CN111470684B - Method for removing heavy metals in electroplating wastewater by using microwaves - Google Patents

Method for removing heavy metals in electroplating wastewater by using microwaves Download PDF

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CN111470684B
CN111470684B CN202010358308.9A CN202010358308A CN111470684B CN 111470684 B CN111470684 B CN 111470684B CN 202010358308 A CN202010358308 A CN 202010358308A CN 111470684 B CN111470684 B CN 111470684B
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wastewater
heavy metal
iron
ferrous
electroplating wastewater
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CN111470684A (en
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刘非
单桃云
张晶
王亮
罗容
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Jiangsu Aixin Environmental Engineering Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/30—Treatment of water, waste water, or sewage by irradiation
    • C02F1/302—Treatment of water, waste water, or sewage by irradiation with microwaves
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/70—Treatment of water, waste water, or sewage by reduction
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes

Abstract

A method for removing heavy metals in electroplating wastewater by using microwaves comprises the following steps: (1) adding a ferrous salt solution and/or a ferric salt solution into the electroplating wastewater under stirring, and then adjusting the pH value to be neutral or alkaline to obtain mixed wastewater; (2) and (2) carrying out microwave hydrothermal reaction on the mixed wastewater obtained in the step (1), and filtering to obtain a heavy metal ferrite mixture and wastewater with the heavy metal ion concentration reaching the standard. The method can be carried out at normal temperature, does not need preheating, has short reaction time and high removal rate, ensures that the concentration of heavy metal ions in the purified wastewater reaches the discharge standard, has simple process and low cost, and is suitable for large-scale industrial continuous production.

Description

Method for removing heavy metals in electroplating wastewater by using microwaves
Technical Field
The invention relates to a method for removing heavy metals in electroplating wastewater, in particular to a method for removing heavy metals in electroplating wastewater by using microwaves.
Background
Electroplating plants or enterprises with multiple plating varieties are the main form of modern electroplating industrial parks, and the wastewater produced by the industrial parks is mixed wastewater consisting of multiple heavy metals, wherein the mixed wastewater mainly contains the heavy metals such as copper, nickel, chromium, zinc, iron and the like. When the content of heavy metal ions in the wastewater is high, most of the heavy metal ions can be recycled, and the content of the remaining heavy metal ions is relatively low and cannot reach the discharge standard, the heavy metal ions in the wastewater need to be removed by adopting a proper method so as to reach the discharge standard.
At present, there are many methods for removing heavy metals in electroplating wastewater, such as neutralization precipitation, sulfide precipitation, barium salt precipitation, ferrite precipitation, etc. The ferrite water purification technology is a wastewater purification method developed in the seventies of the last century, has good purification effect, can remove various pollutants simultaneously, and has wide application range; the solid-liquid separation is easy, and the flow is simple; small secondary pollution, reutilization of waste residue and the like, has a plurality of advantages and is a promising wastewater purification technology. However, at present, ferrite must be generated at a relatively high temperature, and thus the ferrite cannot satisfy the conditions in many cases, and thus the popularization of ferrite technology is limited to a certain extent.
CN101792226A discloses a microwave hydrothermal ferrite treatment method for electroplating wastewater and pickling waste liquid, which takes the electroplating wastewater and the pickling waste liquid as raw materials, takes NaOH as a regulator, regulates the pH value of the raw materials to 10-11, obtains a corresponding hydroxyl complex as a precursor, forms different growth elements at the temperature of 150-200 ℃ under the microwave hydrothermal condition of 5-30 minutes, and forms composite ferrite through connection growth in a certain direction and hydroxyl dehydration, wherein the obtained wastewater can reach the national discharge standard. However, the method is not suitable for treating large-scale electroplating wastewater or acid water, because the reaction temperature is as high as 150-200 ℃, and the unusual condition can be met for tens of or even hundreds of cubic wastewater; and the energy consumption is too large, and the method is difficult to be used for industrial treatment of wastewater from the cost viewpoint. Therefore, its spread is greatly limited.
