JP2006231101A - Fluorine atom-containing ion removing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorine atom-containing ion removing method which realizes zero-emission environmental recycle removing fluorine atom-containing ions in ground water from the ground water by using electrolysis to use it as a cement raw material, a valuable resource. <P>SOLUTION: Ground water contaminated with fluorine atom-containing ions is sucked from a pumping well 1, and made to flow into an electrolytic cell unit 5 to separate ionized substances by the action of electrolysis. Fluorine atom-containing ion water is fed into a settling tank, and a calcium component is added and agitated to generate a precipitate of calcium fluoride by a chemical reaction. The precipitate of calcium fluoride is subjected to solid-liquid separation in a dehydration mean, a solid matter is generated by a drying means, and then particle size is controlled by a downstream crushing means to obtain the valuable resource. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for purifying soil or groundwater contaminated with fluorine atom-containing ions.

Conventionally, as a method for purifying fluorine atom-containing ions, a pair of electrodes are inserted into contaminated soil, an electrolytic cell is provided around the pair of electrodes, and water is supplied into the electrolytic cell. A purification method is known in which a fluorine atom-containing ion that is a pollutant in soil is recovered as an aqueous solution while passing an electric current between a pair of electrodes and adjusting the pH in the electrolytic cell within a certain range (for example, Patent Document 1).
JP 2003-260458 A

  However, in order to provide an electrolytic cell in the soil, excavation work is required, and thus there is a problem that enormous costs and time are required.

  In addition, when tap water is supplied to the electrolytic cell, a minute amount (about 1 ppm) of the chlorine component is mixed, so that this chlorine component is combined with other metal ions, so that chloride is deposited, and the electrolytic cell is There was a problem of creating factors that would shorten the life.

  In addition, since a water-permeable electrolytic cell is provided in the soil, there is a problem that groundwater flows in, the pH varies greatly, and the pH adjustment of the electrolyte solution becomes complicated.

  The present invention solves such a conventional problem, and by removing the fluorine atom-containing ions in the groundwater from the groundwater by electrolyzing the groundwater, it is used as a valuable cement raw material. It aims at providing the removal method of the fluorine atom containing ion which can implement | achieve environmental recycling.

  In order to achieve the above object, the present invention pumps groundwater contaminated with fluorine atom-containing ions with a pump as a pumping means, and flows the pumped groundwater into an electrolytic cell provided on the ground.

  This electrolytic cell is provided with a pair of electrodes (a positive electrode and a negative electrode), and a semipermeable membrane through which only negative ions can pass is provided around the positive electrode side of the electrode.

  By applying a DC voltage between the electrodes of the electrolytic cell to electrolyze groundwater, negative ions containing fluorine atoms in the electrolytic cell move to the positive electrode side and pass through the semipermeable membrane.

  Since ionic water containing high-concentration fluorine atoms can be generated between the semipermeable membrane and the positive electrode by electrolysis, the ionic water is conveyed to the precipitation tank by a pump.

  In this precipitation tank, a calcium-containing component is added to ionic water containing high-concentration fluorine atoms and stirred, whereby a precipitate such as calcium fluoride is generated by a chemical reaction.

  After the precipitate such as calcium fluoride is conveyed to a dehydrating means and separated into solid and liquid, a solid substance is generated by a drying means, and then the particle size is adjusted by a subsequent pulverizing means to generate a valuable material.

  According to the present invention, an apparatus having an electrolytic cell is provided on the ground without excavation work for installing the electrolytic cell in the soil, and the groundwater contaminated by ions containing fluorine atoms can be purified. The investment cost can be kept low.

  In addition, by covering the positive electrode in the electrolytic cell and the periphery thereof with a semipermeable membrane that allows only negative ions to pass therethrough, it is possible to collect ionic water containing high-concentration fluorine atoms between the positive electrode and the semipermeable membrane. .

  This recovered ionic water containing high concentration fluorine atoms is transferred to a precipitation tank, and calcium-containing components can be added to produce calcium fluoride, which can be dehydrated by solid-liquid separation means and dried by drying means. After the adjustment, by adjusting the particle size by the crushing means, there is an effect that a valuable material such as a cement raw material can be obtained from the contaminant.

