Treatment methods for wastewater from ferric phosphate production

Abstract

This invention discloses a method for treating wastewater from ferric phosphate production, belonging to the technical field of wastewater treatment. The wastewater from ferric phosphate production includes wash water and reaction mother liquor generated during the iron / iron red process for producing ferric phosphate. The treatment method includes the following steps: (1) a phosphoric acid purification and recovery process, including: pre-treating the wash water sequentially, the pre-treatment including filtration, cooling, resin adsorption, and ultrafiltration to obtain ultrafiltrate; and recovering phosphoric acid from the ultrafiltrate to obtain recycled phosphoric acid and a first clear liquid; (2) a recycled product water preparation process, including: adjusting the pH of the first clear liquid with alkali to obtain raw water; and concentrating a first mixture including raw water and makeup water to obtain impurity concentrate and recycled product water; (3) a deep purification and discharge process, including: purifying a second mixture including impurity concentrate, reaction mother liquor, and resin regeneration liquid to obtain compliant product water.

Description

Technical Field

[0001] This invention relates to the technical field of wastewater treatment, and more specifically, to a method for treating wastewater from ferric phosphate production. Background Technology

[0002] Anhydrous ferric phosphate (FePO4) is an important chemical raw material, widely used as a cathode material in lithium-ion batteries. The iron process (Fe + H3PO4 → FePO4 + H2) and the iron oxide process (Fe2O3 + 2H3PO4 → 2FePO4 + 3H2O) are commonly used methods for producing battery-grade anhydrous ferric phosphate. The production process of the iron / iron oxide process mainly includes the following steps: synthesis, solid-liquid separation (usually using pressure filtration), washing, drying, and pulverization and packaging. In the above production process, the solid-liquid separation section generates reaction mother liquor, and the washing section generates wash water. The ferric phosphate production wastewater, composed of wash water and reaction mother liquor, contains abundant recyclable resources and water pollutants, and needs to be purified and the resources recovered before being discharged.

[0003] In existing technologies, there are three main methods for treating wastewater from ferric phosphate production. The first method is to directly mix the wash water and the mother liquor before treatment. The second method is to treat the wash water and the mother liquor separately. The third method is to pre-treat the wash water and the mother liquor separately to remove impurities, and then mix them for resource recovery. Among these, the second and third methods are usually carried out in parallel and employ largely the same processes.

[0004] First, taking the production of anhydrous ferric phosphate as an example, the volume of wash water is 40m³. 3 The concentrations of the reactants were: / h, TDS 15.68 g / L, phosphoric acid 15.32 g / L, silicon 22.3 mg / L, and fluoride ion 10 mg / L, while the volume of the mother liquor was only 0.5 m³. 3 The concentrations of phosphoric acid, silicon, and fluoride in the wash water and reaction mother liquor were 179.29 g / L, 159.47 g / L, 1113.5 mg / L, and 500 mg / L, respectively. A comparison reveals significant differences in the volume and concentrations of these parameters between the wash water and the mother liquor. The wash water has a larger volume and lower levels of silicon and fluoride, while the reaction mother liquor, although lower in volume and higher in phosphoric acid, also has higher levels of silicon and fluoride. Therefore, the three treatment methods described above are not conducive to efficient resource recovery and deep removal of pollutants, and cannot simultaneously achieve low cost, high efficiency, and zero emissions. Furthermore, both the wash water and the reaction mother liquor contain significant amounts of phosphoric acid. Traditional methods use calcium hydroxide for neutralization and precipitation, resulting in high alkali consumption and the generation of large amounts of solid waste.

[0005] Secondly, current wastewater treatment methods for ferric phosphate production typically involve evaporation and crystallization at the end of the process to obtain ammonium sulfate and ammonium phosphate. These resources cannot be directly reused by the company itself and are usually sold externally, increasing sales costs. Although Chinese invention patent application CN114873824A and Chinese utility model patent CN219991386U disclose technical solutions using phosphoric acid as a target resource for recovery, they still employ a treatment method that directly mixes the wash water and reaction mother liquor before processing. Furthermore, the final liquid after phosphoric acid recovery still contains a significant amount of impurities and cannot be directly reused or discharged. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method and system for treating wastewater from ferric phosphate production that can both recover phosphoric acid for reuse in the ferric phosphate synthesis process and achieve low cost, high efficiency and zero discharge.

[0007] To achieve the above objectives, the present invention first provides a method for treating wastewater from ferric phosphate production, the technical solution of which is as follows:

[0008] Treatment method for ferric phosphate production wastewater, which includes wash water and reaction mother liquor generated during the iron / iron red process for producing ferric phosphate, includes the following steps:

[0009] (1) The phosphoric acid purification and recovery process includes:

[0010] The wash water is pretreated sequentially, including filtration, cooling, resin adsorption, and ultrafiltration, to obtain ultrafiltrate.

[0011] Phosphoric acid is recovered from the ultrafiltrate to obtain reusable phosphoric acid and the first clear liquid.

[0012] (2) The process for preparing recycled wastewater includes:

[0013] The pH of the first supernatant was adjusted using an alkaline solution to obtain the raw water;

[0014] The first mixture, which includes raw water and makeup water, is concentrated to obtain impurity concentrate and reused product water.

[0015] (3) Deep purification and emission process, including:

[0016] After purifying the second mixture, which includes concentrated impurities, mother liquor, and resin regeneration liquid, qualified permeable water is obtained.

[0017] As a further improvement to the above-mentioned method for treating wastewater from ferric phosphate production:

[0018] The wash water has the following concentrations: TDS ≤ 16500 mg / L, phosphate concentration ≤ 16200 mg / L, sulfate concentration ≤ 150 mg / L, sodium ion concentration ≤ 15 mg / L, total iron ion concentration ≤ 30 mg / L, manganese ion concentration ≤ 30 mg / L, calcium ion concentration ≤ 3 mg / L, magnesium ion concentration ≤ 0.5 mg / L, copper ion concentration ≤ 1 mg / L, zinc ion concentration ≤ 0.5 mg / L, silicon element concentration ≤ 28 mg / L, and fluoride ion concentration ≤ 14 mg / L.

[0019] The ultrafiltrate has the following concentrations: TDS ≤ 16500 g / L, phosphate concentration ≤ 16200 mg / L, sulfate concentration ≤ 150 mg / L, sodium ion concentration ≤ 15 mg / L, total iron ion concentration ≤ 0.5 mg / L, manganese ion concentration ≤ 0.5 mg / L, calcium ion concentration ≤ 0.5 mg / L, magnesium ion concentration ≤ 0.5 mg / L, copper ion concentration ≤ 0.5 mg / L, zinc ion concentration ≤ 0.5 mg / L, silicon element concentration ≤ 28 mg / L, and fluoride ion concentration ≤ 14 mg / L.

[0020] The TDS of recycled phosphoric acid is ≤95000mg / L, phosphoric acid concentration is ≤94000mg / L, sulfate concentration is ≤610mg / L, sodium ion concentration is ≤60mg / L, total iron ion concentration is ≤3mg / L, manganese ion concentration is ≤3mg / L, calcium ion concentration is ≤3mg / L, magnesium ion concentration is ≤3mg / L, copper ion concentration is ≤3mg / L, zinc ion concentration is ≤2.5mg / L, silicon element concentration is ≤140mg / L, and fluoride ion concentration is ≤20mg / L.

[0021] As a further improvement to the above-mentioned method for treating ferric phosphate production wastewater, the process of recovering phosphoric acid from the ultrafiltrate is as follows:

[0022] The ultrafiltrate was concentrated by reverse osmosis to obtain a concentrated phosphoric acid solution with a mass fraction of 8-10% and a purity of ≥96% and the first product water.

