Apparatus and method for water treatment using in-situ activation of manganese dioxide catalyst

Abstract

The apparatus for water treatment using in-situ activation of a manganese dioxide catalyst includes: a reaction bath configured to give a space where aqueous organic contaminants are removed by means of reaction with permanganate (MnO.sub.4.sup.) generated by electrochemical oxidation of manganese oxide (MnO.sub.2); a plurality of manganese dioxide catalysts provided at the reaction bath and electrochemically oxidized into permanganate (MnO.sub.4.sup.) by a voltage applied thereto; and a power supply device configured to apply power to the manganese dioxide catalyst so that the manganese dioxide (MnO.sub.2) is electrochemically oxidized into permanganate (MnO.sub.4.sup.).

Claims

1. An apparatus to treat water using in-situ activation of a manganese dioxide catalyst, the apparatus comprising: a reaction bath container configured to accommodate removal of aqueous organic contaminants by means of a reaction with permanganate (MnO.sub.4.sup.); a manganese dioxide catalyst provided in the reaction bath container; positive electrodes and negative electrodes arranged in an alternating pattern; and a power supply device configured to apply power to the positive electrodes and the negative electrodes to electrochemically oxidize manganese dioxide (MnO.sub.2) of the manganese dioxide catalyst into the permanganate (MnO.sub.4.sup.), wherein the positive electrodes are longer than the negative electrodes and terminate inside the manganese dioxide catalyst, wherein the negative electrodes run parallel to the positive electrodes and terminate above the manganese dioxide catalyst, and wherein the manganese dioxide catalyst is provided as an immobilized packed bed that comprises manganese dioxide particles.

2. The apparatus according to claim 1, wherein the power supply device comprises a power supply unit configured to apply the power to the positive electrodes and the negative electrodes, and a voltage adjuster configured to adjust a voltage applied to the positive electrodes, the positive electrodes are configure to apply a positive voltage so that the manganese dioxide catalyst is guided to be oxidized into the permanganate (MnO.sub.4.sup.), the negative electrodes are configured to retrieve an electron and transfer the electron to a final electron acceptor.

3. The apparatus according to claim 2, wherein the positive electrodes and the negative electrodes are disposed at regular intervals from one another, the positive electrodes and the negative electrodes are connected in parallel, and the voltage adjuster is configured to uniformly distribute voltage to the positive electrodes and the negative electrodes.

4. The apparatus according to claim 1, wherein the manganese dioxide catalyst comprises a support, and manganese dioxide particles provided on a surface of the support.

5. The apparatus according to claim 1, wherein the manganese dioxide catalyst is prepared by chemical or thermal treatment of sand particles to which amorphous manganese oxide is absorbed, so that the amorphous manganese oxide is oxidized into the manganese dioxide.

6. The apparatus according to claim 5, wherein when the amorphous manganese oxide is oxidized into the manganese dioxide (MnO.sub.2), potassium permanganate (KMnO.sub.4) or sodium hypochlorite (NaOCl) is used to oxidize the amorphous manganese oxide into the manganese dioxide (MnO.sub.2).

7. The apparatus according to claim 1, wherein the manganese dioxide catalyst is prepared by putting and stirring a support to a precursor solution containing manganese chloride (MnCl.sub.2) and potassium permanganate (KMnO.sub.4) so that a reaction between the manganese chloride (MnCl.sub.2) and the potassium permanganate (KMnO.sub.4) generates amorphous manganese oxide on a surface of the support, and thermally treating the amorphous manganese oxide to be oxidized into manganese dioxide (MnO.sub.2).

8. The apparatus according to claim 1, wherein the manganese dioxide catalyst is prepared by electrospraying or electrospinning manganese dioxide particles on a support.

9. The apparatus according to claim 1, wherein the manganese dioxide particles comprise -MnO.sub.2 having a rutile crystal structure.

