JPS5815063B2 - Automatic analysis method for trace amounts of nitrate and nitrite ions in factory wastewater - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a new simple and highly accurate analytical method for simultaneously and automatically measuring trace amounts of nitrate ions and nitrite ions contained in factory wastewater, etc. .

In recent years, denitrification treatment has been actively studied, and in order to conduct research on denitrification treatment and smooth operation of this wastewater, it is necessary to accurately and quickly analyze trace amounts of nitrate and nitrite ions during the treatment process or at the point of discharge. is needed.

However, there is currently no method or device that can accurately and quickly analyze minute amounts of nitrate and nitrite ions on the order of ppm contained in industrial wastewater, etc., which is precipitated, turbid, colored, and contains organic compound ions. is strongly requested.

In view of this, the present inventors have found that nitrate ions (hereinafter referred to as NO3-) and nitrite ions (hereinafter referred to as NO2-) in factory wastewater
We have been carrying out research and development for some time with a focus on

Until now, ultraviolet absorption methods have rarely been used to measure NO3- and NO2- in factory wastewater, etc., due to the large influence of coexisting components.

However, as shown in Japanese Patent Application No. 51-152826 (Japanese Unexamined Patent Publication No. 53-77586) and Japanese Patent Application No. 51-152828 (Japanese Unexamined Patent Publication No. 53-77585), the present inventors found that iron ions, which have a particularly large influence on ultraviolet measurement, We have already invented a continuous measurement device for NO, - and NO2 - based on ultraviolet absorption method by introducing a pretreatment method in which metal ions are precipitated and separated as hydroxides.

These inventions were ideal measuring devices for industrial wastewater containing precipitates and metal ions; It was found that there was a problem in showing the correct error in the case of industrial wastewater with

Additionally, there is a need to accurately measure extremely small amounts of both components.

Therefore, the present inventors continued research and development to solve the above problems, and developed a pretreatment technique for removing organic compound ions and solution coloring by activated carbon treatment, and NO3-2NO2 using ion exchange resin. We mainly investigated techniques for measuring trace components by concentrating -.

Through these research and developments, we have improved analytical accuracy and accuracy based on the basic principles of precipitate removal, activated carbon treatment, ion exchange concentration, and ultraviolet absorption method.
The present invention provides a method for simultaneous automatic analysis of trace NO3- and NO2- concentrations in industrial wastewater with high sensitivity.

The present invention will be explained in detail with reference to explanatory diagrams of an embodiment of the present invention shown in FIGS. 1 to 5.

The present invention removes precipitates and turbidity contained in factory wastewater through filtration treatment, removes coloring and organic compound components that interfere with ultraviolet absorption method through activated carbon treatment, and then removes NO.
3- and NO2- are adsorbed and captured on an ion exchange resin, concentrated, and eluted with a small amount of eluent to obtain NO3.
The basic principle is an ultraviolet absorption method that measures the amount of absorption of each of the wavelengths in the ultraviolet region by applying the fact that - has maximum absorption at 302 nm and NO2 - has maximum absorption at 355 nm.

As shown in FIG. 1, the apparatus according to the embodiment of the present invention includes sediment separation sections 1 to 1 for removing precipitates contained in factory wastewater, and activated carbon treatment sections 9 to 1 for removing coloring, organic compound ions, etc. from wastewater.
4a, ion exchange concentrators 14b to 18, which adsorb and concentrate NO3 and NO2- on the ion exchange resin and elute them;
Each part of the detection and measurement units 19a to 21b and sequence programmer 2 for quantifying O3- and NO2- amounts by ultraviolet absorption method
The main body is an automatic control section 2.

Reference numeral 1 denotes a sample collection pipe, which is connected to a discharge point of factory wastewater, etc.

2 is a liquid feeding pump, and 3 is a pipe for supplying the collected wastewater to a continuous filtration device 4.

5 is the main part of the continuous filtration device, and is a filtration drum that filters out sediments and turbidity in the wastewater that interfere with ultraviolet absorption measurement or clog the activated carbon column.

Reference numeral 8 denotes a suction pump, which sucks the clean sample solution filtered by the filter drum through the sample suction tube 7a and sends it to the sample receiver 9.
It is intended to be transferred to

The filtration application drum 5 is a sealed oblong cylinder with a large number of small holes on the outer circumferential surface and a filter cloth wrapped around the holes, and a suction port for the sample suction tube 1a is arranged downward on the inner circumferential surface of the cylinder. The pipe 7a is brought out from the side of the cylinder and connected to the suction pump 8.

