Blue iron ore recovery process and blue iron ore recovery device

Abstract

The invention relates to a blue iron ore recovery process and a recovery device thereof.The process comprises the steps that S1, phosphorus-containing wastewater is pretreated; S2, the phosphorus-containing wastewater and a NaCl electrolyte are inflated for 20 minutes through nitrogen to remove dissolved oxygen; S3, the NaCl electrolyte is added into a cathode chamber, nitrogen is introduced, and meanwhile, a NaOH solution is added into the phosphorus-containing wastewater; and S5, after the electrolytic reaction, the phosphorus-containing wastewater is subjected to solid-liquid separation, acid pickling and drying to obtain a blue iron ore product, a top cover is arranged at the top of the shell, a cation exchange membrane is arranged in the shell, and the cation exchange membrane is arranged in the shell. The inner part of the shell is divided into an anode chamber and a cathode chamber, an iron electrode is arranged in the anode chamber, and a platinum electrode is arranged in the cathode chamber; according to the method, the neutral pH (7 + / -0.5) of the whole system is maintained while the blue iron ore recovery rate is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater resource recovery, and particularly relates to a vivianite recovery process and a recovery device thereof. BACKGROUND

[0002] Sludge anaerobic digestion is one of the effective ways to realize sludge reduction, stabilization and resource utilization, and the digestion process is often accompanied by the release of nitrogen and phosphorus nutrients, among which the phosphate concentration can be as high as 75-300 mg / L. It can be seen that the digestion liquid is rich in a large amount of phosphate, which is a good source for phosphate recovery.

[0003] Vivianite is a secondary mineral with the chemical formula Fe3(PO4)2·8H2O, which has high phosphorus content (28.3% P2O5) and economic value, and is easily soluble in dilute hydrochloric acid. It can be used as a pigment, a raw material for lithium batteries, a fertilizer, etc., and its fertilizer effect is more than 4 times that of superphosphoric acid. The pH value is the most important factor for the formation of vivianite, and the primary factor for crystallization and precipitation is solubility. In the case of low pH value, the solubility of the crystal is high, and the vivianite will be converted into soluble Fe2+ and PO4 3- , with the increase of pH value, the activity of Fe2+ and PO4 3- combination is significantly enhanced, but the competition of OH- and PO4 3- is gradually increased, resulting in the generation of Fe(OH)2 in the product; neutral solution (pH = 6-8) is more conducive to the generation of vivianite crystals. The increase of pH value will increase the supersaturation degree of the crystal in the nucleation process, and then accelerate the growth rate of the crystal. The pH value will also affect the zeta potential of the crystal, resulting in the change of the crystal aggregation property. In addition, the pH value will change the characteristics of the crystal, and a study has reported that high pH conditions will reduce the size of the crystal and increase the diversity of the crystal size at the same time, because the crystal nucleus density is high at this time, so it is particularly important to maintain a suitable pH range in the formation and recovery of the crystal. SUMMARY

[0004] The purpose of the present application is to overcome the problems existing in the prior art, and to provide a vivianite recovery process and a recovery device thereof.

[0005] The technical scheme of the present application is as follows:

[0006] A vivianite recovery process, comprising the following steps:

[0007] S1, adjusting the pH of the phosphorus-containing wastewater to 6.5-7.5 through pretreatment, and the suspended solids are ≤50 mg / L;

[0008] S2, removing dissolved oxygen by charging the phosphorus-containing wastewater pretreated in step S1 and NaCl electrolyte with nitrogen for 20 minutes;

[0009] S3, adding NaCl electrolyte in the cathode chamber and passing nitrogen, and adding NaOH solution to the phosphorus-containing wastewater, so as to keep the pH value of the phosphorus-containing wastewater at 7±0.5;

[0010] S4, the phosphorus-containing wastewater treated in S3 enters the anode chamber of the double-chamber reactor, and under the electrolysis of the iron electrode, the blue vitriol crystal is generated, and the H+ in the phosphorus-containing wastewater is migrated to the cathode chamber through the cation exchange membrane;

[0011] S5, the phosphorus-containing wastewater after the electrolysis reaction in step S4 is subjected to solid-liquid separation, acid washing and drying to obtain the blue vitriol product.

