CN1556045A - Hexa valence chromium in industriel waste water electrolysis treatment method - Google Patents
Hexa valence chromium in industriel waste water electrolysis treatment method Download PDFInfo
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- CN1556045A CN1556045A CNA2004100100078A CN200410010007A CN1556045A CN 1556045 A CN1556045 A CN 1556045A CN A2004100100078 A CNA2004100100078 A CN A2004100100078A CN 200410010007 A CN200410010007 A CN 200410010007A CN 1556045 A CN1556045 A CN 1556045A
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Abstract
A process for treating the 6-valence Cr in industrial sewage features that the industrial sewage is electrolyzed directly by using PbSb alloy as anode and iron plate as cathode to reduce the 6-valence Cr to 3-valence Cr.
Description
The technical field is as follows: the invention relates to a method for treating three wastes, in particular to a method for treating low-concentration hexavalent chromium in wastewater by adopting electrolysis in an alkaline medium.
Background art: the chromium slag is the main waste slag discharged in the production of chromium salt, the chromium slag is mostly stacked in the open air and basically not treated, and because the slag contains hexavalent chromium in a water-soluble state and an acid-soluble state, the soluble hexavalent chromium can be dissolved and seeped along with rainwater, so that the soil, rivers and underground water sources of the surrounding environment are seriously polluted.
Chromium-containing wastewater has various treatment methods, and a ferrite reduction precipitation method is a classical method. The method is adopted by many manufacturers due to mature process, simple equipment and low operation cost. However, this process also has several disadvantages. Firstly, adding acid into the waste water to regulate pH value, reducing hexavalent chromium when the pH value is 2-3, then adding alkali to regulate pH value to 8-9 to make trivalent chromium and other heavy metal ions form precipitate and separate them. The pH value of the general chromium-containing wastewater can not meet the requirements, and the pH value is regulated by adding acid, so that the operation is troublesome, more sediments are generated, and the power consumption is high. Aiming at the problems, if the hexavalent chromium reduction and the precipitation of metal ions are carried out under the alkaline condition, the process is simplified, the acid and alkali dosage is reduced, and the operation cost is correspondingly reduced.
In general, the chromium-containing liquid leached out by rainwater is alkalescent, so that the electrolytic reduction of Cr is directly adopted in alkalescent medium6+The treatment of the chromium slag leaching solution does not need to carry out the pretreatment on the chromium slag leaching solution, thus leading the operation to be simple and the treatment cost to be reduced.
The invention content is as follows:
in order to solve the problem that the wastewater containing chromium (VI) can not be directly treated, the invention provides the method for electrolyzing hexavalent chromium in the industrial wastewater, which has the advantages of simple treatment process, low cost and easy operation.
The technical scheme of the invention is realized in the following mode: an electrolytic treatment method of hexavalent chromium in industrial wastewater, which comprises the following steps:
preparing an electrolyte;
selecting anode and cathode materials, and electrifying and electrolyzing;
sampling and analyzing;
and (5) sediment treatment.
Wherein: (1) the electrolyte is prepared by adding potassium sulfate as an additive into chromium (VI) containing wastewater, wherein the adding amount of the potassium sulfate is as follows: adding 1.2g to 3.5g of potassium sulfate into each liter of wastewater. (2) Selecting anode and cathode materials, namely taking insoluble alloy as the anode and iron plate as the cathode or taking the insoluble alloy and soluble iron plate as the anode together, and electrifying direct current in an open diaphragm-free electrolytic cell, wherein hexavalent chromium is directly reduced to trivalent chromium at the cathode or is reduced to trivalent chromium by reacting with divalent iron ions dissolved out from the anode in a solution, and the generated Cr is in an alkaline medium3+Formation of Cr (OH)3Precipitating to achieve the aim of removing chromium; the electrolysis temperature is less than or equal to 318.15K. (3) Sampling and analyzing: when the hexavalent chromium content in the electrolyte is less than 5mg.L-1When the electrolysis is stopped.
The insoluble alloy is lead-antimony alloy.
The anode is made of insoluble lead-antimony alloy and soluble iron plate, and the lead-antimony alloy and the iron plate are arranged in a crossed manner.
During electrolysis, cell voltage: 1.8-3V, area ratio of yin and yang: 3: 1-8: 1, and the distance between polar plates: 2-8 mm, electrolysis temperature: 283.15K to 318.15K.