[0023] The concentrated phosphoric acid solution is concentrated by reverse osmosis membrane to obtain reusable phosphoric acid with a mass fraction of 20-85% and a second permeate; wherein the first permeate and the second permeate constitute the first clear liquid.

[0024] As a further improvement to the above-mentioned method for treating wastewater from ferric phosphate production:

[0025] The resin adsorption treatment uses a strong acid-type cation exchange resin;

[0026] The resin used for resin adsorption treatment is regenerated by dilute sulfuric acid with a mass fraction of 8-10%, and the resulting resin regeneration solution with a sulfuric acid mass fraction of 6-7% is fed into the second mixture.

[0027] The regenerated resin is rinsed with pure water, and the resulting rinse water is recycled and mixed with the wash water for filtration.

[0028] As a further improvement to the above-mentioned method for treating wastewater from ferric phosphate production:

[0029] The replenishment water is obtained by sequentially treating tap water with sand filtration and activated carbon adsorption. The replenishment water has a TDS ≤ 250 mg / L, sulfate concentration ≤ 160 mg / L, sodium ion concentration ≤ 12 mg / L, calcium ion concentration ≤ 50 mg / L, magnesium ion concentration ≤ 9 mg / L, and silicon element concentration ≤ 9 mg / L.

[0030] The raw water has the following concentrations: TDS ≤ 1100 mg / L, phosphate concentration ≤ 860 mg / L, sulfate concentration ≤ 7 mg / L, sodium ion concentration ≤ 210 mg / L, total iron ion concentration ≤ 0.05 mg / L, manganese ion concentration ≤ 0.05 mg / L, calcium ion concentration ≤ 0.05 mg / L, magnesium ion concentration ≤ 0.05 mg / L, copper ion concentration ≤ 0.05 mg / L, zinc ion concentration ≤ 0.04 mg / L, silicon concentration ≤ 2.5 mg / L, and fluoride ion concentration ≤ 13 mg / L; the pH of the raw water is 6–7.

[0031] The concentrations of impurity concentrates are as follows: TDS ≤ 14200 mg / L, phosphoric acid concentration ≤ 9400 mg / L, sulfate concentration ≤ 1500 mg / L, sodium ion concentration ≤ 2400 mg / L, total iron ion concentration ≤ 0.5 mg / L, manganese ion concentration ≤ 0.5 mg / L, calcium ion concentration ≤ 400 mg / L, magnesium ion concentration ≤ 75 mg / L, copper ion concentration ≤ 0.5 mg / L, zinc ion concentration ≤ 0.4 mg / L, silicon element concentration ≤ 90 mg / L, and fluoride ion concentration ≤ 110 mg / L.

[0032] As a further improvement to the above-mentioned method for treating wastewater from ferric phosphate production, it also includes backwashing the sand filter tank used for sand filtration and the activated carbon tank used for activated carbon adsorption with a portion of the concentrated impurity liquid. The resulting backwash water is mixed with the concentrated impurity liquid, the reaction mother liquor, and the resin regeneration liquid to form a second mixture, which then enters the deep purification and discharge process.

[0033] As a further improvement to the above-mentioned method for treating ferric phosphate production wastewater, the process of concentrating the first mixture is as follows:

[0034] The first mixture is concentrated using a reverse osmosis membrane to obtain primary concentrate and primary permeate.

[0035] The primary concentrate is concentrated using a reverse osmosis membrane to obtain impurity concentrate and secondary permeate.

[0036] The primary and secondary permeate waters are concentrated using a reverse osmosis membrane to obtain secondary concentrate and reusable permeate water; wherein the secondary concentrate is refluxed into the first mixture.

[0037] As a further improvement to the above-mentioned method for treating wastewater from ferric phosphate production:

[0038] The resin regeneration solution has the following concentrations: TDS ≤ 100000 mg / L, sulfate concentration ≤ 95000 mg / L, total iron concentration ≤ 2450 mg / L, manganese concentration ≤ 2200 mg / L, calcium concentration ≤ 165 mg / L, magnesium concentration ≤ 30 mg / L, copper concentration ≤ 80 mg / L, and zinc concentration ≤ 21 mg / L.

[0039] The TDS of the mother liquor is ≤188000mg / L, phosphoric acid concentration is ≤168000mg / L, sulfate concentration is ≤15900mg / L, sodium ion concentration is ≤1450mg / L, total iron ion concentration is ≤30mg / L, manganese ion concentration is ≤30mg / L, calcium ion concentration is ≤2.8mg / L, magnesium ion concentration is ≤0.5mg / L, copper ion concentration is ≤1mg / L, zinc ion concentration is ≤0.5mg / L, silicon element concentration is ≤1150mg / L, and fluoride ion concentration is ≤520mg / L.

[0040] The second mixture has the following concentrations: TDS ≤ 54000 mg / L, phosphoric acid concentration ≤ 36000 mg / L, sulfate concentration ≤ 14500 mg / L, sodium ion concentration ≤ 2000 mg / L, total iron ion concentration ≤ 330 mg / L, manganese ion concentration ≤ 300 mg / L, calcium ion concentration ≤ 330 mg / L, magnesium ion concentration ≤ 60 mg / L, copper ion concentration ≤ 12 mg / L, zinc ion concentration ≤ 4 mg / L, silicon element concentration ≤ 220 mg / L, and fluoride ion concentration ≤ 150 mg / L.

[0041] As a further improvement to the above-mentioned method for treating ferric phosphate production wastewater, the deep purification and discharge process specifically includes:

[0042] A precipitant is added to the second mixture, followed by flocculation sedimentation and solid-liquid separation to obtain a second clear liquid;

[0043] The pH of the second supernatant was adjusted to 4-5 using acid to obtain the third supernatant.

[0044] As a further improvement to the above-mentioned method for treating wastewater from ferric phosphate production, the deep purification and discharge process further includes:

[0045] The third clear liquid was subjected to Fenton oxidation treatment, followed by flocculation sedimentation and solid-liquid separation treatment to obtain the fourth clear liquid;

[0046] The pH of the fourth clear liquid was adjusted to 6-9 using alkaline solution to obtain qualified permeable water.

[0047] To achieve the above objectives, the present invention further provides three treatment systems for ferric phosphate production wastewater, the technical solutions of which are as follows:

[0048] The first type of wastewater treatment system for ferric phosphate production includes:

[0049] The recycled phosphoric acid purification and recovery section is used to treat the wash water to obtain recycled phosphoric acid and the first clear liquid;

[0050] The recycled permeate preparation section is used to treat the first clear liquid to obtain impurity concentrate and recycled permeate;

[0051] The deep purification and discharge section is used to purify the concentrated impurities and reaction mother liquor to obtain qualified product water.

[0052] The recycled phosphoric acid purification and recovery section includes:

[0053] A filtration unit that filters the wash water and outputs filtrate.

[0054] A heat exchange unit that cools the filtrate and outputs coolant.

[0055] A resin adsorption unit, wherein the resin adsorption unit adsorbs the coolant and outputs the adsorbed liquid;

[0056] An ultrafiltration unit, which outputs ultrafiltrate after ultrafiltration treatment of the adsorbed liquid;

[0057] The phosphoric acid concentration unit concentrates the ultrafiltrate and outputs recycled phosphoric acid and the first clear liquid.

[0058] As a further improvement to the first type of wastewater treatment system for ferric phosphate production mentioned above: the filtration unit includes a precision filter and a first filter press. The precision filter filters the wash water to obtain filtrate and filter cake. The filtrate is stored in a filtrate storage tank. The filter cake is collected by backflushing and the resulting sludge is stored in a sludge storage tank. The first filter press filters the sludge and the resulting first filtrate is returned to the wash water storage tank.

