The adsorption and defluorination unit is internally equipped with an adsorption material; the adsorption material includes lanthanum-zirconium bimetallic doped composite metal oxide or zirconium-based metal-organic framework material. The membrane distillation concentration unit is equipped with a hydrophobic microporous membrane.

2. The resource recovery processing device system according to claim 1, characterized in that, The pretreatment unit includes a purification device and an ultrafiltration device connected together. Preferably, the impurity removal device includes a bar screen and / or a sedimentation tank; Preferably, the ultrafiltration device includes an ultrafiltration membrane module; Preferably, the ultrafiltration membrane module includes a polyvinylidene fluoride ultrafiltration membrane module.

3. The resource recovery processing device system according to claim 2, characterized in that, The inlet of the acid-resistant nanofiltration unit is connected to the product water outlet of the ultrafiltration device; Preferably, the hydrofluoric acid resistant nanofiltration membrane comprises a modified polypiperazine amide composite membrane or a polytetrafluoroethylene modified composite nanofiltration membrane; Preferably, the pore size of the hydrofluoric acid resistant nanofiltration membrane is 0.5~2nm; Preferably, the recovery rate of the hydrofluoric acid resistant nanofiltration membrane is 65-75%.

4. The resource recovery processing apparatus system according to any one of claims 1-3, characterized in that, The inlet of the adsorption and defluorination unit is connected to the permeate outlet of the acid-resistant nanofiltration unit. Preferably, the adsorption and defluorination unit is a three-column series adsorption device, including an online adsorption column, an offline regeneration column, and a standby column that operate alternately; Preferably, the adsorbent material is loaded inside the online adsorption column; Preferably, the particle size of the lanthanum-zirconium bimetallic doped composite metal oxide is 0.5~1 mm; Preferably, the static saturated adsorption capacity of the lanthanum-zirconium bimetallic doped composite metal oxide is 20~25 mg / g; Preferably, the particle size of the zirconium-based metal-organic framework material is 0.5~2 mm.

5. The resource recovery processing apparatus system according to any one of claims 1-4, characterized in that, The inlet of the membrane distillation concentration unit is connected to the product water outlet of the adsorption defluorination unit. Preferably, the hydrophobic microporous membrane is made of polytetrafluoroethylene or polyvinylidene fluoride. Preferably, the pore size of the hydrophobic microporous membrane is 0.1~0.45μm; Preferably, the membrane flux of the hydrophobic microporous membrane is 10~12 LMH; Preferably, the condensate outlet of the membrane distillation concentration unit is connected to the backwash water tank; Preferably, the backwash tank has two outlets, one of which is connected to the inlet of the acid-resistant nanofiltration unit, and the other outlet is connected to the inlet of the ultrafiltration device.

6. The resource recovery processing apparatus system according to any one of claims 1-5, characterized in that, The resource recovery processing device also includes a deep desorption unit, an online fluoride ion detection device, and a PLC controller; Preferably, the inlet of the deep desorption unit is connected to the concentrate outlet of the membrane distillation concentration unit; Preferably, the online fluoride ion detection device is installed at the permeate port of the acid-resistant nanofiltration unit and the product water port of the adsorption defluorination unit; Preferably, the PLC controller is used to control the regeneration cycle and influent flow rate of the adsorption defluorination unit based on feedback of fluoride ion concentration.

7. A method for the resource-based treatment of photovoltaic fluoride-containing mixed acid wastewater, characterized in that, The resource recovery method is performed using the resource recovery apparatus system described in any one of claims 1-6.

8. The resource recovery method according to claim 7, characterized in that, The resource recovery method includes the following steps: (1) The fluoride-containing mixed acid wastewater is pretreated and then separated by nanofiltration to obtain a nanofiltration permeate with a pH value of 2 to 4. (2) The nanofiltration permeate is subjected to deep defluorination treatment and membrane distillation concentration treatment in sequence to obtain condensate and concentrated acid solution.

9. The resource recovery method according to claim 8, characterized in that, The pretreatment includes sequential impurity removal and ultrafiltration. Preferably, the separation pressure of the nanofiltration separation process is 0.8~1.2 MPa; Preferably, the separation temperature of the nanofiltration separation process is 20~30℃; Preferably, the residence time for the deep defluorination treatment is 30-40 minutes; Preferably, the deep defluorination treatment further includes sequentially regenerating the adsorbent material with alkaline solution and performing a precipitation reaction after the adsorption saturation. Preferably, the concentration of the alkali solution used for alkali regeneration is 2-5 wt%; Preferably, the precipitant used in the precipitation reaction includes a calcium salt.

10. The resource recovery method according to claim 8 or 9, characterized in that, The hot-side temperature of the membrane distillation concentration process is 70~90℃. Preferably, the cold-side temperature of the membrane distillation concentration process is 20~30℃; Preferably, the vacuum degree of the membrane distillation concentration process is -50 to -80 kPa; Preferably, the conductivity of the condensate is <30 μS / cm; Preferably, the processing method further includes concentrating the concentrated acid solution to obtain industrial hydrochloric acid; Preferably, the concentration of the industrial hydrochloric acid is 31-36%.

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