Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F9/00—Multistage treatment of water, waste water or sewage
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
  • C02F1/4676—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electroreduction
• • 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
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
  • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/72—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
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F2001/46133—Electrodes characterised by the material
• • 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
  • C02F2101/163—Nitrates
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/20—Heavy metals or heavy metal compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
  • C02F2103/06—Contaminated groundwater or leachate
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4611—Fluid flow
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4612—Controlling or monitoring
  • C02F2201/46145—Fluid flow
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4618—Supplying or removing reactants or electrolyte
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4618—Supplying or removing reactants or electrolyte
  • C02F2201/46185—Recycling the cathodic or anodic feed
• • 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
  • C02F2209/001—Upstream control, i.e. monitoring for predictive control
• • 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
  • C02F2209/003—Downstream control, i.e. outlet monitoring, e.g. to check the treating agents, such as halogens or ozone, leaving the process
• • 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
• • 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
  • C02F2209/15—N03-N
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

• the present invention relates to a method of chemical mixed electrochemical treatment of a liquid medium loaded with nitrates.
• the invention also relates to a device for treating such a liquid medium and the applications of this method.
• Liquid effluents resulting from the drainage of crop soils are subject to regulations aimed at reducing the amount of pollutants contained in these effluents.
• nitrates are particularly targeted.
• liquid effluents from drainage waters may contain a nitrate concentration of up to 3 g / L at a maximum flow rate of 31 m 3 / day / hectare.
• the maximum concentration of nitrates acceptable for the environment can be estimated at 50 mg / L.
• the invention provides a method of treating a liquid medium loaded with nitrates making it possible to reduce the concentration of nitrates and not requiring the use of organic species pollutants that could harm the environment.
• the invention also resides in a device for treating a liquid medium loaded with nitrates and in the possible applications of the process of the invention. To this end, the invention relates to a method of chemical mixed electrochemical treatment of a liquid medium loaded with nitrates.
• this process comprises a step of electrolysis of the liquid medium in the presence of a metal salt, the electrolysis being conducted at a pH below 5.
• the process comprises at least one step of forming an electrolytic solution by adding a metal salt to said liquid medium.
• the metal salt is a zinc metal salt.
• the pH of the electrolytic solution is maintained between 2 and 5.
• the electrolysis step is conducted with an anode and a graphite cathode or glassy carbon.
• the electrolysis step is conducted with a graphite anode and a solid zinc cathode.
• the method comprises a step of electrodialysis of the solution at the electrolysis outlet, the electrodialysis being used in demineralization of this solution, in order to form a demineralized effluent of zinc metal salt capable of being discharged.
• the electrodialysis is also used in ionic concentration of the solution at the electrolysis outlet, in order to form a concentrated effluent of metal salt able to serve as source of metal salt for the electrolysis step in the presence of salt. metallic.
• the electrodialysis step is conducted at room temperature. It is possible that the process comprises a step of recirculating the effluent concentrated in the metal salt to an enclosure in which the liquid medium undergoes the step of electrolysis in the presence of metal salt.
• the process comprises a step of oxidation of the ammonium ions of the liquid at the electrolysis outlet, through which a nitrate-rich effluent intended to be treated by electrolysis in the presence of a metal salt is obtained.
• the oxidation step of the ammonium ions is carried out with the chlorine dioxide CIO2 as oxidizing agent.
• the pH of the liquid undergoing the oxidation step of ammonium ions is acidic.
• the process comprises a step of recirculating the nitrate-rich effluent to an enclosure in which this liquid undergoes the electrolysis step in the presence of a metal salt.
• the method comprises a series of steps of electrolysis of the liquid medium in the presence of a metal salt of a transition metal, and of oxidation steps of the medium in the presence of an agent. oxidant, alternating with each other, the first step imposed on the medium being an electrolysis step.
• each electrolysis step and each oxidation step are conducted respectively within an electrolysis compartment and an oxidation compartment, and an electrolysis compartment is located below a compartment.
• the gaseous species produced within an electrolysis compartment being absorbed by the liquid contained in the oxidation compartment above, the passage of the medium to be treated being carried out from the compartment from the lowest electrolysis to the highest oxidation compartment.
