Classifications

• • 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
  • C02F1/76—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens
• • 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
  • C02F2101/16—Nitrogen compounds, e.g. ammonia
  • C02F2101/18—Cyanides
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2209/00—Controlling or monitoring parameters in water treatment
  • C02F2209/06—Controlling or monitoring parameters in water treatment pH

Definitions

• the present invention relates to a method for treating cyanide-containing wastewater, and more particularly, to a method for treating cyanide-containing wastewater by an alkali chlorine method.
• the alkali chlorine method is the most widely used method for treating cyanide-containing wastewater discharged from industrial facilities such as plating factories, steelworks, smelters, power plants, and coke factories.
• a chlorine source for example, sodium hypochlorite is added to cyanide-containing wastewater under alkalinity to oxidize cyanide in the wastewater (Patent Documents 1 and 2).
• Patent Document 2 describes a method of treating cyanide-containing wastewater containing ammonia by a two-stage reaction of the alkali chlorine method.
• An object of the present invention is to solve the above-mentioned conventional problems and to provide a method for treating cyanide-containing wastewater that can sufficiently oxidatively decompose cyanide compounds even when the cyanide-containing wastewater contains ammonium ions and organic matter. To do. Moreover, an object of this invention is to provide the processing method of the cyanate containing waste_water
• the method for treating cyan-containing wastewater of the present invention is a method for treating cyanide-containing wastewater in which a cyanide is decomposed by adding a chlorine source to cyanide-containing wastewater containing cyanide, wherein the cyanate-containing wastewater contains ammonium ions and organic matter.
• the pH of the cyanate-containing wastewater is 11 or more, and the chlorine source is added so that the free residual chlorine concentration is 0.1 mg / L or more even after the cyanide decomposition reaction.
• chlorine source at least one of sodium hypochlorite, chlorine and bleaching powder is preferable.
• a phosphonic acid scale inhibitor is further added to the cyanate-containing wastewater.
• the phosphonic acid-based scale inhibitor is preferably at least one selected from 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and salts thereof.
• the chlorine source is preferably added so that the free residual chlorine concentration is 0.1 to 1 mg / L.
• an alkali agent to the cyanate-containing wastewater to adjust the pH to 11 to 12.5.
• the concentration of soluble iron in the cyanate-containing wastewater is 0.4 mg / L or less.
• the water temperature of the cyanate-containing wastewater is preferably 40 ° C. or higher, for example 40 to 80 ° C., particularly 50 to 70 ° C.
• a chlorine source is added at a pH of 11 or more to cyanide-containing wastewater containing ammonium ions and organic matter.
• the pH is 11 or more, the reaction between the chlorine source and ammonium ions is suppressed, whereby the generation of bonded chlorine is suppressed, and as a result, the generation of cyan due to the reaction between the combined chlorine and organic matter is also suppressed.
• the generation of scale is prevented (including suppression) by adding a phosphonic acid scale inhibitor to the cyanate-containing wastewater.
• an alkali agent to make the pH 11 or more.
• this alkaline agent and scale inhibitor are mixed and added as a single solution, scale troubles in the chemical injection (chemical injection) pump and chemical injection piping are prevented.
• the pH is preferably 11 or more even after completion of the cyanide decomposition reaction.
• cyanide-containing wastewater to be treated is discharged from industrial facilities such as a plating plant, a power plant, a steel mill, a smelter, a coke production plant, and cyan is a metal cyan complex such as Ni, Ag, Although the cyan containing waste water contained as a cyan complex of metals, such as Cu, Zn, Cd, is illustrated, it is not limited to this.
• the cyan concentration of such cyanate-containing wastewater is about 0.1 to 100 mg / L, and the pH is about 6 to 10.
• cyanide-containing wastewater containing ammonium ions and organic substances is treated.
• the concentration of this ammonium ion is preferably 5 mg / L or more, for example, about 5 to 250 mg / L.
