WO2015190161A1

WO2015190161A1 - Method and apparatus for measuring concentration of heavy metal scavenger

Info

Publication number: WO2015190161A1
Application number: PCT/JP2015/060321
Authority: WO
Inventors: 寿和 ▲高▼橋; 義尚岸根
Original assignee: 栗田工業株式会社
Priority date: 2014-06-13
Filing date: 2015-04-01
Publication date: 2015-12-17
Also published as: JP5880625B2; JP2016003878A; TW201610416A

Abstract

Provided are a measurement method and measurement apparatus by which it is possible to stably and reliably measure the concentration of a dithiocarbamate-based heavy metal scavenger in a water sample. The measurement method includes adding a heavy metal compound to a water sample that contains a dithiocarbamate-based heavy metal scavenger, developing a color by allowing the heavy metal compound to react with the dithiocarbamate-based heavy metal scavenger that remains in a waste water containing the heavy metal, then measuring the absorbance or transmittance of light having wavelengths of 400-700 nm, and measuring the concentration of the dithiocarbamate-based heavy metal scavenger in the water sample on the basis of these measurement results, wherein the pH is stabilized by adding a pH buffer solution to the water sample.

Description

Method and apparatus for measuring heavy metal collector concentration

The present invention relates to a method and a measuring apparatus for measuring a concentration of a dithiocarbamic acid heavy metal scavenger in water based on light transmittance or absorbance.

Heavy metal-containing wastewater such as plating wastewater and paint wastewater contains heavy metals such as copper, chromium, zinc, lead, manganese, iron, nickel, and cadmium. These heavy metal-containing wastewater is appropriate according to the Water Pollution Control Law, etc. Is obliged to carry out appropriate processing.

As a method for treating heavy metal-containing wastewater, a method is known in which a chelating heavy metal scavenger mainly composed of dithiocarbamic acid groups is added to perform a coagulation sedimentation treatment (Patent Document 1). In the treatment method of heavy metal containing wastewater using this dithiocarbamic acid type heavy metal scavenger, chelate heavy metal scavenger addition is performed when chelating heavy metal scavenger is added and treated regardless of the water quality fluctuation of heavy metal containing wastewater. The quality of treated water decreases due to insufficient or excessive addition. In the case of excessive addition, the cost of the dithiocarbamic acid heavy metal scavenger increases.

In Patent Document 1, as a method of adding a chelate heavy metal scavenger to heavy metal-containing wastewater to remove heavy metal components in the wastewater, a chelate heavy metal scavenger is added to the heavy metal-containing wastewater, and this chelate heavy metal A method is described in which the addition amount of the scavenger and the amount of change in the oxidation-reduction potential of the wastewater before and after the addition of the chelate heavy metal scavenger are measured, and the required addition amount is determined based on the measurement result. Yes.

The chelate heavy metal scavenger has a chelate-forming group (dithiocarbamic acid group), and this group reacts with heavy metal ions in the wastewater to form an insolubilized product and generate a precipitate. During this reaction, the redox potential (ORP) decreases. According to the method of Patent Document 1, when the ORP is changed, that is, when the addition concentration of the chelate heavy metal scavenger to the wastewater to be treated is changed, the ORP becomes lower as the addition concentration of the heavy metal scavenger increases. It is used to change.

Patent Document 2 describes a method for measuring the concentration of residual dithiocarbamic acid heavy metal scavenger in heavy metal-containing wastewater to which a dithiocarbamic acid heavy metal scavenger is added. In this measurement method, a heavy metal compound such as a water-soluble iron salt or copper salt is added to a heavy metal-containing wastewater to which a dithiocarbamate heavy metal scavenger is added, and a heavy metal ion and a residual dithiocarbamate heavy metal scavenger are added. React to develop color. Then, the absorbance or transmittance at 400 to 700 nm is measured, and the residual scavenger is quantified.

Specifically, after ferrous chloride is added to a sample water containing a dithiocarbamate heavy metal scavenger to cause color development, this liquid to be measured is placed in a transparent measurement cell, and light of a specific wavelength is received. Use to measure the absorbance (or transmittance). Separately from this, for example, the absorbance (or transmittance) is obtained from the transmitted light intensity of light of a specific wavelength with respect to the transparent liquid. Then, the concentration of the dithiocarbamic acid heavy metal scavenger in the sample water is determined using a calibration curve showing the relationship between the absorbance (or transmittance) and the lysate concentration prepared in advance with a sample having a known concentration.