[0059] As a further improvement to the first type of ferric phosphate production wastewater treatment system described above, the heat exchange unit includes a plate heat exchanger.

[0060] As a further improvement to the first type of ferric phosphate production wastewater treatment system mentioned above: the resin adsorption unit includes a resin adsorption tower, a resin regeneration mechanism, and a resin rinsing mechanism. The resin adsorption tower is equipped with a strong acid cation exchange resin. The resin regeneration mechanism uses dilute sulfuric acid to spray and regenerate the strong acid cation exchange resin to obtain the resin regeneration liquid. The resin rinsing mechanism uses pure water to rinse the strong acid cation exchange resin, and the resulting rinsing liquid is returned to the washing water storage tank.

[0061] As a further improvement to the first type of ferric phosphate production wastewater treatment system described above: the resin regeneration mechanism includes a graphite diluent, which treats pure water and concentrated sulfuric acid to obtain dilute sulfuric acid for spray regeneration; the resin rinsing mechanism includes a first pipe for inputting pure water into the graphite diluent and a second pipe for inputting pure water into the resin adsorption tower.

[0062] As a further improvement to the first type of ferric phosphate production wastewater treatment system mentioned above, the resin adsorption unit also includes an adsorption liquid storage tank, a concentrated sulfuric acid storage tank, a dilute sulfuric acid storage tank, a resin regeneration liquid storage tank, a rinsing liquid storage tank, and a pure water storage tank.

[0063] As a further improvement to the first type of ferric phosphate production wastewater treatment system mentioned above: the ultrafiltration unit includes an ultrafiltration device and an ultrafiltration solution storage tank, wherein the ultrafiltration device adopts an internal pressure hollow PES membrane.

[0064] As a further improvement to the first type of ferric phosphate production wastewater treatment system mentioned above: the ultrafiltration unit filters the adsorbed liquid and the resulting ultrafiltration concentrate is returned to the wash water storage tank.

[0065] As a further improvement to the first type of ferric phosphate production wastewater treatment system described above, the phosphoric acid concentration unit includes:

[0066] The first reverse osmosis unit concentrates the ultrafiltrate to obtain concentrated phosphoric acid solution and first product water.

[0067] The second reverse osmosis unit concentrates the phosphoric acid solution to obtain reusable phosphoric acid and second permeate; wherein the first permeate and the second permeate constitute the first clear solution.

[0068] As a further improvement to the first type of ferric phosphate production wastewater treatment system mentioned above, the phosphoric acid concentration unit also includes a concentrated phosphoric acid storage tank, a recycled phosphoric acid storage tank, and a first clear liquid storage tank.

[0069] The second type of wastewater treatment system for ferric phosphate production includes:

[0070] The recycled phosphoric acid purification and recovery section is used to treat the wash water to obtain recycled phosphoric acid and the first clear liquid;

[0071] The recycled permeate preparation section is used to treat the first clear liquid to obtain impurity concentrate and recycled permeate;

[0072] The deep purification and discharge section is used to purify the concentrated impurities and reaction mother liquor to obtain qualified product water.

[0073] The recycled wastewater preparation section includes:

[0074] pH adjustment unit, the pH adjustment unit adjusts the pH of the first clear liquid and then outputs raw water;

[0075] An impurity concentration unit, which concentrates a first mixture including raw water and makeup water and outputs concentrated impurity solution and reusable product water;

[0076] A water replenishment unit is used to input water into the impurity concentration unit.

[0077] As a further improvement to the second type of ferric phosphate production wastewater treatment system described above, the pH adjustment unit includes a pH adjustment tank and a first sodium hydroxide dosing device for adding sodium hydroxide to the pH adjustment tank.

[0078] As a further improvement to the second type of ferric phosphate production wastewater treatment system described above: the impurity concentration unit includes a first mixture storage tank and:

[0079] A primary reverse osmosis unit, wherein the primary reverse osmosis unit concentrates the first mixture to obtain primary concentrate and primary permeate;

[0080] A two-stage reverse osmosis system, wherein the two-stage reverse osmosis system concentrates the first-stage concentrate to obtain impurity concentrate and second-stage permeate;

[0081] The three-stage reverse osmosis equipment concentrates the primary and secondary permeate water to obtain secondary concentrate and reusable permeate water; wherein the secondary concentrate is returned to the first mixture storage tank.

[0082] As a further improvement to the second type of ferric phosphate production wastewater treatment system mentioned above, the impurity concentration unit also includes a primary concentrate storage tank, a secondary product water storage tank, an impurity concentrate storage tank, and a reuse product water storage tank. The primary and secondary product water are stored in the secondary product water storage tank.

[0083] As a further improvement to the second type of ferric phosphate production wastewater treatment system mentioned above, the water replenishment unit includes a tap water storage tank and a sand filter tank and an activated carbon tank for treating the tap water.

[0084] As a further improvement to the second type of ferric phosphate production wastewater treatment system mentioned above, the recycled water preparation section also includes a backwashing unit for rinsing the sand filter tank and activated carbon tank.

[0085] As a further improvement to the second type of ferric phosphate production wastewater treatment system mentioned above: the backwashing unit includes a third pipe connecting the impurity concentrate storage tank and the sand filter tank, a fourth pipe connecting the impurity concentrate storage tank and the activated carbon tank, and a backwash water storage tank for storing the backwash water formed during rinsing.

[0086] As a further improvement to the second type of ferric phosphate production wastewater treatment system mentioned above:

[0087] The recycled phosphoric acid purification and recovery section includes:

[0088] A filtration unit that filters the wash water and outputs filtrate.

[0089] A heat exchange unit that cools the filtrate and outputs coolant.

[0090] A resin adsorption unit, wherein the resin adsorption unit adsorbs the coolant and outputs the adsorbed liquid;

[0091] An ultrafiltration unit, which outputs ultrafiltrate after ultrafiltration treatment of the adsorbed liquid;

[0092] The phosphoric acid concentration unit concentrates the ultrafiltrate and outputs recycled phosphoric acid and the first clear liquid.

[0093] The deep purification and emission section includes a homogenization unit, which is used to mix the impurity concentrate, reaction mother liquor, resin regeneration liquid and backwash water into a second mixture.

[0094] The third type of wastewater treatment system for ferric phosphate production includes:

[0095] The recycled phosphoric acid purification and recovery section is used to treat the wash water to obtain recycled phosphoric acid and the first clear liquid;

[0096] The recycled permeate preparation section is used to treat the first clear liquid to obtain impurity concentrate and recycled permeate;

[0097] The deep purification and discharge section is used to purify the concentrated impurities and reaction mother liquor to obtain qualified product water.

[0098] The recycled phosphoric acid purification and recovery section includes:

[0099] A filtration unit that filters the wash water and outputs filtrate.

[0100] A heat exchange unit that cools the filtrate and outputs coolant.

[0101] A resin adsorption unit, wherein the resin adsorption unit adsorbs the coolant and outputs the adsorbed liquid;

[0102] An ultrafiltration unit, which outputs ultrafiltrate after ultrafiltration treatment of the adsorbed liquid;

[0103] A phosphoric acid concentration unit, which concentrates the ultrafiltration solution and outputs reusable phosphoric acid and a first solution;

[0104] The recycled wastewater preparation section includes:

[0105] pH adjustment unit, the pH adjustment unit adjusts the pH of the first clear liquid and then outputs raw water;

[0106] An impurity concentration unit, which concentrates a first mixture including raw water and makeup water and outputs concentrated impurity solution and reusable product water;

[0107] A water replenishment unit is used to input water into the impurity concentration unit;

[0108] The deep purification and emission control section includes:

[0109] A homogenization unit is used to mix the impurity concentrate, the reaction mother liquor, and the resin regeneration liquid to obtain a second mixture;

[0110] A softening unit is used to remove impurity ions from the second mixture and output a second clear liquid;

[0111] An organic matter degradation unit is used to remove organic matter from the second clear liquid and output qualified product water.

