Electrochemical method for generating persistent chain reactions in aqueous solutions

Abstract

This invention relates to a method for generating at least one long-half-life free radical via an electrochemical device having suitable electrode plates. The method comprises the steps of: passing an aqueous solution containing a contaminant to be removed through at least one pair of electrodes, through which a DC current is passed, such that at least one long-half-life free radical is generated, which initiates a persistent (i.e., continuous) chain reaction that consumes or degrades any contaminant, wherein the DC current is controlled to keep the potential difference across the electrochemical electrodes at a controlled rate, thereby reaching a precise value within a specific time.

Description

Technical Field

[0001] This invention relates to an electrochemical method for initiating a persistent chain reaction in an aqueous solution, which can propagate in a body of water without external influence, thereby removing various solutes from the water. This invention can be applied in many technical fields, including but not limited to (1) removal of PFAS (perfluoroalkyl and polyfluoroalkyl substances) from the environment; (2) capture and removal of carbon dioxide from the atmosphere; (3) removal of organic matter from the environment; (4) wastewater treatment; (5) drinking water treatment; (6) organic chemical manufacturing; (7) removal of perchlorates from the environment; (8) and other unidentified technical fields. Background Technology

[0002] Water is a universal and very effective solvent. In the aforementioned technical fields, there are times when it is necessary to remove contaminants or pollutants from aqueous solutions in order to reduce their concentration in the aqueous solution. Many existing processes can and are used to achieve this. These include biological processes, physicochemical processes, incineration processes, thermal processes, advanced oxidation processes, and several electrochemical processes. All of these currently available existing technological processes have the following disadvantages and some (if not all) drawbacks: (1) they are of limited effectiveness and only partially remove contaminants present in aqueous solutions; (2) they have very high capital costs; (3) they use a lot of energy, resulting in high operating costs; (4) they consume a lot of chemicals, which further increases the high operating costs; (5) these processes themselves cause further adverse environmental problems; and (6) they are difficult to control.

[0003] Therefore, the environmental challenges posed by pollutants and contaminants associated with the reference field have not been adequately addressed. One process that has been considered to address these challenges is electrochemical oxidation, particularly using boron-doped diamond (BDD) electrodes. When current is passed through an electrochemical device containing a BDD electrode, electrochemical oxidation has been shown to reduce the concentration of PFAS dissolved in aqueous electrolytes, reduce dissolved carbon dioxide, and degrade organic pollutants with high, near 100% current efficiency. However, electrochemical oxidation exhibits significant drawbacks and limitations. These drawbacks and limitations of electrochemical oxidation include, but are not limited to: (1) When used to remediate PFAS-contaminated water, this process only achieves partial degradation of some PFAS, producing short-chain PFAS as a byproduct, and generates harmful perchlorates during the reaction. In addition, the reaction rate is very slow, resulting in continuous high energy consumption.

[0004] (2) This process has been shown to reduce dissolved carbon dioxide to carbon monoxide, but the reaction rate is very slow and the energy consumption of the electrochemical electrode is very high. Therefore, this process is not economically feasible for carbon dioxide reduction. In addition, harmful perchlorate is produced as a byproduct.

[0005] (3) When used to degrade organic materials dissolved in wastewater, the reaction rate is slow, resulting in high energy consumption costs, incomplete reactions, undesirable byproducts, perchlorate, and the process efficiency varies depending on the pollutants present in the wastewater.

[0006] (4) In all its applications, the mass of contaminants or pollutants removed by electrochemical oxidation is proportional to the area of ​​the electrode on which it is mounted. Boron-doped diamond electrodes are expensive, and therefore the capital cost of this process is very high.

[0007] (5) The amount of pollutants removed is directly proportional to the energy applied, resulting in high energy consumption.

[0008] Clearly, electrochemical oxidation is not a viable solution to the environmental challenges of the field mentioned above. There is a persistent and, in fact, urgent need for effective and economical means to address the environmental problems described here, as well as many others. A simple, low-cost, high-performance process would help address the environmental pressures we face today. Summary of the Invention

[0009] This invention fully addresses this need by providing a unique method for degrading pollutants to be removed from aqueous solutions, comprising electrochemically initiating a persistent (i.e., continuous) chain reaction in the aqueous solution, which proceeds with minimal external influence to consume the pollutants to be removed.

