CN111573881A

CN111573881A - Method and device for treating alkaline zinc-nickel alloy wastewater

Info

Publication number: CN111573881A
Application number: CN201910121808.8A
Authority: CN
Inventors: 车承丹; 付丹; 王英华; 章莉军
Original assignee: Shanghai Light Industry Research Institute Co Ltd
Current assignee: Shanghai Light Industry Research Institute Co Ltd
Priority date: 2019-02-19
Filing date: 2019-02-19
Publication date: 2020-08-25

Abstract

The invention provides a method and a device for treating alkaline zinc-nickel alloy wastewater. The method comprises the following steps: performing at least one combined treatment of chemical oxidation and precipitation, each combined treatment comprising: adjusting the pH value of the alkaline zinc-nickel alloy wastewater to 2-5; adding an oxidant and a catalyst into the wastewater, and reacting for 1-3 hours; adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and/or a flocculant to remove the zinc-nickel metal from the wastewater in a precipitation manner; performing solid-liquid separation to obtain a supernatant; and wherein at least two oxidizing agents are used in the at least one combined chemical oxidation and precipitation treatment; and carrying out ion exchange adsorption on the supernatant after solid-liquid separation to adsorb zinc-nickel metal ions in the supernatant.

Description

Method and device for treating alkaline zinc-nickel alloy wastewater

Technical Field

The invention mainly relates to the field of wastewater treatment, in particular to a method and a device for treating alkaline zinc-nickel alloy wastewater.

Background

In the electroplating industry, due to the reasons of production process, management, operation and the like, zinc and nickel ions in the produced wastewater exist in a complex state to form a zinc-nickel alloy. In the zinc-nickel alloy wastewater, the alkaline zinc-nickel alloy wastewater is particularly difficult to treat because the zinc-nickel alloy forms abnormal codeposition in the alkaline zinc-nickel alloy wastewater, complex ions formed by metal nickel are more stable, and the removal difficulty is extremely high.

For the alkaline zinc-nickel alloy wastewater, the conventional oxidation technologies such as Fenton and the like are generally adopted in the electroplating industry for treatment. However, the conventional oxidation technology such as fenton generally only contains a single type of oxidant and only carries out primary oxidation in the process of treating wastewater, so that the treatment effect on the alkaline zinc-nickel alloy wastewater is limited, the heavy metal removal rate is low, the chroma of treated effluent is remarkably increased, and the like.

Therefore, the conventional oxidation technology is adopted to treat the alkaline zinc-nickel alloy wastewater, so that the effluent is difficult to meet the new discharge standard required by GB21900-2008 'discharge Standard for electroplating pollutants', particularly the standard of the special discharge limit value of water pollution in Table 3, which is executed by enterprises in areas needing special protection measures.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for treating alkaline zinc-nickel alloy wastewater, which can improve the treatment effect of zinc-nickel metal.

In order to solve the technical problem, the invention provides a method for treating alkaline zinc-nickel alloy wastewater, which comprises the following steps: performing at least one combined treatment of chemical oxidation and precipitation, each combined treatment comprising: adjusting the pH value of the alkaline zinc-nickel alloy wastewater to 2-5; adding an oxidant and a catalyst into the wastewater, and reacting for 1-3 hours; adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and/or a flocculant to remove the zinc-nickel metal from the wastewater in a precipitation manner; performing solid-liquid separation to obtain a supernatant; and wherein at least two oxidizing agents are used in the at least one combined chemical oxidation and precipitation treatment; and carrying out ion exchange adsorption on the supernatant after solid-liquid separation to adsorb zinc-nickel metal ions in the supernatant.

In one embodiment of the invention, the combined treatment of the chemical oxidation and the precipitation is performed once, and at least two oxidants are added into the wastewater in the combined treatment once.

In another embodiment of the present invention, the combined treatment of chemical oxidation and precipitation is performed at least twice, wherein one oxidizing agent is added to the wastewater in each combined treatment, and the type of the added oxidizing agent is different between at least some combined treatments.

In another embodiment of the present invention, the combined treatment of at least two chemical oxidations and precipitations is performed, wherein at least two oxidants are added to the wastewater in each combined treatment.

In an embodiment of the present invention, the amount of the oxidant is 0.1-10 g/L, and the amount of the catalyst is 0.1-10 g/L.

In an embodiment of the present invention, the oxidizing agent is selected from sodium persulfate, hydrogen peroxide and potassium permanganate, and the catalyst is selected from iron, manganese and other simple substances and salts.