• the method comprises a step of electrodialysis of the medium leaving the series of compartments by which is formed a solution enriched in metal salt, and a depleted solution of metal salt.
• the method comprises a step of recirculating the solution enriched in metal salt at the inlet of the first electrolysis compartment.
• the method comprises a step of determining the number of couples "compartment of electrolysis / compartment of oxidation" as a function of the concentration of nitrates ions of the medium to be treated.
• the invention also relates to a device for the chemical treatment of a liquid medium loaded with nitrates.
• This device comprises an electrolytic solution containing the medium to be treated in admixture with a metal salt of a transition metal, an electrolysis chamber accommodating the electrolytic solution, a supply source of a medium loaded with nitrates, and means for regulating the pH of the electrolytic solution below 5.
• This enclosure comprises a liquid inlet to be treated, a treated liquid outlet, a source for supplying a metal salt, and a means for mixing the liquid medium to be treated. with the metallic salt of the source.
• the metal salt is more particularly a zinc metal salt.
• the device comprises means for regulating the concentration of metal salt in the liquid passing through the chamber.
• it comprises at least one pH regulator for maintaining the liquid passing through the electrolysis chamber at a pH of less than 5.
• this device comprises an electrodialyzer mounted at the outlet of the electrolysis enclosure and provided with a metal salt enrichment column and with a metal salt depletion column connected to an electrolysis chamber. evacuation of the treated liquid medium.
• the metal salt enrichment column is then connected to the inlet of the electrolysis chamber and serves as a source of metal salt.
• An improvement consists in providing the device with an oxidation unit of an effluent charged with ammonium ions mounted at the outlet of the electrolysis chamber in order to oxidize the ammonium ions of the effluent in nitrate ions, the latter being intended to be treated within the electrolysis chamber.
• This oxidation unit comprises a liquid inlet communicating with the outlet of the electrolysis chamber, a liquid outlet loaded with nitrate, an inlet of an oxidizing agent called chlorine dioxide (CIO2), and a mixing means. liquid passing through the oxidation unit with the oxidizing agent, the pH of the liquid passing through the oxidation unit being close acid.
• the liquid outlet of the oxidation unit is then connected to the inlet of the electrolysis enclosure, for the purpose of the electrochemical chemical mixed treatment of this liquid.
• the invention also relates to the use of the method and the device described above for treating any liquid medium charged with nitrates.
• the liquid medium is constituted by crop drainage waters.
• the invention further relates to a method for the chemical treatment of a liquid medium charged with ammonium ions, comprising at least one step of oxidizing the ammonium ions.
• This oxidation step is carried out by means of an oxidizing agent called chlorine dioxide (CIO2) •
• the pH of the solution undergoing the ammonium ion oxidation step is acidic.
• the invention also relates to a device for the chemical treatment of a liquid medium filled with ammonium, comprising an ammonium ion oxidation unit.
• the oxidation unit comprises a liquid inlet loaded with ammonium ions, a liquid outlet loaded with nitrate ions, an inlet of an oxidizing agent called chlorine dioxide (CIO2), and a means for mixing the liquid to be treated with the oxidizing agent, the pH of the liquid passing through the oxidation unit being acidic.
• the electrolysis chamber comprises several electrolysis compartments
• the oxidation unit comprises a plurality of oxidation compartments, the electrolysis and oxidation compartments being connected in series and in series. alternating from each other, the first compartment through which the medium to be treated is an electrolysis compartment.
• an electrolysis compartment comprises two electrodes in the form of plates arranged facing each other and located on either side of the axis of the column. In this case, an oxidation compartment is delimited by two plates permeable in the middle, arranged perpendicular to the axis of the column.
• an electrolysis compartment comprises two electrodes in the form of plates arranged opposite one another and intersecting with the axis of the column. In this case, an oxidation compartment is delimited by the electrodes of the electrolysis compartments located above and below this oxidation compartment.
• the device comprises a supply source of an oxidizing agent connected to each oxidation compartment by a tube opening between the elements delimiting the oxidation compartment concerned.
• each electrolysis compartment comprises a stirrer.