As described in Patent Document 2, the absorbance (or transmittance) measuring apparatus includes a transmission type in which a light-emitting element and a light-receiving element are arranged so as to sandwich a measurement cell, and Patent Document 3 There is a reflection type in which a reflector is used and a light emitter and a light receiver are arranged on the same side as described in.

By the way, the reaction between the dithiocarbamic acid-based heavy metal scavenger and heavy metal ions varies depending on the pH. Therefore, the absorbance (or transmittance) of the liquid to be measured varies depending on the pH. For this reason, in order to accurately measure the dithiocarbamic acid heavy metal scavenger, it is necessary to prepare a calibration curve corresponding to the pH of the liquid to be measured.

That is, when the liquid to be measured is alkaline, some of the heavy metal ions become heavy metal hydroxide without reacting with the dithiocarbamic acid heavy metal scavenger. Therefore, when the heavy metal hydroxide absorbs incident light to the measurement cell, the measured absorbance increases (or the transmittance decreases) than the absorbance corresponding to the amount of the dithiocarbamic acid heavy metal scavenger in the sample water. There is. Also, the heavy metal ions added to the sample water are consumed as heavy metal hydroxides, and the dithiocarbamic acid heavy metal collector in the sample water does not react completely, and the dithiocarbamic acid heavy metal collector contained in the sample water The measured absorbance may be lower (or the transmittance increased) than the absorbance corresponding to the amount, and the concentration of the dithiocarbamic acid heavy metal scavenger could not be measured accurately.

Therefore, in order to accurately determine the concentration of the dithiocarbamate heavy metal scavenger in the sample water, it is necessary to create a calibration curve for each pH of the solution to be measured, and prepare a huge calibration curve for the continuous measurement device. There was a problem that had to be. In addition, when the liquid to be measured is alkaline, there is a problem that the concentration of the dithiocarbamic acid heavy metal scavenger cannot be determined accurately.

JP 2001-340874 A JP 2014-28342 A JP 2010-181150 A

In view of the above points, an object of the present invention is to provide a measurement method and a measurement apparatus capable of accurately measuring the concentration of a dithiocarbamic acid heavy metal scavenger in sample water.

The method for measuring the concentration of a dithiocarbamic acid heavy metal scavenger according to the present invention comprises adding a heavy metal compound to sample water containing a dithiocarbamic acid heavy metal scavenger, and dithiocarbamic acid heavy metal remaining in the heavy metal-containing wastewater containing the heavy metal compound. Dithiocarbamine that measures the absorbance or transmittance at a wavelength of 400 to 700 nm after reacting with the collection agent to develop color, and measures the concentration of the dithiocarbamate heavy metal collection agent in the sample water based on the measurement result In the method for measuring the concentration of an acid heavy metal scavenger, a pH buffer solution is added to the sample water to stabilize the pH.

An apparatus for measuring the concentration of a dithiocarbamic acid-based heavy metal scavenger according to the present invention includes an adding means for adding a heavy metal compound to sample water containing a dithiocarbamic acid-based heavy metal scavenger, the heavy metal compound and the heavy metal-containing wastewater remaining in the waste water. A measuring means for measuring the absorbance or transmittance at a wavelength of 400 to 700 nm after reacting with a dithiocarbamic acid heavy metal scavenger to develop a color, and based on the measurement result, collecting the dithiocarbamic acid heavy metal in the sample water An apparatus for measuring the concentration of a dithiocarbamic acid heavy metal scavenger having an arithmetic means for calculating the concentration of the agent, further comprising means for adding a pH buffer solution to the sample water.

The pH buffer solution is preferably a neutral pH buffer solution having a pKa of 6 to 8.

The pH buffer solution contains N- (2-acetamido) -2-aminoethanesulfonic acid, N- (2-acetamido) iminodiacetic acid, N, N-bis (2-hydroxyethyl) -2-amino as a pH buffering agent. Ethanesulfonic acid, bis (2-hydroxyethyl) iminotris (hydroxymethyl) methane, 3- [N, N-bis (2-hydroxyethyl) amino] -2-hydroxypropanesulfonic acid, 3- [4- (2- Hydroxyethyl) -1-piperazinyl] propanesulfonic acid, 2- [4- (2-hydroxylethyl) -1-piperazinyl] ethanesulfonic acid, 2-hydroxy-3- [4- (2-hydroxylethyl) -1- Piperazinyl] propanesulfonic acid, 2-morpholinoethanesulfonic acid, 3-morpholinopropanesulfonic acid, 2-hydroxy 3-morpholinopropanesulfonic acid, piperazine-1,4-bis (ethanesulfonic acid), piperazine-1,4-bis (2-hydroxy-3-propanesulfonic acid), 2-hydroxy-N-tris (hydroxymethyl) It is preferable to contain water containing at least one selected from the group consisting of methyl-3-aminopropanesulfonic acid and N-tris (hydroxymethyl) -2-aminoethanesulfonic acid.