The invention also provides a treatment device of the alkaline zinc-nickel alloy wastewater, which comprises the following components: at least one combined treatment device for chemical oxidation and precipitation, each combined treatment device comprising: the pH value adjusting tank comprises a first pH value adjusting mechanism and is used for adjusting the pH value of the alkaline zinc-nickel alloy wastewater to 2-5; the oxidation tank is connected with the pH value adjusting tank and comprises a first agent adding mechanism and a second agent adding mechanism which are respectively used for adding an oxidant and a catalyst into the wastewater to react for 1-3 hours; the flocculation tank is connected with the oxidation tank, comprises a second pH value adjusting mechanism and a third agent adding mechanism and is used for adjusting the pH value of the wastewater to be more than 11, and a coagulant and/or a flocculant are added to remove the zinc-nickel metal from the wastewater in a precipitation mode; the sedimentation tank is connected with the flocculation tank and is used for carrying out solid-liquid separation to obtain supernatant; wherein the at least one combined chemical oxidation and precipitation treatment device comprises at least two first agent addition mechanisms; and the ion exchanger is connected with the sedimentation tank of the last combined treatment device and is used for carrying out ion exchange adsorption on the supernatant after solid-liquid separation so as to adsorb zinc-nickel metal ions in the supernatant.

In an embodiment of the present invention, the apparatus further includes a pH meter and a controller, the controller is connected to the first pH adjusting mechanism, the second pH adjusting mechanism, the first chemical adding mechanism, the second chemical adding mechanism and the third chemical adding mechanism, and the controller is configured to: controlling the first pH value adjusting mechanism to adjust the pH value of the wastewater to 2-5; controlling the first agent adding mechanism and the second agent adding mechanism to respectively add an oxidant and a catalyst into the wastewater; and controlling the second pH value adjusting mechanism to adjust the pH value of the wastewater to be more than 11, and controlling the third medicament adding mechanism to add a coagulant and/or a flocculant.

In an embodiment of the present invention, the apparatus further includes a flow meter disposed on the first, second and third chemical adding mechanisms for detecting a flow rate of the added chemical.

In an embodiment of the present invention, the above apparatus further comprises an agitator disposed in at least one of the pH adjusting tank, the oxidation tank and the flocculation tank.

Compared with the prior art, the invention realizes the treatment of the alkaline zinc-nickel alloy wastewater by utilizing the principle that different oxidants destroy the complex state of different metals and the ion exchange resin combined process, thereby having the advantages of good treatment performance and stable zinc-nickel ions in the treated effluent.

Drawings

FIG. 1 is a schematic view of an apparatus for treating alkaline zinc-nickel alloy wastewater according to an embodiment of the present invention.

FIG. 2 is a flow chart of a method for treating alkaline zinc-nickel alloy wastewater according to an embodiment of the present invention.

FIG. 3 is a schematic view of an apparatus for treating alkaline zinc-nickel alloy wastewater according to another embodiment of the present invention.

FIG. 4 is a flow chart of a method for treating alkaline zinc-nickel alloy wastewater according to another embodiment of the present invention.

FIG. 5 is a schematic view of an apparatus for treating alkaline zinc-nickel alloy wastewater according to another embodiment of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments disclosed below.

As used in this application and the appended claims, the terms "a," "an," "the," and/or "the" are not intended to be inclusive in the singular, but rather are intended to be inclusive in the plural unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that steps and elements are included which are explicitly identified, that the steps and elements do not form an exclusive list, and that a method or apparatus may include other steps or elements.

It will be understood that when an element or module is referred to as being "connected," "coupled" to another element, module or block, it can be directly connected or coupled or in communication with the other element, module or block or intervening elements, modules or blocks may be present, unless the context clearly dictates otherwise. As used herein, the term "and/or" can include any and all combinations of one or more of the associated listed items.

In principle, zinc and nickel ions in the wastewater exist in a complex state, particularly the complex ions formed by nickel are more stable, and the removal difficulty is extremely high. Therefore, in order to ensure that the wastewater reaches the standard, the wastewater needs to be subjected to decomplexation treatment by adding an oxidant. However, the conventional oxidation technology such as fenton has limited treatment on the high-difficulty alkaline zinc-nickel alloy wastewater, and has the problems of low heavy metal removal rate, obvious increase of the chroma of treated effluent and the like, and the conventional oxidation technology cannot reach the strictest discharge standard in GB21900-2008 'discharge Standard for electroplating pollutants', namely the standard in Table 3.

The embodiment of the invention describes a method and a device for treating alkaline zinc-nickel alloy wastewater, which can improve the treatment effect and ensure that the heavy metal in the treated effluent stably reaches the standard.

