JP2006138660A - Pretreatment method of analysis of metal in soil and fluorescent x-ray analyzing method using method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for analyzing a metal non-uniformly distributed in polluted soil, powdery food or the like with high precision and high sensitivity. <P>SOLUTION: This pretreatment method is characterized in that a mixture process of a sample for use in the analysis of a metal in polluted soil is set to a wet system and, water or an organic liquid in components under wet sieve is dried and removed on a heat-resistant plastic film. The fluorescent X-ray analyzing method employing this pretreatment method is also disclosed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pretreatment method for analyzing metals contained in contaminated soil using a fluorescent X-ray method, a total reflection fluorescent X-ray method, or the like.

  In the conventional pretreatment of metal analysis in contaminated soil by the fluorescent X-ray method, etc., mixing, drying, crushing, sieving, etc. are performed as individual unit operations. Mixing is a normal method, and a method of mixing after pouring water is not usually performed. Moreover, since the under-sieving component has been dried before sieving, it is usually not performed in the subsequent steps. This is thought to be mainly because the method determined by the Ministry of the Environment notification requires air drying, crushing, and sieving. If a simple analysis method not based on this notification is to be carried out, wet pulverization, wet mixing, and wet sieving methods may be devised relatively easily, but a method using a heat-resistant heating belt as the subsequent drying means Is not known.

  Investigation of metal contamination of soil is carried out by measurements such as fluorescent X-ray method, atomic spectrum method, and colorimetric method. While the mined soil is a large quantity of several hundred to several thousand grams and several hundred to several thousand square centimeters, the sample necessary for these measurements is a weight test of 6 g or more in the content test of the official method by the Ministry of the Environment notification. In general operation, it is about 6-15 grams. Moreover, since the irradiation area in the fluorescent X-ray method is several square millimeters, which is several orders of magnitude smaller than that of the mother soil, it is doubtful whether or not it is a part representing the entire sample in the case of non-uniform contamination. For this reason, it is always a problem whether the obtained analysis result indicates a contamination state. The main cause of interlaboratory errors is considered to be insufficient mixing of samples. In order to solve this, measures such as a five-point mixing method have been taken. This method is disadvantageous in that the mixing work is manual, and in order to exert the mixing effect, it is necessary to mix 5 points each of mother soil of the order of kilograms. The method of measuring 5 points instead of the mixing operation is disadvantageous in that the amount of measurement work is 5 times. In particular, mixing clay and moist soil is a labor-intensive task. When clay or wet soil is dried, the soil often hardens and often cannot be mixed without being crushed. Also, drying takes a lot of time of several tens of hours. In order to prevent pollution, this drying waiting time is most disliked because it delays the countermeasure work.

  In addition, the analysis method for the amount of metal contained in the official method is not only drying and sieving time, but also the extraction time and the extraction equipment are heavy loads. As the method, the fluorescent X-ray method for analyzing the solid as it is is becoming mainstream. A simple analysis method using a solution after extraction is not so popular because it takes time not only for extraction time but also for mixing, drying, and sieving in the previous steps. Furthermore, in the case of the fluorescent X-ray method, unlike the atomic spectrum method or the colorimetric method, in order to improve the detection sensitivity, it is required to make the sieve screen finer to about 100 mesh, that is, about 0.2 mm in particle diameter. The load of this sieving work is large. In order to improve the analysis accuracy, it is necessary to keep the measurement surface smooth and keep the distance from the fluorescent X-ray detector constant.

As means for solving these problems, for example, there is Patent Document 1. In the method described in Patent Document 1, since there is no mixing step, the uneven distribution of metal cannot be averaged to increase the accuracy. Although the case of pouring water is also described, the subsequent process is a draining process, there is no drying process, and the water-soluble metal component flows away in the draining process, resulting in a large negative error. That is, the above method is mainly used for efficient selection of contaminated soil, and is insufficient in terms of analysis accuracy.
JP 2003-166156 A

  The present invention has been made in order to solve the above-described problems in the prior art, and is a pretreatment operation for fluorescent X-ray analysis of metals in soil, that is, drying, pulverization, sieving, molding, and conventional methods. There are two characteristic means that are not seen in the above: (1) Wetting of the mixing step, (2) Drying and removing of water or organic liquid after the sieving step, using a heating belt made of a heat-resistant resin It aims to solve the above-mentioned drawbacks.