10. An apparatus to treat water using in-situ activation of a manganese dioxide catalyst, the apparatus comprising: a reaction bath container configured to accommodate removal of aqueous organic contaminants by means of a reaction with permanganate (MnO.sub.4.sup.); a manganese dioxide catalyst provided in the reaction bath container; and a power supply device configured to apply power to the manganese dioxide catalyst so that manganese dioxide (MnO.sub.2) of the manganese dioxide catalyst is electrochemically oxidized into the permanganate (MnO.sub.4.sup.); wherein the power supply device comprises a positive electrode extending from a first level above the manganese dioxide catalyst, and terminating inside the manganese dioxide catalyst at a second level, and a negative electrode extending from the first level, parallel with the positive electrode, and terminating at a third level above the manganese dioxide catalyst, and wherein the negative electrode is not in contact with the manganese dioxide catalyst.

11. The apparatus of claim 10, wherein the first and third levels are above a water level, and the second level is below the water level.

12. The apparatus of claim 10, wherein the reaction bath container comprises an inlet formed in a first wall of the reaction bath container, an outlet formed in a second wall of the reaction bath container, and the first level is above the inlet and above the outlet, the second level is below the inlet, and the third level is below the inlet and above the outlet.

13. An apparatus to treat water using in-situ activation of a manganese dioxide catalyst, the apparatus comprising: a reaction bath container containing aqueous organic contaminants; a manganese dioxide catalyst homogenously provided in a lower portion of the reaction bath, and absent from or non-homogenously provided in an upper portion of the reaction bath container; and a power supply device configured to apply power to the manganese dioxide catalyst so that manganese dioxide (MnO.sub.2) of the manganese dioxide catalyst is electrochemically oxidized into permanganate (MnO.sub.4.sup.), wherein the power supply device comprises a positive electrode extending from a first level above the manganese dioxide catalyst, and terminating inside the manganese dioxide catalyst at a second level, and a negative electrode extending from the first level, parallel with the positive electrode, and terminating at a third level above the manganese dioxide catalyst.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram showing an apparatus for water treatment (hereinafter, also referred to as a water treatment apparatus) using in-situ activation of a manganese dioxide catalyst according to an embodiment of the present disclosure.

(2) FIG. 2 is a flowchart for illustrating a method for water treatment (hereinafter, also referred to as a water treatment method) using in-situ activation of a manganese dioxide catalyst according to an embodiment of the present disclosure.

(3) FIG. 3 shows removal efficiency of Microcystins-LR, which is an algal bloom-causing toxic substance, according to a concentration of permanganate.

DETAILED DESCRIPTION

(4) The present disclosure proposes a technique for electrochemical oxidation of a manganese dioxide (MnO.sub.2) catalyst to produce permanganate (MnO.sub.4.sup.), and allowing the produced permanganate (MnO.sub.4.sup.) to react with aqueous organic contaminants so that the organic contaminants are oxidized and removed and also the permanganate (MnO.sub.4.sup.) is guided to be reduced back to manganese dioxide (MnO.sub.2). Since the process of oxidizing manganese dioxide (MnO.sub.2) into permanganate (MnO.sub.4.sup.) and reducing permanganate (MnO.sub.4.sup.) back into manganese dioxide (MnO.sub.2) is repeatedly performed, aqueous organic contaminants may be removed without a consistent supply of a external oxidizing agent, and since the reduced manganese dioxide (MnO.sub.2) is re-oxidized into permanganate (MnO.sub.4.sup.), it is possible to minimize the generation of reaction byproducts such as manganese ion (II) and manganese dioxide sludge.

(5) Hereinafter, an apparatus and method for water treatment using in-situ activation of a manganese dioxide catalyst according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

(6) Referring to FIG. 1, the apparatus for water treatment using oxidation and reduction of a manganese dioxide catalyst according to an embodiment of the present disclosure includes a reaction bath 110.

(7) The reaction bath 110 gives a space where organic contaminants included in raw water are removed by means of a reaction with permanganate (MnO.sub.4.sup.) generated by an electrochemical oxidation of manganese dioxide. In the reaction bath 110, a manganese dioxide catalyst 120 is provided. The manganese dioxide catalyst 120 is oxidized into permanganate (MnO.sub.4.sup.) by a voltage applied thereto, and the permanganate (MnO.sub.4.sup.) plays a role of oxidizing organic contaminants in the raw water.