The electrolytic sediment is centrifugally dried for use, and the electrolytic solution is recycled or discharged.
The waste iron plate can be used as the cathode during electrolysis.
When non-soluble lead-antimony alloy is used as an anode, the precipitate generated in the solution is mainly blue-gray chromium hydroxide precipitate; the anode adopts insoluble lead-antimony alloy and soluble iron plate which are arranged in a crossed way, and when the cathode is still the iron plate, the precipitate generated in the electrolytic process is mainly the mixed precipitate of chromium hydroxide and brownish red ferric hydroxide.
The invention is characterized in that hexavalent chromium in wastewater is treated by direct electrolytic reduction in an alkaline medium, and the electrolytic principle is as follows:
lead-antimony alloy is used as anode, iron plate is used as cathode, or the anode adopts insoluble lead-antimony alloy and soluble iron plate which are arranged in a crossed way, the cathode is still iron plate, and the anode is straight in an open diaphragm-free electrolytic cellElectrolyzing while stirring to reduce hexavalent chromium ion to trivalent chromium ion, and generating Cr3+Formation of Cr (OH)3Precipitating to achieve the aim of removing chromium. The main reaction formula is as follows:
an anode process:
or
And (3) cathode process:
sampling and analyzing, and when the hexavalent chromium content in the electrolyte is less than 5mg-1When the wastewater reaches the national discharge standard, the electrolysis is stopped.
The sediment is centrifugally dried for use, and the electrolytic solution can be recycled or discharged.
The electrolysis temperature should not be higher than 318.15K, but in a limited temperature range, the electrolysis reaction is favorably carried out when the temperature is higher.
The invention has the positive effects that:
1. the invention can directly electrolyze the chromium-containing wastewater flowing into the water collecting well, and can insert polar plates into the wastewater to electrolyze for a long time by introducing low voltage and low current, so that hexavalent chromium is reduced and removed. Because the electrode adopts lead-antimony alloy and waste iron plates, the material is convenient to obtain, the cost is lower, and a large amount of investment cost can be saved.
2. Before and after electrolysis, acid and alkali are not needed to be added to adjust the pH value of the solution, so that the process is simplified, the acid and alkali consumption is reduced, the operation cost is correspondingly reduced, and the operation is also simple.
The specific implementation mode is as follows:
example 1
Taking hexavalent chromium with the initial concentration of 6 mg.L-1320ml of the electrolyte solution is put into an electrolytic cell with the volume of 650ml, and 0.8gK is added2SO4Then, the mixture was stirred with a stirrer and heated to conduct electrolysis, and electrolysis was conducted while stirring. The anode adopts a lead-antimony alloy mesh electrode, the cathode adopts an iron plate with a uniformly drilled hole, and the area ratio of the cathode to the anode is 7: 1.
During electrolysis, hexavalent chromium is reduced to trivalent chromium at the cathode:
the trivalent chromium reacts with hydroxide ions in the electrolyte to generate precipitate:
the electrolytic reaction is carried out under alkaline conditions, the electrolytic voltage is about 2.2V, the initial pH value of the electrolyte is 11, the pH value is smaller and smaller along with the progress of the electrolytic process, and the pH value of the measured solution is close to neutral at the end of electrolysis. The electrolysis time is 6-12 hours. The greater the initial concentration of hexavalent chromium, the more time is consumed for electrolysis. Because the electrolytic voltage and the electrolytic current are both very small, an electrode plate can be inserted into the waste water storage pool for a long time, and low voltage and low current are introduced for electrolysis, so that hexavalent chromium is reduced into trivalent chromium, and the trivalent chromium is removed in a form of precipitation. Under the condition that the electrolytic voltage is about 2.2V, the distance between the polar plates is selected to be 4mm, and the adding amount of potassium sulfate is 1.5 g.L-1When the electrolyte is stirred at a medium speed, the reduction rate of the hexavalent chromium is highest.
TABLE 1 different initial pH values vs. Cr6+Influence of reduction speed of
pH value 9.0111.0012.91
Cr6+Initial concentration/mg. L-15.36 5.36 7.33
Cr6+End concentration/mg. L-10.31 0.22 0.78
Electrolysis time/min 125166720
Cr6+Reduction rate/% 94.2295.9089.36
The experimental conditions are as follows: the distance between the polar plates is 4mm, K2SO4The content of hexavalent chromium in the electrolyte is measured when the adding amount is 0.8g and the temperature is 294.15K for electrolysis for a certain time, and when the content of hexavalent chromium in the solution is less than 0.5mg·L-1When the electrolysis is stopped. The pH of the assay solution was close to 7. After the electrolysis, the precipitate is separated by filtration.