CN102945717A discloses a composite magnetic material and a preparation method thereof, which is a composite material containing heavy metal type hydrotalcite and composite ferrite synthesized by using heavy metals in pickling waste liquid and electroplating wastewater, and the content of all heavy metals in the wastewater after treatment meets the national discharge standard. However, the reaction temperature still needs to reach 100-180 ℃, the temperature is used for large-scale treatment of pickling waste liquid and electroplating wastewater, the conditions are too harsh, and the treatment cost is unacceptable, so that the method is not suitable for actually treating the acid waste liquid and the electroplating wastewater, and the use of the method is greatly limited. In any case, the emphasis is on preparing the composite magnetic material.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects in the prior art and provide a method for removing heavy metals in electroplating wastewater by using microwaves, which can be carried out at normal temperature, does not need preheating, has short reaction time and high removal rate, ensures that the concentration of heavy metal ions in the purified wastewater reaches the discharge standard, has simple process and low cost, and is suitable for large-scale industrial continuous production.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for removing heavy metals in electroplating wastewater by using microwaves comprises the following steps:
(1) adding a ferrous salt solution and/or a ferric salt solution into the electroplating wastewater under stirring, and then adjusting the pH value to be neutral or alkaline to obtain mixed wastewater;
(2) and (2) carrying out microwave hydrothermal reaction on the mixed wastewater obtained in the step (1), and filtering to obtain a heavy metal ferrite mixture and wastewater with the heavy metal ion concentration reaching the standard.
The method of the invention utilizes microwave to enable bivalent and trivalent iron ions and heavy metal ions to generate ferrite which is easy for solid-liquid separation, thereby achieving the purpose of purifying the heavy metal ions in the wastewater. Ferrite is a composite oxide with a certain crystal structure, has high magnetic conductivity and high resistivity (the resistance of the ferrite is 1013-1014 times greater than that of copper), and is an important magnetic medium. The common lattice type of ferrite is spinel type ferrite, and the chemical composition of spinel type ferrite can be generally represented by the general formula BO.A2O3Wherein B represents a divalent metal such as Fe, Mg, Zn, Mn, Co, Ni, Ca, Cu, Hg, Bi, Sn, etc., and A represents a trivalent metal: such As Fe, Al, Cr, Mn, V, Co, Bi, Ga, As, etc. Ferrites are classified into two major groups, namely natural minerals and artificial products, magnetite (the main component of which is Fe)3O4Or FeO. Fe2O3) Is a natural spinel type ferrite. Heavy metal ion substituted part of Fe in ferrite2+Or Fe3+Stable ferrite is generated and precipitated; the ferrite is insoluble in acid and alkali solution, so that heavy metal ions in the wastewater are separated from the wastewater.
Preferably, in the step (1), the concentration of each heavy metal ion in the electroplating wastewater is as follows: cu2+≤100mg/L、Zn2+≤120mg/L、Ni2+≤100mg/L、Cr3+And/or Cr6+Less than or equal to 1500mg/L, and the pH value is 0-14 (more preferably 2-10). In practical application, the concentration of heavy metal ions is higher than the above indexes, so that the method has no technical problem, but is not applicable in consideration of economic benefit. The electroplating wastewater may contain Fe2+And/or Fe3+Without affecting the implementation of the technical solution inWhen iron salt is added, the total amount of iron ions is also included.