(8) The manganese dioxide catalyst 120 may be made of manganese dioxide particles or a combination of a support 121 and manganese dioxide particles 122. If the manganese dioxide catalyst 120 is made of only manganese dioxide particles, -MnO.sub.2 having a rutile crystal structure may be used as the manganese dioxide particles. If the manganese dioxide catalyst 120 is made of a combination of the support 121 and the manganese dioxide particles 122, the manganese dioxide catalyst 120 is formed so that the manganese dioxide particles 122 are fixed onto the surface of the support 121.

(9) The manganese dioxide catalyst 120 composed of the support 121 and the manganese dioxide particles 122 may be prepared using following methods. As the first method, sand particles to which an amorphous manganese oxide is absorbed may be chemically or thermally treated to oxidize the amorphous manganese oxide so that the manganese dioxide catalyst 120 having the manganese dioxide particles 122 formed on the surface of the sand particles is obtained. The sand particles to which an amorphous manganese oxide is absorbed may be naturally generated at an underground sedimentary layer or a sand filter bed of a water treatment plant, and the amorphous manganese oxide may be oxidized into manganese dioxide by means of chemical treatment using an oxidizer such as potassium permanganate (KMnO.sub.4) and sodium hypochlorite (NaOCl) or thermal treatment where the amorphous manganese oxide is oxidized through thermal treatment.

(10) As a second method, the support 121 may be put into and stirred in a precursor solution containing manganese chloride (MnCl.sub.2) and potassium permanganate (KMnO.sub.4) to form an amorphous manganese oxide by the reaction between manganese chloride (MnCl.sub.2) and potassium permanganate (KMnO.sub.4) on the surface of the support 121, and the amorphous manganese oxide is oxidized into manganese dioxide by means of thermal treatment to prepare the manganese dioxide catalyst 120 having the manganese dioxide particles 122 fixed to the support 121. As a third method, the manganese dioxide catalyst 120 having the manganese dioxide particles 122 fixed on the support 121 may also be prepared by electrospraying or electrospinning the manganese dioxide particles 122 onto the support 121.

(11) A power supply device for applying power to the manganese dioxide catalyst 120 to electrochemically oxidize the manganese dioxide particles 122 so that the manganese dioxide particles 122 are guided to be oxidized into permanganate (MnO.sub.4.sup.) is provided at one side of the reaction bath 110. In detail, the power supply device includes a positive electrode (+) 131, a negative electrode () 132, a voltage adjuster 133 and a power supply unit 134. The power supply unit 134 supplies power to the positive electrode (+) 131 and the negative electrode () 132, and the voltage adjuster 133 plays a role of adjusting the voltage applied to the positive electrode (+) 131. In addition, the positive electrode (+) 131 is in contact with the manganese dioxide catalysts 120 of the reaction bath 110 to apply a positive (+) voltage so that the manganese dioxide is guided to be oxidized into permanganate (MnO.sub.4.sup.), and the negative electrode () 132 plays a role of retrieving an electron and transfer the electron to a final electron acceptor. The positive electrode (+) 131 is in contact with the manganese dioxide catalysts 120, but the negative electrode () 132 is not in contact with the manganese dioxide catalysts 120 so that the reduction reaction does not give any influence on the manganese dioxide catalysts 120.

(12) In order to enhance oxidation efficiency of the manganese dioxide particles 122 into permanganate (MnO.sub.4.sup.), a multiple number of the positive electrode (+) 131 and the negative electrode () 132 may be repeatedly disposed at regular distances, and when a plurality of positive electrodes (+) 131 and a plurality of negative electrodes () 132 are disposed, the positive electrodes (+) 131 and the negative electrodes () 132 may be connected in parallel, and voltage may be uniformly distributed to the positive electrodes (+) 131 and the negative electrode () 132, connected in parallel, by means of the voltage adjuster 133.

(13) Now, operations of the apparatus for water treatment using in-situ activation of a manganese dioxide catalyst according to an embodiment of the present disclosure, configured as above, will be described.

