CN111735678B - Separation, enrichment and determination method of gold, platinum and palladium in geochemical sample - Google Patents

Separation, enrichment and determination method of gold, platinum and palladium in geochemical sample Download PDF

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CN111735678B
CN111735678B CN202010625950.9A CN202010625950A CN111735678B CN 111735678 B CN111735678 B CN 111735678B CN 202010625950 A CN202010625950 A CN 202010625950A CN 111735678 B CN111735678 B CN 111735678B
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CN111735678A (en
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邵坤
范建雄
李刚
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Institute of Multipurpose Utilization of Mineral Resources Chinese Academy of Geological Sciences
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Abstract

The invention discloses a separation, enrichment and determination method of gold, platinum and palladium in a geochemical sample, which is characterized in that based on a polyurethane foam plastic molecular structure, a blocky thiocarbamic foam plastic with thiocarbamic functional groups is synthesized according to an organic synthesis principle, saturated chlorine water is prepared, then the geochemical sample is subjected to oscillation decomposition under normal temperature conditions by adopting the saturated chlorine water, trace gold, platinum and palladium in the blocky thiocarbamic foam plastic is subjected to static oscillation enrichment, and the gold, platinum and palladium in a solution is determined by adopting an inductively coupled plasma mass spectrometry (ICP-MS). The saturated adsorption capacity of the blocky thiocarbamic acid functionalized foam plastic in the invention to gold, platinum and palladium is obviously higher.

Description

Separation, enrichment and determination method of gold, platinum and palladium in geochemical sample
Technical Field
The invention belongs to the technical field of noble metal analysis and test, and particularly relates to a separation, enrichment and determination method of gold, platinum and palladium in a geochemical sample.
Background
Noble metals, e.g. gold, platinum, palladium, are very rare distributed in the crust and are very low, e.g. gold is only 5X 10 -7 The content of platinum group element is only 10 percent -7 %-10 -6 % by weight. Because of the rare and important application value, the analysis of trace and ultra-trace noble metal elements is researched, and the method has important significance for geological exploration, evaluation and reasonable exploitation of noble metal mineral resources. With the wide use of noble metals, new requirements and challenges are provided for noble metal prospecting, and in recent years, the task of testing noble metals in geochemical investigation samples is increasing, but the composition of the samples is often very complex, and a large amount of other metal, nonmetal and other matrix components exist, so that separation and enrichment are one of important research contents when carrying out noble metal element content analysis. On the basis of effective enrichment and separation, a proper analysis and test means is adopted, so that satisfactory analysis results can be provided for noble metals in geochemical samples.
The separation and enrichment method of gold, platinum and palladium in the geochemical sample mainly comprises fire test (lead test, nickel matte test, antimony test, bismuth test, etc.), liquid-liquid extraction, precipitation and coprecipitation, ion exchange and adsorption methods, etc. Wherein:
(1) The fire test method is most classical in application, has the advantages of large sampling quantity, capability of guaranteeing the representativeness of samples, and the fire test method (GB/T17418.6-2010, DZ/T0279.31-2016 and the like) is adopted as the gold platinum palladium analysis method in the national and industry standards at present. However, the disadvantages are also apparent: large reagent dosage, higher blank value, environmental pollution and high analysis cost.
(2) The liquid-liquid extraction has the defects that the organic solvent pollutes the environment, the manual operation is complicated, the automation is difficult to realize, and the like.
(3) Precipitation and coprecipitation (tellurium, selenium, thiourea and the like which are common precipitants) also have the problems of complicated operation, time consumption and the like.
(4) The ion exchange has the defects of harsh separation conditions, troublesome operation and long separation period although the separation efficiency is high.
In contrast, the adsorption method is widely applied due to the advantages of simple operation, low cost, high efficiency and the like, and the commonly used adsorption materials of gold, platinum and palladium are activated carbon, foam plastics and the like. The activated carbon has a good effect of adsorbing gold, but has the following problems:
(1) The adsorption capacity for platinum and palladium is limited.