[0112] As a further improvement to the above-mentioned third type of ferric phosphate production wastewater treatment system: the resin adsorption unit includes a resin adsorption tower, a resin regeneration mechanism, and a resin rinsing mechanism. The resin adsorption tower is equipped with a strong acid cation exchange resin. The resin regeneration mechanism uses dilute sulfuric acid to spray and regenerate the strong acid cation exchange resin to obtain the resin regeneration liquid. The resin rinsing mechanism uses pure water to rinse the strong acid cation exchange resin, and the resulting rinsing liquid is returned to the washing water storage tank.

[0113] As a further improvement to the aforementioned third type of ferric phosphate production wastewater treatment system, the phosphoric acid concentration unit includes:

[0114] The first reverse osmosis unit concentrates the ultrafiltrate to obtain concentrated phosphoric acid solution and first product water.

[0115] The second reverse osmosis unit concentrates the phosphoric acid solution to obtain reusable phosphoric acid and second permeate; wherein the first permeate and the second permeate constitute the first clear solution.

[0116] As a further improvement to the aforementioned third type of ferric phosphate production wastewater treatment system: the impurity concentration unit includes a first mixture storage tank and:

[0117] A primary reverse osmosis unit, wherein the primary reverse osmosis unit concentrates the first mixture to obtain primary concentrate and primary permeate;

[0118] A two-stage reverse osmosis system, wherein the two-stage reverse osmosis system concentrates the first-stage concentrate to obtain impurity concentrate and second-stage permeate;

[0119] The three-stage reverse osmosis equipment concentrates the primary and secondary permeate water to obtain secondary concentrate and reusable permeate water; wherein the secondary concentrate is returned to the first mixture storage tank.

[0120] As a further improvement to the treatment system for the third type of ferric phosphate production wastewater mentioned above: the water replenishment unit includes a tap water storage tank and a sand filter tank and an activated carbon tank for treating the tap water;

[0121] The recycled water preparation section also includes a backwashing unit for rinsing the sand filter tank and the activated carbon tank; the backwashing unit includes a third pipe connecting the impurity concentrate storage tank and the sand filter tank, a fourth pipe connecting the impurity concentrate storage tank and the activated carbon tank, and a backwash water storage tank for storing the backwash water generated during rinsing.

[0122] As a further improvement to the third type of ferric phosphate production wastewater treatment system mentioned above: the homogenization unit includes a homogenization tank in which impurity concentrate, reaction mother liquor, resin regeneration liquid and backwash water are mixed to form a second mixture.

[0123] As a further improvement to the third type of ferric phosphate production wastewater treatment system mentioned above, the softening unit includes a chemical reaction tank, a flocculation tank, a sludge tank, a second filter press, a precipitant dosing device for adding precipitant to the chemical reaction tank, and a first flocculant dosing device for adding flocculant to the flocculation tank, which are connected in sequence.

[0124] As a further improvement to the above-mentioned third type of ferric phosphate production wastewater treatment system: the precipitant dosing device includes a second sodium hydroxide dosing device and a calcium hydroxide dosing device, wherein the calcium hydroxide dosing device includes a silo for storing quicklime or hydrated lime and a slurry preparation tank for preparing calcium hydroxide slurry.

[0125] As a further improvement to the third type of ferric phosphate production wastewater treatment system mentioned above, the organic matter degradation unit includes a pH adjustment tank, a Fenton reaction tank, a sedimentation tank, a pH adjustment tank connected in sequence, an acid dosing device for adding acid to the pH adjustment tank, a ferrous sulfate dosing device for adding ferrous sulfate to the Fenton reaction tank, a hydrogen peroxide dosing device for adding hydrogen peroxide to the Fenton reaction tank, a second flocculant dosing device for adding flocculant to the sedimentation tank, and a third sodium hydroxide dosing device for adding sodium hydroxide to the pH adjustment tank.

[0126] As a further improvement to the third type of ferric phosphate production wastewater treatment system mentioned above: the sedimentation tank is an inclined plate sedimentation tank, and the sludge deposited in the inclined plate sedimentation tank flows into the second filter press.

[0127] The method and system for treating ferric phosphate production wastewater of the present invention have the following advantages:

[0128] (1) This invention fully considers the differences in water quality parameters between the wash water and the reaction mother liquor. It first takes the wash water with large volume and few impurities as the target, first recovers the phosphoric acid and product water in the wash water, and then mixes the residual liquid (i.e. the concentrated impurity liquid) with the reaction mother liquor for deep purification, which significantly improves the treatment efficiency and reduces the treatment cost.

[0129] (2) The target resource recovery materials of the present invention are phosphoric acid and product water, which can be directly reused in the iron phosphate synthesis section without external sales, thus saving raw material costs and sales costs.

[0130] (3) The process and structure of the present invention are simple, the equipment investment cost is low, the energy consumption is low, and the wastewater can be reused and discharged in compliance with standards. It takes into account low cost, high efficiency and zero discharge, and has strong practicality.

[0131] The embodiments of the invention provided in this specification will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the embodiments of the invention provided in this specification will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the invention provided in this specification. Attached Figure Description

[0132] The accompanying drawings, which form part of the embodiments of the invention provided in this specification, are used to aid in understanding the embodiments of the invention provided in this specification. The content provided in the drawings and the related descriptions in the embodiments of the invention provided in this specification can be used to explain the embodiments of the invention provided in this specification, but do not constitute an improper limitation on the embodiments of the invention provided in this specification.

[0133] Figure 1 This is a schematic diagram illustrating a specific embodiment of the wastewater treatment system for ferric phosphate production according to the present invention.

[0134] Figure 2 This is a water quality change diagram of each treatment unit in the phosphoric acid purification and recovery process in a specific embodiment of the method for treating wastewater from ferric phosphate production of the present invention.

[0135] Figure 3 This is a water quality change diagram of each treatment unit in the wastewater preparation process of the ferric phosphate production method of the present invention.

[0136] Figure 4 This is a water quality change diagram of each treatment unit in the deep purification and discharge process of the wastewater treatment method for ferric phosphate production of the present invention.

[0137] The relevant markings in the above figures are:

[0138] 100-Wash water storage tank, 111-Precision filter, 112-First filter press, 113-Filtrate storage tank, 114-Sludge storage tank, 120-Plate heat exchanger, 131-Resin adsorption tower, 132-Graphite diluent, 1331-First pipeline, 1332-Second pipeline, 134-Post-adsorption liquid storage tank, 135-Dilute sulfuric acid storage tank, 136-Resin regeneration liquid storage tank, 137-Leachate storage tank, 138-Pure water storage tank, 141-Ultrafiltration equipment, 142-Ultrafiltration clarified liquid storage tank, 151-First reverse osmosis equipment, 152-Second reverse osmosis equipment, 153-Concentrated phosphoric acid solution storage tank, 154-Recycled phosphoric acid storage tank, 155-First clarified liquid storage tank, 210-pH adjustment tank, 221-The... 1. Mixture storage tank; 222. Primary reverse osmosis equipment; 223. Secondary reverse osmosis equipment; 224. Tertiary reverse osmosis equipment; 225. Primary concentrate storage tank; 226. Two-stage product water storage tank; 227. Impurity concentrate storage tank; 228. Reclaimed product water storage tank; 231. Sand filter tank; 232. Activated carbon tank; 233. Backwash water storage tank; 234. Third pipeline; 235. Fourth pipeline; 310. Reaction mother liquor storage tank; 320. Homogenizing tank; 331. Chemical reaction tank; 332. Flocculation tank; 333. Sludge tank; 334. Second filter press; 335. Silo; 336. Pulping tank; 341. pH adjustment tank; 342. Fenton reaction tank; 343. Inclined plate sedimentation tank; 344. pH adjustment tank. Detailed Implementation

[0139] The embodiments of the invention provided in this specification will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. Before describing the embodiments of the invention provided in this specification in conjunction with the accompanying drawings, it should be particularly noted that:

[0140] The technical solutions and features provided in the embodiments of the invention provided in this specification, including the following description, can be combined with each other without conflict.