The filter cloth used was one in which a filter paper with a small pore diameter (such as Type 5 B) was layered on the inside and a filter cloth with a large pore diameter (such as felt) was layered on the outside, and this was wrapped around the cylinder of the filtration drum 5. .

Factory wastewater containing sediment is supplied from the sample supply pipe 3 so as to fall onto the filter cloth surface around the outer periphery of the filtration drum 5.

Since the pressure inside the filtration drum is reduced by the suction pump 8, the precipitates in the supplied wastewater remain on the surface of the filter cloth, and the filtrate, which has become transparent after the precipitates have been removed, passes through the sample suction tube 7a. It is sucked into the suction pump and sent to the receiver 9.

Generally, industrial wastewater contains a lot of sediment and is often turbid, but according to the above filtration method, it was possible to perform continuous filtration treatment with a quick response without causing clogging or leakage. .

In addition, even in the case of wastewater that is suspended with precipitates such as iron hydroxide, such as neutralized pickling wastewater containing a large amount of iron ions, the sample supply pipe 3 can be Since the filter cloth is supplied by dropping it onto the filter, no sediment is deposited on the surface of the filter cloth that the waste water hits, and the surface of the filter cloth is always clean, so no clogging occurs and smooth continuous filtration can be carried out. .

On the other hand, the extra wastewater sample that was not subjected to suction filtration was
The sample residual liquid is discharged to the outside together with the removed precipitate through the sample residual liquid discharge pipe 6.

Reference numeral 10a denotes a constant flow pump for sending the cleaned wastewater sample sent from the continuous filtration device and received in the sample receiver 9 to the activated carbon column via the sample suction tube 7b.

Reference numeral 10b is a constant flow pump for adding and mixing a certain amount of salt solution to the above-mentioned wastewater sample, and reference numeral 11 is a chest for storing the salt solution.

12 is a 1-shaped 3 for mixing the wastewater sample and the saline solution.
It is a bifurcation joint.

13 is an activated carbon column, which is a cylindrical tube with an inner diameter of about 10 to 20 mmφ and a length of 500 mrnf and 50 to 100 mm.
It is filled with coconut shell activated carbon about the size of a mesh.

Although the aforementioned continuous filtration equipment removed the sediments and turbidity contained in the factory wastewater, the coloring of the wastewater and the coexisting organic compound ions often exhibit ultraviolet absorption, and NO3- and N
In order to accurately measure the concentration of O2-, these must also be removed.

It is generally said that these colors and organic compound ions can be removed by activated carbon treatment, but
There was a problem that NO3- and NO2- were also adsorbed by activated carbon.

According to the study results of the present inventors, NO3- and NO2-
The adsorption of NO3-N onto activated carbon depends on the pH of the solution, the amount of activated carbon, and the amount of NO3-N.
Although it depends on the concentration of O2-, if about 10 g of coconut shell activated carbon is added to 100 rIL of a solution containing about 1 ppm of NO3- and NO2-, the NO3 concentration will be about 40%.
The result was that -2N02- was adsorbed on activated carbon.

It has also been found that when the pH of the solution is 4 or less, and as the amount of activated carbon increases, the adsorption and capture rate on activated carbon becomes even higher.

Therefore, as a result of research and study on conditions in which the solution is colored and organic compound ions are selectively adsorbed, while NO3- and NO2- are not adsorbed, we found that over a certain amount of Na+, K+, Ca2+Mg2+, etc. in the wastewater. It has become clear that this objective can be achieved by coexisting alkali metal ions or alkaline earth metal ions.

FIG. 2 shows test results regarding the recovery rates of NO3 and NO2- in activated carbon treatment when Na+ was added.

Figure 2 shows 100 ml of a solution containing 1.0 ppm of NO3- and NO2- using NaCl to convert Na+ from 0 to 0.
．． This is the result of determining the recovery rate by quantifying the amount of NO3- and NO2- in the liquid obtained by adding 2 g of activated carbon after 8% phase addition and suction filtration.

According to this result, when almost no Na+ is included, only 60% of NO3- and NO2- can be recovered, but 0
．． When it contained 4% or more, 100% recovery was possible.

In the experiment shown in Figure 2, instead of Na, +Mg'', Ce2
Similar results can be obtained when + or NH4+, etc. are added, and by adding and mixing solutions of inorganic salts such as chlorides and sulfates containing these elements to the wastewater sample, coloring of the wastewater sample and organic compound ions can be removed. is adsorbed and captured on activated carbon,
No.

It became possible to recover 100% of NO2- and NO2-.