As the heavy metal compound, a water-soluble iron salt and / or copper salt, particularly an iron salt is preferable.

In the present invention, a pH buffer solution is added to sample water containing a dithiocarbamate heavy metal scavenger to stabilize the pH of the solution to be measured. Thereby, the concentration of the dithiocarbamic acid heavy metal scavenger in sample water of various pHs can be accurately measured.

The concentration of the dithiocarbamic acid heavy metal scavenger can be obtained without preparing a large amount of calibration curve data for each pH in the calculation unit for the concentration of the dithiocarbamic acid heavy metal scavenger.

It is a block diagram which shows the processing system of heavy metal containing waste_water | drain. It is a block diagram of the measuring apparatus of the dithiocarbamic acid type heavy metal scavenger which concerns on embodiment. It is a perspective view of a measurement cell part. It is a circuit diagram of a light emission part. It is a circuit diagram of a light-receiving part. It is a flowchart which shows the density | concentration measuring method of the dithiocarbamic-acid type heavy metal scavenger which concerns on embodiment. It is a graph which shows an experimental result.

Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

The method and apparatus according to the present invention adds an inorganic flocculant and a dithiocarbamic acid heavy metal scavenger in this order to a heavy metal containing wastewater, and reacts the heavy metal in the wastewater with the scavenger to insolubilize the heavy metal containing wastewater. In the processing method, it is suitable for use when measuring the concentration of the scavenger.

This heavy metal-containing wastewater includes steel, semiconductor, and automobile manufacturing plating processes, smoke cleaning of garbage factories and power plants, dust collection processes, batteries, glass manufacturing processes, metal processing processes, landfill leachate from industrial waste treatment plants, etc. Although the drainage from is illustrated, it is not limited to this.

Examples of heavy metals in the heavy metal-containing wastewater include, but are not limited to, mercury, cadmium, arsenic, lead, hexavalent chromium, selenium, copper, zinc, manganese, iron, nickel, tin, and cobalt.

The heavy metal ion concentration in the wastewater containing heavy metal is usually about 100 ppm or less, for example, about 1 to 50 ppm, but is not limited thereto.

Examples of the dithiocarbamate heavy metal scavenger include dithiocarbamate, dialkyldithiocarbamate, cycloalkyldithiocarbamate, piperazine bisdithiocarbamate, tetraethylenepentamine dithiocarbamate, and polyamine dithiocarbamate. However, the present invention is not limited to this. In addition, these 1 type may be used independently and may use 2 or more types together.

An insolubilized product is generated by adding a dithiocarbamic acid heavy metal scavenger to the heavy metal-containing wastewater and preferably stirring slowly.

It is possible to add an inorganic flocculant and a polymer flocculant to this insolubilized material-containing liquid, and preferably agitate slowly to agglomerate this insolubilized material with the inorganic flocculant and coarsen the floc with the polymer flocculant. It becomes.

As the inorganic flocculant, PAC, aluminum sulfate, iron (I) chloride, iron (II) chloride, iron (I) sulfate, polyiron sulfate (II) and the like can be used. Polymer flocculants include anionic polymer flocculant homopolymers of acrylamide, copolymers of sodium acrylate and acrylamide, terpolymers of sodium acrylate, acrylamide and 2-acrylamido-2-methylpropanesulfonic acid. Can be used.

As described above, an inorganic flocculant and a polymer flocculant are added to the liquid containing the insolubilized material generated by the addition of the dithiocarbamic acid heavy metal scavenger, if necessary, and then subjected to solid-liquid separation treatment. . A heavy metal compound is added to the solid-liquid separation treated water to cause color development, and the concentration of the dithiocarbamic acid heavy metal scavenger in the treated water is measured.

Examples of heavy metal compounds (coloring reagents) that are added to the heavy metal scavenger-added water and react with the residual scavenger to develop a color (Fe2 ⁺ , Fe3 ⁺ , Cu2 ⁺ , Zn2 ⁺ , Pb2 ⁺ , Ni2 ⁺ , Cd2 ^+). , Sulfate salts such as Mn ^2+, and water-soluble salts such as hydrochloride, etc. However, since no special treatment is required at the time of discharge after the degree of color development or analysis, a salt of Fe ²⁺ or Fe ³⁺ Ferrous, ferrous sulfate, ferric chloride, and ferric sulfate are preferred.