• the device comprises an electrodialyzer, mounted at the outlet of the column, and producing a solution enriched in metal salt and a solution depleted of metal salt.
• the device comprises a recirculation line of the solution enriched with metal salt towards the inlet of the column.
• the invention finally relates to the use of the above method and device for treating any liquid medium charged with ammonium ions.
• FIG. 1 is a schematic diagram a first embodiment of a chemical electrochemical mixed treatment device of a liquid medium charged with nitrates according to the invention
• FIG. 2 illustrates the evolutions of the concentrations of nitrate ions during three experiments carried out on a stock solution containing a known initial concentration of nitrates in the presence of a zinc electrode, without current applied to the electrode and without zinc ions at the start (diamond curve), with current and without zinc ions at the beginning (square curve), with current and initially with zinc ions (triangular curve);
• FIG. 3 is a figure similar to that of FIG. 2, but which illustrates the evolutions of the concentrations of nitrite ions
• FIG. 4 is a figure similar to that of FIG. 2 but which defines the evolutions of the concentrations of zinc ions
• FIG. 5 shows the evolutions of the zinc ion concentrations of the two electrodialysis depletion columns of the device of FIG. 1
• FIG. 6 shows the evolutions of the zinc ion concentrations of the enrichment column of the electrodialyzer of FIG. 1
• FIG. 7 represents a block diagram of a second embodiment of the mixed-channel treatment device
• FIG. 8 represents an alternative embodiment of the electrolysis compartments of the device of FIG. 7.
• FIG. 1 shows a first embodiment of a device for the electrochemical chemical mixed treatment of a liquid medium charged with nitrates according to the invention.
• This device 1 mainly comprises an electrolysis chamber 2 using a metal in ionic form to reduce the nitrate concentration of the medium to be treated at low pH.
• the metal is selected with respect to its ability to donate electrons and catalyze the reduction of nitrate ions.
• Transition metals are particularly suitable for these applications, especially those of the most straight columns of Mendeleyev's table.
• a working solution is formed by mixing the medium to be treated with a solution enriched with zinc ions.
• This solution is introduced at the inlet of the electrolyzer 2 so that the nitrate ions it contains are reduced.
• a portion of the liquid already treated by the electrolyser 2 is fed from the outlet of the latter to the inlet 8 of the electrolyser 2 by means of a recirculation line 5 in order to undergo again the medium already treated, an electrolysis in the presence of ionic zinc to further reduce the nitrate concentration of this medium.
• the device according to the invention comprises a pH regulator connected to the chamber in which the electrolysis is conducted.
• the device comprises an electrodialyzer 3 and an ammonium ion oxidation unit 4, both mounted at the output of
• electrolyzer 2 to treat the zinc respectively in ionic form that was used during the electrolysis and the ammonium ions generated during this same electrolysis.
• the electrodialyzer 3 allows on the one hand the depletion in zinc ions of a part of the liquid coming out of the electrolyser 2, which will be able to be evacuated, and the enrichment in zinc ions of the other part of the liquid which will be reused as a source of zinc ion supply within the electrolyser 2.
• the device comprises a recirculation line 7 connecting the output of the enrichment column of the electrodialyzer 3 to the inlet of the
• the device according to the invention comprises a regulator which controls the opening of the inlet valve of the concentrated solution of ionic zinc coming from the electrodialyzer. .
• the oxidation unit 4 used to treat the liquid leaving the electrolyzer 2, containing ammonium ions, one of the products of the nitrate ion transformation, comprises a source of an oxidizing agent and a pH control means.
• the oxidizing agent chosen is chlorine dioxide CIO2 which reacts, under controlled pH, with the ammonium ions to be removed in order to reform nitrate ions which will be reprocessed in the electrolyser 2.
• the output of the ammonium ion oxidation unit is connected via a line 9 to the inlet of the electrolyser 2.
• the device according to the invention operates in a closed loop and allows the discharge of an effluent that complies not only with the standards for nitrate rejection. and ammonium, but also zinc ion rejection standards.
• the electrodes used are a vitrified carbon electrode and a zinc electrode (surface of 20 cm 3 ).
