Bioelectrochemical system having polyvalent ion removing function

Abstract

The present invention provides a bioelectrochemical system for removing a polyvalent ion present in seawater etc., capable of producing electricity. The bioelectrochemical system according to the present invention comprises: an anode chamber comprising an anode which accommodates an electron produced when treating an organic material in wastewater with a microorganism; a cathode chamber comprising a cathode receiving the electron from the anode, for producing a hydroxide ion by reacting the electron with oxygen and water provided from the outside, and depositing the polyvalent ion inside an electrolyte by using the hydroxide ion; and an anion exchange membrane for blocking the polyvalent ion inside the electrolyte from moving to the anode chamber. Also, the present invention provides the bioelectrochemical system capable of removing the polyvalent ion present in seawater etc., and simultaneously producing hydrogen. The present invention comprises: the anode chamber, provided with the anode to which electrochemically active bacteria are attached, for producing the electron by having organic wastewater, as a substrate, injected thereto; the cathode chamber, provided with the cathode, for removing the polyvalent ion and simultaneously producing a hydrogen gas by having seawater, as an electrolyte, injected thereto; the anion exchange membrane for separating the anode chamber and the cathode chamber and preventing the polyvalent cation in seawater from moving to the anode chamber; and a power source connected between the anode and the cathode.

Claims

1. A bioelectrochemical system for removing polyvalent ions related to scale deposits in an electrolyte solution while generating energy, the system comprising: a microbial fuel cell comprising: an anode chamber housing an anode and microorganisms adhered to the anode, a cathode chamber housing a cathode, and an anion exchange membrane configured for blocking movement of polyvalent ions from the cathode chamber into the anode chamber; a wastewater supply in fluid communication with the anode chamber; an aqueous electrolyte supply in fluid communication with the cathode chamber; and an oxygen supply in fluid communication with the cathode chamber, wherein the anode chamber accepts electrons generated when organic matter present in the wastewater is treated by the microorganisms, the cathode chamber receives the electrons from the anode and the electrons react in the cathode chamber with the supplied water from the electrolyte and the supplied oxygen to produce hydroxide ions, the hydroxide ions react with and precipitate polyvalent ions present in the electrolyte, and the anion exchange membrane blocks movement of the polyvalent ions from the cathode chamber to the anode chamber.

2. The bioelectrochemical system of claim 1, wherein the microorganisms are electrochemically active bacteria.

3. The bioelectrochemical system of claim 1, wherein the anode chamber maintains a neutral pH and a temperature of 20 C. to 100 C.

4. The bioelectrochemical system of claim 3, wherein to maintain the neutral pH the anode chamber is fed with a precipitate of the cathode chamber or a chemical when the pH of the anode chamber is lower than the neutral pH.

5. The bioelectrochemical system of claim 1, wherein the anode comprises a plurality of anodes.

6. The bioelectrochemical system of claim 1, wherein the anode is in a form of brush or felt made of graphite or carbon.

7. The bioelectrochemical system of claim 1, wherein the cathode comprises a platinum catalyst or a platinum replacement catalyst.

8. The bioelectrochemical system of claim 1, wherein the cathode is an air-cathode.

9. The bioelectrochemical system of claim 1, wherein the cathode chamber is under an aerobic condition.

10. The bioelectrochemical system of claim 1, further comprising: a power source configured for connecting the anode to the cathode, wherein the generated electrons react in the cathode chamber with the water from the electrolyte to produce hydrogen gas.

11. The bioelectrochemical system of claim 10, wherein the cathode chamber allows for generation of OH.sup. ions through a reduction reaction, thereby precipitating polyvalent cations present in the seawater with the OH.sup. ions.

12. The bioelectrochemical system of claim 10, wherein both the anode chamber and the cathode chamber are under an anaerobic condition.

13. The bioelectrochemical system of claim 10, wherein the anode comprises a plurality of anodes.

14. The bioelectrochemical system of claim 10, further comprising a sensor configured for measuring a concentration of organic matter in the organic wastewater.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic view illustrating an organization of a microbial fuel cell for use as a bioelectrochemical system in accordance with an embodiment of the present disclosure,

(2) FIG. 2 is a graph showing a polyvalent removal result obtained by an experiment in the microbial fuel cell of FIG. 1

(3) FIG. 3 is a schematic view illustrating an organization of a microbial electrolysis cell for use as a bioelectrochemical system in accordance with an embodiment of the present disclosure,

DESCRIPTION OF THE REFERENCE NUMERALS IN THE DRAWINGS

(4) TABLE-US-00001 10: anode chamber 11: anode 12: microorganisms 13: anode reactor body 20: cathode chamber 21: cathode 22: cathode reactor body 30: anion exchange membrane 40: external circuit 50: wastewater 60: seawater 100: microbial electrolysis device 102: anode chamber 104: cathode chamber 106: anion exchange membrane 107: anode reactor body 108: anode 110: electrochemically active bacteria 111: cathode reactor body 112: cathode 113: power supply 114: wastewater reservoir 116: seawater reservoir

Best Mode

(5) Reference now should be made to the drawings, throughout which the same reference numerals are used to designate the same or similar components. Below, a description will be given of preferred embodiments of the present invention in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components. It should be apparent to those skilled in the art that although many specified elements such as concrete components are elucidated in the following description, they are intended to aid the general understanding of the invention and the present invention can be implemented without the specified elements. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted.