In general, when the heavy metal compound is added to a dilute aqueous solution of the dithiocarbamic acid heavy metal scavenger, the color becomes deeper as the amount of the heavy metal compound increases, but the total amount of the scavenger in water and the added heavy metal compound When the reaction amount exceeds the reaction amount, the color development does not become deeper even if the heavy metal compound addition amount is increased. Therefore, in the present invention, when the concentration of the residual scavenger in water is quantified, the heavy metal compound (coloring reagent) is more than the above reaction amount (for example, about 1 to 10 times, particularly about 1.5 to 5 times the reaction amount). ) Is preferably added. Usually, it is desirable to add a heavy metal compound (coloring reagent) to the sample water in an amount of 20 mg / L or more, particularly 50 mg / L or more, for example, 20 to 200 mg / L, particularly 50 to 150 mg / L.

In the present invention, not only the coloring heavy metal compound but also a pH buffer solution is added to sample water containing heavy metal to stabilize the pH. In particular, when the pH is stabilized at 6 to 8, the measurement sensitivity is improved. Therefore, the pH buffer in this pH buffer is preferably a pH buffer having an acid dissociation constant pKa of 6 to 8, particularly 6 to 7.

Also, heavy metal-containing wastewater may contain a large amount of metals such as calcium and magnesium. These metals reduce the pH buffer capacity by reacting with the pH buffer solution. Therefore, it is preferable that the pH buffer in the pH buffer is a pH buffer having poor reactivity with metals. Specifically, pH buffering agents include N- (2-acetamido) -2-aminoethanesulfonic acid, N- (2-acetamido) iminodiacetic acid, N, N-bis (2-hydroxyethyl) -2- Aminoethanesulfonic acid, bis (2-hydroxyethyl) iminotris (hydroxymethyl) methane, 3- [N, N-bis (2-hydroxyethyl) amino] -2-hydroxypropanesulfonic acid, 3- [4- (2 -Hydroxyethyl) -1-piperazinyl] propanesulfonic acid, 2- [4- (2-hydroxylethyl) -1-piperazinyl] ethanesulfonic acid, 2-hydroxy-3- [4- (2-hydroxylethyl) -1 -Piperazinyl] propanesulfonic acid, 2-morpholinoethanesulfonic acid, 3-morpholinopropanesulfonic acid, 2-hydroxy-3 Morpholinopropanesulfonic acid, piperazine-1,4-bis (ethanesulfonic acid), piperazine-1,4-bis (2-hydroxy-3-propanesulfonic acid), 2-hydroxy-N-tris (hydroxymethyl) methyl- Although at least one selected from the group consisting of 3-aminopropanesulfonic acid and N-tris (hydroxymethyl) -2-aminoethanesulfonic acid is preferred, it is not limited thereto.

The pH buffering agent is not limited as long as the pH of the sample water can be adjusted to a neutral pH of about 6 to 8. Since the pH buffering capacity increases as the pH buffer solution becomes higher in concentration, it is usually preferable to adjust the concentration of the pH buffering agent to 10 to 40% by mass and add 0.5 to 2% by mass in the sample water.

It is preferable that the pH buffer solution is added to the sample water before the heavy metal compound (coloring reagent). When the pH of the sample water fluctuates, the reaction rate between the heavy metal scavenger and the color developing heavy metal compound fluctuates, which may cause an error in the concentration measurement result.

On the other hand, the concentration of the dithiocarbamic acid heavy metal scavenger in the sample water can be accurately measured by adding the pH buffer before adding the color developing heavy metal compound, regardless of the pH of the sample water.

After adding a pH buffer and a heavy metal compound and measuring the absorbance or transmittance, the residual collector concentration in the heavy metal collector-added water is determined based on a calibration curve (or calibration relationship) determined in advance. This calibration curve (or calibration relationship) is obtained from the absorbance or transmittance measured by adding a heavy metal compound of the reaction amount or higher to a collecting agent aqueous solution having a known concentration. In the present invention, it is sufficient to prepare a calibration curve (or calibration relationship) having a pH range of about 6-8.