[0012] Further, the material of the cation exchange membrane is an alkali-resistant material, and the surface of the cation exchange membrane is covered with a hydrophilic coating.

[0013] Further, the hydrophilic coating is polyethylene glycol or polyethylene imine, and the thickness of the hydrophilic coating is 0.1-1 μm.

[0014] Further, the coating of the hydrophilic coating comprises the following steps:

[0015] S41, cutting the cation exchange membrane into 8x8 cm squares and pretreating;

[0016] S42, soaking the pretreated cation exchange membrane in a 0.5-5 mg / L polyethylene glycol or polyethylene imine solution for 5-10 min;

[0017] S43, wiping the residual modified solution on the surface of the cation exchange membrane with filter paper, placing it in a plasma irradiation instrument, and vacuumizing or injecting nitrogen, and irradiating it with a power of 0.2-1.2 W / cm 2 Next, the cation exchange membrane is subjected to timed plasma glow discharge;

[0018] S44, soaking the cation exchange membrane treated in step S43 in 0.5-2% hydrochloric acid for 8-24 h, and then washing it with pure water to obtain the cation exchange membrane with a hydrophilic coating.

[0019] Further, the pretreatment of the cation exchange membrane comprises the following steps:

[0020] S411, after washing and absorbing the water on the surface of the cation exchange membrane with filter paper, soaking the cation exchange membrane in 0.2-1 mol / L NaCl for 2-6 h;

[0021] S412, washing the soaked cation exchange membrane and drying it in an oven at 50-100°C;

[0022] S413. Immerse the dried cation exchange membrane in a 5-20% benzophenone solution for 10-20 minutes, then air dry naturally.

[0023] The present invention also proposes a recovery device for a blue iron ore recovery process, comprising a shell with a top cover, wherein a cation exchange membrane is provided inside the shell to divide the interior of the shell into an anode chamber and a cathode chamber, wherein an iron electrode is provided in the anode chamber and a platinum electrode is provided in the cathode chamber.

[0024] Furthermore, the area ratio of the iron electrode to the platinum electrode is 0.4-2.4, and the electrode spacing is 2.5-9 cm.

[0025] Furthermore, the surface of the cation exchange membrane is covered with a porous metal mesh or an injection-molded plastic mesh.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. This invention uses an alkali-resistant cation exchange membrane to separate the anode chamber and the cathode chamber, achieving physical isolation between the two chambers and allowing selective ion migration, which enables the maintenance of a neutral pH (7±0.5) during the recovery of vivianite, thereby increasing the crystallization efficiency by >30%.

[0028] 2. The present invention coats the surface of the cation exchange membrane with a hydrophilic coating to reduce organic matter, and sets a porous metal mesh or injection-molded plastic mesh on the surface of the cation exchange membrane to reduce particulate matter deposition and extend the life of the cation exchange membrane by more than 2 times. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the recycling device of the present invention.

[0030] In the diagram, 1. Porous metal mesh; 2. Cation exchange membrane; 3. Top cover; 4. Platinum electrode; 5. Cathode chamber; 6. Support; 7. Valve; 8. Anode chamber; 9. Iron electrode. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] A process for recovering lapis lazuli includes the following steps:

[0034] S1, the phosphorus-containing wastewater (anaerobic sludge supernatant or industrial wastewater with phosphorus concentration of 60-400 mg / L) is pretreated to adjust pH = 6.5-7.5, and SS≤50 mg / L;

[0035] S2, the pretreated phosphorus-containing wastewater and NaCl electrolyte in step S1 are aerated by nitrogen for 20 minutes to remove dissolved oxygen;

[0036] S3, NaCl electrolyte is added to the cathode chamber 5, and nitrogen is introduced, and NaOH solution is added to the phosphorus-containing wastewater from which the dissolved oxygen is removed, so that the pH value of the phosphorus-containing wastewater is maintained at 7±0.5;