[0141] Furthermore, the embodiments of the inventions provided in this specification mentioned below are generally only a portion of the embodiments of the inventions provided in this specification, and not all of them. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the inventions provided in this specification without creative effort should fall within the scope of protection of the embodiments of the inventions provided in this specification.

[0142] Regarding the terminology and units in the embodiments of the invention provided in this specification: The terms "comprising," "including," "having," and any variations thereof in the description, claims, and related parts of the embodiments of the invention provided in this specification are intended to cover non-exclusive inclusion. Furthermore, other relevant terms and units in the embodiments of the invention provided in this specification can be reasonably interpreted based on the relevant content of the embodiments of the invention provided in this specification.

[0143] The specific implementation of the method for treating ferric phosphate production wastewater of the present invention includes the following steps:

[0144] (1) The phosphoric acid purification and recovery process includes: pre-treating the wash water sequentially, wherein the pre-treatment includes filtration, cooling, resin adsorption and ultrafiltration to obtain ultrafiltrate; and performing phosphoric acid recovery treatment on the ultrafiltrate to obtain recycled phosphoric acid and a first clear liquid; as follows:

[0145] Step 110: Filter the wash water to remove larger particles and suspended solids, and obtain a filtrate with SS ≤ 2 mg / L;

[0146] Step 120: Cool the filtrate to adapt to the processing effect of subsequent processes, and obtain a coolant with a temperature of ≤35℃ after cooling.

[0147] Step 130: The coolant is subjected to resin adsorption treatment to remove metals such as iron, manganese, and copper, resulting in an adsorbed liquid.

[0148] Step 140: The adsorbed liquid is subjected to ultrafiltration to remove larger particles and suspended solids, resulting in ultrafiltrate. The resin adsorption treatment uses a strong acid cation exchange resin. The resin used for the adsorption treatment is regenerated with dilute sulfuric acid with a mass fraction of 8-10%, and the resulting regenerated resin solution with a sulfuric acid mass fraction of 6-7% is fed into the second mixture. The regenerated resin is rinsed with pure water, and the rinse water is recycled and mixed with the wash water for filtration.

[0149] Step 150: The ultrafiltrate is concentrated by reverse osmosis membrane treatment to obtain a concentrated phosphoric acid solution with a mass fraction of 8-10% and a purity of ≥96% and the first product water;

[0150] Step 160: The concentrated phosphoric acid solution is concentrated by reverse osmosis membrane to obtain recycled phosphoric acid with a mass fraction of 20-85% and a second permeate; wherein the first permeate and the second permeate constitute the first clear liquid.

[0151] The wash water has the following characteristics: TDS ≤ 16500 mg / L, phosphate concentration ≤ 16200 mg / L, sulfate concentration ≤ 150 mg / L, sodium ion concentration ≤ 15 mg / L, total iron ion concentration ≤ 30 mg / L, manganese ion concentration ≤ 30 mg / L, calcium ion concentration ≤ 3 mg / L, magnesium ion concentration ≤ 0.5 mg / L, copper ion concentration ≤ 1 mg / L, zinc ion concentration ≤ 0.5 mg / L, silicon element concentration ≤ 28 mg / L, and fluoride ion concentration ≤ 14 mg / L; the wash water temperature is 60℃, and SS ≤ 50 mg / L.

[0152] The ultrafiltrate has the following concentrations: TDS ≤ 16500 g / L, phosphate concentration ≤ 16200 mg / L, sulfate concentration ≤ 150 mg / L, sodium ion concentration ≤ 15 mg / L, total iron ion concentration ≤ 0.5 mg / L, manganese ion concentration ≤ 0.5 mg / L, calcium ion concentration ≤ 0.5 mg / L, magnesium ion concentration ≤ 0.5 mg / L, copper ion concentration ≤ 0.5 mg / L, zinc ion concentration ≤ 0.5 mg / L, silicon element concentration ≤ 28 mg / L, and fluoride ion concentration ≤ 14 mg / L.

[0153] The TDS of recycled phosphoric acid is ≤95000mg / L, phosphoric acid concentration is ≤94000mg / L, sulfate concentration is ≤610mg / L, sodium ion concentration is ≤60mg / L, total iron ion concentration is ≤3mg / L, manganese ion concentration is ≤3mg / L, calcium ion concentration is ≤3mg / L, magnesium ion concentration is ≤3mg / L, copper ion concentration is ≤3mg / L, zinc ion concentration is ≤2.5mg / L, silicon element concentration is ≤140mg / L, and fluoride ion concentration is ≤20mg / L.

[0154] (2) The process for preparing recycled permeate includes: adjusting the pH of the first clarified liquid with alkali solution to obtain raw water; concentrating the first mixture including raw water and makeup water to obtain concentrated impurity solution and recycled permeate; specifically as follows:

[0155] Step 210: The pH of the first supernatant is adjusted using a 32% sodium hydroxide solution to obtain raw water with a pH of 6-7;

[0156] Step 220: The first mixture is concentrated by reverse osmosis membrane treatment to obtain primary concentrate and primary permeate.

[0157] Step 230: The primary concentrate is concentrated by reverse osmosis membrane to obtain impurity concentrate and secondary permeate.

[0158] Step 240: The primary and secondary permeate waters are concentrated using a reverse osmosis membrane to obtain secondary concentrate and reusable permeate water; wherein the secondary concentrate is recycled back to the first mixture.

[0159] Step 250: Use a portion of the concentrated impurity solution to backwash the sand filter tank used for sand filtration and the activated carbon tank used for activated carbon adsorption to obtain backwash water.

[0160] The replenishment water is obtained by sequentially treating tap water with sand filtration and activated carbon adsorption. The replenishment water has a TDS ≤ 250 mg / L, sulfate concentration ≤ 160 mg / L, sodium ion concentration ≤ 12 mg / L, calcium ion concentration ≤ 50 mg / L, magnesium ion concentration ≤ 9 mg / L, and silicon element concentration ≤ 9 mg / L.

[0161] The raw water has the following concentrations: TDS ≤ 1100 mg / L, phosphoric acid concentration ≤ 860 mg / L, sulfate concentration ≤ 7 mg / L, sodium ion concentration ≤ 210 mg / L, total iron ion concentration ≤ 0.05 mg / L, manganese ion concentration ≤ 0.05 mg / L, calcium ion concentration ≤ 0.05 mg / L, magnesium ion concentration ≤ 0.05 mg / L, copper ion concentration ≤ 0.05 mg / L, zinc ion concentration ≤ 0.04 mg / L, silicon element concentration ≤ 2.5 mg / L, and fluoride ion concentration ≤ 13 mg / L.

[0162] The concentrations of impurity concentrates are as follows: TDS ≤ 14200 mg / L, phosphoric acid concentration ≤ 9400 mg / L, sulfate concentration ≤ 1500 mg / L, sodium ion concentration ≤ 2400 mg / L, total iron ion concentration ≤ 0.5 mg / L, manganese ion concentration ≤ 0.5 mg / L, calcium ion concentration ≤ 400 mg / L, magnesium ion concentration ≤ 75 mg / L, copper ion concentration ≤ 0.5 mg / L, zinc ion concentration ≤ 0.4 mg / L, silicon element concentration ≤ 90 mg / L, and fluoride ion concentration ≤ 110 mg / L.