[0010] Specifically, the benefits and advantages of the method of the present invention can be summarized as follows: (1) It degrades all organic pollutants and target inorganic pollutants in aqueous solution non-selectively at very low cost; (2) It degrades all PFAS to very low concentrations; (3) It reduces dissolved carbon dioxide in water at low cost; (4) It eliminates dissolved ammonia nitrogen and nitrates in water at low cost; (5) It reduces inorganic phosphates and organic phosphates from aqueous solution; (6) It eliminates many inorganic compounds from any water, including but not limited to sulfides and perchlorates; (7) It generates at least one long half-life free radical at low temperature and low pressure, which can be used in other processes that require the generation of free radicals; (8) Once initiated, the chain reaction is not affected by the analytical properties of the aqueous solution; (9) Once initiated, the chain reaction does not require a large amount of additional energy input and can proceed to termination without external influence; (10) And it has a low cost of ownership.

[0011] The important objects, features and additional advantages of the present invention will become apparent to those skilled in the art from the foregoing, the following detailed description, and the appended claims in conjunction with the accompanying drawings. Attached Figure Description

[0012] For a more complete understanding of the present invention and its novel features and advantages, please refer to the following detailed description taken in conjunction with the accompanying drawings, wherein: Figure 1 A general process flow diagram is shown for systems employing the method of the present invention in various applications and with various water supply functions; Figure 2 This demonstrates how power is applied in the method of the present invention; and Figure 3 A process flow diagram of the equipment used in a series of laboratory tests incorporating the methods of the present invention is shown.

[0013] The foregoing figures are merely exemplary and contain various steps, which may be included or omitted in the actual implementation as appropriate.

[0014] The drawings are intended to illustrate at least those elements that are meaningful for understanding the various embodiments and aspects of the invention. However, various other method steps can be used to provide a complete processing system for use in a particular set of situations. Detailed Implementation

[0015] Now refer to the attached diagram, Figure 1 This is a general process diagram illustrating one application of the method of the present invention for treating industrial wastewater. Feed water (industrial wastewater 10 containing organic compound solutes) is provided in storage tank 12. The wastewater is directed to the inlet of pump 20 and then to the inlet of electrochemical electrode 30. Electrochemical electrode 30 comprises at least two electrodes made of boron-doped diamond (BDD), designed such that wastewater can flow between and contact the at least two pairs of electrodes. In an embodiment, electrochemical electrode 30 comprises several pairs of BDD electrodes designed to form a parallel flow through the unit. The water is then returned to storage tank 12. Power supply 40 is connected to electrochemical electrode 30, and according to… Figure 2The power curve shown indicates that at least one direct current is applied through the electrochemical electrode 30. One power cycle is all that is needed to initiate a persistent chain reaction in the aqueous solution, although several cycles can be applied rapidly and continuously. The power is then turned off. The application of power generates at least one long-half-life free radical, which is maintained in the pipe for several seconds as water flows from the electrochemical electrode 30 to the tank 12. Once the water enters the tank 12, the tank 12 can be isolated. The chain reaction then propagates through the tank 12, consuming the available target reactants. Once all the available reactants have been consumed, the chain reaction terminates. The chain reaction typically lasts for tens of seconds, or even several minutes, depending on the concentration of the available reactants in the aqueous solution. During this period of proliferation and reaction in the isolated tank 12, water from one or more additional tanks 13 can continuously flow through the electrochemical electrode 30 and be applied as shown in the diagram. Figure 2 The diagram shows at least one power cycle to rapidly and continuously initiate a chain reaction in several tanks.

[0016] Figure 2 This is an illustration of a method for applying power to an electrochemical electrode in one embodiment of the present invention. Figure 2 A single complete cycle of the applied power sequence shown is sufficient to trigger a persistent chain reaction. The fundamental characteristics of the applied power sequence can be described as follows: Time period T1: Direct current flows through the electrochemical electrode, thereby generating a potential difference V across the electrochemical electrode unit. A .

[0017] Time period T2: Change the current flowing through the electrochemical electrode so that the potential difference across the electrode increases to a specific voltage V. B At this voltage, at least one desired long-half-life free radical is generated, thereby initiating a chain reaction. The rate of current change is controlled to achieve a specific desired rate of increase in the potential difference across the electrochemical electrode. V B The value is a specific desired value that makes the anodic voltage on each pair of electrodes in the electrochemical electrode range from about 2.3 V to about 2.9 V relative to the SHE (standard hydrogen electrode).

[0018] Time period T3: Once V has been reached B The potential difference across the electrochemical electrode or the current flowing through it remains constant for a short period of time. This period of time can be less than one second or greater.

[0019] Time period T4: Changing the current usually (but not always) reduces the potential difference across the electrochemical electrode to the initial voltage V. A The durations of T4 and T1 are not critical and can be less than or greater than a few seconds.