The above experiments were carried out three times in total, but the initial pH of the electrolyte was different for each time, and the results of the experiments are shown in table 1.
The experimental results are as follows: the electrolyzed waste water meets the national discharge standard, and the hexavalent chromium content is less than 0.5 mg.L-1。
Example 2
Taking hexavalent chromium with initial concentration of 25 mg.L-1320ml of the electrolyte solution is placed in an electrolytic cell with the volume of 650ml, and 0.8gK is added2SO4The anode and the cathode are both iron plates with uniformly drilled holes, and the area ratio of the cathode to the anode is 1: 1. Then, the mixture was stirred with a stirrer, heated and electrified to perform electrolysis, and electrolysis was performed while stirring. During electrolysis, the following chemical reactions occur:
an anode process:
and (3) cathode process:
hydroxide precipitate is separated out from trivalent chromium and trivalent iron in alkaline solution
In addition, trivalent chromium can also be precipitated as insoluble iron chromite salts
The trivalent chromium reacts with hydroxide ions in the electrolyte to generate precipitate:
the electrolytic reaction is carried out under alkaline conditions, the initial pH value of the electrolyte is 9, the pH value is smaller along with the progress of the electrolytic process, and the pH value of the measured solution is close to neutral at the end of the electrolysis. The electrolysis time was about 10 minutes. The larger the initial concentration of hexavalent chromium, the more time is required for electrolysis. Electrolytic voltage is about 2V, electricityThe decomposition temperature is normal temperature, the space between the polar plates is 4mm, and the adding amount of potassium sulfate is 1.5 g.L-1And (4) stirring the electrolyte at a medium speed, wherein the reduction rate of the hexavalent chromium is the highest.
Electrolyzing for a certain time to determine the content of hexavalent chromium in the electrolyte, wherein when the content of hexavalent chromium in the solution is less than 0.5 mg.L-1When the electrolysis is stopped. The pH of the assay solution was close to 7. After the electrolysis, the precipitate is separated by filtration.
The above experiments were carried out three timesin total, but the initial pH of the electrolyte was different for each time, and the results of the experiments are shown in table 2.
TABLE 2 comparison of electrolytic effectiveness of electrolytes at different initial pH values
pH value 7.019.0411.00
Cr6+Initial concentration/mg. L-125.07 25.05 25.10
Cr6+End concentration/mg. L-10.97 0.80 0.41
Reduction rate/% 96.6496.8298.72
The electrolysis conditions are as follows: the volume of the electrolyte is 320ml, K2SO4The addition amount is 0.8g, the temperature is 293.15K, the cell voltage is 2V, and the distance between polar plates is 4mm
The experimental results are as follows: the electrolyzed waste water meets the national discharge standard, and the hexavalent chromium content is less than 0.5 mg.L-1。
Claims (6)
1. An electrolytic treatment method of hexavalent chromium in industrial wastewater, which comprises the following steps:
preparing an electrolyte; selecting anode and cathode materials, and electrifying and electrolyzing; sampling and analyzing; treating sediments;
the method is characterized in that: (1) adding potassium sulfate as an additive into the alkaline chromium (VI) containing wastewater, wherein the adding amount of the potassium sulfate is as follows: adding 1.2-3.5 g of potassium sulfate into each liter of wastewater; (2) selecting anode and cathode materials, namely taking insoluble alloy as the anode and iron plate as the cathode or taking the insoluble alloy and solubleiron plate as the anode together, and electrifying direct current in an open diaphragm-free electrolytic cell, wherein hexavalent chromium is directly reduced to trivalent chromium at the cathode or reacts with divalent iron ions dissolved out from the anode in solution to be reduced to trivalent chromium, and the generated Cr3+Formation of Cr (OH)3Precipitating; the electrolysis temperature is less than or equal to 318.15K; (3) sampling and analyzing: when the hexavalent chromium content in the electrolyte is less than 5mg.L-1When the electrolysis is stopped.
2. The electrolytic treatment method of hexavalent chromium in industrial wastewater according to claim 1, wherein: the insoluble alloy is a lead-antimony alloy.