[0163] (3) Deep purification and discharge process, including: purifying the second mixture, which includes concentrated impurities, reaction mother liquor, and resin regeneration liquid, to obtain qualified permeable water; specifically as follows:

[0164] Step 310: Add a 32% sodium hydroxide solution and a 15% calcium hydroxide solution (precipitant) to the second mixture, and then perform flocculation sedimentation and solid-liquid separation treatment to obtain the second clear liquid;

[0165] Step 320: Adjust the pH of the second supernatant to 4-5 using 30% sulfuric acid to obtain the third supernatant;

[0166] Step 330: The third clear liquid is subjected to Fenton oxidation treatment using a 30% ferrous sulfate solution and a 30% hydrogen peroxide solution, followed by flocculation sedimentation and solid-liquid separation treatment to obtain the fourth clear liquid.

[0167] Step 340: Adjust the pH of the fourth clear liquid to 6-9 using alkaline solution to obtain qualified permeable water.

[0168] The resin regeneration solution has the following characteristics: TDS ≤ 100000 mg / L, sulfate concentration ≤ 95000 mg / L, total iron ion concentration ≤ 2450 mg / L, manganese ion concentration ≤ 2200 mg / L, calcium ion concentration ≤ 165 mg / L, magnesium ion concentration ≤ 30 mg / L, copper ion concentration ≤ 80 mg / L, and zinc ion concentration ≤ 21 mg / L.

[0169] The TDS of the mother liquor is ≤188000 mg / L, phosphoric acid concentration is ≤168000 mg / L, sulfate concentration is ≤15900 mg / L, sodium ion concentration is ≤1450 mg / L, total iron ion concentration is ≤30 mg / L, manganese ion concentration is ≤30 mg / L, calcium ion concentration is ≤2.8 mg / L, magnesium ion concentration is ≤0.5 mg / L, copper ion concentration is ≤1 mg / L, zinc ion concentration is ≤0.5 mg / L, silicon element concentration is ≤1150 mg / L, and fluoride ion concentration is ≤520 mg / L.

[0170] The second mixture has the following concentrations: TDS ≤ 54000 mg / L, phosphoric acid concentration ≤ 36000 mg / L, sulfate concentration ≤ 14500 mg / L, sodium ion concentration ≤ 2000 mg / L, total iron ion concentration ≤ 330 mg / L, manganese ion concentration ≤ 300 mg / L, calcium ion concentration ≤ 330 mg / L, magnesium ion concentration ≤ 60 mg / L, copper ion concentration ≤ 12 mg / L, zinc ion concentration ≤ 4 mg / L, silicon element concentration ≤ 220 mg / L, and fluoride ion concentration ≤ 150 mg / L.

[0171] The flocculants used for flocculation sedimentation are PAM and / or PAC. Total iron ions refer to Fe...3+ and Fe 2+ .

[0172] Among them, the third clear liquid has reached the Class III discharge standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996). No pollutants were detected in the resulting compliant produced water, achieving zero discharge. It can also be directly discharged or reused in the sections of the system that require water.

[0173] To achieve the above-mentioned method for treating wastewater from ferric phosphate production, the specific implementation of the wastewater treatment system for ferric phosphate production adopted in this invention is as follows.

[0174] Figure 1 This is a schematic diagram illustrating a specific embodiment of the wastewater treatment system for ferric phosphate production according to the present invention.

[0175] like Figure 1 As shown, the wastewater treatment system for iron phosphate production includes a phosphoric acid purification and recovery section, a recycled product water preparation section, and a deep purification and discharge section.

[0176] The recycled phosphoric acid purification and recovery section is used to treat the wash water to obtain recycled phosphoric acid and a first clear liquid. The recycled phosphoric acid purification and recovery section includes a filtration unit, a heat exchange unit, a resin adsorption unit, an ultrafiltration unit, and a phosphoric acid concentration unit.

[0177] The filtration unit filters the wash water and outputs filtrate. The filtration unit includes a precision filter 111 and a first filter press 112. The precision filter 111 filters the wash water to obtain filtrate and filter cake. The filtrate is stored in a filtrate storage tank 113, and the filter cake is collected by backflushing to form a sludge liquid, which is stored in a sludge liquid storage tank 114. The first filter press 112 filters the sludge liquid to obtain a first filtrate, which is then returned to the wash water storage tank 100.

[0178] The heat exchange unit cools the filtrate and outputs coolant. The heat exchange unit includes a plate heat exchanger 120.

[0179] The resin adsorption unit adsorbs the coolant and outputs the adsorbed liquid. The resin adsorption unit includes a resin adsorption tower 131, a resin regeneration mechanism, and a resin rinsing mechanism. The resin adsorption tower 131 contains a strong acid-type cation exchange resin. The resin regeneration mechanism regenerates the strong acid-type cation exchange resin by spraying it with dilute sulfuric acid to obtain the regenerated resin liquid. The resin regeneration mechanism includes a graphite diluent 132, which treats pure water and concentrated sulfuric acid to obtain dilute sulfuric acid for spray regeneration. The resin rinsing mechanism rinses the strong acid-type cation exchange resin with pure water, and the resulting rinsing liquid is returned to the wash water storage tank 100. The resin rinsing mechanism includes a first pipe 1331 for inputting pure water into the graphite diluent 132 and a second pipe 1332 for inputting pure water into the resin adsorption tower 131. The resin adsorption unit also includes an adsorbed liquid storage tank 134, a concentrated sulfuric acid storage tank, a dilute sulfuric acid storage tank 135, a regenerated resin liquid storage tank 136, a rinsing liquid storage tank 137, and a pure water storage tank 138.

[0180] The ultrafiltration unit outputs ultrafiltrate after ultrafiltration of the adsorbed liquid. The ultrafiltration unit includes an ultrafiltration device 141 and an ultrafiltrate storage tank 142. The ultrafiltration device 141 uses an internally pressurized hollow PES membrane. The ultrafiltrate concentrate obtained after filtration of the adsorbed liquid is returned to the wash water storage tank 100.

[0181] The phosphoric acid concentration unit concentrates the ultrafiltrate and outputs recycled phosphoric acid and a first clarified liquid. The phosphoric acid concentration unit includes a first reverse osmosis unit 151 and a second reverse osmosis unit 152. The first reverse osmosis unit 151 concentrates the ultrafiltrate to obtain concentrated phosphoric acid and a first permeate; the second reverse osmosis unit 152 concentrates the concentrated phosphoric acid to obtain recycled phosphoric acid and a second permeate; wherein the first permeate and the second permeate constitute the first clarified liquid. The phosphoric acid concentration unit also includes a concentrated phosphoric acid storage tank 153, a recycled phosphoric acid storage tank 154, and a first clarified liquid storage tank 155.

[0182] The recycled permeate preparation section is used to treat the first clarified liquid to obtain a concentrated impurity solution and recycled permeate. The recycled permeate preparation section includes a pH adjustment unit, an impurity concentration unit, a water replenishment unit, and a backwashing unit.

[0183] The pH adjustment unit adjusts the pH of the first clarified liquid and then outputs raw water. The pH adjustment unit includes a pH adjustment tank 210 and a first sodium hydroxide dosing device for adding sodium hydroxide to the pH adjustment tank 210.