The measurement of absorbance or transmittance is preferably performed after removing turbidity such as insolubilized material in order to eliminate the influence of insolubilized material. When a heavy metal compound (coloring reagent) is added to the treated water after the solid-liquid separation treatment, the absorbance can be measured as it is, but the heavy metal compound is added to the heavy metal collector-added water before the solid-liquid separation. In this case, it is desirable to separately remove turbidity by sedimentation separation or filtration before measuring the absorbance.

Based on the thus obtained concentration of the collection agent in the heavy metal collection agent-added water, it is possible to control the amount of the dithiocarbamic acid heavy metal collection agent added to the aggregating treatment liquid using the inorganic flocculant. .

The measurement wavelength of absorbance or transmittance is 400 to 700 nm, preferably 400 to 660 nm, and particularly preferably 400 to 500 nm. When the wavelength is shorter than this range, it is affected by other organic compounds in the waste water, and the sensitivity is also lowered. If the wavelength is longer than this range, the sensitivity decreases.

Hereinafter, a flow of a wastewater treatment method for controlling the amount of the collection agent added to the wastewater based on the concentration of the collection agent in the solid-liquid separation treated water obtained by adding a dithiocarbamic acid heavy metal collection agent to the heavy metal-containing wastewater and performing solid-liquid separation. An example will be described with reference to FIG.

In FIG. 1, heavy metal-containing wastewater flows in the order of a reaction tank 1, a coagulation tank 2, a precipitation tank 3, and a treated water tank 4. Add the dithiocarbamic acid heavy metal scavenger aqueous solution in the tank 7 to the heavy metal-containing wastewater introduced into the reaction tank 1 with the chemical injection pump 8, and stir with a stirrer (not shown) to react the heavy metal with the scavenger. To produce an insolubilized product. The insolubilized substance-containing liquid in the reaction tank 1 is introduced into the agglomeration tank 2, and the inorganic flocculant and the polymer flocculant are added by the adding

devices

2a and 2b to aggregate the insolubilized substances in the liquid and coarsely aggregate flocs. Make it. The water containing the coarsened floc is subjected to solid-liquid separation processing in the settling tank 3, and the settled sludge is extracted from the bottom of the settling tank 3 and sent to the dehydration process. The supernatant water of the sedimentation tank 3 is introduced into the treated water tank 4 as treated water.

Most of the treated water is sent from the submersible pump 5 to the outside of the system through the pipe 6. A part of the treated water is supplied to a dithiocarbamic acid heavy metal scavenger concentration measuring device 10 (hereinafter referred to as concentration measuring device 10) via a pipe 6a branched from the pipe 6 and a valve 6b to collect the dithiocarbamic acid heavy metal. The concentration of the collecting agent is measured.

According to the measurement result, the chemical injection control device 9 controls the discharge amount of the chemical injection pump 8, and the amount of the heavy metal scavenger aqueous solution added to the reaction tank 1 is controlled. The chemical injection control device 9 decreases the chemical injection amount of the dithiocarbamic acid heavy metal collector by the chemical injection pump 8 by a predetermined amount when the concentration of the heavy metal collector in the treated water is larger than a preset value. . On the other hand, when the concentration of the heavy metal scavenger in the treated water is smaller than a preset value, the amount of medicine injected by the medicine pump 8 is increased by a predetermined amount. The method of increasing / decreasing the amount of the chemical injection is not particularly limited, but the on / off timing of the chemical injection pump 8 may be adjusted, or the frequency of the current supplied to the chemical injection pump 8 may be adjusted. After changing the chemical injection amount, the system waits for a predetermined time. After the predetermined time has elapsed, the concentration of the dithiocarbamic acid heavy metal scavenger in the treated water is measured again, and the chemical injection amount is adjusted according to the result.

Among the treated water taken into the concentration measuring device 10, surplus waste that is not used for measuring the concentration of the heavy metal scavenger is returned to the treated water tank 4. Further, the measured drainage is sent to a drainage treatment system (not shown) for processing.

<Concentration measuring device 10>
FIG. 2 is a block diagram for explaining an example of the concentration measuring apparatus 10, and FIG. 3 is a schematic perspective view of a cell portion.

A cell 11 is provided so that treated water as sample water is introduced from the pipe 6a. The pipe 6a for introducing the sample water is connected to the lower surface of the cell 11, and the pipe 12 for discharging the measurement waste liquid is connected to the upper surface.

The pair of side surfaces of the cell 11 is made of a transparent material such as acrylic, glass, or quartz. A light emitting device 13 having a light emitting element 13a is disposed on one side of the cell 11 and a light receiving device 14 having a light receiving element 14a is disposed on the other side.