3. The electrolytic treatment method of hexavalent chromium in industrial wastewater according to claim 1, wherein: the insoluble lead-antimony alloy and soluble iron plate are used as anode, and the lead-antimony alloy and the iron plate are arranged in a cross way.
4. The electrolytic treatment method of hexavalent chromium in any industrial wastewater according to claims 1, 2 and 3, wherein: cell voltage: 1.8-3V, area ratio of yin and yang: 3: 1-8: 1, and the distance between polar plates: 2-8 mm, electrolysis temperature: 283.15K to 318.15K.
5. The electrolytic treatment method of hexavalent chromium in industrial wastewater according to claim 4, wherein: the sediment is centrifugally dried for use, and the electrolytic solution is discharged or recycled.
6. The electrolytic treatment method of hexavalent chromium in industrial wastewater according to claim 5, wherein: the waste iron plate is used as a cathode.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100381370C (en) * | 2006-06-14 | 2008-04-16 | 浙江大学 | System for removing and retrieving hexavalent chrome from wastewater |
| CN101723490A (en) * | 2009-11-17 | 2010-06-09 | 中国环境科学研究院 | Pulse electro-flocculation treatment process and device of berberine waste water |
| CN101321698B (en) * | 2005-11-30 | 2011-07-20 | 德诺拉工业有限公司 | Electrochemical treatment of solutions containing hexavalent chromium |
| CN102728602A (en) * | 2011-03-29 | 2012-10-17 | 栗田工业株式会社 | Processing method of solid objects having heavy metal |
| CN102887559A (en) * | 2011-07-21 | 2013-01-23 | 中国科学院生态环境研究中心 | Electrochemical reduction assistance-based biosorption integrated reactor and treatment method of hexavalent chromium-containing wastewater |
| CN105858991A (en) * | 2016-03-08 | 2016-08-17 | 侯绪华 | Chrome-containing wastewater treatment device |
| CN107720891A (en) * | 2017-11-21 | 2018-02-23 | 中国石油大学(华东) | A kind of method for promoting the reduction of heavy metal chromium ion electrochemical |
-
2004
- 2004-01-02 CN CN 200410010007 patent/CN1255327C/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101321698B (en) * | 2005-11-30 | 2011-07-20 | 德诺拉工业有限公司 | Electrochemical treatment of solutions containing hexavalent chromium |
| CN100381370C (en) * | 2006-06-14 | 2008-04-16 | 浙江大学 | System for removing and retrieving hexavalent chrome from wastewater |
| CN101723490A (en) * | 2009-11-17 | 2010-06-09 | 中国环境科学研究院 | Pulse electro-flocculation treatment process and device of berberine waste water |
| CN102728602A (en) * | 2011-03-29 | 2012-10-17 | 栗田工业株式会社 | Processing method of solid objects having heavy metal |
| CN102728602B (en) * | 2011-03-29 | 2015-10-14 | 栗田工业株式会社 | Containing the processing method of the solid of heavy metal |
| CN102887559A (en) * | 2011-07-21 | 2013-01-23 | 中国科学院生态环境研究中心 | Electrochemical reduction assistance-based biosorption integrated reactor and treatment method of hexavalent chromium-containing wastewater |
| CN102887559B (en) * | 2011-07-21 | 2014-03-19 | 中国科学院生态环境研究中心 | Electrochemical reduction assistance-based biosorption integrated reactor and treatment method of hexavalent chromium-containing wastewater |
| CN105858991A (en) * | 2016-03-08 | 2016-08-17 | 侯绪华 | Chrome-containing wastewater treatment device |
| CN107720891A (en) * | 2017-11-21 | 2018-02-23 | 中国石油大学(华东) | A kind of method for promoting the reduction of heavy metal chromium ion electrochemical |
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Assignee: Luxi Xinxing Chemical Industry Co., Ltd. Assignor: Zhengzhou University Contract fulfillment period: 2009.7.28 to 2022.7.28 contract change Contract record no.: 2009430000213 Denomination of invention: Hexa valence chromium in industriel waste water electrolysis treatment method Granted publication date: 20060510 License type: Exclusive license Record date: 2009.12.1 |
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Free format text: EXCLUSIVE LICENSE; TIME LIMIT OF IMPLEMENTING CONTACT: 2009.7.28 TO 2022.7.28; CHANGE OF CONTRACT Name of requester: LUXI COUNTY XINXING METALLURGICAL CO., LTD. Effective date: 20091201 |