Preferably, in step (1), the ferrous and/or ferric salt solution is added in an amount such that: the mass of iron ions in the mixed wastewater is 20-30 times of the sum of the masses of heavy metals except iron in the electroplating wastewater, and the ratio of the sum of the mole numbers of divalent heavy metal ions to the sum of the mole numbers of trivalent heavy metal ions in the mixed wastewater is 0.9-1.1: 2. The abbreviation is: (Fe)2++Fe3+) Mass ratio of M = 20-30, (Fe)2++M2+) And (Fe)3++M3+) Wherein M represents a heavy metal other than iron, and the molar ratio of (a) to (b) is =0.9 to 1.1: 2. When the electroplating wastewater contains Fe2+And Fe3+In the meantime, Fe in the mixed wastewater is taken into account2+Or Fe3+Total amount of the components. Cr (chromium) component6+In Fe2+Or other reducing agent to Cr3+，Cr6+The mol number of the trivalent heavy metal is counted. The iron salt added into the wastewater ensures that the crystals in the ferrite are FeO & Fe2O3Mainly, other heavy metal ions in the wastewater are embedded in the crystal lattices of the ferrite to replace part of iron ions. The dielectric loss number of iron oxides in the mixed wastewater and a small amount of generated ferrite and the dielectric constant of the material are larger, so that the temperature is quickly raised under the action of microwaves; meanwhile, because the iron oxide and the generated ferrite have magnetic domains inside, under the action of microwaves, the ferrite not only rotates in an integral mode and has large energy when polarized, but also forms a regional electric field under the action of an external electric field, thereby being more beneficial to temperature rise. Therefore, the ferrous iron or the ferric iron with a certain mass ratio corresponding to the content of the heavy metals except iron can ensure that the mixed wastewater can complete the generation of ferrite without higher temperature under microwave, which is the key point of reducing the microwave hydrothermal reaction temperature by the method.
Preferably, in the step (1), the mass concentration of iron ions in the ferrous salt solution or the ferric salt solution is 3-5%.
Preferably, in the step (1), the ferrous salt is one or more of ferrous sulfate and/or ferrous chloride, and hydrates thereof. More preferably ferrous sulfate.
Preferably, in the step (1), the ferric salt is one or more of ferric sulfate and/or ferric chloride, and hydrates thereof. More preferably iron sulphate.
Preferably, in the step (1), when the ferrous salt or the ferric salt is added separately, part of the ferrous iron is oxidized into ferric iron by adding an oxidizing agent, or part of the ferric iron is reduced into ferrous iron by adding a reducing agent.
Preferably, the oxidant is one or more of hydrogen peroxide, air, oxygen or ozone. The mass fraction of the hydrogen peroxide is 30-50%. When hydrogen peroxide is used as an oxidant, the reaction equation is as follows: 2Fe2++H2O2+2H+= 2Fe3++2H2And O, wherein the dosage of the oxidant is 1.0-1.2 times of the stoichiometric ratio.
Preferably, the reducing agent is sodium sulfide and/or sodium hydrosulfide. The reaction equation is: s2-+2Fe3+=2Fe2++ S ↓, the amount of the reducing agent is 1.0-1.2 times of the stoichiometric ratio.
Preferably, in the step (1), the pH value is adjusted to 7-14 (more preferably 8-11).
Preferably, in step (1), the pH is adjusted with a base.
Preferably, the alkali is one or more of sodium carbonate, sodium bicarbonate or sodium hydroxide and the like.
Preferably, in the step (2), the mixed wastewater subjected to the microwave hydrothermal reaction is at normal temperature (more preferably 5-30 ℃), has a frequency of 300 MHz-300 GHz (more preferably 500-3000 MHz), is used for 3-20 min, and has a reaction end point temperature of less than or equal to 70 ℃. The wavelength range corresponding to the frequency of 300MHz to 300GHz is 1mm to 1000 mm. Under the action of microwaves, along with the extension of the microwave time, the temperature of the mixed wastewater can gradually rise without an external heating source and is not required to be controlled.
The conventional ferrite is generated at a temperature of not less than 60 ℃ for not less than 20min, but because no heat source is provided in many occasions, the method for treating heavy metal ions in wastewater by using the ferrite technology is limited to a certain extent. Although a small amount of ferrite is generated under the condition of 10-60 ℃, most of the ferrite is a mixture of ferrous hydroxide and ferric hydroxide, ferrite precipitation cannot be generated, and if the ferrite precipitation is hydroxide precipitation, heavy metal ions cannot be combined well to form a stable precipitate, so that the heavy metal ions cannot be completely precipitated.