[0020] By correctly and accurately controlling the power transient, a single pulse or cycle is sufficient to initiate a chain reaction. To ensure the generation of at least one long-half-life free radical required to initiate the desired chain reaction, additional power cycles can be applied rapidly and continuously, and polarity can also be reversed. All successive power cycles are combined in a certain way with time periods T1 to T4, and in particular, the voltage rise rate and V indicated in T2 above are precisely controlled. B The parameters.

[0021] exist Figure 3 The general flow diagram illustrates a laboratory apparatus already used to test various types of water. Water containing the contaminants to be removed is supplied to feed tank 101. The water is then directed to the inlet of pump 102 and then to the inlet of electrochemical electrode 103. Electrochemical electrode 103 comprises four pairs of boron-doped diamond (BDD) electrodes, arranged such that water can flow between the electrodes and contact two electrodes in each pair. A DC power supply 105 is connected to electrochemical electrode 103 and enables the water to flow according to the specified flow path. Figure 2 The power curve shown controls the current flowing through the electrode and water. After exiting the electrochemical electrode 103, the water returns to the storage tank 101; approximately 6 seconds after exiting the electrochemical electrode 103, it enters the tank 101. Figure 2 After at least one cycle of the power curve shown, the power is cut off and water is circulated through the system to promote mixing as the chain reaction propagates throughout tank 101. The chain reaction continues for several minutes until it terminates after the available target reactant has been consumed.

[0022] Through extensive research and experimentation, the inventors have developed a means to generate a chain reaction in aqueous solution using long-half-life free radicals. Importantly, the inventors have demonstrated that this chain reaction can propagate and sustain, enabling the degradation and removal of target pollutants from the system. This is a unique method for treating water to remove contaminants from the environment at very low cost, low temperature, and low pressure, which has not been demonstrated by existing technologies.

[0023] The methods described in this article can be practiced in many industrial and municipal applications. For many important applications, the feedwater may contain a mixture of organic solutes. The relative concentration of each of the different solutes is uncontrolled, and the total dissolved organic matter concentration can be variable. Organic solutes can be removed to any desired final concentration.

[0024] In other applications, the water supply may contain PFAS, perfluoroalkyl substances, and polyfluoroalkyl substances. The method of this invention is capable of reducing the total PFAS concentration from any initial value to a low ppt (parts per trillion) concentration.

[0025] In another application of the method of the present invention, the feed water may contain perchlorate. The method of the present invention is able to remove perchlorate to a low concentration.

[0026] In another application of the method of the present invention, the feed water may contain a mixture of ammonia nitrogen, organic phosphates, nitrates, and inorganic phosphates. All of the above-mentioned solutes are effectively degraded by the method of the present invention.

[0027] In other applications of the method of the present invention, the water supply may contain solutes that act as effective bactericides, such as compounds containing CN groups or active pharmaceutical preparations. All such solutes are degraded by the method of the present invention.

[0028] In another application, the method of the present invention can be used to produce at least one long half-life free radical capable of initiating chain reactions that lead to the synthesis of organic chemicals.

[0029] Therefore, the inventive features of the method disclosed herein are: (1) a persistent chain reaction initiated by applying power in a small volume of water with a single pulse; (2) once initiated, the chain reaction continues as it is transferred to a larger volume of water; (3) once in a larger volume of water, the chain reaction propagates and continues unaffected by external influences until all available reactants are removed, at which point the chain reaction terminates; (4) the method is very low cost; and (5) the chain reaction can be initiated and propagated in several water bodies using a single electrochemical electrode, allowing several chain reactions to continue simultaneously.

[0030] Example The invention is described in more detail in the following non-limiting examples, which are intended to be illustrative only, as many modifications and variations therein will be apparent to those skilled in the art.

[0031] Example 1 In a test, such as Figure 3 As shown, an 8-liter volume of aqueous solution containing 3,334 ppm sulfide anions was placed in a tank. The wastewater was circulated through the electrochemical electrode at a flow rate of 7 liters / minute. The power applied to the electrochemical electrode had the following characteristics: Figure 2 The curve shown is applied continuously for a total of three cycles. The total energy consumed is less than 100 joules. The sulfide concentration in the water is reduced to less than 300 ppm. The reaction takes approximately 5 minutes to complete and terminate.

[0032] Example 2 In the second test, a 20-liter volume of aqueous solution containing 3,334 ppm sulfide anions and 2,150 ppm phenol was placed in a tank. The water was circulated through the electrochemical electrode at a flow rate of approximately 7 liters per minute. The power applied to the electrochemical electrode had the following characteristics: Figure 2 The curve is shown, and a total of four cycles were applied. The total energy consumed was less than 120 joules. The sulfide concentration was reduced to less than 300 ppm, and the phenol concentration was reduced to less than 250 ppm. The reaction took approximately five minutes to complete and terminate.