A reflective cell in which a reflective material is provided on the other side surface of the cell 11 and the light emitting device 13 and the light receiving device 14 are arranged so as to face the one side surface of the cell 11 may be used.

In the cell 11, a coloring reagent solution made of the heavy metal compound aqueous solution in the tank 15 can be introduced by the pump 16 and the pipe 17. Further, a pH buffer solution can be introduced into the cell 11 through a tank 18, a pump 19 and a pipe 20.

The

pumps

16 and 19, the light emitting device 13, and the bulb 6b are controlled by the measurement control device 22. The detection signal of the light receiving device 14 is input to the measurement control device 22, and the concentration of the dithiocarbamic acid heavy metal scavenger in the sample water (treated water) is calculated. The calculation result is given to the medicine injection control device 9.

Preferred forms of the cell 11, the light emitting device 13, the light receiving device 14, etc. will be described next.

The measurement cell 11 is preferably formed of a black material except for the light transmitting portion in order to prevent reflection on the inner surface.

An example of the size of the cell 11 is a transparent part for light transmission of about 2 mm thick, a cell lateral width T of about 50 m, a cell depth of about W 4 mm, a cell height of about H 8 mm, and a capacity of the cell 11 of about 1.6 mL. It is not limited to this.

<Light-emitting device 13>
As shown in FIG. 3, the light-emitting device 13 includes a light-emitting element 13a and a circuit board (not shown) housed in a case 13b. A power supply connector is installed on the circuit board, and a power supply cable 13c is connected to the circuit board.

The emission wavelength of the light emitting element 13a is not particularly limited as long as it includes the visible light region. As the light emitting element 13a, for example, a white light emitting diode (white LED) can be used. A measurement wavelength may be adjusted by installing a filter in front of the light emitting element 13a. A lens may be disposed in front of the light emitting element 13a to diffuse or collect light.

As shown in FIG. 4, the energization circuit to the light emitting element 13a is composed of a light emitting element 13a and a variable resistor 13d. The variable resistor 13d may be a resistance value selection type resistor. By adjusting the resistance value of the variable resistor 13d, the current flowing through the light emitting element 13a is adjusted, and the light emission intensity is adjusted. Note that the light emission intensity may be adjusted by adjusting the power supply voltage Vcc shown in FIG. 4 to adjust the current flowing through the light emitting element 13a.

<Light receiving device 14>
As shown in FIG. 3, the light receiving device 14 includes a light receiving element 14a and a circuit board (not shown) housed in a case 14b. The internal circuit board is provided with a power supply connector, to which a power supply cable 14c is connected.

As shown in FIG. 5, in this embodiment, the light receiving device 14 includes three photodiodes D1 to D3 as light receiving elements and a wavelength body of light in the visible light region (590 nm to 720 nm, 480 nm). Red (R, R, R, R, R, R) light (red, green, blue, and blue light in sequence) that is obtained through a red, green, and blue region component light obtained by the following method. ) Filter, green (G) filter, and blue (B) filter.

As shown in FIG. 5, the internal circuit of the light receiving device 14 amplifies the currents flowing through the photodiodes D1, D2, and D3 by the main circuits C1 to C3 and converts them into voltages, and amplifies the voltages by the operational amplifiers O1 to O3. It is configured to be given to the arithmetic processing unit 14d. The arithmetic processing device 14d is installed in the light receiving device 14, but may be installed in the measurement control device 22.

The light receiving element is not limited to a photodiode, and a phototransistor, a solar cell, or the like may be used.

<Arithmetic processing device 14d>
14 d of arithmetic processing units are the relationship between the calculation part which performs specific arithmetic processing, each light transmittance (absorbance) in red, green, and blue band light for every kind of heavy metal collection agent, and a heavy metal collection agent. The storage part which memorize | stores the data regarding the analytical curve which shows this, and the transmission part which transmits the density | concentration of a heavy metal collection agent.

The calculation unit can calculate the time average intensity for each band light based on the intensity signals of the red, green, and blue band lights output from the light receiving device 14. In addition, the calculation unit subtracts the transmitted light intensity of the non-absorbed light from the transmitted light intensity of the light in which the specific color is absorbed to obtain the absorbance (or light transmittance) obtained by performing baseline correction in the red, green, and blue band light. ) Can also be calculated.

The calculation unit can also calculate the concentration of the heavy metal scavenger from the absorbance (or light transmittance) in red, green, and blue band light. Specifically, a calibration curve indicating the relationship between the light transmittance and the heavy metal scavenger concentration is stored in the storage unit, and the concentration of the heavy metal scavenger can be calculated from the absorbance or the light transmittance.