• organic substances include those derived from coal and coke, and the concentration is preferably 1 mg / L or more, for example, about 1 to 30 mg / L.
• the cyan-containing wastewater to be treated by the method of the present invention preferably has a total cyan concentration of iron cyano complex of 1.0 mg / L or less and a concentration of soluble iron of less than 0.4 mg / L. .
• Examples of chlorine sources added to cyanide-containing wastewater include chlorine, bleached powder, and sodium hypochlorite.
• Examples of phosphonic acid scale inhibitors to be added to cyanate-containing wastewater include 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), and those At least one selected from these salts is exemplified, and examples of the salt include sodium salt and potassium salt, among which 1-hydroxyethylidene-1,1-diphosphonic acid is preferable.
• the pH of the cyanate-containing wastewater is adjusted to 11 or more, preferably 11 to 12.5, particularly 11 to 12 by adding an alkali such as NaOH and / or KOH as necessary.
• the alkali addition may be performed before or after the addition of the chlorine source, or may be performed simultaneously. If the pH of the cyanate-containing wastewater is 11 or more, the alkali may not be added. In addition, it is preferable that pH of the water after process reaction is 11 or more.
• the alkali agent and the scale inhibitor may be mixed to form one liquid. In this way, scale generation in the chemical injection pump and chemical injection piping is prevented.
• the amount of scale inhibitor added is preferably determined experimentally according to the water quality of the cyanate-containing wastewater, but in the usual case, it is preferably about 1 to 100 mg / L, particularly about 5 to 30 mg / L.
• the amount of chlorine source added is controlled such that the free residual chlorine concentration after the reaction is 0.1 mg / L or more, preferably 0.1 to 1 mg / L, particularly 0.1 to 0.5 mg / L.
• the predetermined value is preferably a value selected from 0 to 0.1 mg / L / min.
• the residence time in the tank is made longer than the reaction end time.
• the free residual chlorine concentration measured at the reaction vessel outlet is preferably treated as the free residual chlorine concentration after the reaction.
• the pH is set to 11 or more, so that the generation of bonded chlorine is suppressed, and the generation of cyanide due to the reaction between the bonded chlorine and organic matter is also suppressed. Moreover, scale adhesion is prevented by adding a scale inhibitor, and cyanide-containing wastewater can be treated stably.
• Cyanide is sufficiently decomposed by adding a chlorine source so that the free residual chlorine concentration after the reaction is 0.1 mg / L or more.
• a chlorine source so that the free residual chlorine concentration after completion of the reaction is 0.1 mg / L or more.
• the free residual chlorine concentration after completion of the reaction is 1 mg / L or less.
• excessive addition of the chlorine source is prevented, and the cost of the chlorine source is suppressed.
• corrosion of metal materials, such as steel materials which comprise a liquid-contact member is also suppressed.
• the water temperature of the cyanide-containing wastewater is preferably 40 ° C. or higher, for example, 40 to 80 ° C., particularly about 50 to 70 ° C., thereby increasing the cyan decomposition reaction rate.
• the cyan decomposition rate is increased, the contact time between the water to be treated containing free residual chlorine and the liquid contact member made of steel or the like is short, and corrosion of the liquid contact member is suppressed.
• the water temperature is preferably 80 ° C. or lower, particularly 70 ° C. or lower.
• an aqueous NaOH solution (concentration 48 wt%) is used as the alkaline agent
• an aqueous NaClO solution concentration 12 wt%) is used as the chlorine source
• HEDP, PBTC acrylic acid polymer (polyethylene is used as the scale inhibitor).
• Sodium acrylate (weight average molecular weight 3500)) or maleic acid polymer (isobutylene / maleic anhydride copolymer sodium salt (weight average molecular weight 15000) was used.
• the total CN analysis was performed by adding L (+)-ascorbic acid to reduce residual chlorine, adjusting the pH to 12 with NaOH, and measuring by a 4-pyridine-pyrazolone spectrophotometry method according to JIS K 0102 without filtration. .