  In the present invention, groundwater contaminated with fluorine atom-containing ions is pumped up by pumping means, and the pumped-up groundwater is put into an electrolytic cell provided on the ground.

  By using a screw pump as the pumping means, groundwater can be pumped at a constant rate.

  The electrolytic cell is a movable unit, and a pair of positive and negative electrodes is provided in the electrolytic cell.

  In addition, although it does not specifically limit as a material of an electrode, Platinum, palladium, and gold with a small ionization tendency are desirable for the positive electrode side.

  By applying DC voltage from 40V to 60V to the pair of electrodes in this electrolytic cell and electrolyzing the injected groundwater, negative ions such as fluorine atom-containing ions, hydroxide ions, nitrate ions, etc. are on the positive electrode side. The metal ions such as copper and lead move to the negative electrode side.

  By changing the DC voltage from 40 V to 60 V, it is possible to prevent the deposition on the electrode on the positive electrode side in particular due to the movement of the ionized product.

  The reason why the DC voltage to be applied is preferably 40V to 60V is as follows.

  That is, when the applied voltage is in the range of 0 V to less than 40 V, the force attracting each ion to the electrode is weak, and conversely, when the applied voltage exceeds 60 V, the force attracting each ion to the electrode is rapidly increased.

  A semi-permeable membrane that allows only negative ions such as fluorine atom-containing ions to pass through is provided around the positive electrode side of the pair of electrodes.

  Ionized water containing fluorine atom-containing ions having a high concentration between the semipermeable membrane and the positive electrode is transported to the precipitation tank by a transport pump.

  By adding a calcium-containing component to the precipitation tank, a precipitate is generated, and the precipitate is transported to a horizontal centrifugal separator as a dehydrating means for solid-liquid separation.

  By adding slaked lime or calcium carbonate that does not contain chlorine as an additive to the settling tank, it is not necessary to remove chlorine from the cake after dehydration, which makes it easy to make it a valuable resource.

  The solid-liquid separated liquid is returned to the electrolytic cell.

  Moreover, the dehydrated cake component can produce a solid substance by drying the moisture content to 5% or less by a paddle type drying device as a drying means.

  As a means for reducing the moisture content of the dehydrated cake to 5% or less, a paddle type drying apparatus that can draw up the dehydrated cake with a paddle and increase the number of times of contact with the heating surface is optimal.

  Moreover, since the produced | generated solid component has added slaked lime or calcium carbonate, it becomes calcium fluoride or its mixture by a chemical reaction.

  However, since these calcium fluorides and mixtures thereof have various particle shapes, by adjusting the particle size using a pulverizer as a pulverizing means, fluorine atom-containing ions can be used as a valuable cement material or soil improvement. It can be used as a material.

  Further, in groundwater containing a large amount of fluorine atom-containing ions, it can also be used as a raw material for hydrogen fluoride.

  That is, zero emission type environmental recycling can be realized.

  Embodiments of the present invention will be described below with reference to the drawings.

(Example)
As shown in FIGS. 1 and 2, in order to pump up contaminated groundwater, one or more pumping wells 1 are provided in the underground permeable layer, and one or more observation wells 2 are used for observing the pollution state downstream of the pumping well 1. The contaminated groundwater containing fluorine atom-containing ions is pumped up by a pumping means 3 such as a screw pump installed in each well while controlling the flow rate to a constant amount.

  The pumped ground water flows into a flow rate adjustment tank 4 provided on the ground.

  Then, the clean water from the flow rate adjustment tank 4 flows into the electrolytic cell unit 5.

  The electrolytic cell unit 5 is provided with a pair of electrodes, and a DC voltage of 40V to 60V is applied between the electrodes.

  By applying a DC voltage, positive ions (eg, copper ions, lead ions, zinc ions, etc.) are on the negative electrode 6 side, and negative ions (eg, fluorine ions, hydroxide ions, cyan ions, nitrate ions, etc.) are , Move to the positive electrode 7 side.

