Method for recovering high-purity zinc aluminoferrite spinel and stable residues from zinc-containing electroplating waste mud

Abstract

The invention discloses a method for recovering high-purity zinc aluminoferrite spinel and stable residues from zinc-containing electroplating waste mud. The method comprises the following steps: pretreating the electroplating waste mud; calcining at high temperature; gathering the spinel; and optionally stabilization of the remaining particles. The method comprises the following steps: mixing electroplating waste mud and demulsification slag, calcining at high temperature, and enriching through magnetic separation to obtain a zinc aluminoferrite spinel product, thereby obtaining high-dispersion, large-size and high-crystallinity spinel particles.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technologies, and particularly to a method for pyrometallurgical treatment of electroplating waste sludge. Background Art

[0002] Electroplating waste sludge is a hazardous waste containing heavy metals and has been strictly controlled by environmental protection departments. In electroplating, heavy metals such as zinc, nickel, chromium, and copper are widely used. Correspondingly, with the discharge and treatment of electroplating waste liquid, they are ultimately transferred to electroplating waste sludge. In addition to heavy metals, the impurities in electroplating waste sludge are mainly hydrates of iron and aluminum, which come from the iron and aluminum metals peeled off and corroded during the cleaning process of plated parts and the iron and aluminum coagulants used in the treatment of electroplating waste liquid. In addition, to promote the precipitation of heavy metals, some special heavy metal capturers are also widely used and transferred to the waste sludge. Therefore, electroplating waste sludge is a waste with complex components, and its treatment and resource utilization have always been the key issues concerned by environmental protection workers.

[0003] Wet recovery of heavy metal ions from electroplating waste sludge can obtain high-purity heavy metal products, showing certain application advantages and being a hot topic currently concerned by scientific researchers. Wet recovery of electroplating waste sludge generally includes steps such as strong acid leaching, selective precipitation / extraction / crystallization, and final treatment of the remaining waste liquid. The second step is the key to obtaining high-purity heavy metal products. During the strong acid leaching process, heavy metals and hydrates of iron and aluminum dissolve, and the remaining insoluble residue is very little, usually less than 20% of the volume of the original waste sludge. However, the output of the remaining waste liquid is large and the salt content is high, which brings trouble to subsequent treatment. Some reports show that strong base leaching and electro-deposition can recover amphoteric heavy metal ions from electroplating waste sludge, and the alkali solution is completely recycled without generating secondary waste liquid. In actual operation, affected by the condensation crystallization of iron hydrate and the formation of coated bodies, the leaching efficiency of amphoteric heavy metal ions is usually less than 85%, and the reduction efficiency of electroplating waste sludge is less than 30%.

[0004] Pyrometallurgical treatment of electroplating waste sludge mainly focuses on the following directions. (1) Treatment of electroplating waste sludge in a cement rotary kiln and co-incineration to prepare cement products. Similar reports include the preparation of building materials such as geopolymers, bricks, and black crystal glass. (2) Treatment by high-temperature molten salt chlorination method, cooling and crystallizing to collect copper chloride. The chlorine reagents used in the reports include calcium chloride, HCl, magnesium chloride, etc., and the product separation is mainly affected by the boiling points of chlorides; (3) High-temperature calcination pretreatment, adding additives such as lime, NaOH, etc. during the process to promote the decomposition of silicon-aluminum minerals and facilitate the improvement of leaching efficiency. The subsequent pretreatment usually uses a wet process, usually as described in the previous paragraph. Summary of the Invention

[0005] The object of the present invention is to provide a method for recovering high-purity zinc ferrite spinel and stable residue from zinc-containing electroplating waste sludge. The method is completed by mixing the electroplating waste sludge with demulsification residue, calcining at high temperature, and enriching by magnetic separation to obtain the zinc ferrite spinel product.