• the concentration of nitrate ions becomes zero after three hours of electrolysis, whereas with electrolysis current and without zinc ions (square curves), only a low concentration of nitrate ions and not zero, could be reached (33 mg.L " ⁇ ) and only after 7 hours of electrolysis.
• electrolysis current and without zinc ions square curves
• only a low concentration of nitrate ions and not zero could be reached (33 mg.L " ⁇ ) and only after 7 hours of electrolysis.
• there remains 274 mg .L "1 of nitrate ions diamond curve. Consequently, the initial presence of zinc ions in the electrolytic solution makes it possible to reduce the time required for the reduction of nitrate ions by more than twice compared to experiments without zinc ions at the start of the electrolysis.
• the electrical efficiency represents the ratio in percentage of the amount of theoretical current required to reduce the nitrate ions to ammonia on the amount of current consumed.
• an electrolyser cooperating with a metal salt source is adapted to form the base of the treatment device according to the invention.
• an electrodialyser of three reservoirs was filled with a solution of known ionic zinc concentration, independently of the electrolyser 2.
• This electrodialyzer is of batch type, and provided with a metal salt enrichment column, two metal salt depletion columns connected to a discharge line of the treated liquid medium and a zinc electrode.
• the solution of known concentration of ionic zinc is prepared with zinc chloride and its temperature is maintained at room temperature.
• the pH and conductivity of the medium were monitored continuously.
• the stirring was done through circulation pumps connected to each compartment.
• the circulation loop of the zinc ions thus formed is almost autonomous, so as to limit the amounts of zinc ions necessary for the treatment of nitrates.
• the device according to the invention is provided with an oxidation unit mounted at the outlet of the electrolysis chamber in order to oxidize the ammonium ions of the effluent.
• CIO2 for example produced by mixing HCl from the storage unit 13 and NaClO from the storage unit 12
• HCl for example produced by mixing HCl from the storage unit 13 and NaClO from the storage unit 12
• a solution comprising ammonium ions at a given time to reach a concentration close to 5% in volume
• oxidant concentration plays an important role at the level of the abatement but not very important in terms of kinetics.
• a solution containing ammonium ions can be treated with low pH C102 to remove almost 100% of these ammonium ions.
• One of the products of the oxidation of these ammonium ions are the nitrate ions.
• these nitrate ions can ideally be redirected to the entrance of the electrolysis enclosure 2 in order to be eliminated.
• the oxidation unit integrated in the device according to the invention will thus comprise a liquid inlet communicating with the outlet of the electrolysis chamber, a liquid outlet loaded with nitrate, an inlet of an oxidizing agent called chlorine dioxide. (CIO2), and a means for mixing the liquid passing through the oxidation unit with the oxidizing agent.
• a liquid inlet communicating with the outlet of the electrolysis chamber, a liquid outlet loaded with nitrate, an inlet of an oxidizing agent called chlorine dioxide. (CIO2), and a means for mixing the liquid passing through the oxidation unit with the oxidizing agent.
• CIO2 chlorine dioxide
• the pH of the liquid passing through the oxidation unit is kept close to 2 through the pH indicated in FIG. 1, and the HCl storage unit 13.
• the liquid outlet of the oxidation unit is connected to the inlet of the electrolysis chamber, for the electrolysis treatment of this liquid.
• the oxidation unit described above is ideally integrated within the device according to the invention because it makes it possible to treat the effluents at the outlet of the electrolyser to deplete them in ammonium ions and is connected to the input of the electrolyser 2 so that the latter eliminates the nitrates reformed.
• this oxidation unit can be used independently of the electrolyser of the device according to the invention, to treat any effluent charged with ammonium ions.
• CIO2 as an oxidizing agent is particularly suitable for the oxidation of ammonium ions since, on the one hand, this agent has a high oxidizing power with respect to ammonium ions and thus reacts quickly and naturally with these, and that on the other hand, it does not react with zinc ions and remains in solution for the treatment of ammonium ions.
• the device according to the invention provided with one electrolyzer, the electrodialyzer and the oxidation unit as described above, can advantageously be controlled by an autonomous control system, able to manage the openings of the control valves.