First embodiment

Treatment device for alkaline zinc-nickel alloy wastewater

FIG. 1 is a schematic view of an alkaline zinc-nickel alloy wastewater treatment apparatus according to a first embodiment of the present invention. Referring to fig. 1, the treatment apparatus 100 for alkaline zinc-nickel alloy wastewater of the present embodiment includes a combined treatment apparatus for chemical oxidation and precipitation, the treatment apparatus 100 for alkaline zinc-nickel alloy wastewater performs a combined treatment of primary chemical oxidation and precipitation, and at least two kinds of oxidants are added into the wastewater in the secondary combined treatment, the adding amount of the oxidants is 0.1-10 g/L, and the oxidants are selected from sodium persulfate, hydrogen peroxide and potassium permanganate. The combined treatment device for chemical oxidation and precipitation comprises a pH value adjusting tank 111, a first pH value adjusting mechanism 111a, an oxidation tank 112, a first medicament adding mechanism 112a, a second medicament adding mechanism 112b, a flocculation tank 113, a second pH value adjusting mechanism 113a, a third medicament adding mechanism 113b and a precipitation tank 114.

The pH value adjusting tank 111 is used for accommodating wastewater and adjusting the pH value of the wastewater to 2-5. The wastewater may be introduced into the pH adjustment tank 111 through a line 110a by, for example, a primary lift pump 110, the primary lift pump 110 may be disposed in a water inlet tank, a valve (not shown) may be disposed on the water inlet tank to control the introduction of the wastewater, and a control valve (not shown) may be disposed on the line 110a to control the flow of the fluid in the line 110 a. The pH adjusting tank 111 includes a first pH adjusting mechanism 111a, and the first pH adjusting mechanism 111a is used to add an acid to the pH adjusting tank 111. The first pH adjusting mechanism 111a may be one or more, and accordingly, the control valve may be one or more. The oxidation pond 112 is connected to the pH adjusting pond 111, and the oxidation pond 112 is used for accommodating wastewater to react for 1-3 hours. The oxidation pond 112 includes a first chemical adding mechanism 112a and a second chemical adding mechanism 112b, wherein there are at least two first chemical adding mechanisms 112a, and in this embodiment, the alkaline zinc-nickel alloy wastewater treatment apparatus 100 has two first chemical adding mechanisms 112 a. The first agent adding mechanism 112a and the second agent adding mechanism 112b are used for adding an oxidant and a catalyst into the wastewater respectively, the adding amount of the catalyst is 0.1-10 g/L, and the catalyst is selected from elementary substances and salts such as iron and manganese. The flocculation tank 113 is connected to the oxidation tank 112 and is used for adjusting the pH value of the wastewater to be more than 11 and adding coagulant and/or flocculant to remove the zinc-nickel metal from the wastewater in a precipitation manner. The flocculation tank 113 comprises a second pH value adjusting mechanism 113a and a third agent adding mechanism 113b, the second pH value adjusting mechanism is used for adding alkali into the flocculation tank 113, and the third agent adding mechanism 113b is used for adding a coagulant and/or a flocculant into the flocculation tank. The second pH adjusting mechanism may be one or more, and accordingly, the third agent adding mechanism 113b may be one or more. The sedimentation tank 114 is connected to the flocculation tank 113, and is used for performing solid-liquid separation on the wastewater and the sediment containing zinc and nickel metals to obtain supernatant.

The device 100 for treating alkaline zinc-nickel alloy wastewater of the embodiment further comprises an ion exchanger 119, and the ion exchanger 119 is connected with the sedimentation tank 114. Between the sedimentation tank 114 and the ion exchanger 119, there may be arranged, for example, a secondary filtration device which may comprise a secondary lifting device, a sand filter 117 and a line mixer 118. The secondary lift may include an intermediate water sump 115 and a secondary lift pump 116. The intermediate reservoir 115 is provided with a pipe 115a for delivering the supernatant to the secondary lift pump 116, and the intermediate reservoir 115 may be provided with a valve (not shown) for controlling the output water amount of the supernatant. The secondary lift pump 116 is used to raise the water level and deliver the supernatant to the next step through a pipe 116a, and a control valve (not shown) may be disposed on the pipe 116a for controlling the flow of the fluid in the pipe 116 a. The secondary lifting means may be connected to, for example, a sand filter 117, the sand filter 117 being arranged to remove suspended impurities present in the supernatant that are finer than the precipitate of zinc-nickel metal or the like. The sand filter 117 may be connected to, for example, a line mixer 118, and the line mixer 118 serves to uniformly mix the filtered supernatant. The ion exchanger 119 is connected to the combined treatment device of chemical oxidation and precipitation, and is used for performing ion exchange adsorption on the supernatant after solid-liquid separation to adsorb zinc-nickel metal ions in the supernatant. The ion exchange resin in the ion exchanger 119 may be a strongly acidic or weakly acidic cation resin, and due to the difference in the acid-base conditions for the operation of the different ion exchange resins, a third pH adjusting mechanism 118a may be provided between the ion exchanger 119 and the combined treatment apparatus for chemical oxidation and precipitation, for example, the third pH adjusting mechanism 118a being connected to the line mixer 118, the third pH adjusting mechanism 118a being used to add an acid or an alkali to the line mixer 118. A valve (not shown) may be provided on the ion exchanger 119 to control the discharge of the supernatant.

