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
  • C02F1/722—Oxidation by peroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/755—Nickel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/85—Chromium, molybdenum or tungsten
  • B01J23/86—Chromium
  • B01J23/866—Nickel and chromium
• • 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
  • C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
• • 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
  • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic 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
  • C02F2101/16—Nitrogen compounds, e.g. ammonia

Definitions

• the present invention relates to a process for decomposing hydrazine contained in an aqueous liquid such as water from a nuclear or thermal boiler, or any other industrial unit producing aqueous effluents containing hydrazine.
• the German patent application published under the number DE 36 44 080 proposes using hydrogen peroxide to purify industrial waste water containing in particular hydrazine, operating at a pH greater than 7 and in the presence of a salt d a heavy metal, such as copper sulphate, and / or a catalyst which may be potassium permanganate or a nickel, chromium or cobalt salt.
• the Japanese patent application published under the number JP 09234473 relates to a process for treating wastewater containing hydrazine, which essentially consists in adding hydrogen peroxide, as an oxidant, to the water to be treated. a copper-based compound as catalyst, and subjecting the hydrazine to oxidative decomposition by exposing it to air for 0.5 to 12 hours, the pH being maintained at a value of 10-11, 5.
• the object of the invention is to propose a process for decomposing hydrazine contained in water which does not have these drawbacks.
• the hydrazine contained in an aqueous liquid is reacted with at least one peroxide, in the presence of a catalyst comprising at least one metal alloy.
• the invention also relates to a device capable of implementing this method.
• FIG. 1 is a diagram showing a device according to the invention, capable of implementing the method according to the invention
• - Figure 2 is a graphical representation of the evolution curves of the hydrazine and hydrogen peroxide contents as a function of time, during the implementation of the method according to the invention and of a method of the prior art
• - Figure 3 is a graphical representation of the evolution curves, as a function of time, of the hydrazine contents of demineralized water, during three similar tests of implementation of the process according to the invention
• FIG. 4 is a graphic representation of the evolution curves, as a function of time, of the hydrazine contents of demineralized water and of water of the Seine type, during the implementation of the method according to the invention and a method of the prior art;
• FIG. 5 is a graphical representation of the evolution of the hydrazine and hydrogen peroxide contents as a function of time, during the implementation of the process according to the invention according to two successive phases;
• FIG. 6 is a graphical representation showing the evolution of the oxidant contents, namely hydrogen peroxide or sodium hypochlorite, during the implementation of the method according to the invention and three methods of prior art.
• hydrazine generally in the form of hydrazine hydrate, contained in any aqueous liquid, for example, waste water, water coming from nuclear or thermal boilers at the outlet of the die, or water coming from waste or accidental spillage of hydrazine, can be destroyed quickly, using a peroxide as an oxidant, following a reaction catalyzed by a solid catalyst that includes a metal alloy.
• an alloy of a transition metal is advantageously used.
• Catalysts comprising such an alloy have the particularity of self-regenerating during the process of decomposition of hydrazine.
• these catalysts have the advantage of not forming a passivating protective layer on their surface, a layer which would prevent the passage of electrons and would decrease their activity.
• these catalysts because they do not contain precious metals, have a relatively low Nernst potential, which amounts to saying that they easily transmit electrons to the environment.
• the surface of these catalysts corresponds to a metal-oxygen bronze. This type of structure is a very favorable condition for the reversibility of electron migration: the electrons are thus transmitted and recovered without generating metal cations in solution. As a result, the catalyst remains stable throughout the hydrazine decomposition process.