(6) FIG. 1 is a schematic diagram showing an organization of a microbial fuel cell for use as a bioelectrochemical system in accordance with an embodiment of the present disclosure. With reference to FIG. 1, the microbial fuel cell 1 comprises an anode chamber 10, a cathode chamber 20, and an ion exchange membrane 30. The anode chamber 10 comprises a reactor body 13 housing an anode 11 that accepts electrons generated when organic matter of wastewater is treated by microorganisms. The cathode chamber 20 has a reactor body 22 housing a cathode 21 that receives the electrons from the anode 11 and at which the electrons moving from the anode chamber 10 react with externally fed oxygen and water to produce hydroxide ions which, in turn, precipitate polyvalent ions of an electrolyte. The ion exchange membrane 30 may be an anion exchange membrane that prevents polycations of the electrolyte from moving toward the anode chamber 10.

(7) In the anode chamber 10, an anaerobic condition is established for the activity of the microorganisms 12. Wastewater is supplied to the anode chamber 10 from a wastewater reservoir 50. The microorganisms 12 is electrochemically active bacteria that can utilized as a substrate for organic matter-containing wastewater, anaerobic digests, urban sewage, industrial wastewater, acid fermentation liquid, etc. In addition, the anode chamber 10 is set to have a temperature of 20 C. to 100 C. with neutral pH so as to maintain the activity of the electrochemically active bacteria. When the pH of the anode chamber 10 is lower than the neutral pH, the precipitate formed in the cathode chamber 20 or a chemical may be fed to the anode chamber 10. In addition, part of the precipitate of the cathode chamber 20 or an effluent from the cathode chamber 20 may be transferred into the anode chamber 10 to enhance the electroconductivity of the anode chamber 10.

(8) In the cathode chamber 20 comprising the cathode 21, an aerobic condition is established for a reduction reaction. Between the anode 11 of the anode chamber 10 and the cathode 21 of the cathode chamber 20, there is a connection via an external circuit 40.

(9) For wastewater treatment and polyvalent ion removal, wastewater is fed into the anode chamber 10 while an electrolyte containing polyvalent ions, e.g., seawater, is supplied to the cathode chamber 20. The wastewater to be fed into the anode chamber 10 contains organic matter, such as in urban sewage, acid fermentation liquid, anaerobic digests, wastewater from food processing plants, etc. In order to maintain a proper concentration of organic matter in the wastewater, a sensor 52 may be used for monitoring the concentration of organic matter.

(10) In the anode chamber 10, electrochemically active bacteria adhere to and grow on the anode 11, oxidizing the organic matter of wastewater to generate protons (H.sup.+) and electrons (e.sup.). Here, the anode 11 may be made of graphite or carbon and may be in the form of a brush or felt. The electrons are transferred from the bacteria 12 to the anode 11 and then to the cathode chamber 20 through the external circuit 40 comprising a resistance, with the concomitant production of electrical energy. The resistance of the external circuit may range from 1 to 1000. In addition, a plurality of anodes 11 may be provided to produce a sufficient amount of electrons.

(11) On the other hand, the electrons transferred from the anode chamber 10 react with oxygen and water in the cathode chamber 20 to produce OH.sup., as illustrated in Chemical Formula 4.
O.sub.2+4e.sup.+2H.sub.2O.fwdarw.4OH.sup.[Chemical Equation 4]

(12) The OH.sup. that is produced in the cathode 20 during the generation of electrical energy increase the pH of the seawater in contact with the cathode 21. At the cathode 21, OH.sup. precipitates Ca.sup.2+ and Mg.sup.2+ of the seawater in the form of CaCO.sub.3 and Mg(OH).sub.2, respectively. In addition, Ca.sup.2+ and Mg.sup.2+ may be removed as other precipitate forms. In this regard, an anion exchange membrane 30 is employed to prevent cations of seawater from moving into the anode chamber 10.
Ca.sup.2++HCO.sub.3.sup.+OH.sup..fwdarw.CaCO.sub.3+H.sub.2O
Mg.sup.2++2OH.sup..fwdarw.Mg(OH).sub.2[Chemical Formula 5]

(13) FIG. 2 is a graph depicting a polyvalent removal result obtained by an experiment in the microbial fuel cell of FIG. 1. As is understood from the data of FIG. 2, comparison of polyvalent cations between pre- and post-reaction indicates the removal of Ca.sup.2+ by 96%, and Mg.sup.2+ by 55%.

(14) To supply oxygen to the cathode chamber 20, an aerobic condition is maintained. For this, an aerator is needed. However, an air-cathode with one side exposed to air as shown in FIG. 1 may be employed in place of an aerator, so as to reduce the cost of aeration. The cathode 21 may be made of an anti-corrosive, conductive material and may be coated with a catalyst such as platinum or a platinum replacement.