The alkaline zinc-nickel alloy wastewater treatment apparatus 100 of the present embodiment further includes a pH meter (not shown), a controller (not shown), a flow meter (not shown), and a stirrer 120.

The pH value meter is connected with the pH value adjusting tank 111 and the flocculation tank 113 and is used for detecting and displaying the pH value of the wastewater discharged by the neutralization pipeline mixer 118 in the pH value adjusting tank 111 and the flocculation tank 113. The controller is connected with the first pH value adjusting mechanism 111a, the second pH value adjusting mechanism 113a, the third pH value adjusting mechanism 118a, the first medicament adding mechanism 112a, the second medicament adding mechanism 112b and the third medicament adding mechanism 113b, and the controller can monitor and control the operation of the processing device. The controller is configured to: controlling the first pH value adjusting mechanism 111a to adjust the pH value of the wastewater to 2-5; controlling the first agent adding mechanism 112a and the second agent adding mechanism 112b to respectively add an oxidant and a catalyst into the wastewater; the second pH value adjusting mechanism 113a is controlled to adjust the pH value of the wastewater to be more than 11, and the third agent adding mechanism 113b is controlled to add a coagulant and/or a flocculant. The controller of each of the above configurations may be provided as one or more. The flow meters are provided in the first, second, and third

chemical adding mechanisms

112a, 112b, and 113b, and detect the flow rate of the added chemical. The agitator 120 is provided in at least one of the pH adjusting tank, the oxidation tank and the flocculation tank, and may agitate during the reaction to make the reaction more complete.

Treatment method of alkaline zinc-nickel alloy wastewater

FIG. 2 is a flow chart of the method for treating alkaline zinc-nickel alloy wastewater according to the first embodiment of the present invention. The treatment method can be carried out in the apparatus shown in FIG. 1, or in other apparatuses, as long as the apparatus satisfies the conditions for carrying out the method. Referring to fig. 2, the method of the present embodiment may include the following steps.

In step 201, the pH value of the alkaline zinc-nickel alloy wastewater is adjusted to 2-5.

In this step, the current pH of the wastewater is monitored during the adjustment. Taking fig. 1 as an example, the pH value of the wastewater in the pH adjusting tank 111 can be detected by the pH meter, if the current pH value is within 2-5, the controller controls the first pH adjusting mechanism 111a to stop adding acid to the pH adjusting tank 111, if the current pH value is higher than 5, the controller controls the first pH adjusting mechanism 111a to continue adding acid to the pH adjusting tank 111, and the pH meter can feed back the pH value to the controller during the adjusting process, so that the controller knows whether the pH value has been adjusted in place.

In step 202, an oxidant and a catalyst are added into the wastewater to react for 1-3 hours.

In this step, taking fig. 1 as an example, the controller controls the first chemical adding mechanism 112a and the second chemical adding mechanism 112b to respectively add an oxidant and a catalyst into the oxidation pond 112, and the wastewater and the oxidant react for 1-3 hours.

In the step, at least two oxidants are used, and the oxidant is the combination of at least two of sodium persulfate, hydrogen peroxide and potassium permanganate. Sodium persulfate, hydrogen peroxide and potassium permanganate all have strong oxidizing property, but strong oxidizing groups are different, and the action principle and the treated pollutants are different. Sodium persulfate is produced by activation

The oxidation-reduction potential is 2.5-3.1V. H₂O₂The redox potential of the generated OH is 1.8 to 2.7V.

OH has the characteristics of liveness, strong reactivity, small selectivity, high reaction rate and high mineralization, and theoretically can degrade most organic matters in the wastewater.

The ability of abstracting pi electrons is stronger than that of HO, and the ability of abstracting α -H is weaker than that of HO, potassium permanganate is a strong oxidant, MnO4^-Has an oxidation-reduction potential of 0.5 to 1.5V, and potassium permanganate is combined with olefins and aminesThe reaction rate of the product is high. The catalyst is selected from iron, manganese and other simple substances and salts. Under the acidic condition and the catalysis and activation of the catalyst, the oxidant can oxidize the zinc-nickel ions in the complexing state, so that the complexing agent is oxidized and decomposed, and the complex breaking of zinc and nickel is realized.

In step 203, the pH value of the wastewater is adjusted to be more than 11, and coagulant and/or flocculant are added to remove the zinc-nickel metal from the wastewater in a precipitation manner.

In this step, the pH of the wastewater is adjusted to above 11 so that zinc-nickel metal forms a precipitate. Taking fig. 1 as an example, the pH meter can detect the pH value of the wastewater in the flocculation tank 113, if the current pH value has fallen above 11, the controller controls the second pH value adjustment mechanism 113a to stop adding alkali to the pH value adjustment tank 111, if the current pH value is lower than 11, the controller controls the second pH value adjustment mechanism 113a to continue adding alkali to the pH value adjustment tank 111, and the pH value can be fed back to the controller by the pH meter during the adjustment process, so that the controller knows whether the pH value has been adjusted in place. Further, the addition of the coagulant and/or flocculant by the third agent addition mechanism 113b may be controlled by the controller.