(2) Simultaneously, the method adsorbs the interference elements such as iron, thallium, antimony, tungsten and the like, thereby increasing the subsequent treatment difficulty.
(3) Long analysis time, low analysis rate, high energy consumption and high production cost.
In order to overcome the obvious defects of the separation and enrichment method, researchers have designed a new method. Polyurethane foam is an excellent noble metal adsorption material, the application of the material is very wide, the cost is very low, the material is very suitable for practical production, for example, in the analysis of trace and ultra-trace gold, the method is established as the industry standard (DZ/T0279.4-2016) of the analysis of trace and ultra-trace gold at present by directly putting polyurethane foam in aqua regia with a certain concentration for static oscillation adsorption, and the method is popularized and applied in most of the mining laboratories of the whole country.
Meanwhile, for simultaneous enrichment measurement of gold, platinum and palladium, a mixture liquid of sodium chloride, concentrated hydrochloric acid and saturated potassium permanganate is directly adopted for leaching a decomposed sample, and then polyurethane foam plastic is used for enrichment measurement of gold, platinum and palladium (Liang Huizhen and the like, gold and 2018) in a geochemical sample. But the leaching process is long in time consumption, large in reagent consumption and high in cost.
Thus, by aqua regia, HCl-H 2 O 2 After wet sample dissolution such as alkali melting-acidification, the sample is dissolved in proper hydrochloric acid-SnCl 2 In the adsorption medium with the system concentration, the polyurethane foam plastic can quantitatively enrich gold, platinum and palladium, and then, the content analysis is carried out by combining a modern test instrument, which is the main method for enrichment and measurement of gold, platinum and palladium at present (Ding Yao, metallurgical analysis, 1990; lin Zhihui and the like, physical and chemical examination-chemical division, 2005; wang Ruimin, rock and mineral test, 2011; liu Xianglei and the like, rock and mineral test, 2013).
However, the polyurethane foam plastic enrichment materials adopted by the method have the problems of low adsorption capacity, poor selectivity and the like. Meanwhile, because of the difference in production process of polyurethane foam plastics of different manufacturers or the fine difference in production process of polyurethane foam plastics of different batches of the same manufacturer, the adsorption capacity of the polyurethane foam plastics of different manufacturers or different batches on the market to gold, platinum and palladium is different to some extent, so that the addition amount of the foam plastics cannot be accurately calculated in the actual operation process, on one hand, material waste is caused, and on the other hand, analysis result deviation is caused. This problem directly results in the inability of the polyurethane foam enrichment assay to form a uniform national standard analytical method for gold platinum palladium.
The functional polyurethane foam plastic is characterized in that a certain amount of organic functional groups with specific selectivity to noble metal ions are loaded on the surface of the foam plastic, and the noble metal ions are precisely adsorbed through the functional groups, so that the limitation of the quality of polyurethane foam plastic products is avoided, the influence on the adsorption capacity and accuracy of gold, platinum and palladium caused by the property difference of the polyurethane foam plastic is overcome, the anti-interference capability of the polyurethane foam plastic is enhanced, and the directional adsorption performance of the polyurethane foam plastic is improved. Currently, there are a great deal of researches on functional modification of the surface of polyurethane foam plastic, such as tri-n-octylamine foam plastic (Meng Gong, etc., gold, 2005; yang Zhong, etc., analytical laboratory, 2006), butyl acetate foam plastic (Li Chengyuan, etc., gold, 2005), dithizone foam plastic (Liu Tao, etc., gold, 2005), tributyl phosphate foam plastic (Zheng Xiaozhong, etc., gold science technology, 2014), etc. The modification method of the foam plastics generally comprises the steps of directly adding a large amount of organic solvents for mixing, then carrying out preparation modification by using simple modes of soaking, extruding, kneading and the like, is rough from the whole preparation process flow, does not strictly operate according to the condition of organic synthesis reaction, and leads to the difficulty of loading a large amount of effective functional groups on the surface of the foam plastics, and the loading is mainly physical adsorption, so that the phenomenon that the functional groups fall off is unavoidable when separation and enrichment are carried out, particularly when a common static oscillation adsorption or dynamic column adsorption method is adopted, and the complete enrichment and recovery of gold, platinum and palladium cannot be ensured, so that the instability, the precision reduction and the larger deviation of test results are caused. Meanwhile, the preparation method has long time consumption, serious raw material waste, low yield, large consumption of reagents and environmental pollution caused by a large amount of waste reagents generated after the preparation.