[0033] Example 3 In the third test, an 8-liter volume of aqueous solution containing 4,000 ppm bicarbonate / carbonate anions was placed in a tank. The water was circulated through the electrochemical electrodes at a flow rate of approximately 7 liters per minute. The applied power had the following characteristics: Figure 2 The curve is shown, and a total of three consecutive power cycles are applied. The total energy consumed is less than 150 joules. The carbon dioxide / bicarbonate / carbonate concentration is reduced to less than 2,000 ppm. The reaction takes approximately five minutes to complete and terminate. The exemplary results of such a test, and in particular the low energy required, the short duration of its application, and the long duration of the chain reaction for removing contaminants present in aqueous solutions without the application of additional power, demonstrate the remarkable effectiveness of the unique method of the present invention.

[0034] Therefore, it is evident that the objectives set forth above, including those readily apparent above, are achieved effectively and efficiently. Furthermore, since certain modifications can be made in implementing the methods described above and constructing suitable equipment (in which the methods are practiced and the desired products as described herein are produced), it should be understood that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. For example, while exemplary designs for treating aqueous solutions via chain reactions initiated by long-half-life free radicals have been described, other embodiments can also yield results based on the principles of the methods disclosed herein. Therefore, it should be understood that the foregoing description of representative embodiments of the invention is presented for illustrative purposes and to provide an understanding of the invention, and is not intended to be exhaustive or limiting, or to confine the invention to the precise forms disclosed. Rather, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as expressed in the appended claims. Therefore, the claims are intended to cover not only the methods and structures described herein, but also their equivalents or structural equivalents, and equivalent structures or methods. Therefore, as indicated by the appended claims, the scope of the invention is intended to include variations from the provided embodiments, however, these variations are described by the broad meaning and scope appropriately provided in the language of the claims or their equivalents.

[0035] Claims:

Claims

1. A method for initiating and propagating a persistent chain reaction in an aqueous solution in an electrochemical device, said electrochemical device comprising at least one electrochemical cell having suitable electrodes for preparing a body of water containing a low concentration of a specific solute, said method comprising: (a) Provide an influent water stream containing one or more solutes selected from the following: organic matter or molecules, ammonia nitrogen, organic nitrogen, inorganic phosphates, organic phosphates, inorganic sulfides, organic sulfides, nitrates, perfluorinated and polyfluoroalkyl substances, carbon dioxide, bicarbonates, carbonates or combinations thereof. (b) Pass the influent from step (a) through the electrochemical device, ensuring that the water flow is in contact with the electrodes therein; (c) Passing a direct current through an electrochemical device to generate at least one long half-life free radical, thereby initiating a persistent chain reaction in an aqueous solution, wherein the direct current is regulated to apply a specific power scheme to an electrochemical electrode, the scheme comprising at least one cycle or pulse, wherein the potential difference applied across the electrochemical electrode is increased to a specific value at a precisely controlled voltage rise rate, and the voltage is reduced after the specific voltage value is reached. (d) The aqueous solution is allowed to flow into a larger volume of water containing some or all of the solute from step (a), thereby allowing the persistent chain reaction to propagate throughout the larger volume and reducing the concentration of the solute.

2. The method according to claim 1, wherein, After step (d) is completed, steps (a) through (d) are repeated once or more, thereby initiating and propagating the persistent chain reaction in one or more separate additional bodies of water.

3. The method according to claim 1, wherein, In step (c), the direct current is changed to increase the potential difference across the electrochemical electrode, thereby bringing the anode potential of each electrode pair in the electrochemical electrode to a specific value within a time period of one second or less, which is in the range of 2.50 V to 2.85 V relative to SHE.

4. The method according to claim 1, wherein, In step (c), the direct current is changed to increase the potential difference across the electrochemical electrode, thereby bringing the anode potential of each electrode pair in the electrochemical electrode to a specific value within a time period of half a second or less, which is in the range of 2.50 V to 2.85 V relative to SHE.

5. The method according to claim 1, wherein, In step (c), the direct current is changed to increase the potential difference across the electrochemical electrode, thereby bringing the anode potential of each electrode pair in the electrochemical electrode to a specific value within a time period of one-third of a second or less, which is in the range of 2.50 V to 2.85 V relative to SHE.

6. The method according to claim 1, wherein, In step (d), the chain reaction is allowed to propagate, thereby synthesizing different organic chemicals or polymers as the desired products.

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