[0006] The main points of the present invention are as follows:

[0007] 1. Pretreatment of electroplating waste sludge

[0008] (1) Definition of electroplating waste sludge: The electroplating waste sludge is the yellow waste sludge generated from the treatment of zinc electroplating wastewater, with the iron, aluminum, calcium, and silicon contents being 9.85%, 1.67%, 4.12%, and 0.711% respectively, and the zinc, chromium, and nickel contents being 35.64%, 0.537%, and 0.446% respectively, with a water content of approximately 70%;

[0009] (2) Definition of batching: The emulsified oil residue is the scum generated from the demulsification of emulsified liquid wastewater, with the calcium, iron, aluminum, and silicon contents being 23.58%, 15.41%, 10.30%, and 3.21% respectively, and the main inorganic crystal being calcium sulfate, with a water content of approximately 80%;

[0010] (3) Preparation of solution: Mix dichloromethane, methanol, sodium chloride, and N,N-dimethylformamide in the following volume ratio of 65.8:28.4:3.5:0.3, and continuously stir.

[0011] (4) Pretreatment: Mix the electroplating waste sludge, emulsified oil residue, and the prepared solution in the following volume ratio of 1:1:20; stir at 60 - 90 rpm, start the condensation reflux device, heat to 60 - 65 °C, and maintain for 30 min - 60 min; turn off the condensation reflux device, turn on the condensation collection device, operate for 30 min, collect the mixed liquid of dichloromethane and methanol for the next waste sludge pretreatment; stop stirring and collect the viscous mixture.

[0012] 2. High-temperature calcination

[0013] (1) Closed pyrolysis: Collect the mixture and put it into the reaction kettle, where the mixture accounts for 60 - 80% of the effective volume of the reaction kettle; heat it in a closed manner to 500 - 550 °C, keep it at a constant temperature for 20 - 60 min, and control the pressure at 0.7 - 1.3 MPa to promote particle dispersion and generate zinc ferrite crystal nuclei;

[0014] (2) High-temperature calcination: Continue to heat up to 1100 - 1200 °C, keep it at a constant temperature for 10 - 30 min to promote the growth of zinc ferrite crystal nuclei; after natural cooling to room temperature, the final product is a highly dispersed powder.

[0015] 3. Spinel enrichment

[0016] (1) First stage enrichment: The collected powder is sprayed into the separator at a solid-gas ratio of Z = 0.2-0.5. A powder collector is set in the middle of the separator; the collector diameter is 10-15cm, and the outer ring is set with an electromagnetic field of 5000-10000 Gauss. The sprayed powder runs at high speed with the airflow, is sheared by the high-speed airflow during the acceleration stage, and is dispersed into finer powder, which moves downward with the airflow; under the action of the magnetic field, the magnetic particles are separated from the weakly magnetic particles, deviate toward the central magnetic field, and are gradually driven by the central airflow and move upward in the opposite direction, entering the powder collector, and attached to the wall of the device, gradually accumulating, and sliding to the bottom of the collector under the action of gravity; the remaining particles are collected and captured by the end bag filter.

[0017] (2) Second stage enrichment: The previously collected particles are sprayed into a venturi tube at a flow rate of 0.5-1 g / s; a solution (containing 0.01%-0.08% of an aqueous solution of sodium dodecylbenzene sulfonate) is sprayed into the throat of the venturi tube at a flow rate of 5-10 ml / s; the outlet of the venturi tube is connected to the aforementioned separation device; the magnetic particles adhere to the wall of the collector, gradually lose moisture, and fall off into the bottom of the collector under the action of gravity; the remaining particles are collected and captured by the end bag filter.

[0018] Optionally, (3) enriched product: in the enriched product, the spinel particle size is 0.5-2.0 μm, the contents of zinc aluminoferrite / chromium / nickel are 93%, 1.24%, 0.70% respectively, and the total content is as high as nearly 95%.

[0019] 4. Stabilization of remaining particles

[0020] (1) The remaining particles (rich in Si / Ca) are mixed with electroplating waste mud in a mass ratio of 4:1; since the excess ZnO will rob Al atoms to form zinc aluminoferrite spinel, it will inhibit the formation of Si / Al minerals and accelerate the combination of Si / Ca to form calcium silicate glass. The remaining metal atoms such as Zn / Cr / Ni will enter the glass network and be fixed.

[0021] (2) Collect the product in the bag filter, quickly heat it to 1200°C, then introduce nitrogen, with a gas-solid volume ratio of 1:75-200 and a renewal rate of 1-3min; then heat it to 1400°C at a rate of 10-20°C / min and keep it at a constant temperature for 10-60min; cool it naturally to room temperature to obtain a block-like black glassy product.