At step 204, solid-liquid separation is performed to obtain a supernatant.

In this step, the liquid in the wastewater and the precipitate are subjected to solid-liquid separation to obtain a supernatant, and the supernatant can be sent to the next step.

In step 205, the supernatant after the solid-liquid separation is subjected to ion exchange adsorption to adsorb zinc-nickel metal ions in the supernatant.

In the step, the supernatant after solid-liquid separation may still have the problem that zinc and nickel ions exceed standards, and the content of zinc and nickel metal ions in the supernatant is reduced by carrying out ion exchange adsorption on the supernatant. Taking fig. 1 as an example, the supernatant after the solid-liquid separation is subjected to ion exchange adsorption by an ion exchanger 119.

First embodiment example

In the alkaline zinc-nickel alloy wastewater of a certain electroplating plant, the concentration of nickel in the wastewater is 10.5mg/L, the concentration of zinc is 116mg/L, and the pH value is 13.18. Adding acid liquor into the wastewater, and adjusting the pH value of the wastewater to 4. Adding an oxidant and a catalyst into the wastewater, wherein the adding amount of sodium persulfate in the oxidant is 2g/L, the adding amount of potassium permanganate is 4g/L, the catalyst is ferrous sulfate, and the adding amount of the ferrous sulfate is 2 g/L. The oxidation reaction time was 2 hours. And after the oxidation reaction is finished, adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and a flocculant into the wastewater. After the waste water is coagulated and separated from the precipitate, the concentration of nickel in the supernatant of the discharged water is 5.88mg/L, and the concentration of zinc is 5.77 mg/L. And then treated by an ion exchange resin column, the concentration of nickel in the discharged water is 0.09mg/L, the concentration of zinc is 0.14mg/L, the pH value is adjusted to 6-9, and the concentration of zinc and nickel ions in the discharged water is far lower than the strictest discharge standard in GB21900-2008 'discharge Standard for electroplating pollutants', namely the standard in Table 3. The raw water and the discharged water quality are shown in the table 1:

TABLE 1

The results in Table 1 show that the concentration of total nickel and total zinc in the discharged water reaches the strictest discharge standard GB 21900-2008.

Second embodiment

Treatment device for alkaline zinc-nickel alloy wastewater

FIG. 3 is a schematic view of an alkaline zinc-nickel alloy wastewater treatment apparatus according to a second embodiment of the present invention. On the basis of the first embodiment, referring to fig. 3, the alkaline zinc-nickel alloy wastewater treatment apparatus 300 of this embodiment includes at least two stages of combined treatment apparatus for chemical oxidation and precipitation, each stage of combined treatment apparatus for chemical oxidation and precipitation includes a pH adjusting tank, an oxidation tank, a flocculation tank and a precipitation tank, the alkaline zinc-nickel alloy wastewater treatment apparatus 300 performs at least two times of combined treatment of chemical oxidation and precipitation, and includes at least two first agent adding mechanisms, one oxidant is added into wastewater in each combined treatment, and at least some of the oxidants added between combined treatments are different in type, in this case, the combined treatment apparatus 300 of alkaline zinc-nickel alloy wastewater, except for one stage of combined treatment apparatus for chemical oxidation and precipitation, must include at least one first pH adjusting mechanism, one first agent adding mechanism, and one second agent adding mechanism, The second pH adjusting mechanism and the third chemical adding mechanism, and the other stages of the combined chemical oxidation and precipitation treatment apparatus may not include the first pH adjusting mechanism, the first chemical adding mechanism, the second pH adjusting mechanism, and the third chemical adding mechanism. In this embodiment, the alkaline zinc-nickel alloy wastewater treatment device 300 is added with a secondary chemical oxidation and precipitation combined treatment device on the basis of the first embodiment, and the secondary chemical oxidation and precipitation combined treatment device comprises a pH value adjusting tank 311, an oxidation tank 312, a flocculation tank 313 and a precipitation tank 314. The pH value adjusting tank is provided with a pipeline 311a connected with a first pH value adjusting mechanism 111 a. The oxidation pond 312 is provided with pipelines 312a and 312b connected to the first chemical adding mechanism 112a and the second chemical adding mechanism 112b, respectively, the oxidation pond 312 further comprises a first chemical adding mechanism 312c, the first chemical adding mechanism 312c is used for adding an oxidizing agent into the wastewater, and the oxidizing agents added by the first chemical adding mechanism 112a and the first chemical adding mechanism 312c are different from each other. The flocculation tank 313 is provided with

pipelines

313a and 313b for connecting the second pH value adjustment mechanism 113a and the third chemical adding mechanism 113 b.