In summary, in order to solve the problems of low adsorption capacity, poor anti-interference capability and the like when gold, platinum and palladium in a geochemical sample are enriched in polyurethane foam plastics, and in order to facilitate the formation of a unified method for separating, enriching and measuring gold, platinum and palladium in polyurethane foam plastics, development of a functional polyurethane foam plastic enrichment material which has higher selectivity for gold, platinum and palladium, has a stable structure and is easy to apply is urgently needed, so that the precision and accuracy of analysis results are improved.
Disclosure of Invention
The invention synthesizes a block foam plastic material with a thiocarbamic acid functional group according to the organic synthesis principle on the basis of knowing the molecular structure of polyurethane foam plastic in detail. The geochemical sample adopts newly prepared chlorine water to be oscillated and decomposed under normal temperature, the thiocarbamic acid functionalized bulk foam plastic material is adopted to statically oscillate and enrich trace gold platinum palladium in the bulk foam plastic material, and a novel method for separating, enriching and measuring trace gold platinum palladium in the geochemical sample is established by combining an inductively coupled plasma mass spectrometry (ICP-MS).
The technical scheme of the invention is as follows:
the separation, enrichment and determination method of gold, platinum and palladium in the geochemical sample is characterized by comprising the following main steps:
(1) The preparation of thiocarbamic foam plastic comprises the following steps:
firstly, placing a cube-shaped polyurethane foam plastic block into a position of 10-15%V/V) Boiling in hydrochloric acid for 2-3 h, washing with water to neutrality, and drying at 50 ℃ to obtain the amino foam plastic.
Adding 50-60 mL of anhydrous ethanol and 10-12 pieces of amino foam into a 250mL three-neck flask with a magnetic stirring device, dropwise adding 15-20 mL of carbon disulfide into a water bath at 30-40 ℃, and preserving heat for 30-40 min at 35-40 ℃ after the dropwise adding is finished; and then dropwise adding 10-15 mL of 50% (m/V) sodium hydroxide solution, preserving heat for 30-40 min, continuously dropwise adding 5-10 mL of 50% (m/V) sodium hydroxide solution, preserving heat for 1-1.5 h at 35-40 ℃ after the dropwise adding is finished, alternately washing to be neutral by using absolute ethyl alcohol and distilled water, and drying at 50 ℃ to obtain the blocky thiocarbamic acid functionalized foam plastic, and placing the blocky thiocarbamic acid functionalized foam plastic in a brown bottle for standby.
(2) Saturated chlorine water is prepared by adopting concentrated hydrochloric acid, potassium chlorate and water and is taken as a sample decomposition solvent, and specifically comprises the following steps:
15-20 mL of concentrated hydrochloric acid, 3-4 g of potassium chlorate and a rubber plug with a conduit are added into a 250mL conical flask, the conduit is inserted into a beaker containing 300-400 mL of water, and the generated chlorine is absorbed until the chlorine is saturated, so that saturated chlorine water is obtained.
(3) Decomposing the geochemical sample to obtain digestion mixed solution;
accurately weighing 10.0g of geochemical sample in a square porcelain boat, placing in a muffle furnace, roasting for 1.5-2 h at a low temperature of 650 ℃, taking out, cooling, transferring into a 250mL polyethylene plastic bottle, wetting the sample with a little water, adding 20-25 mL saturated chlorine water prepared in the step (2), fully shaking the sample, screwing a bottle cap, oscillating for 2-3 h at a ventilation position, taking down, and standing to obtain a digestion mixed solution.