[0022] In the process of closed high-temperature pyrolysis, an oil phase is generated, combustible gas is collected, and crystal nuclei are generated in the oil phase: zinc oxide robs iron-aluminum hydrate to generate zinc aluminate crystal nuclei; the pressure in the kettle is controlled to be less than 1.7MPa, and the pressure is released when it is higher than the pressure, and combustible gas is collected at a temperature of 500-550℃ for 30-60min;

[0023] High-temperature calcination for degreasing, molten salt melting, rapid crystal growth in the liquid at 1100 - 1200 °C; after cooling, zinc ferrite spinel particles are formed.

[0024] The temperature is less than 1300 °C to prevent the decomposition of calcium sulfate and form calcium silicate glass.

[0025] The present invention provides a two-stage cyclone magnetic separation. In the first stage, a magnetic field is set in the middle with a magnetic field range of 2000 - 5000 GS; in the second stage, a magnetic field is set on the outer ring with an intensity of 5000 - 10000 GS; an atomization field is set, where the liquid captures and wets the particles, changes the surface potential, promotes the growth of gypsum crystals, captures silicon impurities, and separates them from the zinc ferrite crystals.

[0026] The features and advantages of the present invention are as follows:

[0027] (1) Mixing with demulsification residue: The demulsification residue provides CaSO4 and the organic phase, captures silicon-based hydrates, increases the melting point, prevents the formation of glass, and promotes the dispersion of spinel particles.

[0028] (2) Adding KCl salt to promote the growth of zinc ferrite spinel and reduce the synthesis temperature.

[0029] (3) Enrichment by cyclone magnetic separation to obtain zinc ferrite spinel products.

[0030] (4) Recovering high-purity zinc ferrite spinel from electroplating waste sludge.

[0031] (5) Preparing spinel particles with high dispersion, large size, and high crystallinity.

[0032] (6) Magnetic separation to obtain high-purity zinc ferrite products.

[0033] (7) Resource utilization of cutting fluid emulsification slag to achieve waste treatment with waste.

[0034] (8) No waste liquid is generated, and high-purity zinc ferrite spinel products are enriched.

[0035] (9) Avoiding cluster polymerization and crystal caking to obtain highly dispersed zinc ferrite spinel particles. Description of the Drawings

[0036] Figure 1 Showing zinc ferrite spinel prepared by calcination with KCl doping at 1200 °C, namely 0% KCl / 10% KCl / 50% KCl;

[0037] Figure 2 Showing zinc ferrite spinel prepared by calcination with KCl doping at 1200 °C, namely 0% KCl / 10% KCl / 50% KCl;

[0038] Figure 3 The zinc - ferrite spinel prepared by calcination with KCl doping at 1000 °C is shown, with 0% KCl / 50% KCl respectively;

[0039] Figure 4 The SEM / XRD / VSM of the ZnAlFeO4 spinel particles in the magnetic separation product are shown;

[0040] Figure 5 The SEM / XRD of the vitrified product are shown Detailed implementation manners

[0041] The present invention will be further described below in conjunction with specific embodiments, accompanying drawings, but the present invention is not limited thereto.

[0042] Example 1

[0043] 1. Pretreatment of electroplating waste sludge

[0044] (1) Define electroplating waste sludge: The electroplating waste sludge is the yellow waste sludge generated from the treatment of zinc electroplating wastewater, in which the contents of iron, aluminum, calcium, and silicon are 9.85%, 1.67%, 4.12%, and 0.711% respectively, and the contents of zinc, chromium, and nickel are 35.64%, 0.537%, and 0.446% respectively, with a moisture content of about 70%;

[0045] (2) Define the ingredients: The emulsified oil sludge is the scum generated from the demulsification of emulsified liquid wastewater, in which the contents of calcium, iron, aluminum, and silicon are 23.58%, 15.41%, 10.30%, and 3.21% respectively, and the main inorganic crystal is calcium sulfate, with a moisture content of about 80% and an organic component content of about 30%;

[0046] (3) Prepare the solution: Mix dichloromethane, methanol, sodium chloride, and N,N - dimethylformamide in the following volume ratio of 65.8:28.4:3.5:0.3, and continuously stir.

[0047] (4) Pretreatment: Mix the electroplating waste sludge, emulsified oil sludge, and the prepared solution in a volume ratio of 1:1:20; stir at 90 rpm, start the condensation reflux device, heat to 65 °C, and continue for 60 min; turn off the condensation reflux device, turn on the condensation collection device, run for 30 min, collect the mixed liquid of dichloromethane and methanol for the next waste sludge pretreatment; stop stirring and collect the viscous mixture.