Treatment method of alkaline zinc-nickel alloy wastewater

FIG. 4 is a flow chart of a method for treating alkaline zinc-nickel alloy wastewater according to a second embodiment of the present invention. The method of treatment may be carried out in the apparatus shown in FIG. 3 or in other apparatus, provided that the apparatus satisfies the conditions for carrying out the method. Referring to FIG. 4, in the method of the present embodiment, steps 301 to 304 are added to the method for treating alkaline zinc-nickel alloy wastewater of the first embodiment, and steps 301 to 304 are the same as steps 201 to 204. In the method of the present embodiment, the oxidizing agents used in step 202 and step 302 are all a single kind of oxidizing agent, and the oxidizing agents used in step 202 and step 302 are different from each other.

Second embodiment example

In the alkaline zinc-nickel alloy wastewater of a certain electroplating plant, the concentration of nickel in the wastewater is 35.8mg/L, the concentration of zinc is 60.4mg/L, and the pH value is 13.4. Adding acid liquor into the wastewater, and adjusting the pH value of the wastewater to 4. Adding oxidant and catalyst into the wastewaterAnd (2) performing primary oxidation, wherein the oxidant is sodium persulfate, the adding amount of the sodium persulfate is 2g/L, the catalyst is ferrous sulfate, and the adding amount of the ferrous sulfate is 1 g/L. The primary oxidation reaction time was 2 hours. And after the first-stage oxidation reaction is finished, adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and a flocculant into the wastewater. The waste water is treated by coagulation and separated from the precipitate, and then is discharged. Adding acid liquor into the wastewater, adjusting the pH value of the wastewater to 2.5, and then performing secondary oxidation under the conditions of: the oxidant is H₂O₂，H₂O₂The adding amount is 4ml/L, the catalyst is ferrous sulfate, and the adding amount of the ferrous sulfate is 2 g/L; the secondary oxidation reaction time was 1 hour. And after the secondary oxidation reaction is finished, adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and a flocculant into the wastewater. The nickel concentration in the supernatant of the discharged water after coagulation treatment and separation from the precipitate is 1.19mg/L, and the zinc concentration is 0.02 mg/L. And then treated by an ion exchange resin column, the concentration of nickel in the discharged water is 0.04mg/L, the concentration of zinc is 0.02mg/L, the pH value is adjusted to 6-9, and the concentration of zinc and nickel ions in the discharged water is far lower than the strictest discharge standard in GB21900-2008 'discharge Standard for electroplating pollutants', namely the standard in Table 3. The raw water and the discharged water quality are shown in the table 2:

TABLE 2

Third embodiment

Treatment device for alkaline zinc-nickel alloy wastewater

FIG. 5 is a schematic view of an alkaline zinc-nickel alloy wastewater treatment apparatus according to a third embodiment of the present invention. On the basis of the first embodiment, referring to fig. 5, the alkaline zinc-nickel alloy wastewater treatment apparatus 500 of this embodiment includes at least two stages of combined treatment apparatuses for chemical oxidation and precipitation, each stage of combined treatment apparatus for chemical oxidation and precipitation includes a pH adjusting tank, an oxidation tank, a flocculation tank and a precipitation tank, the alkaline zinc-nickel alloy wastewater treatment apparatus 500 performs at least two times of combined treatment for chemical oxidation and precipitation, and includes at least two first agent adding mechanisms, at least two oxidants are added to wastewater in each combined treatment, in the basic zinc-nickel alloy wastewater treatment apparatus 500, except for the combined treatment apparatus for one stage of chemical oxidation and precipitation, at least one of the first pH adjusting mechanism, the first agent adding mechanism, the second pH adjusting mechanism and the third agent adding mechanism must be included, the combined chemical oxidation and precipitation treatment device of the other stage may not include the first pH adjusting mechanism, the first chemical addition mechanism, the second pH adjusting mechanism, and the third chemical addition mechanism. In this embodiment, the alkaline zinc-nickel alloy wastewater treatment device 500 is added with a secondary chemical oxidation and precipitation combined treatment device on the basis of the first embodiment, and the secondary chemical oxidation and precipitation combined treatment device comprises a pH adjusting tank 511, an oxidation tank 512, a flocculation tank 513 and a precipitation tank 514. The pH value adjusting tank is provided with a pipeline 511a connected with a first pH value adjusting mechanism 111 a. The oxidation pond 512 is provided with pipelines 512a and 512b respectively connected with the first chemical adding mechanism 112a and the second chemical adding mechanism 112 b. The flocculation tank 513 is provided with pipelines 513a and 513b to connect the second pH adjusting mechanism 113a and the third chemical adding mechanism 113 b.