The microwave is that dipole molecules in the heated body do high-frequency violent movement to generate 'internal friction heat', so that the temperature of the heated material is raised, the inside and the outside of the material can be simultaneously heated and simultaneously raised without any heat conduction process, the heating speed is high and uniform, the heating purpose can be achieved only by one or more than one of the energy consumption of the traditional heating mode, the heating is fast, and the integral heating is realized.
Ferrite is a good microwave absorbing material, and ferric hydroxide also absorbs microwaves. When the mixed solution containing the generated ferrite is placed under conditions where microwaves are generated, iron oxides (converted iron hydroxide) in the mixed solution and a part of the generated ferrite absorb the microwaves, and high-speed collision occurs to promote the generation of the ferrite in the solution. The movement speed of ions is increased to promote the rapid generation of ferrite, and the precipitates absorb microwaves to increase the temperature, so that the generation of ferrite is accelerated. After the material absorbs microwave energy, the temperature rises, and the formula of the temperature rise of the material is as follows:
Figure 59384DEST_PATH_IMAGE001
in the formula (I), the compound is shown in the specification,
delta T-temperature variation of the material in the microwave field, DEG C/min;
f-microwave frequency, Hz;
e- -electric field strength, V/cm;
ετ-the dielectric constant of the material;
tan delta-dielectric loss number;
d-density of the material, g/cm;
c- -specific heat capacity of the material, cal/g.degree.C.
Because ferrite or ferric hydroxide can absorb microwaves, mixed wastewater directly enters a microwave system at normal temperature without preheating in advance under the action of microwaves, and can generate ferrite after reaction for a period of time.
The method has the following beneficial effects:
(1) in the method, under the action of microwaves, the concentration of heavy metal ions in the electroplating wastewater is reduced to the following value by using a ferrite technology: cu is less than or equal to 0.1mg/L, Zn and less than or equal to 1.1mg/L, Ni and less than or equal to 0.1mg/L, Cr and less than or equal to 0.36mg/L (wherein Cr is6+Less than 0.1 mg/L), Fe less than 1.0mg/L, and the discharge standard of GB21900-2008 electroplating pollutants is completely achieved;
(2) compared with the conventional ferrite treatment technology for treating the heavy metal ions in the electroplating wastewater, the method can be carried out at normal temperature without preheating, and the heavy metal ions in the electroplating wastewater can be separated by adopting the ferrite technology even under the condition of no heat source, so that the application range of the ferrite is expanded;
(3) the method has the advantages of short reaction time, simple process and low cost, and is suitable for large-scale industrial continuous production.
Detailed Description
The present invention will be further described with reference to the following examples.
The concentration of each heavy metal ion in the electroplating wastewater 1 used in the embodiment of the invention is as follows: cu2+ 100mg/L、Zn2+100mg/L、Ni2+ 100mg/L、Cr3+ 500mg/L、Fe2+200mg/L, pH8.52; the concentration of each heavy metal ion in the electroplating wastewater 2 is as follows: cu2+ 3.5mg/L、Zn2+ 65.0mg/L、Ni2+ 89.0mg/L、Cr3+ 250.0mg/L、Fe2+482.0mg/L, pH5.20; the concentration of each heavy metal ion in the electroplating wastewater 3 is as follows: cu2+ 18.6mg/L、Zn2+ 49.0mg/L、Ni2+ 15.0mg/L、Cr6+ 150.0mg/L、Fe3+10.0mg/L, pH2.59; the concentration of each heavy metal ion in the electroplating wastewater 4 is as follows: cu2+ 2.5mg/L、Zn2+ 3.4mg/L、Ni2+2.5mg/L、Cr3+ 10.0mg/L、Fe2+23.0mg/L, pH9.82; the concentration of each heavy metal ion in the electroplating wastewater 5 is as follows: cu2+ 2.5mg/L、Zn2+ 120.0mg/L、Ni2+ 2.5mg/L、Cr3+ 1108mg/L、Fe2+ 11mg/L, pH6.48; the concentration of each heavy metal ion in the electroplating wastewater 6 is as follows: cu2+ 2.5mg/L、Zn2+ 3.4mg/L、Ni2+ 5.2mg/L、Cr3 + 35mg/L、Fe2+ 18mg/L, pH9.82; the wastewater is derived from wastewater obtained by preliminarily recovering or treating mixed electroplating wastewater in an electroplating park, and M represents heavy metal except iron; the mass fraction of the hydrogen peroxide used in the embodiment of the invention is 50%; the starting materials or chemicals used in the examples of the present invention are, unless otherwise specified, commercially available in a conventional manner.