  In the present invention, water or organic liquid is poured into a soil of kilogram order to make a slurry or soften before drying, and then pulverized and mixed with energy such as mechanical force, ultrasonic wave, and heating, and then sieved in a slurry state. And dripping the soil slurry under the sieve onto a belt of several tens of centimeters in width and several tens of centimeters made of heat-resistant plastic material or an independent sheet, and then drying by heating and blowing on the belt or sheet. Then, it is formed into about several millimeters, which is the minimum thickness required for the fluorescent X-ray method, and variations of about several hundred micrometers, which is the minimum smoothness required. The dry-molded lamellar soil is analyzed with a fluorescent X-ray apparatus having one or more detection heads while moving or stopping on a belt or sheet. After the analysis is completed, the soil on the belt or sheet is scraped off by a scraping knife. By such means, a pretreatment method for metal analysis in soil that solves the problems of the prior art and various analysis methods using the same are provided.

  According to the present invention, by pre-processing metal-contaminated soil analysis and analyzing by fluorescent X-ray analysis or the like, the distribution of soil-contaminated metal is unevenly distributed or localized. However, it can be analyzed with high accuracy, and the probability of suffering an economic and social loss due to a wrong determination of the presence or absence of contamination is reduced.

  FIG. 1 shows a schematic diagram of a main part of a fluorescent X-ray analysis method to which a pretreatment method according to an embodiment of the present invention is applied. In this pretreatment method, a premixing tank 1 for premixing a soil sample and water or an organic liquid, a stirrer 2 for stirring in the premixing tank and the hopper, a funnel 3 constituting the hopper, supplied soil 4, water 5, The first sieve 6 constituting the hopper, the pinch valve 7 for supplying the mixed and pulverized soil slurry to the second sieve, the second sieve 8 finer than the first sieve, the finer third sieve, and the belt for heating and drying the soil slurry Nozzle 10 to be fed to, heat-resistant plastic soil slurry heating and drying belt 11, belt driving rotation mechanism 12, belt presser 13 for bringing the belt into close contact with the fluorescent X-ray detection head, belt rotation mechanism motor 14, belt heating heater 15. Lifting mechanism 16 for contacting / separating the heater with the belt, fan 17 for blowing dry / cooling air, and scraping the soil on the belt Soil scraper rubber 18 to be recovered in this manner, holder 19 for bringing soil scraper rubber into contact with and separating from the belt, recovered soil container 20, sieve base 21, belt base 22, control mechanism base 23, fluorescent X-ray analyzer and pre-processing unit control Notebook computer 24 and fluorescent X-ray analyzer 25.

  An example of preferable conditions in the present invention is shown below as operation specifications.

(1) The amount of soil is preferably about 500 g, and if it is 5 g or less, the representativeness of the contaminated soil is bad, and if it is 2000 g or more, it overflows from the stirring tank. Here, about 500 g was taken in a plastic pre-stirring tank (1 liter diameter: about 10 cm, depth: about 13 cm). : Time required 30 seconds (2) The amount of injected water is preferably about the same as the soil weight. Here, 400 milliliters of about 1 times the soil weight was injected. : About 10 seconds (3) Stirring with a propeller: 3 minutes (4) The mixture was poured into a funnel through a first sieve having an opening of 3 mm. The pre-stirring tank was washed with 100 ml of water, and the cleaning solution was also poured into the funnel: 30 seconds (5) After setting the stirrer in the funnel and starting stirring, the pinch valve solenoid valve was opened for about 5 seconds, and the nylon 1 mm and 0 .Inject into 2nd and 3rd sieves consisting of 3 mm (sieve diameter 50 mm, sieve interval: 10 mm) (changed every time). Large particles fall a little earlier due to natural flow, but get caught on the first sieve. About 100 ml of the soil component of 0.3 mm or less to be analyzed passed through the sieve for about 5 seconds while the electromagnetic valve was opened while being well homogenized throughout the dispersion. The solenoid valve was closed in about 5 seconds. This was seen to be representative of the entire sample of 0.3 mm or less. The passing amount is preferably about 1/50 to 1/2 of the input amount. Below 1/50, the representativeness is poor. At 1/2 or above, stirring in the second half cannot be performed idly, the sieve cannot withstand the weight, the sieve underflows from the belt, the analysis time is long, and the efficiency is high. There are disadvantages such as lowering.