• the scale prevention effect it judged based on the calcium ion concentration and the presence or absence of the scale adherence to the SUS test piece in the reaction vessel.
• test water As test water, the collected water from the following power generation facilities was used.
• Test water 50 mL was placed in a glass container with a lid, the water temperature was kept at 20 ° C., 40 ° C., 50 ° C. or 60 ° C., and an alkali agent and a chlorine source were added so as to satisfy the conditions shown in Table 1.
• the reaction time was as follows.
• Table 1 shows the pH after 5 minutes from the addition of the chemical and after the passage of each time, the added amount of NaClO, the residual chlorine concentration, the ORP and the total cyan concentration after the reaction time.
• free represents free residual chlorine.
• test water As test water, the collected water from the following power generation facilities was used.
• Example 8 Place 100 mL of test water in a 1000 mL beaker, keep the water temperature at 60 ° C., add an alkaline agent and a chlorine source under the conditions shown in Table 2, put an iron test piece, and stir with a stirrer (rotation speed 150 rpm) for 3 days. did. The results are shown in Table 2.
• a test piece made of iron (SPCC) was put in each beaker, and after 3 days, the water quality and the amount of corrosion were measured, the corrosion rate was measured, and the result was It is shown in Table 2.
• Example 8 As shown in Table 2, the corrosion rate of Example 8 having a lower free residual chlorine concentration is lower than that of Example 9.
• test water As test water, the collected water from the following power generation facilities was used.
• Test water 500 mL was placed in a beaker with a lid, the water temperature was kept at 25 ° C., 40 ° C., 50 ° C., 60 ° C. or 80 ° C., and an alkali agent and a chlorine source were added under the conditions shown in Table 3.
• the measured water quality after 60 minutes is shown in Table 3.
• Test water having a soluble iron concentration of 0.1 mg / L, 0.3 mg / L, 0.4 mg / L or 0.5 mg / L by adding an aqueous ferric chloride solution to the same power generation facility dust collection water as in Example 1. was prepared. Take 500 mL of each test water in a glass container with a lid, keep the water temperature at 60 ° C., add an alkaline agent so that the pH is 11 after the reaction, and the concentration immediately after adding the chlorine source is 33.5 mg / L. Was added and allowed to react for 60 minutes. Table 4 shows the measured water quality after 60 minutes.
• test water As test water, the collected water from the following power generation facilities was used. pH: 8.7 Total cyan: 3 mg / L, Ammonium ion: 120 mg / L, TOC: 10 mg / L, Soluble iron: less than 0.1 mg / L
• Test water 500 mL was placed in a glass container with a lid, the water temperature was kept at 60 ° C., and a scale inhibitor, an alkali agent and a chlorine source were added so as to satisfy the conditions shown in Table 1.
• the test piece made from SUS was put in the container. The reaction time was 60 minutes.
• Table 5 shows the pH after the elapse of 5 minutes and 60 minutes after the addition of the chemical, the added amount of NaClO, the calcium ion concentration after the elapse of the reaction time, the presence or absence of scale adhesion to the test piece, and the total cyan concentration.
• cyan can be sufficiently decomposed and scale is also prevented.
• Comparative Example 10 since the pH is less than 11, the residual cyan density is high.
• Comparative Example 11 no scale inhibitor was added, and scale was generated.
• Comparative Examples 12 and 13 a scale inhibitor was added, but the scale adhered because it was not a phosphonic acid scale inhibitor.

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• Life Sciences & Earth Sciences (AREA)
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• 2013
  • 2013-03-29 WO PCT/JP2013/059476 patent/WO2013147128A1/ja active Application Filing
  • 2013-03-29 KR KR1020147026020A patent/KR102054535B1/ko active Active
  • 2013-03-29 DE DE112013001804.7T patent/DE112013001804T5/de active Pending
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