Example 1
(1) In 500mL of electroplating wastewater 1 (M)2+Has a mass of 0.15g, M3+0.25g of (1), and 0.4g of M), 65.75g of a ferrous sulfate solution (Fe) was added with stirring2+Has a mass concentration of 4% and Fe2+Has a mass of 2.63 g) and 131.75g of iron sulfate solution (Fe)3+Has a mass concentration of 4% and Fe3+The mass of the mixed wastewater is 5.27 g), and then the pH value is adjusted to 8.00 by sodium carbonate to obtain mixed wastewater; (Fe)2++Fe3+) Mass ratio to M =8/0.4=20, (Fe)2++M2+) And (Fe)3++M3+) (ii) a molar ratio of =1.03: 2;
(2) and (2) placing the mixed wastewater obtained in the step (1) in a microwave oven at an initial temperature of 10 ℃, carrying out microwave hydrothermal reaction for 15min at a frequency of 915MHz, and filtering at a final temperature of 68 ℃ to obtain 15.22g (dry basis) of a heavy metal ferrite mixture and 650mL of wastewater with the heavy metal ion concentration reaching the standard.
Through detection, the heavy metal ferrite mixture obtained in the embodiment of the invention comprises the following main components: the ferrite comprises the following components of Fe 52.56%, Cu 0.33%, Zn 0.33%, Ni 0.33% and Cr 1.64%, and the ferrite has magnetic characteristics and can be used as a magnetic material and slagging in the metallurgical industry.
Through detection, the concentration of the heavy metal ions in the wastewater with the concentration reaching the standard obtained by the embodiment of the invention is as follows: cu 0.1mg/L, Zn 0.2.2 mg/L, Ni 0.1.1 mg/L, Cr 0.1.1 mg/L, Fe 0.00.00 mg/L, pH8.00, and the concentration of heavy metal ions completely reaches GB21900-2008 electroplating pollutant discharge standard.
Example 2
(1) In 1000mL of electroplating wastewater 2 (M)2+Has a mass of 0.16g, M3+To 0.25g of (1), and 0.41g of M), 112.67g of a ferrous chloride solution (Fe) was added with stirring2+Has a mass concentration of 3% and Fe2+Has a mass of 3.38 g) and 151g of a ferric chloride solution (Fe)3+Has a mass concentration of 5% and Fe3+The mass of the wastewater is 7.55 g), and then the pH value is adjusted to 9.50 by using sodium hydroxide to obtain mixed wastewater; (Fe)2++Fe3+) Mass ratio to M =11.4/0.41=28, (Fe)2++M2+) And (Fe)3++M3+) (ii) a molar ratio of =1.02: 2;
(2) and (2) placing the mixed wastewater obtained in the step (1) in a microwave oven at an initial temperature of 5 ℃, carrying out microwave hydrothermal reaction for 20min at a frequency of 2450MHz, and filtering at a final temperature of 70 ℃ to obtain 20.42g (dry basis) of a heavy metal ferrite mixture and 1200mL of wastewater with the heavy metal ion concentration reaching the standard.
Through detection, the heavy metal ferrite mixture obtained in the embodiment of the invention comprises the following main components: 55.89% of Fe, 0.02% of Cu, 0.32% of Zn, 0.44% of Ni and 1.22% of Cr, wherein the ferrite has magnetic characteristics, can be used as a magnetic material and can also be used for slagging in the metallurgical industry.