[0048] 2. High - temperature calcination

[0049] (1) Closed pyrolysis: Collect the mixture and put it into a reaction kettle, where the mixture accounts for 60% of the effective volume of the reaction kettle. Then add 0%, 10%, and 50% of KCl (by mass percentage of the mixture) respectively. Heat it in a closed state to 500 °C, keep it at a constant temperature for 30 min, and control the pressure at 0.7 - 1.3 MPa to promote particle dispersion and generate zinc ferrite spinel nuclei.

[0050] (2) High-temperature calcination: Continue to heat up to 1200 °C and keep it at a constant temperature for 10 - 30 min to promote the growth of zinc ferrite spinel nuclei. After natural cooling to room temperature, the final product is a highly dispersed powder.

[0051] 3. Spinel enrichment

[0052] (1) First-stage enrichment: Spray the collected powder into a separator at a solid-gas ratio of Z = 0.5. A powder collector is set in the middle of the separator. The diameter of the collector is 10 cm, and an electromagnetic field with a strength of 5000 Gauss is set in the outer ring. The sprayed powder and the air flow run at high speed together. During the acceleration stage, it is sheared by the high-speed air flow and dispersed into finer powders, and moves downward with the air flow. Under the action of the magnetic field, the magnetic particles are separated from the weakly magnetic particles, shift towards the central magnetic field, are gradually driven by the central air flow and move upward in the reverse direction, enter the powder collector, adhere to the wall of the collector, gradually accumulate, and slide into the bottom of the collector under the action of gravity. The remaining particles are collected and captured by the end bag filter.

[0053] (2) Second-stage enrichment: Spray the previously collected particles into a Venturi tube at a flow rate of 0.5 - 1 g / s. Spray a solution (an aqueous solution containing 0.01% - 0.08% of sodium dodecylbenzenesulfonate) into the throat of the Venturi tube at a flow rate of 5 ml / s. The outlet of the Venturi tube is connected to the aforementioned separation device. The magnetic particles adhere to the wall of the collector, gradually lose moisture, and fall off into the bottom of the collector under the action of gravity. The remaining particles are collected and captured by the end bag filter.

[0054] (3) Enriched product: In the enriched product, the spinel particle size is 0.5 - 2.0 μm, and the contents of zinc ferrite / chromium / nickel are 93%, 1.24%, and 0.70% respectively, with a total content of nearly 95%.

[0055] The SEM / XRD / VSM of the ZnAlFeO4 spinel particles in the magnetic separation product are as Figure 4 shown.

[0056] 4. Stabilization of the remaining particles

[0057] (1) The remaining particles (rich in Si / Ca) are mixed with electroplating waste mud in a mass ratio of 4:1; since the excess ZnO will rob Al atoms to form zinc aluminoferrite spinel, it will inhibit the formation of Si / Al minerals and accelerate the combination of Si / Ca to form calcium silicate glass. The remaining metal atoms such as Zn / Cr / Ni will enter the glass network and be fixed.

[0058] (2) Collect the product in the bag filter, quickly heat it to 1200°C, then introduce nitrogen, with a gas-to-solid volume ratio of 1:100 and a renewal rate of 1min; then heat it to 1400°C at a rate of 10°C / min and keep it at a constant temperature for 10-60min; cool it naturally to room temperature to obtain a block-like black glassy product.

[0059] SEM / XRD of the vitrified product Figure 5 shown.

[0060] Example 2

[0061] The process was carried out in the same manner as in Example 1, except that: (1) during the closed pyrolysis, 0% and 50% KCl were added respectively; and (2) the high temperature calcination temperature was 1000°C.

Claims

1. A method for recovering high-purity zinc aluminate spinel and stabilized residue from zinc-containing electroplating waste mud, comprising the following steps: Electroplating waste sludge pretreatment; High temperature calcination; Spinel enrichment; and Optionally, stabilization of the remaining particles.