(4) Adding water into the digestion mixed solution obtained in the step (3), shaking uniformly, and then adding a piece of thiocarbamic acid functionalized foam plastic for static oscillation enrichment; taking out the enriched thiocarbamic acid foam plastic blocks, cleaning the sediment and squeezing the sediment to remove water.
(5) Ashing the thiocarbamic acid foam plastic block enriched in the step (4) from low temperatureAfter ashing, 2mL of the mixture is used for 50%V/V) Is subjected to aqua regia heat extraction, cooling, constant volume and standing for measurement.
(6) And (3) measuring by adopting an inductive coupling plasma mass spectrometry method.
Aiming at the method, the blocky thiocarbamic acid functional foam plastic prepared in the step (1) is soaked in clear water for 20-30 min before being used.
For the above method, the geochemical sample in step (3) was prepared according to the protocol of DZ/T0130.2-2006, with a sample size of 0.075 mm.
For the method, the inductively coupled plasma mass spectrometry (ICP-MS) is adopted in the step (6), so that the method has extremely low detection limit, extremely high sensitivity and small interference, is a powerful trace and ultra trace element analysis technology which is widely accepted in the world at present, and has obvious advantages in the aspect of trace noble metal determination. In the steps: the model of the instrument is ICP-MS PerkinElmer NexION s, and the analysis isotopes of gold, platinum and palladium are respectively 197 Au、 106 Pd、 195 Pt, using 115 In and 185 re double internal standard correction; the model of the oscillator is HY-8A, and the oscillating speed is set to be 100r/min in the invention.
Aiming at the method, in the step (6), the first-class standard substances GBW07288 and GBW07289 of the geochemistry country are selected for parallel measurement for 5 times, and the average value is taken to examine the accuracy of the method; for trace gold, platinum and palladium in the geochemical sample, the enrichment effect of the blocky thiocarbamic acid functionalized foam plastic is good, and the final measured value is matched with the identification value, so that the method can meet the measurement requirement of trace gold, platinum and palladium in the geochemical sample.
Compared with the traditional measurement scheme, the invention has the following beneficial effects:
1. the invention prepares the blocky thiocarbamic acid functional foam plastic, the preparation process is very easy to realize application in actual production, and the thiocarbamic acid group selected in the preparation process can overcome the problems of weak coordination ability of other organic functional groups and noble metal ions, poor adsorption recovery rate and the like; the prepared blocky thiocarbamic acid functionalized foam plastic has obviously higher saturated adsorption capacity to gold, platinum and palladium.
2. The process for preparing the blocky thiocarbamic acid functionalized foam plastic is a reasonable nucleophilic addition organic reaction route, the thiocarbamic acid functional group is grafted to the surface of the blocky polyurethane foam plastic for the first time, and the blocky foam plastic is applied to static enrichment analysis of trace gold platinum method in geochemical samples for the first time; the material overcomes the problems of low adsorption capacity, poor selectivity and the like of polyurethane foam plastic, the application process is not limited by the quality of polyurethane foam plastic products, and simultaneously, the thiocarbamic acid functional groups are firmly grafted on the surfaces of the blocky polyurethane foam plastic in a covalent bond mode, thereby overcoming the risk that the functional groups are easy to fall off in the enrichment process due to weak adsorption force. The preparation method has reasonable price of raw materials which are all common chemical reagents in laboratories, the preparation process is easy to control, the cost is lower, waste gas is hardly generated in the whole process, the dosage of the carbon disulfide is strictly controlled, and the carbon disulfide is completely participated in chemical reaction, so that the residue after the reaction is less.