The salt solution is stored in a tank 11, and the constant flow pump 1
A salt solution is fed into the flow of the wastewater sample fed into the activated carbon column 13 by the constant flow pump 10b at a constant flow rate so as to have a predetermined concentration, and mixed through a three-way branch joint.

The flow path switching device 14a located next to the activated carbon column has the role of switching the flow path to replace the previous analysis sample remaining in the activated carbon column with the sample solution to be analyzed this time.
The initial flow of the sample solution supplied by the pump 10a is through the discharge pipe 15a.
discharge from.

Next, after the inside of the activated carbon column 13 is replaced with a new sample solution to be analyzed, the switch 14a is switched so that the flow path is connected to the ion exchange column.

The constant flow pump 10a measures the sample solution.
Constant flow performance of the pump is required.

A constant flow pump with a set of double plungers with little pulsation used for liquid chromatographs is suitable.

When such a pump is used, a fixed amount of sample solution can be easily sampled automatically by automatically controlling the operating time of the pump 10a.

Reference numeral 14b is a flow path switching device for sending the sample solution that has passed through the activated carbon column 13 and the eluent or regeneration liquid that is sent by the constant flow pump 10c to the ion exchange column 16.

14d is a flow path switch for sending the eluent in the eluent tank 17 and the regenerating liquid in the regenerating liquid tank 18 to the ion exchange column 16 via the constant flow pump 10c.The eluent is 10% NaCl. Pure water was used as the solution and regeneration liquid.

14c is a flow path switching device for sending the solution discharged from the ion exchange column 16 to the discharge pipe 15b or to the flow cell of the ultraviolet absorption meter.

The ion exchange column has an inner diameter of approximately 110 mmφ and a length of 100 m.
This is a cylindrical column with a diameter of approximately 5 ml filled with an anion exchange resin of approximately 5 ml.

The wastewater sample that has passed through the activated carbon column 13 is transferred to the switching devices 14a and 1.
4b and sent to the ion exchange column 16, NO￥
and NO2 are adsorbed and captured by the ion exchange resin.

Adsorption to this resin is reliable and 0. Trace amount of N below lppm
Even in the case of O, No, no leakage is observed.

Next, a 10% NaCl solution is sent from the eluent tank to the ion exchange column using a constant flow pump 10c.

NO3- and N that had been adsorbed and captured by the ion exchange resin
O□- and the like are immediately eluted and sent to a flow cell of an ultraviolet absorption meter, where the concentrations of both ions are measured and recorded.

Next, the switch 14d is switched to supply pure water from the regenerating liquid tank 18 to the column 16 using the pump 10c to regenerate the resin.

As shown in Figure 3, NO3- and NO2- both exhibit absorption in the ultraviolet region, with wavelengths of 302 nm and 355 nm, respectively.
It has a very thick absorption wavelength in nm.

The curve shown at 23 in FIG. 3 is the absorption spectrum of NO3-, and the curve shown at 24 is the absorption spectrum of NO,7.

Therefore, the ultraviolet absorption meters 20a and 20b must have a structure that can measure ultraviolet absorption at wavelengths around 302 nm and 355 nm.

Although FIG. 1 shows the case where two ultraviolet absorption meters 20a and 20b are provided, it is also possible to use one ultraviolet absorption meter with one light source and two types of measurement wavelengths.

Alternatively, a spectrophotometer that can accurately set measurement wavelengths of 302 nm and 355 nm or an ultraviolet absorption meter with a set of interference filters that can set measurement wavelengths of around 302 nm and 355 nm may also be used.

However, as shown in Figure 3, the absorption spectrum of NO,- is interfered with by the absorption spectrum of NO2-, causing a positive error, so it is necessary to correct the NO2- concentration when measuring the NO3- concentration. .

The correction is made by first investigating the percentage of correct error due to NO2- concentration at the NO3- measurement wavelength, and then correcting it by subtracting the affected absorption amount.1N03- and NO2- measurement wavelengths are set to 302 nm and 355 nm. In this case, the measured value of NO3- will have a positive error equivalent to about 30% of the measured value of NO2-, which was present, so the measured value of NO2- will change by around 0.3 from the measured value of NO2-. Correct by subtracting the value multiplied by the numerical value.

This correction may be calculated and corrected based on the measured values, but
Automatic correction can be easily performed by incorporating an electric circuit.