(15) In the cathode chamber 20, a scale deposit on the cathode 21 may be eliminated using a skimmer. Alternatively, the cathode 21 may be vibrated with ultrasound or the cathode chamber 20 may be periodically injected with bubbles, so as to remove the scale deposit from the cathode 21.

(16) FIG. 3 is a schematic diagram showing an organization of a microbial electrolysis cell 100 for use as a bioelectrochemical system in accordance with another embodiment of the present disclosure. As shown, the microbial electrolysis cell 100 comprises two chambers, that is, an anode chamber 102 and a cathode chamber 104, which are separated by an anion exchange membrane 106. In the microbial electrolysis cell 100, wastewater is introduced into the anode chamber 102 while seawater is supplied into the cathode chamber 104, with a connection between an anode 108 and a cathode 112 via a direct current power source 113.

(17) The anode chamber 102 has a reactor body 107 that houses an anode 108 and in which an anaerobic condition is established. Wastewater is supplied to the anode chamber 102 from a wastewater reservoir 114. Electrochemically active bacteria 110 adhere to and grow on the anode 108 while oxidizing the organic matter of wastewater to generate protons (H.sup.+) and electrons (e.sup.). The electrons are transferred from the bacteria to the anode 108 and then to the cathode chamber 104 through the external circuit. The external circuit may have a resistance of from 1 to 20.

(18) In addition, the anode chamber 102 is set to have a temperature of 25 C. or higher with neutral pH so as to maintain the activity of the electrochemically active bacteria 110. Since the pH of the anode chamber 102 decreases with the progress of the oxidation reaction, part of the precipitate formed in the cathode chamber 104 or part of an effluent from the cathode chamber 104 may be transferred into the anode chamber 102. The transfer of the precipitate or the effluent is advantageous in that the electroconductivity of the anode chamber 102 can be enhanced without feeding other additives.

(19) In the anode chamber 102, a plurality of anodes 108 may be provided to produce a sufficient amount of electrons. In addition, the anode 108 may be in the form of a brush to maximize its specific surface area, thereby enhancing the reaction rate thereat.

(20) The wastewater to be fed into the anode chamber 102 contains organic matter, such as in urban sewage, acid fermentation liquid, anaerobic digests, wastewater from food processing plants, etc. The wastewater fed into the anode chamber 102 has to contain organic matter at a proper concentration. For this, the wastewater reservoir 114 is installed with a sensor 115 for monitoring concentrations of organic matter. When the concentration of organic matter is below a proper level, the wastewater is concentrated using solar heat before introduction into anode chamber 102.

(21) When the electrical potential of the cathode 112 is made lower than that of the anode 108 by applying at least 0.3 V from the direct current power source 113, hydrogen gas can be generated. Theoretically, the generation of hydrogen requires that the cathode 112 be lower in potential by about 0.6 V than the anode 108. Instead of the direct current power source 113, RED (reverse electrodialysis) power generation or new renewable energy may be used as a power supply.

(22) The cathode chamber 104 has a reactor body 111 housing a cathode 112. The cathode chamber 104 is supplied with seawater from a seawater reservoir 116. The cathode 112 may be made of an anti-corrosive, conductive material coated with a catalyst such as platinum.

(23) The cathode chamber 104 should comprise a hydrogen gas collector (not shown) because hydrogen gas is generated as illustrated in the following Chemical Formula 6. The hydrogen gas generated may be utilized to remove particulate matter of seawater.
2H.sub.2O+2e.sup..fwdarw.H.sub.2+2OH.sup.[Chemical Formula 6]

(24) The OH.sup. that is produced in the cathode 112 precipitates polyvalent cations, such as Ca.sup.2+ and Mg.sup.2+, of the seawater. In addition, Ca.sup.2+ and Mg.sup.+ may be deposited in the form of CaCO.sub.3 and Mg(OH).sub.2, respectively, or in other forms in which Ca.sup.2+ and Mg.sup.2+ are associated with each other. In conjunction with FDFO (Fertiliser Drawn Forward Osmosis), the precipitates may be utilized as a fertilizer.
Ca.sup.2++HCO.sub.3.sup.+OH.sup..fwdarw.CaCO.sub.3+H.sub.2O
Mg.sup.2++2OH.sup..fwdarw.Mg(OH).sub.2[Chemical Formula 7]

(25) Given a scale deposit thereon, the cathode 112 is unlikely to perform a reduction reaction. Hence, the cathode 112 needs to be descaled. For this, a skimmer may be used. Alternatively, the cathode 21 may be vibrated with ultrasound or the cathode chamber 20 may be periodically injected with bubbles, so as to remove the scale deposit from the cathode 21.

(26) The cathode chamber 104 and the anode chamber 102 are separated from each other by the anion exchange membrane 106. Separation between the anode chamber 102 and the cathode chamber 104 by anion exchange membrane 106 is to prevent the cations of seawater from moving into the anode chamber 102. The anion exchange membrane 104 also needs to be decaled by using a skimmer, by vibrating or sonicating, or by periodically injecting bubbles.

(27) Although the preferred embodiment(s) of the present invention have(has) been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.