3. The saturated chlorine water provided by the invention has extremely strong oxidizing property and coordination property formed in the decomposition process, and can realize high-efficiency leaching of gold, platinum and palladium in the geochemical sample by adopting a normal-temperature oscillation decomposition method, so that the saturated chlorine water does not need heating at all and is shorter than the traditional normal-temperature decomposition method; in addition, the process of preparing the saturated chlorine water is safe and efficient, no chlorine leakage exists, the process is used in the present process, and the process is convenient and quick, so that the purposes of energy conservation and emission reduction can be achieved.
4. The blocky thiocarbamic acid functional foam plastic prepared by the invention not only can meet the requirement of the novel saturated chlorwater normal-temperature decomposition system adopted by the invention, but also is applicable to the aqua regia system after the traditional aqua regia decomposition, and can overcome NO 3 - Influence on platinum palladium adsorption.
5. The invention establishes a new method for measuring gold, platinum and palladium in a geochemical sample by a saturated chlorine water normal temperature decomposition sample-thiocarbamic acid functional foam plastic separation enrichment-inductance coupling plasma mass spectrometry for the first time.
Drawings
FIG. 1 is a schematic flow chart of the present invention.
FIG. 2 is a flow chart of the preparation of a slabstock thiocarbamic functional foam in the examples.
FIG. 3 is a schematic representation of the formulation of saturated chlorine water in the examples.
FIG. 4 is an infrared spectrum of a bulk thiocarbamic acid functionalized foam prepared in the example.
Detailed Description
The present invention will be described in further detail with reference to the following specific examples and drawings, but the embodiments of the present invention are not limited thereto.
Examples
As shown in FIG. 1, the specific steps of the separation, enrichment and determination method of gold, platinum and palladium in the geochemical sample are as follows:
1. preparation of Block thiocarbamic foam
Cutting polyurethane foam plastic sold in the market into cube small blocks with the side length of 0.8-1 cm, and placing the cube small blocks in a range of 10-15%V/V) Boiling in hydrochloric acid for 2-3 h, washing with water to neutrality, and drying at 50 ℃ to obtain the amino foam plastic.
Adding 50-60 mL of anhydrous ethanol and 10-12 pieces of amino foam plastic into a 250mL three-neck flask with a magnetic stirring device, dropwise adding 15-20 mL of carbon disulfide into a water bath at 30-40 ℃, and preserving heat for 30-40 min at 35-40 ℃ after the dropwise adding is finished; and then dropwise adding 10-15 mL of 50% (m/V) sodium hydroxide solution, preserving heat for 30-40 min, continuously dropwise adding 5-10 mL of 50% (m/V) sodium hydroxide solution, preserving heat for 1-1.5 h at 35-40 ℃ after the dropwise adding is finished, alternately washing to be neutral by using absolute ethyl alcohol and distilled water, and drying at 50 ℃ to obtain the blocky thiocarbamic acid functionalized foam plastic, and placing the blocky thiocarbamic acid functionalized foam plastic in a brown bottle for standby. The stored thiocarbamic acid functional foam plastic is taken out of a brown bottle before use and is soaked in clear water for 20-30 min.
FIG. 4 is an infrared spectrum of the prepared bulk thiocarbamic acid functionalized foam, wherein: 3379.7cm -1 Is amino extensionPeak of vibration shrinkage, 1321.9cm -1 As an amino bending vibration peak, 1592.5cm -1 And 1474.1cm -1 The absorption peaks at are those caused by C-S bonds and c=s bonds.
In the above specific preparation scheme, the foam is modified as shown in FIG. 2.
2. Sample decomposition solvent preparation
As shown in FIG. 3, 15-20 mL of concentrated hydrochloric acid, 3-4 g of potassium chlorate and a rubber plug with a guide pipe are added into a 250mL conical flask, the guide pipe is inserted into a beaker containing 300-400 mL of water, and generated chlorine is absorbed until the chlorine is saturated, namely, saturated chlorine water is newly prepared.