  (6) The bottom of the sieve was discharged from a funnel-shaped nozzle having an outlet diameter of 10 mm onto the belt-shaped heating element. Discharge time is about 6 seconds. The belt starts to move with the opening operation of the solenoid valve, and stops 3 seconds after the closing operation. The belt speed was about 4 cm per second. The belt moved for about 8 seconds in 5 seconds in the open state and 3 seconds thereafter, and moved about 32 cm. On the belt, a paste-like soil having a length of about 25 cm × 10 cm and a thickness of about 3 mm was formed. The sieve, solenoid valve and stirring tank were removed by hand after one batch and washed with water. The remainder of the stirring tank was stored in a soil collection tank.

  (7) The soil riding on the 150 ° C. movable belt-like heater with a blowing function is dried on the stopped belt and changed to film-like soil.

(8) Belt material: Polyimide resin film Thickness of about 0.1mm
(9) Heat generation method: Heat generation roller and heating plate indirect heating method (10) Heater width 25 cm Heating body upper length 50 cm The width is preferably 15 to 30 cm. When it is narrower than 15 cm, the soil overflows from the belt side, which is not preferable. If it is wider than 30 cm, the portability of the device is poor. Here, the width was 25 cm. When the length is shorter than 40 cm, the feeding speed is slow, and overflow from the belt side tends to occur. If it is longer than 80 cm, the portability of the device is poor. Here, the length was 50 cm.

  (11) The dropping speed is about 20 ml per second. The dripping rate is almost determined by the clay nature of the soil, so there is little room for selection. Therefore, the lower limit of quantification is secured by adjusting the total dropping time. The total dropping time is preferably from 2 seconds to 10 seconds. If it is shorter than 2 seconds, the lower limit of quantification is bad. If it is longer than 10 seconds, overflow from the belt side tends to occur due to the belt speed.

  (12) The evaporation rate was about 30 ml per minute.

  (13) The belt moving speed is preferably slightly faster than the speed at which the sieved soil flows and spreads, and is selected to be about 4 cm per second. Belt stop time in the drying process is about 3 minutes. Usually, a moderately dry state was obtained in 2.5 to 3.5 minutes. Thereafter, the heating plate was lowered several mm to stop the heating.

  (14) The thickness of the membranous soil formed is 1.5 mm.

  (15) Following the drying step, the belt was moved at a moving speed of about 0.3 mm per second, and analysis was started with a fluorescent X-ray head. To suppress the lifting of the belt running on the fluorescent X-ray head, a guide slit with a groove width of 0.13 mm and a groove depth of 10 mm is provided near the fluorescent X-ray head so that the fluorescent X-ray head is always in close contact with the belt. To keep.

  (16) The total accumulated time of the soil was 14 minutes. The total accumulated time is preferably 3 to 30 minutes. When the time is less than 3 minutes, the sensitivity of the fluorescent X-rays is deteriorated. When the time is more than 30 minutes, the efficiency of the entire process is lowered.

(17) Irradiation beam diameter 10 mm
(18) Thereafter, the heating plate is raised again to preheat the belt. Further, in order to continue the soil recovery on the belt, the robot moves forward by about 5 cm at 0.3 mm per second for another 3 minutes. This completes the collection of soil on the belt. The belt starts moving at 4 cm per second on the next start. This is repeated. During the fluorescent X-ray measurement of the next sample, that is, in the process where the belt speed is 0.3 mm per second, the previous sample is scraped off by a rubber knife. During this time, because of the low speed of 0.3 mm per second, the wear of the belt due to the friction between the knife and the belt is relatively small.

  (19) As a result of scraping the detection-completed soil with a urethane rubber knife, the residual soil was not visible. The peeled soil was stored in a recovered soil case.