In addition, the absorption amount of NO2- at the maximum absorption wavelength of NO3- is as shown by the arrow in Figure 3 (NO2- at 384 nm).
Since the absorption amount is the same as that of NO3 at 302 nHl, the absorption at a wavelength of 384 nm is measured separately.
Correction can also be easily carried out by a two-wavelength photometry method in which the value is subtracted from the absorption amount of -.

The flow cells 19a and 19b are made of quartz and have a small internal volume so that the solution can be replaced quickly.

The NO, - and NO- adsorbed on the ion exchange resin are
When the 0% NaCl eluent is eluted at a flow rate of 10 ml/mrn, the entire amount of NO,- and NO' is eluted in an extremely short period of time and passes through the flow cell.

FIG. 4 shows the elution curve of NO recorded on the recorder 21a under the above conditions.

Figure 5 shows an example of a calibration curve for a constant amount of NO3- and NO2 when 100 ml of a wastewater sample is analyzed and a flow cell with an optical path length of 40 mvIL is used. I was able to find it with good accuracy.

22 is an automatic controller, which controls each pump 2.8,
10a, 10b, 10c, each flow path switch 14a, 14b
, 14c, 14d and the ultraviolet absorption meter 20ay'20b, etc. are lead wires 23a, 23b.

23c..., and functions to automatically control all operations as described above according to a predetermined operation program.

The present invention, which has been explained in detail above, allows the analysis sample to be collected in the sample collection tube.
All operations are automatically processed after sampling, and the amount of nitrate ions and nitrite ions are simultaneously and quickly measured.

In addition, Zn”, Pb”, Cr”t, which may coexist
Metal ions such as Ni2+y Cu2'' or Fi c
There is no interference of ions such as l, 5(J4, NH4", ca", etc.).

The coexistence of Cr6>, Fe2+, and Fe3+ may give a positive error, but if the former is reduced to Cr3+ by adding a reducing agent during the wastewater sampling stage, and the latter is made alkaline and precipitated as iron hydroxide, then the Interference can be easily prevented.

This is a new device that is useful and practical as a simultaneous automatic analyzer for trace amounts of nitrate ions and nitrite ions, with excellent quantitative sensitivity and accuracy, and capable of rapid quantitative determination.

The present invention greatly contributes to the field of environmental analysis of factory wastewater, etc., which has become particularly important in recent years, as well as to fields such as wastewater treatment processes, monitoring of wastewater, and process management analysis of production plants.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the apparatus according to the present invention, Figure 2 is an explanatory diagram of the effect of salt addition in activated carbon treatment, Figure 3 is an ultraviolet absorption spectrum diagram of nitrate ions and nitrite ions, and Figure 4 is an illustration of the present invention. An example of a measurement chart using the apparatus and FIG. 5 are diagrams showing a calibration curve. 1...Sample collection tube, 2...Liquid pump, 3...Sample supply tube, 4...Continuous filtration device, 5...・Filtration drum, 6... Sample residual liquid discharge pipe, 7a, 7b... Sample suction tube, 8...
...Suction pump, 9...Sample receiver, 10
a, 10 b, 10 c”... Constant flow pump, 11... Salt solution tank, 12...
3-way branch joint, 13... activated carbon column,
14a, 14b. 14 c, 14 cl"""1ffl three-way switch, 15a. 15b, 15c...Discharge pipe, 16...
Ion exchange resin column, 17... Eluent tank, 18... Regeneration liquid tank, 19a, 19b...
... Distribution cell, 20a. 20b... Ultraviolet absorption meter, 21a, 21b...
... Recorder, 22 ... Automatic controller, 23a
, 23b. 23c... Automatic controller lead wire, 24...
...Nitrate ion absorption spectrum, 25...Nitrite ion absorption spectrum.

Claims (1)

[Claims] 1 After adding and mixing a salt solution containing an alkali metal or alkaline earth metal ion to the filtrate obtained by filtering an analysis sample solution such as factory wastewater, the mixture is passed through an activated carbon layer, and the activated carbon layer effluent is transferred to an ion exchange resin layer. nitrate ions and nitrite ions are adsorbed and captured by the resin, then an eluent is fed into the resin layer at a constant flow rate to elute the adsorbed and captured ions, and the eluate is passed through an ultraviolet absorption meter. 302n of eluate is fed into a flow cell and filtered through the cell.
Measure and record the absorption amount near m and 355 nm, and
The amount of nitrite ion is determined from the absorption amount near 55 nm, 302
An automatic analysis method for trace amounts of nitrate ions and nitrite ions in factory wastewater, characterized in that the amount of nitrate ions is simultaneously determined from the absorption amount in the vicinity of nm, and each of these operations is automatically performed.