• a nickel-based alloy is used as an alloy of at least one transition metal.
• nickel-based alloys mention may be made of nickel and copper alloys, in particular those comprising from 25 to 35% of nickel and from 75 to 65% of copper, these percentages being expressed by weight relative to the total weight. of the alloy.
• alloys of nickel, cobalt and chromium in particular those comprising from 5 to 15% of nickel, from 80 to 60% of cobalt and from 15 to 25% of chromium, these percentages being expressed by weight by relative to the total weight of the alloy.
• the catalyst may be in the form of a metal grid or a strip of wire mesh.
• Catalysis is therefore of the heterogeneous type and, therefore, easy to implement.
• the peroxide On the surface of the catalyst, the peroxide is activated and generates OH- radicals, the oxidizing effect of which is very effective. Indeed, the electrochemical oxidation potential of an OH- radical is 2.8 V, against 1.78 V for hydrogen peroxide and 1.36 V for chlorine.
• the peroxide used can be organic or mineral.
• hydrogen peroxide is used.
• the decomposition of hydrazine by hydrogen peroxide can then be illustrated by the following simplified equation: N 2 H 4 + 2H 2 0 2 ⁇ N 2 + 4H 2 0
• Hydrogen peroxide is thus activated without any external energy supply (UV rays, etc.) or external oxygen and without forming by-products. Hydrogen peroxide is generally introduced in the form of an aqueous solution. The stability of the aqueous hydrogen peroxide solution is not affected by the catalyst as such.
• reaction does not release metals into the water during treatment. This has the great advantage of not causing induced pollution.
• the hydrazine / hydrogen peroxide molar ratio is generally between 1 and 4, preferably between 1.6 and 2.2.
• the duration of the reaction between hydrazine and hydrogen peroxide can be between 1 minute and 8 hours. Preferably, it is between 30 minutes and 3 hours.
• Another advantage of the process according to the invention is that it is not necessary to carry it out at a particular pH. It can therefore be implemented at a neutral pH or close to neutral, and there is also no need to maintain this pH at a particular value. However, it is desirable that the pH is not too low, as this could cause the metals in the catalyst to dissolve.
• the method according to the invention can be implemented in a very wide range of temperatures. Generally, it is carried out at a temperature between 15 and 60 ° C, and preferably between 20 and 25 ° C, so that it is not necessary to heat the reaction medium.
• the process according to the invention due to the automatic regeneration of the catalyst, exhibits a high reproducibility of the hydrazine decomposition reaction without loss of efficiency over time.
• It can be used to detoxify the water from nuclear or thermal boilers at the outlet of the pipeline, to decontaminate containers containing hydrazine or to safely decompose waste or accidental spillage of hydrazine.
• the method according to the invention can be implemented by means of a device essentially comprising:
• a catalyst comprising at least one metal alloy, this catalyst being in a container;
• the liquid to be treated loaded with hydrazine is placed in a tank 1 to which is connected by a line 2 a pump 3 whose outlet is connected by a line 4 to the inlet of a column 5 containing the catalyst 6.
• the peroxide is introduced in the aqueous liquid to be treated by means of a metering pump (not shown) and a pipe 7 preferably connecting to the pipe 4 upstream of the column 5.
• the operation of the pump 3 passes the aqueous liquid containing the hydrazine and the peroxide in the column 5, through the catalyst 6.
• the decontaminated aqueous liquid leaving the column 5 is brought back through a pipe 8 into the tank 1.
• the device according to the invention constitutes a system of "going around in circles" allowing to maintain a certain agitation of the liquid in contact with the catalyst.
• relatively low reagent concentrations for example hydrogen peroxide at 10% by weight of hydrogen peroxide.
• an exchanger can be added to the recirculation loop to regulate the exotherm. If the proportions of the reactants and the catalyst are chosen appropriately, the decomposition of the hydrazine can be maintained at ambient temperature with satisfactory kinetics.
• Example 1 Using the device in FIG. 1, the hydrazine contained in demineralized water solutions (pH approximately 7.2) is removed.