[0037] S4, the phosphorus-containing wastewater treated in S3 enters the anode chamber 8 of the double-chamber reactor, and generates blue vitriol crystals under the electrolysis of the iron electrode 9, and H+ in the phosphorus-containing wastewater migrates to the cathode chamber 5 through the cation exchange membrane 2;

[0038] The material of the cation exchange membrane 2 is an alkali-resistant material such as perfluorosulfonic acid resin, polyether ether ketone or fluorinated polyarylether sulfone, and the surface of the cation exchange membrane 2 is covered with a hydrophilic coating;

[0039] The hydrophilic coating is polyethylene glycol PEG or polyethylene imine PEI, and the thickness of the hydrophilic coating is 0.1-1 μm;

[0040] The coating of the hydrophilic coating includes the following steps:

[0041] S41, the cation exchange membrane 2 is cut into 8x8 cm squares and pretreated;

[0042] The pretreatment of the cation exchange membrane 2 includes the following steps:

[0043] S411, after washing and absorbing the water on the surface of the cation exchange membrane 2 with filter paper, the cation exchange membrane 2 is soaked in 0.2-1 mol / L NaCl for 2-6 h;

[0044] S412, the soaked cation exchange membrane 2 is washed and dried in an oven at 50-100°C;

[0045] S413, the dried cation exchange membrane 2 is immersed in a 5-20% benzophenone solution (solvent is acetone) for 10-20 min, and is naturally dried;

[0046] S42, the pretreated cation exchange membrane 2 is soaked in a 0.5-5 mg / L polyethylene glycol or polyethylene imine solution for 5-10 min;

[0047] S43, the surface of the cation exchange membrane 2 is wiped dry with filter paper, and the modified solution remaining on the surface is placed in a plasma irradiation instrument, vacuumed or injected with other gases, at a power of 0.2-1.2 W / cm 2 Next, the membrane is subjected to timed plasma glow discharge;

[0048] S44, the cation exchange membrane 2 treated in step S43 is immersed in 0.5-2% hydrochloric acid for 8-24 hours, and then washed with pure water to obtain a cation exchange membrane 2 with a hydrophilic coating.

[0049] S5, after the electrolysis reaction in step S4, the phosphorus-containing wastewater is subjected to solid-liquid separation, acid washing, and drying to obtain a blue vitriol product.

[0050] Example 2

[0051] As Figure 1 shown, a recovery device for a blue vitriol recovery process includes a housing provided with a top cover 3 at the top, the housing is internally provided with a cation exchange membrane 2 to divide the housing into an anode chamber 8 and a cathode chamber 5, the anode chamber 8 is internally provided with an iron electrode 9, the cathode chamber 5 is internally provided with a platinum electrode 4, the anode chamber 8 and the cathode chamber 5 are both communicated with a valve 7 at the bottom, and the housing is also fixed with a bracket 6 at the bottom.

[0052] The area ratio of the iron electrode 9 to the platinum electrode 4 is 0.4-2.4, and the electrode spacing is 2.5-9 cm.

[0053] The iron electrode 9 (blue vitriol iron source) is a circular industrial low-carbon steel plate (purity ≥ 99%, thickness 0.5-2 mm), which releases Fe 2+ directly combines with PO4 3- to form blue vitriol (Fe3(PO4)2·8H2O);

[0054] The platinum electrode 4 (high-efficiency ORR catalysis) is a circular platinum sheet that catalyzes oxygen reduction reaction, accelerates electron transfer, and avoids interference from cathode hydrogen evolution side reactions.

[0055] The material of the housing is organic glass.

[0056] The surface of the cation exchange membrane 2 is covered with an alkali-resistant sealant, a porous metal mesh 1 (such as 316L stainless steel), or an injection molded plastic grid (PP / PTFE), and the grid shape is hexagonal honeycomb (strong pressure resistance) or square grid (easy to process).