3. Geochemical sample decomposition
Accurately weighing 10.0g of geochemical sample in a square porcelain boat, placing in a muffle furnace, roasting for 1.5-2 h at a low temperature of 650 ℃, taking out, cooling, transferring into a 250mL polyethylene plastic bottle, wetting the sample with a little water, adding 20-25 mL saturated chlorine water prepared in the step (2), fully shaking the sample, screwing a bottle cap, oscillating for 2-3 h at a ventilation position, taking down, and standing to obtain a digestion mixed solution.
The geochemical sample was prepared according to the protocol of DZ/T0130.2-2006 with a sample size of 0.075 mm.
4. Static oscillation enrichment
Adding 100-110 mL of water into the digestion mixed solution obtained in the step (3), shaking uniformly, adding a piece of thiocarbamic acid functional foam plastic, oscillating for 50-60 min, taking out the enriched thiocarbamic acid foam plastic blocks, cleaning sediment, and squeezing out water.
The model of the oscillator is HY-8A, and the oscillating speed is set to be 100r/min in the invention.
5. Preparation of assay solution
Placing the thiocarbamic acid foam plastic block enriched in the step (4) into a 50mL porcelain crucible, ashing in a muffle furnace from low temperature, and using 2mL of the obtained product for 50% after the ashing is completedV/V) And carrying out aqua regia heat extraction, cooling, fixing the volume to 10mL, and standing for testing.
6. Instrument measurement
Using inductively coupled plasmaAnd (5) measuring by mass spectrometry. Inductively coupled plasma mass spectrometry (ICP-MS) has extremely low detection limit, extremely high sensitivity and small interference, is a powerful trace and ultra trace element analysis technology which is widely accepted in the world at present, and has obvious advantages in the aspect of trace noble metal measurement. The model of the instrument is ICP-MS PerkinElmer NexION s, and the analysis isotopes of gold, platinum and palladium are respectively 197 Au、 106 Pd、 195 Pt, using 115 In and 185 re double internal standard correction.
The first-class standard substances GBW07288 and GBW07289 of the national geochemistry are selected for parallel measurement for 5 times, and the average value is taken to examine the accuracy of the method. The measurement and analysis results are shown in Table 1, and the enrichment effect of the block thiocarbamic acid functionalized foam plastic is good for trace gold-platinum-palladium in the geochemical sample, and the final measurement value is identical with the identification value, so that the method can meet the measurement requirement of trace gold-platinum-palladium in the geochemical sample.
TABLE 1 comparison of measured and recognized values for gold platinum palladium (ng/g)
Figure DEST_PATH_IMAGE001
Note that: the authentication value is provided by a standard substance authentication certificate.
When the method is used for separation, enrichment and measurement, the method has the following characteristics:
1. because thiocarbamate is a metal ion chelating agent with excellent performance, the molecule contains N-CS 2 The group has strong coordination capability, almost can form complexes with all transition metals, because the S atom is not only a coordination atom, but also can form sulfide precipitation with metal ions, so that the strong complexing force of the thiocarbamate can directly precipitate and compound or complex the metal ions, and the strong stability of the complex avoids the desorption phenomenon when the gold platinum palladium is enriched by static oscillation; therefore, the thiocarbamate group selected by the invention can overcome the problems of weak coordination ability of other organic functional groups and noble metal ions, poor adsorption recovery rate and the like.
2. The preparation process of the blocky thiocarbamic acid functionalized foam plastic is very easy to realize application in actual production. In the prior preparation methods of other types of thiocarbamate metal chelating agents, the product exists in the form of powder or fine particles, and the application is limited in the static oscillation adsorption process of noble metal ions. The invention provides a reasonable nucleophilic addition organic reaction route, wherein a thiocarbamic acid functional group is grafted to the surface of a blocky polyurethane foam plastic for the first time, and the blocky polyurethane foam plastic is applied to static enrichment analysis of trace gold platinum method in geochemical samples for the first time; the material overcomes the problems of low adsorption capacity, poor selectivity and the like of polyurethane foam plastic, the application process is not limited by the quality of polyurethane foam plastic products, and simultaneously, the thiocarbamic acid functional groups are firmly grafted on the surfaces of the blocky polyurethane foam plastic in a covalent bond mode, thereby overcoming the risk that the functional groups are easy to fall off in the enrichment process due to weak adsorption force. The preparation method has reasonable price of raw materials which are all common chemical reagents in laboratories, the preparation process is easy to control, the cost is lower, waste gas is hardly generated in the whole process, the dosage of the carbon disulfide is strictly controlled, and the carbon disulfide is completely participated in chemical reaction, so that the residue after the reaction is less.