• the container is filled with 1 liter of demineralized water containing 463 mg of hydrazine (molar mass: 32 g). Then 9.2484 g of hydrogen peroxide containing 10% hydrogen peroxide (molar mass: 34 g) are added.
• the hydrazine / hydrogen peroxide molar ratio is therefore 0.534.
• the temperature remains substantially stable.
• the reaction is complete in about 2 hours.
• the pH progressively changes from 9 to 6. We make sure that it does not drop below 6, possibly adding sodium hydroxide.
• Example 1 In order to check the repeatability of the hydrazine elimination reaction, two successive new tests are carried out, as in Example 1, with the catalyst which has already been used in Example 1 and without changing or treating in no way whatsoever this catalyst during these two tests.
• Example 2 successive tests are carried out with the nickel / copper catalyst of Example 1, under conditions which are similar to those of Example 1.
• the water initially contains 400 ppm of hydrazine.
• the amount of hydrogen peroxide (in 10% solution in water) added is 9 ml.
• the amount of catalyst used is 2.0065 g / l.
• the catalyst is washed with demineralized water between the two tests.
• the hydrazine / hydrogen peroxide molar ratio is 0.49.
• the curves in FIG. 4 represent the variations in the contents of hydrazine and of hydrogen peroxide as a function of time, for tests 1 and 2 of this example. Given that in the absence of a catalyst, no difference as regards the kinetics of decomposition of hydrazine by hydrogen peroxide was observed between demineralized water and synthetic water of the Seine type, the curve obtained in Example 1 (see Figure 2) was added to Figure 4.
• Example 1 the curve obtained in Example 1 was also added to Figure 4 using a catalyst and deionized water.
• the yield of hydrazine decomposition is 100% and the amount of hydrogen peroxide consumed is 95.9%.
• Example 4 The purpose of this example is to show the maintenance of the efficiency of the process according to the invention in continuous mode operation.
• demineralized water containing 400 ppm of hydrazine is treated with a 10% aqueous solution of hydrogen peroxide, in the presence of the catalyst of Example 1.
• 400 ppm of hydrazine and 920 ppm of hydrogen peroxide are reinjected to carry out a second phase of decomposition of the hydrazine, in the same medium and without washing the catalyst.
• the amount of catalyst used is 2.0065 g / l.
• the hydrazine / hydrogen peroxide molar ratio is 0.47.
• the yield of hydrazine decomposition is 100%.
• the amount of hydrogen peroxide consumed is 93%.
• the reaction time is 2 hours.
• the hydrazine / hydrogen peroxide molar ratio is 0.444.
• the yield of hydrazine decomposition is 100%.
• the amount of hydrogen peroxide consumed is 85.2%.
• the reaction time is 30 minutes. The results are collated in the following table.
• Example 5 the method according to the invention is compared with the following methods of the prior art:
• process B implementing a homogeneous catalysis by means of an aqueous solution of copper sulphate; and - a process C where the catalyst is nonexistent and where the oxidant is no longer hydrogen peroxide but sodium hypochlorite.
• the starting aqueous solution is demineralized water containing 400 ppm of hydrazine. Hydrogen peroxide is used in a 10% aqueous solution.
• process B the copper sulphate is used in the form of an aqueous solution at 5 ppm of Cu.
• the sodium hypochlorite is in the form of an aqueous solution at 13.5% (weight / weight percentage) or 42 ° C1.
• the catalyst of Example 1 is used, at a rate of 2 g / 1.
• sodium hypochlorite leads to instant elimination of the hydrazine, but it has the disadvantage of requiring a high mass of oxidant, i.e. 149 g of sodium hypochlorite per 32 g of hydrazine and of introducing chloride sodium in the solution because hydrazine reacts with sodium hypochlorite to give sodium chloride, nitrogen and water.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Materials Engineering (AREA)
• Treatment Of Water By Oxidation Or Reduction (AREA)
• Catalysts (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=8864652

Family Applications (1)

Country Status (3)

Families Citing this family (3)

Family Cites Families (3)

• 2001
  • 2001-06-22 FR FR0108254A patent/FR2826354B1/fr not_active Expired - Fee Related
• 2002
  • 2002-06-18 WO PCT/FR2002/002097 patent/WO2003000597A1/fr not_active Ceased
  • 2002-06-18 EP EP02751267A patent/EP1401772A1/de not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events