Treatment method of alkaline zinc-nickel alloy wastewater

FIG. 4 is a flow chart of a method for treating alkaline zinc-nickel alloy wastewater according to a third embodiment of the present invention. The method of treatment may be carried out in the apparatus shown in FIG. 5 or in other apparatus, provided that the apparatus satisfies the conditions for carrying out the method. Referring to FIG. 4, in the method of the present embodiment, steps 301 to 304 are added to the method for treating alkaline zinc-nickel alloy wastewater of the first embodiment, and steps 301 to 304 are the same as steps 201 to 204. In the method of this embodiment, at least two kinds of oxidizing agents are used in step 202 and step 302, and the oxidizing agents used in step 202 and step 302 may be the same or different.

Third embodiment example

Example 1

In the alkaline zinc-nickel alloy wastewater of a certain electroplating plant, the concentration of nickel in the wastewater is 11.3mg/L, the concentration of zinc is 153mg/L, and the pH value is 13.38. Adding acid liquor into the wastewater, and adjusting the pH value of the wastewater to 3. Adding an oxidant and a catalyst into the wastewater for primary oxidation, wherein the adding amount of sodium persulfate in the oxidant is 2g/L, the adding amount of potassium permanganate is 1g/L, the catalyst is ferrous sulfate, and the adding amount of the ferrous sulfate is 2 g/L. The primary oxidation reaction time was 1 hour. And after the first-stage oxidation reaction is finished, adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and a flocculant into the wastewater. The waste water is treated by coagulation and separated from the precipitate, and then is discharged. Adding acid liquor into the wastewater, adjusting the pH value of the wastewater to 3, then performing secondary oxidation, wherein the secondary oxidation condition is the same as the primary oxidation, adjusting the pH value of the wastewater to be more than 11 after the secondary oxidation reaction is finished, and adding a coagulant and a flocculant into the wastewater. The nickel concentration in the supernatant of the discharged water after coagulation treatment and separation from the precipitate is 1.26mg/L, and the zinc concentration is 0.14 mg/L. And then treated by an ion exchange resin column, the concentration of nickel in the discharged water is 0.05mg/L, the concentration of zinc is 0.07mg/L, the pH value is adjusted to 6-9, and the concentration of zinc and nickel ions in the discharged water is far lower than the strictest discharge standard in GB21900-2008 'discharge Standard for electroplating pollutants', namely the standard in Table 3. The raw water and the discharged water quality are shown in Table 3:

TABLE 3

The results in Table 3 show that the concentration of total nickel and total zinc in the wastewater both reach the most strict discharge standard GB 21900-2008.

Example two

In the alkaline zinc-nickel alloy wastewater of a certain electroplating plant, the concentration of nickel in the wastewater is 20.4mg/L, the concentration of zinc is 204mg/L, and the pH value is 12.68. Adding acid liquor into the wastewater, and adjusting the pH value of the wastewater to 4. Adding an oxidant and a catalyst into the wastewater for primary oxidation, wherein the adding amount of sodium persulfate in the oxidant is 2g/L, the adding amount of hydrogen peroxide is 5ml/L, the catalyst is ferrous sulfate, and the adding amount of the ferrous sulfate is 2 g/L. The primary oxidation reaction time was 2 hours. And (4) adding a coagulant and a flocculant into the wastewater after the first-stage oxidation reaction is finished. The waste water is treated by coagulation and separated from the precipitate, and then is discharged. Adding acid liquor into the wastewater, adjusting the pH value of the wastewater to 3, and then performing secondary oxidation under the conditions of: the adding amount of sodium persulfate in the oxidant is 2g/L, the adding amount of potassium permanganate is 1g/L, the catalyst is ferrous sulfate, and the adding amount of ferrous sulfate is 2 g/L; the secondary oxidation reaction time was 1 hour. And after the secondary oxidation reaction is finished, adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and a flocculant into the wastewater. The nickel concentration in the supernatant of the discharged water after coagulation treatment and separation from the precipitate is 2.24mg/L, and the zinc concentration is 1.41 mg/L. And then treated by an ion exchange resin column, the concentration of nickel in the discharged water is 0.07mg/L, the concentration of zinc is 0.11mg/L, the pH value is adjusted to 6-9, and the concentration of zinc and nickel ions in the discharged water is far lower than the strictest discharge standard in GB21900-2008 'discharge Standard for electroplating pollutants', namely the standard in Table 3. The raw water and the discharged water quality are shown in Table 4:

TABLE 4

The results in Table 4 show that the concentration of total nickel and total zinc in the wastewater both reach the most strict discharge standard GB 21900-2008.

Numerals describing the number of components, attributes, etc. are used in some embodiments, it being understood that such numerals used in the description of the embodiments are modified in some instances by the use of the modifier "about", "approximately" or "substantially". Unless otherwise indicated, "about", "approximately" or "substantially" indicates that the number allows a variation of ± 20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximations that may vary depending upon the desired properties of the individual embodiments. In some embodiments, the numerical parameter should take into account the specified significant digits and employ a general digit preserving approach. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the range are approximations, in the specific examples, such numerical values are set forth as precisely as possible within the scope of the application.