[0184] The impurity concentration unit concentrates a first mixture including raw water and makeup water, outputting concentrated impurity solution and recycled permeate. The impurity concentration unit includes a first mixture storage tank 221, a first-stage reverse osmosis unit 222, a second-stage reverse osmosis unit 223, and a third-stage reverse osmosis unit 224. The first-stage reverse osmosis unit 222 concentrates the first mixture to obtain first-stage concentrate and first-stage permeate; the second-stage reverse osmosis unit 223 concentrates the first-stage concentrate to obtain concentrated impurity solution and second-stage permeate; the third-stage reverse osmosis unit 224 concentrates the first-stage permeate and second-stage permeate to obtain second-stage concentrate and recycled permeate; wherein the second-stage concentrate is returned to the first mixture storage tank 221. The impurity concentration unit also includes a first-stage concentrate storage tank 225, a two-stage permeate storage tank 226, a concentrated impurity solution storage tank 227, and a recycled permeate storage tank 228. The first-stage and second-stage permeate are stored in the two-stage permeate storage tank 226.

[0185] The water replenishment unit is used to supply water to the impurity concentration unit. The water replenishment unit includes a tap water storage tank, a sand filter tank 231 and an activated carbon tank 232 for treating tap water.

[0186] The backwashing unit is used to rinse the sand filter tank 231 and the activated carbon tank 232. The backwashing unit includes a third pipe 234 connecting the impurity concentrate storage tank 227 and the sand filter tank 231, a fourth pipe 235 connecting the impurity concentrate storage tank 227 and the activated carbon tank 232, and a backwash water storage tank 233100 for storing the backwash water generated during rinsing.

[0187] The deep purification and discharge section is used to purify a second mixture, including concentrated impurities, mother liquor (from mother liquor storage tank 310), resin regeneration liquid, and backwash water, to obtain compliant permeable water. The deep purification and discharge section includes a homogenization unit, a softening unit, and an organic matter degradation unit.

[0188] The homogenization unit is used to mix the impurity concentrate, the reaction mother liquor, and the resin regeneration liquid to obtain a second mixture. The homogenization unit includes a homogenization tank 320, in which the impurity concentrate, the reaction mother liquor, the resin regeneration liquid, and the backwash water are mixed to form the second mixture.

[0189] The softening unit is used to remove impurity ions from the second mixture and output a second clear liquid. The softening unit includes, in sequence, a chemical reaction tank 331, a flocculation tank 332, a sludge tank 333, a second filter press 334, a precipitant dosing device for adding precipitant to the chemical reaction tank 331, and a first flocculant dosing device for adding flocculant to the flocculation tank 332. The precipitant dosing device includes a second sodium hydroxide dosing device and a calcium hydroxide dosing device. The calcium hydroxide dosing device includes a silo 335 for storing quicklime or hydrated lime and a slurry preparation tank 336 for preparing calcium hydroxide slurry.

[0190] The organic matter degradation unit is used to remove organic matter from the second clarified liquid and output qualified permeable water. The organic matter degradation unit includes, in sequence, a pH adjustment tank 341, a Fenton reaction tank 342, a sedimentation tank, a pH adjustment tank 344, and an acid dosing device for adding acid to the pH adjustment tank 341, a ferrous sulfate dosing device for adding ferrous sulfate to the Fenton reaction tank 342, a hydrogen peroxide dosing device for adding hydrogen peroxide to the Fenton reaction tank 342, a second flocculant dosing device for adding flocculant to the sedimentation tank, and a third sodium hydroxide dosing device for adding sodium hydroxide to the pH adjustment tank 344. The sedimentation tank is an inclined plate sedimentation tank 343, and the sludge deposited in the inclined plate sedimentation tank 343 flows into a second filter press 334.

[0191] The following specific application examples illustrate the beneficial effects of the present invention.

[0192] First, in the phosphoric acid purification and recovery process, the following is adopted: Figure 1 The recycled phosphoric acid purification and recovery section treats the wash water. Through the coordinated operation of filtration, heat exchange, resin adsorption, ultrafiltration, and phosphoric acid concentration units, the phosphoric acid resources in the wash water are effectively enriched in the recycled phosphoric acid. The water quality changes in each treatment unit during this process are shown in [see details]. Figure 2 .

[0193] Then, for the first clear liquid composed of the first and second product waters, the following method is adopted: Figure 1 The treated wastewater is processed in the reuse permeate preparation section, resulting in a large volume of reuse permeate with TDS levels as low as 0.8 mg / L and sulfate levels as low as 0.55 mg / L. This wastewater can be reused in the ferric phosphate synthesis process or other processes. Water quality changes in each treatment unit within this process are shown in [link to relevant documentation]. Figure 3 .

[0194] Finally, for the second mixture consisting of all by-product wastewater generated in the phosphoric acid purification and recovery process and the recycled permeate preparation process, as well as the reaction mother liquor, a method was adopted... Figure 1 The wastewater is treated in a deep purification emission section, where the amount of sodium hydroxide solution used in chemical reaction tank 331 is 0.081 m³. 3 / h, the amount of calcium hydroxide solution used is 0.432m 3 The amount of sulfuric acid used in pH adjustment tank 341 is 0.1 m³ / h. 3 / h, the amount of ferrous sulfate solution used in Fenton reaction tank 342 is 11.83m³. 3 / h, the amount of hydrogen peroxide solution used is 6.13m 3 / h, ultimately resulting in deep removal of pollutants. The water quality changes in each treatment unit during this process are shown in [see figure]. Figure 4 .

[0195] Verification has shown that the treatment method and system of this invention for treating ferric phosphate production wastewater yields significant benefits from the reuse of phosphoric acid and treated water, far exceeding the equipment investment and operating costs of the treatment system. Ultimately, this brings excellent economic benefits to enterprises and is highly suitable for ferric phosphate production enterprises.

[0196] The embodiments of the invention provided in this specification have been described above. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. All other preferred embodiments and implementations obtained by those skilled in the art based on the above description of the embodiments of the invention provided in this specification without inventive effort should fall within the protection scope of the embodiments of the invention provided in this specification.

Claims

1. A method for treating iron phosphate production wastewater, the iron phosphate production wastewater comprising wash water and reaction mother liquor generated in the process of producing iron phosphate by the iron process / iron red process, characterized in that: The method comprises the following steps: ​ (1) a recycling phosphoric acid purification and recovery process, comprising: sequentially pretreating the washing water, the pretreatment comprising filtration treatment, temperature reduction treatment, resin adsorption treatment and ultrafiltration treatment, to obtain an ultrafiltration clear liquid; recovering phosphoric acid from the ultrafiltration clear liquid to obtain recycled phosphoric acid and a first clear liquid; (2) a recycled product water preparation process, comprising: adjusting the pH of the first clear liquid using an alkali solution to obtain raw water; sequentially subjecting tap water to sand filtration treatment and activated carbon adsorption to obtain make-up water; concentrating a first mixture comprising the raw water and the make-up water to obtain an impurity concentrate and recycled product water; (3) a deep purification and discharge process, comprising: purifying a second mixture comprising the impurity concentrate, reaction mother liquor and resin regeneration liquid to obtain qualified product water; the process of recovering phosphoric acid from the ultrafiltration clear liquid comprises: subjecting the ultrafiltration clear liquid to reverse osmosis membrane concentration treatment to obtain phosphoric acid concentrate with a mass fraction of 8-10% and a purity of ≥96% and first product water; subjecting the phosphoric acid concentrate to reverse osmosis membrane concentration treatment to obtain recycled phosphoric acid with a mass fraction of 20-85% and second product water; wherein the first product water and the second product water constitute the first clear liquid; the process of concentrating the first mixture comprises: subjecting the first mixture to reverse osmosis membrane concentration treatment to obtain first-stage concentrated water and first-stage product water; subjecting the first-stage concentrated water to reverse osmosis membrane concentration treatment to obtain the impurity concentrate and second-stage product water; subjecting the first-stage product water and the second-stage product water to reverse osmosis membrane concentration treatment to obtain second-stage concentrated water and recycled product water; wherein the second-stage concentrated water is returned to the first mixture; the deep purification and discharge process specifically comprises: adding a precipitant to the second mixture, and then performing flocculation sedimentation and solid-liquid separation treatment to obtain a second clear liquid; adjusting the pH of the second clear liquid to 4-5 using an acid solution to obtain a third clear liquid; performing Fenton oxidation treatment on the third clear liquid, and then performing flocculation sedimentation and solid-liquid separation treatment to obtain a fourth clear liquid; adjusting the pH of the fourth clear liquid to 6-9 using an alkali solution to obtain qualified product water.