Through detection, the concentration of the heavy metal ions in the wastewater with the concentration reaching the standard obtained by the embodiment of the invention is as follows: cu 0.08mg/L, Zn 0.15.15 mg/L, Ni 0.09.09 mg/L, Cr 0.15.15 mg/L, Fe 0.00.00 mg/L, pH 9.50 and heavy metal ion concentration completely reach GB21900-2008 electroplating pollutant discharge standard.
Example 3
(1) In 400mL of electroplating wastewater 3 (M)2+Has a mass of 0.033g, M3+To 0.06g of (1), and 0.093g of M, 58g of a ferrous sulfate solution (Fe) was added with stirring2+Has a mass concentration of 4% and Fe2+Has a mass of 2.32g) 0.82g of hydrogen peroxide (1.34 g of Fe oxide) is added2+Is Fe3+) Cr in wastewater6+Oxidize 0.19gFe2+Is Fe3+Then, adjusting the pH value to 10.15 by using sodium carbonate to obtain mixed wastewater; (Fe)2++Fe3+) Mass ratio to M =2.324/0.093=25, (Fe)2++M2+) And (Fe)3++M3+) (ii) a molar ratio of =1.02: 2;
(2) and (2) placing the mixed wastewater obtained in the step (1) in a microwave oven at an initial temperature of 25 ℃, carrying out microwave hydrothermal reaction for 3min at a frequency of 915MHz, and filtering at a final temperature of 55 ℃ to obtain a heavy metal ferrite mixture of 3.95g (dry basis) and 430mL of wastewater with the heavy metal ion concentration reaching the standard.
Through detection, the heavy metal ferrite mixture obtained in the embodiment of the invention comprises the following main components: the ferrite comprises 58.89% of Fe, 0.19% of Cu, 0.49% of Zn, 0.15% of Ni and 1.52% of Cr, has magnetic characteristics, can be used as a magnetic material, and can also be used for slagging in the metallurgical industry.
Through detection, the concentration of the heavy metal ions in the wastewater with the concentration reaching the standard obtained by the embodiment of the invention is as follows: cu 0.1mg/L, Zn 0.24.24 mg/L, Ni 0.089.089 mg/L, Cr 0.28.28 mg/L, Fe 0.00.00 mg/L, pH 10.15 and heavy metal ion concentration completely reach GB21900-2008 electroplating pollutant discharge standard.
Example 4
(1) In 1200mL of electroplating wastewater 4 (M)2+Has a mass of 0.01g, M3+To 0.012g of (1), and 0.022g of M, 12.6g of a ferrous sulfate solution (Fe) was added under stirring2+Has a mass concentration of 5% and Fe2+0.63 g), 0.27g hydrogen peroxide (oxidizing 0.44g Fe)2+Is Fe3+) Then, adjusting the pH value to 8.95 by using sodium hydroxide to obtain mixed wastewater; (Fe)2++Fe3+) Mass ratio to M =0.66/0.022=30, (Fe)2++M2+) And (Fe)3++M3+) (ii) a molar ratio =1: 2;
(2) and (2) placing the mixed wastewater obtained in the step (1) in a microwave oven at an initial temperature of 30 ℃, carrying out microwave hydrothermal reaction for 10min at a frequency of 2450MHz, and filtering at a final temperature of 69 ℃ to obtain 1.28g (dry basis) of a heavy metal ferrite mixture and 1100mL of wastewater with the heavy metal ion concentration reaching the standard.
Through detection, the heavy metal ferrite mixture obtained in the embodiment of the invention comprises the following main components: fe 51.59%, Cu 0.23%, Zn 0.31%, Ni 0.23%, Cr 0.93%, the heavy metal ferrite has magnetic characteristics, can be used as a magnetic material, and can also be used for slagging in the metallurgical industry.