[0057] Implementation case:

[0058] Experimental conditions: wastewater: anaerobic sludge supernatant, phosphorus concentration = 180 mg / L; parameters: area ratio = 2.0, spacing = 5 cm, current density = 5 mA / cm 2 ;

[0059] Results: Phosphorus removal rate: 98.2%; vivianite purity: XRD detection ≥95%; membrane flux maintenance: 92% (after 120 days of operation);

[0060] Compared with the conventional technology, the lifting effect of the present application is shown in the following table:

[0061] Indicator The present invention Conventional technology Lifting effect Phosphorus recovery rate >95％ ≤60％ +58％ Product phosphorus content 12.4% (blue vitriol) 5.7% (struvite) +117％ Membrane life > 24 months <6 months +300％ Energy consumption 0.8 kWh / kg P 1.2 kWh / kg P -33％

[0062] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to part of the technical features, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the recovery of blue vitriol, characterised in that: The method comprises the following steps: S1, the pH of the phosphorus-containing wastewater is adjusted to 6.5-7.5 by pretreatment, and the suspended solids are less than or equal to 50 mg / L; S2, the pretreated phosphorus-containing wastewater and NaCl electrolyte in step S1 are aerated by nitrogen for 20 minutes to remove dissolved oxygen; S3, NaCl electrolyte is added to the cathode chamber, and nitrogen is introduced, and NaOH solution is added to the phosphorus-containing wastewater, so that the pH of the phosphorus-containing wastewater is maintained at 7±0.5; S4, the phosphorus-containing wastewater treated in step S3 enters the anode chamber of the double-chamber reactor, and under the action of iron electrode electrolysis, the blue vitriol is crystallized, and H+ in the phosphorus-containing wastewater is migrated to the cathode chamber through the cation exchange membrane; S5, the phosphorus-containing wastewater after the electrolytic reaction in step S4 is subjected to solid-liquid separation, acid washing and drying to obtain the blue vitriol product.

2. A process for the recovery of blue vitriol according to claim 1, characterized in that: The material of the cation exchange membrane is an alkali-resistant material, and the surface of the cation exchange membrane is covered with a hydrophilic coating.

3. A process for the recovery of blue vitriol according to claim 2, characterized in that: The hydrophilic coating is polyethylene glycol or polyethylene imine, and the thickness of the hydrophilic coating is 0.1-1 μm.

4. A process for the recovery of blue vitriol according to claim 3, characterized in that: The coating of the hydrophilic coating comprises the following steps: S41, the cation exchange membrane is cut into 8x8 cm squares and pretreated; S42, the pretreated cation exchange membrane is soaked in a 0.5-5 mg / L polyethylene glycol or polyethylene imine solution for 5-10 minutes; S43, the residual modified solution on the surface of the cation exchange membrane is wiped dry with filter paper, and the cation exchange membrane is placed in a plasma irradiation instrument, vacuum is drawn or nitrogen is injected, and the cation exchange membrane is irradiated with plasma at a power of 0.2-1.2 W / cm 2 Next, the cation exchange membrane is subjected to timed plasma glow discharge; S44, the cation exchange membrane treated in step S43 is soaked in 0.5-2% hydrochloric acid for 8-24 hours, and then washed with pure water to obtain the cation exchange membrane with a hydrophilic coating.

5. A process for the recovery of vivianite according to claim 4, characterized in that: The pretreatment of the cation exchange membrane comprises the following steps: S411, after washing and absorbing the water on the surface of the cation exchange membrane with filter paper, the cation exchange membrane is soaked in 0.2-1 mol / L NaCl for 2-6 hours; S412, the soaked cation exchange membrane is washed and dried in an oven at 50-100°C; S413, the dried cation exchange membrane is immersed in a 5-20% benzophenone solution for 10-20 minutes, and then naturally air-dried.

6. A recovery device for the recovery of blue vitriol according to claims 1-5, characterized in that: The shell is provided with a top cover at the top, and the inside of the shell is provided with a cation exchange membrane to divide the inside of the shell into an anode chamber and a cathode chamber, the anode chamber is provided with an iron electrode, and the cathode chamber is provided with a platinum electrode.

7. The barite recovery device of claim 6, wherein: The area ratio of the iron electrode to the platinum electrode is 0.4-2.4, and the electrode spacing is 2.5-9 cm.

8. The barite recovery device of claim 6, wherein: The surface of the cation exchange membrane is covered with a porous metal mesh or an injection molded plastic grid.

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