(14) As shown in FIG. 2, in a state where raw water is supplied to the reaction bath 110 including the manganese dioxide catalysts 120 (S201), if a voltage is applied to the positive electrode (+) 131 in contact with the manganese dioxide catalysts 120, the manganese dioxide particles 122 of the manganese dioxide catalyst 120 are oxidized into permanganate (MnO.sub.4.sup.) by means of electrochemical oxidization (see Formula 1 below) (S202). A standard oxidation-reduction potential required for electrochemical oxidation of the manganese dioxide particles 122 into permanganate (MnO.sub.4.sup.) is 1.679V, which however may vary depending on pH of the raw water. In detail, the voltage applied through the positive electrode (+) 131 is determined according to Formula 3 below. For example, if the raw water has pH of 7, the voltage applied through the positive electrode (+) 131 is determined to be 1.127V.

(15) Subsequently, the permanganate (MnO.sub.4.sup.) produced by the electrochemical oxidation of the manganese dioxide (MnO.sub.2) reacts with organic contaminants contained in the raw water, and by doing so, the organic contaminants are oxidized into carbon dioxide (CO.sub.2) or the like and removed, and the permanganate (MnO.sub.4.sup.) reacting with the organic contaminants is reduced back into manganese dioxide (MnO.sub.2) (see Formula 2 below) (S203). If the permanganate (MnO.sub.4.sup.) is reduced into manganese dioxide (MnO.sub.2), this means that the manganese dioxide catalyst 120 returns to an initial state, namely to a state before the manganese dioxide catalyst 120 is electrochemically oxidized into permanganate (MnO.sub.4.sup.). In other words, as an electrochemical oxidation process for oxidizing the manganese dioxide particles 122 into permanganate (MnO.sub.4.sup.) and a reduction process for reducing the permanganate (MnO.sub.4.sup.) into manganese dioxide by means of the reaction with organic contaminants are performed sequentially, the manganese dioxide catalyst 120 may be functioning for a number of times without deactivation.
MnO.sub.2+2H.sub.2O.fwdarw.MnO.sub.4.sup.+4H.sup.+3e.sup.,E.sup.0=1.679 VFormula 1
MnO.sub.4.sup.+Org..fwdarw.MnO.sub.2+Org..sub.oxFormula 2
E=E.sup.00.079pHFormula 3

(16) (E represents a voltage applied to the positive electrode, and E.sup.0 represents a standard oxidation-reduction potential)

(17) Since the manganese dioxide catalyst 120 may be reduced into an initial state by performing the electrochemical oxidation process for oxidizing the manganese dioxide particles 122 into permanganate (MnO.sub.4.sup.) and the reduction process for reducing the permanganate (MnO.sub.4.sup.) into manganese dioxide by means of the reaction with organic contaminants, the oxidation process and the reduction process may be repeatedly performed, which may allow continuous water treatment. In addition, since the manganese dioxide reduced back from the permanganate (MnO.sub.4.sup.) may be still attached to the support 121, it is possible to minimize the generation of manganese dioxide sludge.

(18) Meanwhile, as the permanganate has a greater concentration, the aqueous organic contaminants may be removed more efficiently. FIG. 3 shows removal efficiency of Microcystins-LR, which is an algal bloom-causing toxic substance, under variable initial concentrations of the permanganate, and from this, it can be found that the removal efficiency of Microcystins-LR increases if the permanganate has a higher initial concentration. In the present disclosure, since the permanganate is continuously produced by repeating catalytic processes of manganese dioxide, aqueous organic contaminants may be continuously removed.

(19) When the manganese dioxide catalyst is electrochemically oxidized, the magnitude of current may be calculated as a function of the amount of raw water to be treated. If the raw water has a flow rate of 10 m.sup.3/day and a hydraulic residence time of 60 minutes, the reaction bath is demanded to have a volume of about 0.42 m.sup.3, and in order to treat 0.1 g/day of Microcystins-LR, 100 g/day of permanganate is required. In this case, the required magnitude of current is determined to be about 2.12 A by means of Formula 4 below.
I=nFQFormula 4

(20) (I represents a required magnitude of current, n represents the number of electrons required for the reaction of Formula 1, F represents a Faraday constant, and Q an generation rate (mol/sec) of permanganate)

(21) TABLE-US-00001 Reference Symbols 110: reaction bath 120: manganese dioxide catalyst 121: support 122: manganese dioxide particles 130: power supply device 131: positive electrode 132: negative electrode 133: voltage adjuster 134: power supply unit