<Measurement control device 22>
The measurement control device 22 has a timing for flowing the treated water into the cell 11, a timing for adding the pH buffer in the tank 18 into the cell 11, and a timing for adding the color reagent in the tank 15 into the cell 11. Control. Further, the concentration data of the dithiocarbamic acid heavy metal scavenger in the treated water sent from the arithmetic processing device 14d is recorded, and a signal indicating the concentration of the dithiocarbamic acid heavy metal scavenger in the treated water is sent to the drug injection control device 9. Send.

The measurement control device 22 has a storage element such as an element having a calculation function and a semiconductor memory. The storage element is preferably a nonvolatile memory. For example, a microcontroller, a microprocessor, an FPGA, or the like can be used as an element having an arithmetic function, and a storage element can be configured by an EEROM, a flash memory, a hard disk, or the like. In the memory element, an OS, a program for executing each process related to the concentration measurement method described below, and the like are stored.

The measurement process of the concentration of the dithiocarbamic acid heavy metal scavenger in the sample water (treated water) according to this program will be described below. FIG. 6 is a flowchart showing an example of this process.

First, treated water is flowed into the cell 11 from the pipe 6a. The flow rate and the flow time are not particularly limited, but for example, the flow rate is 33 mL / min for about 3 minutes. Thereafter, the flow of treated water is stopped. Then, light is emitted from the light emitting device 13 to the cell 11 filled with treated water for 1 minute.

The arithmetic processing unit 14d calculates the light intensity of the red, green, and blue band light by averaging the intensity of the light received by the light receiving device 14 for about one minute. Thereby, the light absorbency or light transmittance of the treated water before adding the coloring reagent can be measured.

Next, the pump 19 is operated for a predetermined time, a predetermined amount of a pH buffer solution is added into the cell 11 filled with the treated water to stabilize the pH of the treated water, and then the pump 16 is operated for a predetermined time. A predetermined amount of coloring reagent is added into the cell 11. After the coloring reagent is added, it is allowed to stand for a predetermined time and the coloring reaction proceeds sufficiently, and then the absorbance or light transmittance is measured in the same manner as in the treated water.

The arithmetic processing unit 14d calculates the absorbance using the measurement result for the treated water before the addition of the coloring reagent and the measurement result for the measurement target liquid to which the coloring reagent is added.

When the liquid to be measured in the cell 11 is colored yellow by adding a coloring reagent such as ferrous chloride, the liquid to be measured hardly absorbs red band light and green band light, Only the blue band light which is complementary color light is absorbed. Therefore, the absorbance or transmittance can be obtained only from the blue band light.

When the measurement target liquid is colored blue, for example, the measurement target liquid absorbs almost no blue band light but absorbs red band light and green band light. Therefore, the absorbance or transmittance can be obtained from only red band light and green band light.

When the liquid to be measured is colored white, brown, black, etc. by adding a coloring reagent such as ferrous chloride, the liquid to be measured has red band light, green band light, and blue band light. Absorbs light in all wavelength bands. Therefore, the wavelength band may be selected according to the concentration of the heavy metal scavenger and the concentration of the heavy metal scavenger may be calculated.

[Example 1]
The following seven dithiocarbamic acid heavy metal scavenger aqueous solutions with different pH were prepared as sample water, and a pH buffer solution was added to the sample water to measure absorbance.
<Dithiocarbamic acid heavy metal scavenger aqueous solution>
Dissolve sodium hydroxide in pure water to prepare sodium hydroxide aqueous solution adjusted to

pH

6, 7, 8, 9, 10, 11 or 12, and collect dithiocarbamic acid heavy metal in each sodium hydroxide aqueous solution. An agent (Wellclean (registered trademark) (manufactured by Kurita Kogyo Co., Ltd.)) was added so that the concentration was 10 mg / L.

Sample water was prepared by adding 5 mL of piperazine-1,4-bis (ethanesulfonic acid) (PIPES) 20% by mass aqueous solution as a pH buffer solution to 50 mL of each aqueous solution. The aqueous pH buffer solution was adjusted to pH 6.5 using sodium hydroxide.

For each sample water, the light transmittance G ₀ of the green band (480 nm to 600 nm) was measured. This light transmittance was set to 100%.

Next, 1 mL of a 0.025 mass% aqueous solution of iron (I) chloride was added as a coloring reagent to 55 mL of each sample water. After 6 minutes from the addition of the coloring reagent, the light transmittance G ₁ of the green band (480 nm to 600 nm) of each solution was measured, and the absorbance was calculated by the following equation. The results are shown in FIG.