2. The method of claim 1, wherein: The electroplating waste mud pretreatment step includes the following processes: (1) Providing electroplating waste mud: the electroplating waste mud is yellow waste mud produced by zinc electroplating wastewater treatment, preferably, wherein the contents of iron, aluminum, calcium and silicon are 9.85%, 1.67%, 4.12% and 0.711% respectively, and the contents of zinc, chromium and nickel are 35.64%, 0.537% and 0.446% respectively, and the water content is about 70%; (2) Providing emulsified oil residue: the emulsified oil residue is the scum produced by demulsification of emulsified wastewater, preferably, wherein the contents of calcium, iron, aluminum and silicon are 23.58%, 15.41%, 10.30% and 3.21% respectively, wherein the main inorganic crystal is calcium sulfate, the water content is about 80%, and the organic component content is about 30%; (3) Preparing the solution: Mix dichloromethane, methanol, sodium chloride and N,N-dimethylformamide in the following volume ratio of 65.8:28.4:3.5:0.3, and continue stirring; (4) Pretreatment: Electroplating waste mud, emulsified oil residue and the prepared solution are mixed in the following volume ratio of 1:1:20; Stir at 60-90 rpm, start the condensation reflux device, heat to 60-65°C, and continue for 30-60 min; Close the condensation reflux device, open the condensation collection device, run for 30 min, collect the mixed solution of dichloromethane and methanol for the next waste mud pretreatment; Stop stirring and collect the viscous mixture.

3. The method of claim 1, wherein: The high temperature calcination step includes the following process: (1) Closed pyrolysis: The mixture is collected and placed in a reactor, wherein the mixture occupies 60-80% of the effective volume of the reactor; the temperature is raised to 500-550° C. in a closed manner, and the temperature is kept constant for 20-60 minutes, and the pressure is controlled to be 0.7-1.3 MPa to promote particle dispersion and generate zinc aluminoferrite crystal nuclei; (2) High temperature calcination: Continue to raise the temperature to 1100-1200°C and keep the temperature constant for 10-30 minutes to promote the growth of zinc aluminoferrite nuclei; after naturally cooling to room temperature, the final product is a highly dispersed powder.

4. The method of claim 1, wherein: The spinel enrichment step The process includes: (1) The collected powder is mixed with a solid-gas ratio of Z = 0.2-0.

5. At normal temperature and pressure, the gas flows into the venturi tube along the axis at U = 20 m / s and flows out from the other side: During the airflow acceleration stage, the powder is sheared by the high-speed airflow and dispersed into finer particles; (2) Spraying into a separator, and setting a powder collector in the middle of the separator; the collector has a diameter of 10-15 cm, and an electromagnetic field with a strength of 5000-10000 Gauss is set on the outer ring. The sprayed powder runs at high speed with the airflow and is sprayed together with the airflow; under the action of the magnetic field, the magnetic particles are separated from the weakly magnetic particles, deviate toward the central magnetic field, and are gradually driven by the central airflow and move upward in the opposite direction, enter the powder collector, and attach to the wall of the device, gradually accumulate, and slide to the bottom of the collector under the action of gravity; the remaining particles are collected and captured by the end bag dust collector; (3) Second stage enrichment: The previously collected particles are sprayed into a venturi tube at a flow rate of 0.5-1 g / s; a solution (containing 0.01%-0.08% of an aqueous solution of sodium dodecylbenzene sulfonate) is sprayed into the throat of the venturi tube at a flow rate of 5-10 ml / s; the outlet of the venturi tube is connected to the aforementioned separation device; the magnetic particles adhere to the wall of the collector, gradually lose moisture, and fall off into the bottom of the collector under the action of gravity; the remaining particles are collected and captured by the end bag filter.

5. The method of claim 1, wherein: The stabilization step of the remaining particles includes the following process: (1) The remaining particles (rich in Si / Ca) are mixed with electroplating waste mud in a mass ratio of 4:1; since the excess ZnO will rob Al atoms to form zinc aluminoferrite spinel, it will inhibit the formation of Si / Al minerals and accelerate the combination of Si / Ca to form calcium silicate glass. The remaining metal atoms such as Zn / Cr / Ni will enter the glass network and be fixed; (2) Collect the product in the bag filter, quickly heat it to 1200°C, then introduce nitrogen, with a gas-solid volume ratio of 1:75-200 and a renewal rate of 1-3min; then heat it to 1400°C at a rate of 10-20°C / min and keep it at a constant temperature for 10-60min; cool it naturally to room temperature to obtain a block-like black glassy product.

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