Through detection, the concentration of the heavy metal ions in the wastewater with the concentration reaching the standard obtained by the embodiment of the invention is as follows: cu 0.05mg/L, Zn 0.10.10 mg/L, Ni 0.09.09 mg/L, Cr 0.11.11 mg/L, Fe 0.00.00 mg/L, pH 8.95 and heavy metal ion concentration completely reach the discharge standard of GB21900-2008 electroplating pollutants.
Example 5
(1) In 600mL of electroplating wastewater 5 (M)2+Has a mass of 0.08g, M3+To 0.66g of (1), and 0.74g of M), 325.4g of a ferric sulfate solution (Fe) was added with stirring3+Has a mass concentration of 5% and Fe3+16.27 g), 6.57g of sodium sulfide (Na) was added2S content 60%, reduction of 5.64g Fe3+Is Fe2+) Then, adjusting the pH value to 8.98 by using sodium hydroxide to obtain mixed wastewater; (Fe)2++Fe3+) Mass ratio to M =16.277/0.74=22, (Fe)2++M2+) And (Fe)3++M3+) (ii) a molar ratio =1: 2;
(2) and (2) placing the mixed wastewater obtained in the step (1) in a microwave oven at an initial temperature of 18 ℃, carrying out microwave hydrothermal reaction for 8min at a frequency of 915MHz, and filtering at a final temperature of 56 ℃ to obtain 29.60g (dry basis) of a heavy metal ferrite mixture and 910mL of wastewater with the heavy metal ion concentration reaching the standard.
Through detection, the heavy metal ferrite mixture obtained in the embodiment of the invention comprises the following main components: the heavy metal ferrite comprises the following components of Fe 55.08%, Cu 0.0053%, Zn 0.26%, Ni 0.0053% and Cr 2.47%, has magnetic characteristics, and can be used as a magnetic material and slagging in the metallurgical industry.
Through detection, the concentration of the heavy metal ions in the wastewater with the concentration reaching the standard obtained by the embodiment of the invention is as follows: cu 0.08mg/L, Zn 1.10.10 mg/L, Ni 0.09mg/L, Cr 0.36.36 mg/L, Fe 0.00.00 mg/L, pH 8.98 and heavy metal ion concentration completely reach the discharge standard of GB21900-2008 electroplating pollutants.
Example 6
(1) In 600mL of electroplating wastewater 6 (M)2+Has a mass of 0.007g, M3+To 0.02g of (1), and 0.027g of (M), 17g of a ferric sulfate solution (Fe) was added with stirring3+Has a mass concentration of 4% and Fe3+0.68 g), 0.16g of sodium hydrosulfide (the NaHS content is 70%, 0.23g of Fe is reduced3+Is Fe2+) Then, adjusting the pH value to 11.00 by using sodium bicarbonate to obtain mixed wastewater; (Fe)2++Fe3+) Mass ratio to M =25, (Fe)2++M2+) And (Fe)3++M3+) (ii) a molar ratio of =1.04: 2;
(2) and (2) placing the mixed wastewater obtained in the step (1) in a microwave oven at an initial temperature of 21 ℃, carrying out microwave hydrothermal reaction for 13min at a frequency of 2450MHz, and filtering at a final temperature of 65 ℃ to obtain 1.13g (dry basis) of a heavy metal ferrite mixture and 650mL of wastewater with the heavy metal ion concentration reaching the standard.
Through detection, the heavy metal ferrite mixture obtained in the embodiment of the invention comprises the following main components: the heavy metal ferrite comprises the following components of Fe 61.45%, Cu 0.13%, Zn 0.17%, Ni 0.27% and Cr 1.85%, and has the magnetic characteristic, can be used as a magnetic material, and can also be used for slagging in the metallurgical industry.
Through detection, the concentration of the heavy metal ions in the wastewater with the concentration reaching the standard obtained by the embodiment of the invention is as follows: cu 0.04mg/L, Zn 0.16.16 mg/L, Ni 0.10.10 mg/L, Cr 0.26.26 mg/L, Fe 0.00.00 mg/L, pH 11.00 and heavy metal ion concentration completely reach GB21900-2008 electroplating pollutant discharge standard.