Absorbance ABS = Log ₁₀ (G ₀ / G ₁ )

[Example 2]
The light transmittance was measured and the absorbance was calculated in the same manner as in Example 1 except that 5 mL of a 20% strength by weight aqueous solution of 2-morpholinoethanesulfonic acid (MES) was added as a pH buffer solution. The results are shown in FIG.

[Comparative Example 1]
The light transmittance was measured in the same manner as in Example 1 except that no pH buffer solution was added, and the absorbance was calculated. The results are shown in FIG.

<Discussion>
As shown in FIG. 7, in the case of Comparative Example 1 in which no pH buffer solution is added to the sample water, the absorbance changes depending on the pH of the sample water. On the other hand, in Examples 1 and 2 to which a pH buffer solution was added, the absorbance was almost constant regardless of the pH of the sample water. In addition, about the sample of less than pH 6, since the dithiocarbamic acid type heavy metal scavenger decomposes | disassembles and it cannot perform comparative examination, it was not implemented. However, by adjusting the pH of the sample water, the concentration of the dithiocarbamic acid heavy metal scavenger can be accurately measured even for sample water having a pH of less than 6.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2014-122461 filed on June 13, 2014, which is incorporated by reference in its entirety.

Claims

Add a heavy metal compound to sample water containing a dithiocarbamic acid heavy metal scavenger,
After reacting the heavy metal compound and the dithiocarbamic acid heavy metal scavenger remaining in the heavy metal-containing wastewater to cause color development, the absorbance or transmittance at a wavelength of 400 to 700 nm is measured,
Based on this measurement result, in the concentration measurement method of the dithiocarbamic acid heavy metal scavenger for measuring the concentration of the dithiocarbamic acid heavy metal scavenger in the sample water,
A method for measuring the concentration of a dithiocarbamic acid-based heavy metal scavenger, wherein a pH buffer solution is added to the sample water to stabilize the pH.
2. The method for measuring the concentration of a dithiocarbamic acid heavy metal scavenger according to claim 1, wherein the pH buffer solution is a neutral pH buffer solution of pKa 6-8.
3. The pH buffer according to claim 2, wherein the pH buffer is N- (2-acetamido) -2-aminoethanesulfonic acid, N- (2-acetamido) iminodiacetic acid, N, N-bis (2-hydroxyethyl) as a pH buffering agent. ) -2-aminoethanesulfonic acid, bis (2-hydroxyethyl) iminotris (hydroxymethyl) methane, 3- [N, N-bis (2-hydroxyethyl) amino] -2-hydroxypropanesulfonic acid, 3- [ 4- (2-hydroxyethyl) -1-piperazinyl] propanesulfonic acid, 2- [4- (2-hydroxylethyl) -1-piperazinyl] ethanesulfonic acid, 2-hydroxy-3- [4- (2-hydroxyl) Ethyl) -1-piperazinyl] propanesulfonic acid, 2-morpholinoethanesulfonic acid, 3-morpholinopropanesulfone 2-hydroxy-3-morpholinopropanesulfonic acid, piperazine-1,4-bis (ethanesulfonic acid), piperazine-1,4-bis (2-hydroxy-3-propanesulfonic acid), 2-hydroxy-N- A dithiocarbamic acid system comprising water containing at least one selected from the group consisting of tris (hydroxymethyl) methyl-3-aminopropanesulfonic acid and N-tris (hydroxymethyl) -2-aminoethanesulfonic acid Method for measuring concentration of heavy metal scavenger.
4. The method for measuring the concentration of a dithiocarbamic acid heavy metal scavenger according to any one of claims 1 to 3, wherein the heavy metal compound is a water-soluble iron salt and / or copper salt.
An adding means for adding a heavy metal compound to a sample water containing a dithiocarbamic acid heavy metal scavenger;
A measuring means for measuring the absorbance or transmittance at a wavelength of 400 to 700 nm after reacting the heavy metal compound and the dithiocarbamic acid heavy metal scavenger remaining in the heavy metal-containing wastewater to cause color development;
On the basis of this measurement result, in a concentration measurement apparatus for a dithiocarbamic acid heavy metal scavenger having a computing means for calculating the concentration of the dithiocarbamic acid heavy metal scavenger in the sample water,
An apparatus for measuring a concentration of a dithiocarbamic acid heavy metal scavenger, comprising means for adding a pH buffer solution to the sample water.