  Here, a semi-permeable membrane 8 through which only negative ions pass is provided around the positive electrode 7 side of the electrolytic cell unit 5, and a high concentration collected between the semi-permeable membrane 8 and the positive electrode 7 is provided. Negative ion water such as fluorine atom-containing ions can be transported to the precipitation tank 10 by the transport pump 9.

  The above-described precipitation tank 10 is provided with a stirring blade 11, and by adding a calcium chemical 12 (slaked lime, calcium carbonate) to the precipitation tank 10, a chemical reaction can be generated to generate calcium fluoride. Calcium fluoride is precipitated at the bottom of the precipitation tank 10 by performing neutralization treatment for pH adjustment after charging the calcium chemical 12.

  Since the precipitated calcium fluoride has a high water content, it is sent to the horizontal centrifugal separator 13 by the transport pump (B) 14 in the dehydration step, and is solid-liquid separated.

  The centrifuge 13 adjusts the water content of calcium fluoride, which is a solid content, to about 60%, and the dehydrated liquid is sent to the flow rate adjustment tank 4.

  Since calcium fluoride, which is a dehydrated solid, still has a high water content, it is conveyed to the paddle-type drying device 15 by a conveyor 16 in the subsequent drying step, and dried until the water content becomes 5% or less. .

  Since the dried calcium fluoride does not have a uniform particle size, it can be obtained by adjusting the particle size through a pulverizer 17 to obtain a calcium fluoride having a uniform particle size, which is sent to the storage tank 18 at the subsequent stage.

  This granular calcium fluoride can be reused as a raw material for cement or a raw material for hydrogen fluoride, so that contaminated groundwater is rendered harmless and zero emission type valuables can be treated.

  The purification method of the present invention is, for example, a method for purifying groundwater contaminated with harmful pollutants in the vicinity of places where substances that can be harmful pollutants are used or discharged, such as electronic parts factories, metal product factories, and glass manufacturing factories. Is extremely useful.

1 is a schematic cross-sectional view showing an outline of an embodiment of the present invention. Process flow diagram showing an overview of an embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pumping well 2 Observation well 3 Pumping means 4 Flow control tank 5 Electrolytic cell unit 6 Negative electrode 7 Positive electrode 8 Semipermeable membrane 9 Transport pump 10 Precipitation tank 11 Stirring blade 12 Calcium medicine 13 Centrifuge 14 Transport pump ( B)
15 Drying device 16 Conveyor 17 Crusher 18 Storage tank

Claims (8)

The groundwater contaminated with fluorine atom-containing ions is pumped by pumping means, and the groundwater is put into the electrolytic cell, and then the groundwater is electrolyzed by applying a DC voltage to the positive and negative electrodes provided in the electrolytic cell. A method of recovering the fluorine atom-containing ions in the groundwater, comprising a semipermeable membrane around the positive electrode, and the groundwater between the semipermeable membrane and the positive electrode. After transporting to a sedimentation tank, adding a calcium-containing component to the sedimentation tank to produce a precipitate, transporting the precipitate to a dehydrating means and separating it into solid and liquid, and then generating a solid substance by a drying means The method for removing fluorine atom-containing ions is characterized in that the particle size is adjusted by a pulverizing means subsequent to the drying means. 2. The method for removing fluorine atom-containing ions according to claim 1, wherein the solid material whose particle size is adjusted by the pulverizing means is used as a valuable material. 2. The method for removing fluorine atom-containing ions according to claim 1, wherein an applied voltage of the DC voltage is 40V to 60V. 2. The method for removing fluorine atom-containing ions according to claim 1, wherein the pumping means is a screw-type pump that controls pumping of groundwater. The method for removing fluorine atom-containing ions according to claim 1, wherein the calcium-containing component is at least slaked lime or calcium carbonate. The method for removing fluorine atom-containing ions according to claim 1, wherein the dehydrating means returns the separated liquid separated to an electrolytic cell. 2. The method for removing fluorine atom-containing ions according to claim 1, wherein the drying means is a paddle type drying apparatus. 2. The fluorine atom-containing ion removal method according to claim 1, wherein the dehydrating means is a horizontal centrifugal separator.

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