  In the above example, the total analysis time is about 21 minutes for the first sample, and the second and subsequent samples are processed at intervals of about 21 minutes. During this time, if preparatory work such as washing, assembly, and the like for the next sample processing of the stirring tank, electromagnetic valve, sieve, and data processing are performed, the worker can efficiently perform pretreatment and analysis. Comparison was made between the case where lead in 3 kg of lead-contaminated soil was subjected to a fluorescent X-ray simple on-site analysis by the method of the present invention and the case where a conventional method was used to analyze the fluorescent X-ray simple on-site. In the conventional method, about 10 g each is collected from 6 places, about 60 g in total is dried with a dryer for about 40 minutes, pulverized and mixed in an agate mortar for about 5 minutes for a total of 30 minutes, and the sieve is measured for about 3 minutes each. It took 20 minutes. The analysis took 30 minutes in total, 5 minutes per piece, and took about 120 minutes in total. As a result, according to the conventional method, the average value of the six analyzes from the pretreatment was 110 mg / kg, and the individual data was 10 g at one time even though lead was relatively unevenly distributed. 50 to 640 mg / kg, and the range was 590 mg / kg. On the other hand, in the case of the method of the present invention, the required time is approximately the same at about 120 minutes, and since the amount collected at one time is 500 g and pretreated six times, that is, the method of pretreating the whole amount of 3 kg, the average value is 190 mg / kg, individual data is 140 to 200 mg / kg, and the range is 60 mg / kg, which is reduced to about 1/10. Furthermore, 15 g was sampled by the method of Ministry of the Environment Notification No. 19 and the results of pretreatment and ICP emission analysis of 6 locations were 170 mg / kg on average, individual data was 80-490 mg / kg, and the range was 410 mg / Kg. The range of the present invention was smaller than that of the conventional method, and the deviation from the official method was also small. In an actual site, it is rare to analyze six locations of one sample of mined kg-order soil, and it is often the case that the presence or absence of contamination is determined by analysis at one location. In that case, the possibility of misjudgment is considerably less than in the conventional method.

  Furthermore, the soil of the fluorescent X-ray head part is less soiled by the lower surface irradiation than the upper surface irradiation, and continuous use for a long period of time becomes possible.

  In 2 of FIG. 1, water containing 30 v / v% ethanol was used as the stirring tank injection water. The drying speed was reduced by about 1 minute to about 2 minutes.

  As mentioned above, although the Example of this invention was described, this invention is not limited to this Example, Even if there is a design change in the range which does not deviate from a summary, it is contained in this invention. For example, in Example 1, the amount of soil input is 500 g. However, even if it is about 200 g, for example, the same analysis is possible. In addition, the analysis method is not limited to the X-ray fluorescence method, but is a comparatively local analysis such as a total reflection X-ray fluorescence method or a laser excitation emission method. This pretreatment method is also effective for analyzes that require uniformity. In addition, the target sample is not limited to soil, and can be applied to food, minerals, chemicals, pharmaceuticals, and the like as long as it is in powder form.

(Industrial applicability)
To provide a highly accurate and sensitive method for analyzing metals that are unevenly distributed in contaminated soil and powdered foods.

  The metal detected by the method of the present invention is a metal having high sensitivity in a fluorescent X-ray apparatus such as lead, cadmium, chromium, arsenic, and selenium.

1 is a pretreatment mechanism and a fluorescent X-ray analyzer according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Preliminary mixing tank 2 Stirrer 3 Funnel 4 Soil 5 Water 6 First sieve 7 Pinch valve 8 Second sieve 9 Third sieve 10 Nozzle 11 Belt heating element 12 Rotating mechanism 13 Belt presser 14 Motor 15 Heater 16 Vertical mechanism 17 Fan 18 Soil scraping rubber 19 Holder 20 Collected soil container 21 Sieve mount 22 Belt mount 23 Control mechanism mount 24 Notebook PC (for fluorescent X-ray device and pre-treatment device)
25 X-ray fluorescence analyzer

Claims (4)

  It comprises a step of injecting water or organic liquid into a sample for metal analysis in soil and performing wet mixing, followed by drying and removing the water or organic liquid in the wet sieving component, and comprises a heat-resistant plastic film as a drying means. A pretreatment method using a sheet-like or belt-like heating element.   An analysis method using the pretreatment method according to claim 1.   After injecting water or organic liquid into a sample for metal analysis in soil and wet-mixing it, dry the water or organic liquid in the wet sieving components and remove the water or organic liquid from the heat-dried film side. And a sheet-like or belt-like heating element made of a heat-resistant plastic film as a drying means.   The fluorescent X-ray analysis method according to claim 3, further comprising a step of scraping the soil on the belt of the previous sample during X-ray irradiation.

Images