Although the present invention has been described with reference to the present specific embodiments, it will be appreciated by those skilled in the art that the above embodiments are merely illustrative of the present invention, and various equivalent changes and substitutions may be made without departing from the spirit of the invention, and therefore, it is intended that all changes and modifications to the above embodiments within the spirit and scope of the present invention be covered by the appended claims.

Claims

1. A method for treating alkaline zinc-nickel alloy wastewater comprises the following steps:

performing at least one combined treatment of chemical oxidation and precipitation, each combined treatment comprising:

adjusting the pH value of the alkaline zinc-nickel alloy wastewater to 2-5;

adding an oxidant and a catalyst into the wastewater, and reacting for 1-3 hours;

adjusting the pH value of the wastewater to be more than 11, and adding a coagulant and/or a flocculant to remove the zinc-nickel metal from the wastewater in a precipitation manner;

performing solid-liquid separation to obtain a supernatant; and

wherein at least two oxidizing agents are used in the at least one combined chemical oxidation and precipitation treatment; and

and carrying out ion exchange adsorption on the supernatant after solid-liquid separation to adsorb zinc-nickel metal ions in the supernatant.

2. The method according to claim 1, wherein a combined treatment of chemical oxidation and precipitation is performed, and at least two kinds of oxidizing agents are added to the wastewater in the combined treatment.

3. The method according to claim 1, wherein the combined treatment of chemical oxidation and precipitation is performed at least twice, and one oxidizing agent is added to the wastewater in each combined treatment, and the type of the added oxidizing agent is different between at least some combined treatments.

4. The method according to claim 1, wherein the combined treatment of chemical oxidation and precipitation is performed at least twice, and at least two oxidants are added to the wastewater in each combined treatment.

5. The method for treating alkaline zinc-nickel alloy wastewater according to claim 1, further comprising adding 0.1 to 10g/L of an oxidizing agent and 0.1 to 10g/L of a catalyst.

6. The method for treating alkaline zinc-nickel alloy wastewater as claimed in claim 1, wherein the oxidizing agent is selected from sodium persulfate, hydrogen peroxide and potassium permanganate, and the catalyst is selected from iron, manganese and other simple substances and salts.

7. An alkaline zinc-nickel alloy wastewater treatment device comprises:

at least one combined treatment device for chemical oxidation and precipitation, each combined treatment device comprising:

the pH value adjusting tank comprises a first pH value adjusting mechanism and is used for adjusting the pH value of the alkaline zinc-nickel alloy wastewater to 2-5;

the oxidation tank is connected with the pH value adjusting tank and comprises a first agent adding mechanism and a second agent adding mechanism which are respectively used for adding an oxidant and a catalyst into the wastewater to react for 1-3 hours;

the flocculation tank is connected with the oxidation tank, comprises a second pH value adjusting mechanism and a third agent adding mechanism and is used for adjusting the pH value of the wastewater to be more than 11, and a coagulant and/or a flocculant are added to remove the zinc-nickel metal from the wastewater in a precipitation mode; and

the sedimentation tank is connected with the flocculation tank and is used for carrying out solid-liquid separation to obtain supernatant;

wherein the at least one combined chemical oxidation and precipitation treatment device comprises at least two first agent addition mechanisms; and

and the ion exchanger is connected with the sedimentation tank of the last combined treatment device and is used for carrying out ion exchange adsorption on the supernatant after solid-liquid separation so as to adsorb zinc-nickel metal ions in the supernatant.

8. The apparatus for treating alkaline zinc-nickel alloy wastewater as set forth in claim 7, further comprising a pH meter and a controller, the controller being connected to the first pH adjusting mechanism, the second pH adjusting mechanism, the first chemical adding mechanism, the second chemical adding mechanism, and the third chemical adding mechanism, the controller being configured to:

controlling the first pH value adjusting mechanism to adjust the pH value of the wastewater to 2-5;

controlling the first agent adding mechanism and the second agent adding mechanism to respectively add an oxidant and a catalyst into the wastewater;

and controlling the second pH value adjusting mechanism to adjust the pH value of the wastewater to be more than 11, and controlling the third medicament adding mechanism to add a coagulant and/or a flocculant.

9. The apparatus for treating alkaline zinc-nickel alloy wastewater as set forth in claim 7, further comprising flow meters provided in said first, second and third chemical adding means for detecting the flow rate of the added chemical.

10. The apparatus for treating alkaline zinc-nickel alloy wastewater as set forth in claim 7, further comprising an agitator provided in at least one of the pH-adjusting tank, the oxidation tank and the flocculation tank.