• 14 connecting lines between these three elements and the supply line of medium to be treated 16 depending on the concentrations of nitrate ions, zinc ions and ammonium ions recorded at the output of the electrolyzer, the electrodialyzer and the oxidation unit, in order to optimize the treatment of the liquid medium and to purify the treated effluent.
• FIG. 6 The second embodiment of the device for the electrochemical chemical mixed treatment of a liquid medium charged with nitrates according to the invention is illustrated in FIG. 6.
• the working solution resulting from the mixing of the effluent to be treated with a solution enriched with zinc ions, circulates from bottom to top within a receptacle arranged vertically and comprising an alternation of electrolysis compartments and oxidation compartments in the presence of CIO2.
• the first compartment through which the working solution passes during its path through the nitrate treatment column is an electrolysis compartment 2A, in order to reduce a portion of the nitrate ions that it contains, which are converted into ammonium ions, into nitrogen, and nitrogen oxides NOx.
• the second compartment through which this solution passes is an oxidation compartment 4A in the presence of C10 2 so that the ammonium ions formed in the underlying electrolysis compartment 2A are oxidized and converted into nitrate ions. Since the oxidizing agent used (C1O2) has a high oxidation power, all the ammonium ions that reach this oxidation compartment are converted into nitrate ions.
• the third compartment through which the solution then passes is again an electrolysis compartment 2B, in order to reduce on the one hand the nitrate ions which had not been reduced during the electrolysis conducted in the first electrolysis compartment 2A, and on the other hand to reduce the nitrate ions produced within the underlying oxidation compartment 4A.
• the compartments 4B, 2C, 4C, which the solution then passes through respect the alternation between the oxidation compartment and the electrolysis compartment and still allow the reduction of the nitrates which have not been reduced in the underlying electrolysis compartments, and that of the nitrates produced within the underlying oxidation compartments.
• the last compartment crossed by the solution is a 4C oxidation compartment.
• an electrolysis and oxidation compartment "stage" as indicated by 20 in FIG. 7 allows a 50% reduction of the incoming nitrate ions.
• this vertical arrangement makes it possible to dissolve a particularly undesirable gaseous species constituted by the chlorine formed in the electrolysis compartments 2A, 2B, 2C because of the presence of C10 2 in the solution passing through the nitrate treatment column 21.
• the CIO2 is injected at the level of the oxidation compartments 4A, 4B, 4C, this CIO2 is found at the level of the electrolysis compartments 2A, 2B, 2C since the solution flows from one compartment to another. At the level of these electrolysis compartments, the CIO2 also undergoes a reduction which produces chlorine CI2.
• the nitrate treatment column 21 is constituted by a cylindrical tube 22 supplied with working solution via a pipe 23, opening in its lower part and delivering from its upper part the solution treated by a pipe 24, the solution circulation from bottom to top.
• This tube is separated into three stages 2OA, 2OB, 2OC each split into an electrolysis compartment and an ammonium ion oxidation compartment as described below.
• Each electrolysis compartment 2A, 2B, 2C is delimited by two circular horizontal electrode plates 25, 26, 27, 28, 29, 30 arranged concentrically along the axis of the column, between which a difference of potential by means of a power source 43.
• the lower plates 25, 27 and 29 of the electrolysis compartments 2 are brought to a potential lower than that of the overlying plate 26, 28, 30.
• a rotary stirrer 34 actuated by means of an axis 35 driven by a motor 36.
• This axis 35 coincides with that of the column 21 and passes through the plates 25, 26
• the passage from the solution of an electrolysis compartment to the overlying oxidation compartment takes place through this opening 32. Because of the potential difference existing between the two plates 25, 26 of the same electrolysis compartment, the solution which passes between it undergoes electrolysis during which the nitrate ions are reduced for the most part.
• the first 4A and second 4B oxidation compartments are each delimited by the upper plate 26, 28 of the underlying electrolysis compartment and by the lower plate 27, 29 of the overlying electrolysis compartment.
• CIO2 is introduced by means of a tube 37 connected to a source 4 of CIO2.