Claims (5)

1. A method for removing heavy metals in electroplating wastewater by using microwaves is characterized by comprising the following steps:
(1) adding ferrous salt and/or ferric salt solution into the electroplating wastewater under stirring, and then regulatingThe pH value is neutral or alkaline, and mixed wastewater is obtained; the concentration of each heavy metal ion in the electroplating wastewater is as follows: cu2+18.6～100mg/L、Zn2+49～120mg/L、Ni2+5.2～100mg/L、Cr3+And/or Cr6+10-1500 mg/L, pH 0-14; the ferrous and/or ferric salt solution is added in an amount such that: the mass of iron ions in the mixed wastewater is 20-30 times of the sum of the masses of heavy metals except iron in the electroplating wastewater, and the ratio of the sum of the mole numbers of divalent heavy metal ions to the sum of the mole numbers of trivalent heavy metal ions in the mixed wastewater is 0.9-1.1: 2; the iron ion is Fe2++Fe3+The divalent heavy metal ion is Fe2++M2+The trivalent heavy metal is Fe3++M3+Wherein M represents a heavy metal other than iron; cr (chromium) component6+Counting the mole number of the trivalent heavy metal;
(2) carrying out microwave hydrothermal reaction on the mixed wastewater obtained in the step (1), and filtering to obtain a heavy metal ferrite mixture and wastewater with the heavy metal ion concentration reaching the standard; the initial temperature of the mixed wastewater subjected to the microwave hydrothermal reaction is normal temperature, the frequency is 300 MHz-300 GHz, the time is 3-20 min, and the reaction end temperature is less than or equal to 70 ℃.
2. The method for removing heavy metals from electroplating wastewater by using microwaves as claimed in claim 1, wherein the method comprises the following steps: in the step (1), the mass concentration of iron ions in the ferrous salt solution or the ferric salt solution is 3-5%; the ferrous salt is one or more of ferrous sulfate and/or ferrous chloride and hydrates thereof; the ferric salt is one or more of ferric sulfate and/or ferric chloride and hydrates thereof.
3. The method for removing heavy metals from electroplating wastewater by using microwaves according to claim 1 or 2, wherein: in the step (1), when ferrous salt or ferric salt is added separately, oxidizing part of ferrous iron into ferric iron by adding an oxidizing agent, or reducing part of ferric iron into ferrous iron by adding a reducing agent; the oxidant is one or more of hydrogen peroxide, air, oxygen or ozone; the reducing agent is sodium sulfide and/or sodium hydrosulfide.
4. The method for removing heavy metals from electroplating wastewater by using microwaves according to claim 1 or 2, wherein: in the step (1), adjusting the pH value to 7-14; adjusting the pH value by using alkali; the alkali is one or more of sodium carbonate, sodium bicarbonate or sodium hydroxide.
5. The method for removing heavy metals from electroplating wastewater by using microwaves as claimed in claim 3, wherein the method comprises the following steps: in the step (1), adjusting the pH value to 7-14; adjusting the pH value by using alkali; the alkali is one or more of sodium carbonate, sodium bicarbonate or sodium hydroxide.
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CN102945717A (en) * 2012-10-11 2013-02-27 上海大学 Composite magnetic material and preparation method thereof
CN103332810A (en) * 2013-07-24 2013-10-02 武汉大学 Treatment method of heavy metals in desulfurization waste water
CN105236543A (en) * 2015-11-26 2016-01-13 湖南康盟环保科技有限公司 Heavy metal precipitant, preparation method thereof and heavy metal wastewater treatment method
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CN101792226A (en) * 2010-03-17 2010-08-04 上海大学 Ferrite treatment method for electroplating wastewater and pickle liquor by using microwave hydrothermal
CN102945717A (en) * 2012-10-11 2013-02-27 上海大学 Composite magnetic material and preparation method thereof
CN103332810A (en) * 2013-07-24 2013-10-02 武汉大学 Treatment method of heavy metals in desulfurization waste water
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