2. The method according to claim 1, wherein: the TDS of the washing water is ≤16500 mg / L, the phosphoric acid concentration is ≤16200 mg / L, the sulfate radical concentration is ≤150 mg / L, the sodium ion concentration is ≤15 mg / L, the total iron ion concentration is ≤30 mg / L, the manganese ion concentration is ≤30 mg / L, the calcium ion concentration is ≤3 mg / L, the magnesium ion concentration is ≤0.5 mg / L, the copper ion concentration is ≤1 mg / L, the zinc ion concentration is ≤0.5 mg / L, and the silicon element concentration is ≤28 mg / L, and the fluorine ion concentration is ≤14 mg / L. The TDS of the ultrafiltration clear liquid is less than or equal to 16500 g / L, the phosphoric acid concentration is less than or equal to 16200 mg / L, the sulfate radical concentration is less than or equal to 150 mg / L, the sodium ion concentration is less than or equal to 15 mg / L, the total iron ion concentration is less than or equal to 0.5 mg / L, the manganese ion concentration is less than or equal to 0.5 mg / L, the calcium ion concentration is less than or equal to 0.5 mg / L, the magnesium ion concentration is less than or equal to 0.5 mg / L, the copper ion concentration is less than or equal to 0.5 mg / L, the zinc ion concentration is less than or equal to 0.5 mg / L, the silicon element concentration is less than or equal to 28 mg / L, and the fluorine ion concentration is less than or equal to 14 mg / L; The TDS of the reused phosphoric acid is less than or equal to 95000 mg / L, the phosphoric acid concentration is less than or equal to 94000 mg / L, the sulfate radical concentration is less than or equal to 610 mg / L, the sodium ion concentration is less than or equal to 60 mg / L, the total iron ion concentration is less than or equal to 3 mg / L, the manganese ion concentration is less than or equal to 3 mg / L, the calcium ion concentration is less than or equal to 3 mg / L, the magnesium ion concentration is less than or equal to 3 mg / L, the copper ion concentration is less than or equal to 3 mg / L, the zinc ion concentration is less than or equal to 2.5 mg / L, the silicon element concentration is less than or equal to 140 mg / L, and the fluorine ion concentration is less than or equal to 20 mg / L.

3. The method according to claim 2, wherein: the resin adsorption treatment uses a strong acid type cation resin; the resin used in the resin adsorption treatment is regenerated by using dilute sulfuric acid with a mass fraction of 8-10%, and the obtained resin regeneration liquid with a sulfuric acid mass fraction of 6-7% is used in the second mixture; the regenerated resin is eluted by using pure water, and the elution water is returned to the filter treatment after being mixed with the washing water.

4. The method according to claim 1, wherein: the TDS of the make-up water is less than or equal to 250 mg / L, the sulfate radical concentration is less than or equal to 160 mg / L, the sodium ion concentration is less than or equal to 12 mg / L, the calcium ion concentration is less than or equal to 50 mg / L, the magnesium ion concentration is less than or equal to 9 mg / L, and the silicon element concentration is less than or equal to 9 mg / L; the TDS of the raw water is less than or equal to 1100 mg / L, the phosphoric acid concentration is less than or equal to 860 mg / L, the sulfate radical concentration is less than or equal to 7 mg / L, the sodium ion concentration is less than or equal to 210 mg / L, the total iron ion concentration is less than or equal to 0.05 mg / L, the manganese ion concentration is less than or equal to 0.05 mg / L, the calcium ion concentration is less than or equal to 0.05 mg / L, the magnesium ion concentration is less than or equal to 0.05 mg / L, the copper ion concentration is less than or equal to 0.05 mg / L, the zinc ion concentration is less than or equal to 0.04 mg / L, the silicon element concentration is less than or equal to 2.5 mg / L, and the fluorine ion concentration is less than or equal to 13 mg / L; the pH of the raw water is 6-7; the TDS of the impurity concentrated liquid is less than or equal to 14200 mg / L, the phosphoric acid concentration is less than or equal to 9400 mg / L, the sulfate radical concentration is less than or equal to 1500 mg / L, the sodium ion concentration is less than or equal to 2400 mg / L, the total iron ion concentration is less than or equal to 0.5 mg / L, the manganese ion concentration is less than or equal to 0.5 mg / L, the calcium ion concentration is less than or equal to 400 mg / L, the magnesium ion concentration is less than or equal to 75 mg / L, the copper ion concentration is less than or equal to 0.5 mg / L, the zinc ion concentration is less than or equal to 0.4 mg / L, the silicon element concentration is less than or equal to 90 mg / L, and the fluorine ion concentration is less than or equal to 110 mg / L. ​ ​ ​ ​ ​ ​ 5. The method for treating ferric phosphate production wastewater as described in claim 4, characterized in that: The sand filter tank used for sand filtration treatment and the activated carbon tank used for activated carbon adsorption are backwashed with the part of the impurity concentrated solution, and the backwashing water is mixed with the impurity concentrated solution, the reaction mother liquor and the resin regeneration liquid to form a second mixture, and then the second mixture is sent to the deep purification and discharge process.

6. The method according to claim 1, wherein: the TDS of the resin regeneration liquid is less than or equal to 100000 mg / L, the sulfate radical concentration is less than or equal to 95000 mg / L, the total iron ion concentration is less than or equal to 2450 mg / L, the manganese ion concentration is less than or equal to 2200 mg / L, the calcium ion concentration is less than or equal to 165 mg / L, the magnesium ion concentration is less than or equal to 30 mg / L, the copper ion concentration is less than or equal to 80 mg / L, and the zinc ion concentration is less than or equal to 21 mg / L; the TDS of the reaction mother liquor is less than or equal to 188000 mg / L, the phosphoric acid concentration is less than or equal to 168000 mg / L, the sulfate radical concentration is less than or equal to 15900 mg / L, the sodium ion concentration is less than or equal to 1450 mg / L, the total iron ion concentration is less than or equal to 30 mg / L, the manganese ion concentration is less than or equal to 30 mg / L, the calcium ion concentration is less than or equal to 2.8 mg / L, the magnesium ion concentration is less than or equal to 0.5 mg / L, the copper ion concentration is less than or equal to 1 mg / L, the zinc ion concentration is less than or equal to 0.5 mg / L, the silicon element concentration is less than or equal to 1150 mg / L, and the fluorine ion concentration is less than or equal to 520 mg / L; the TDS of the second mixture is less than or equal to 54000 mg / L, the phosphoric acid concentration is less than or equal to 36000 mg / L, the sulfate radical concentration is less than or equal to 14500 mg / L, the sodium ion concentration is less than or equal to 2000 mg / L, the total iron ion concentration is less than or equal to 330 mg / L, the manganese ion concentration is less than or equal to 300 mg / L, the calcium ion concentration is less than or equal to 330 mg / L, the magnesium ion concentration is less than or equal to 60 mg / L, the copper ion concentration is less than or equal to 12 mg / L, the zinc ion concentration is less than or equal to 4 mg / L, the silicon element concentration is less than or equal to 220 mg / L, and the fluorine ion concentration is less than or equal to 150 mg / L. ​

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