• the plates 26 and 27 on the one hand and 28 and 29 on the other hand, which delimit the oxidation compartments 4A, 4B are subjected to a potential difference since the plates of the column are fed alternately negatively and positively. This potential difference is also equal to that imposed within each electrolysis compartment.
• Compartments 4A, 4B are therefore oxidation-electrolysis compartments.
• the two plates defining an oxidation compartment have identical potentials, so that these compartments are not the seat of an electrolysis, but only an oxidation.
• the third oxidation compartment 4C is delimited by the upper plate 30 of the underlying electrolysis compartment 2C and by the upper part of the column.
• Electrodes electrolysis compartments are not circular and horizontal but rectangular and vertical.
• Two electrodes of this type 25, 26; 27, 28; 29, 30 are arranged facing each other and each along the wall of the column 21. A voltage difference is imposed between the two electrodes of the same compartment.
• An agitator 34 is again interposed between the two electrodes.
• the first 4A and second 4B oxidation compartments of the variant embodiment of FIG. 8 are delimited by two plates 51, 52 between which the strong oxidant CIO2 is injected. These plates 51, 52 are provided with an opening for the passage of the axis of rotation of the electrolysis chamber stirrers 34, which also ensures the passage of the solution from or to an electrolysis compartment.
• the last oxidation compartment 4C is delimited in its lower part by a plate 51 and in its upper part by the top of the column 21.
• this solution contains a high concentration of zinc ions, higher than the standards of rejection. It is redirected to an electrodialyzer 3 as described above, in order to prepare from this solution a liquid enriched in zinc ions which will be recycled, and a liquid depleted of zinc ions and meeting the standards of rejection, which will be evacuated without further treatment. .
• the liquid enriched with zinc ions is redirected to the inlet of the nitrate treatment column 21 by means of line 7 and the associated control valve 14.
• an adjustment in zinc ions may be performed by means of a tank provided for this purpose 44, mounted on the recirculation pipe 7.
• the device according to the invention provided with the reservoir
• control system autonomous capable of managing the openings of the regulating valves 14 of the connection pipes between these four elements, as a function of the concentrations of nitrate ions, zinc ions, C102 ions and ammonium ions detected within the circuit, in order to optimize the treatment of the medium liquid and to meet the current discharge standards.
• the number of stages of the nitrate treatment column 21 can be adapted as a function of the nitrate ion concentration of the solution to be treated in order to reach a desired nitrate concentration at the column outlet, since it is possible to to determine a percentage of nitrate reduction carried out by a stage,
• the flow rate of the solution passing through the column may be adapted depending on the desired nitrate concentration at the column outlet 21, for example to increase the residence time of the solution within the column,
• the injection of CIO2 may be adapted as a function of the flow rate of the solution and / or function of compounds other than the nitrate ions present in the initial solution.
• the injection of CIO2 may be adapted as a function of the flow rate of the solution and / or function of compounds other than the nitrate ions present in the initial solution.
• counting only nitrate ions about 200 mg of CIO2 per gram of nitrate ions are sufficient for the oxidation of ammonium ions resulting from the electrolysis of nitrate ions.
• 230 to 240 mg per grams of nitrates of CIO2 will then be necessary,
• each electrolysis compartment can also be adapted as a function of the gas evolution observed within these electrolysis compartments to achieve a complete dissolution of these gases, the temperature of the solution traversing the relatively small column (ambient temperature ) slows the precipitation of iron ions in the form of complexes, and also the evolution of chlorine.

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• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Water Treatment By Electricity Or Magnetism (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Treatment Of Water By Oxidation Or Reduction (AREA)

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• 2007
  • 2007-06-19 FR FR0755851A patent/FR2917734B1/fr not_active Expired - Fee Related
• 2008
  • 2008-06-19 WO PCT/FR2008/051106 patent/WO2009004257A2/fr active Application Filing
  • 2008-06-19 US US12/665,363 patent/US8591721B2/en not_active Expired - Fee Related
  • 2008-06-19 JP JP2010512752A patent/JP5228242B2/ja not_active Expired - Fee Related
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  • 2008-06-19 CA CA002691535A patent/CA2691535A1/fr not_active Abandoned
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