3. The decomposition reagent of gold platinum palladium in traditional geochemical sample comprises aqua regia and HCl-H 2 O 2 And the like, the gold platinum palladium is dissolved and leached by the reagents under the condition of heating and boiling. Particularly, aqua regia has the most wide application due to strong oxidizing property and coordination, but generates a large amount of nitrogen dioxide in the heating and dissolving process, so that the aqua regia seriously pollutes the environment and influences the body health of analysts.
The saturated chlorine water provided by the invention has extremely strong oxidizing property and coordination property formed in the decomposition process, and the gold platinum palladium in the geochemical sample can be efficiently leached by adopting a normal-temperature oscillation decomposition method, so that the saturated chlorine water is completely unnecessary to be heated and is shorter than the traditional normal-temperature decomposition method.
4. Influence of acidity. Foam plastic needs to overcome NO when enriching platinum and palladium 3 - And thus the enrichment process is oftenIn a reducing medium. The invention respectively examines the enrichment effect of the blocky thiocarbamic acid functionalized foam plastic on gold, platinum and palladium in hydrochloric acid and aqua regia, prepares hydrochloric acid solutions (5%, 10%, 15%, 20%, 25%) with a series of concentrations, 50mL of aqua regia solutions (5%, 10%, 15%, 20%, 25%) respectively, wherein 50ng of gold, platinum and palladium are contained; and respectively adding 1 piece of thiocarbamic acid functional foam plastic, oscillating for 50-60 min, taking out the enriched thiocarbamic acid functional foam plastic blocks, cleaning, and squeezing to remove water. The treatment and determination are carried out according to steps (5) and (6) of the invention. The result shows that the blocky thiocarbamic acid functionalized foam plastic can obtain satisfactory recovery rate in 15% -25% of hydrochloric acid medium and 10% -20% of aqua regia medium.
5. Influence of coexisting ions. According to the characteristics of noble metal sample composition in geochemical investigation, the influence of common coexisting ions on the measurement result is examined. Experimental results show that the blocky thiocarbamic acid functional foam plastic has higher selectivity in 15% -25% of hydrochloric acid medium and 10% -20% of aqua regia medium in both environment mediums, and has high selectivity to common alkali metal (1000 times of K + 、Na + ) Alkaline earth metal (1000 times Ca 2+ 、Mg 2+ ) And 500 times Al 3+ 50 times of Fe 2+ 、Cu 2+ 、Pb 2+ 、Ni 2+ Etc. are hardly adsorbed.
6. The saturated adsorption capacity of the bulk thiocarbamic acid functionalized foam plastic prepared by the invention to gold, platinum and palladium is obviously improved.
Obviously, compared with the traditional scheme, the invention has the following specific differences:
the present invention differs from CN201510551056.0, which discloses a method for simultaneously measuring trace gold, silver and palladium in a geochemical sample, wherein diphenyl thiourea is used as an adsorption functional group, and the diphenyl thiourea is loaded on foam plastics in a form of physical adhesion after being treated in a simple manner. The physical adsorption effect between the diphenyl thiourea and the foam plastic is weaker, the phenomenon that the diphenyl thiourea falls off inevitably exists in the process of repeated static oscillation adsorption, and the complex structure formed by the diphenyl thiourea and the gold is unstable, so that the analysis and test results are unstable.
The invention is different from patent CN201610982022.1, which discloses an improved analysis method for enriching gold by using 5-aminomethyluracil modified foam, wherein 5-aminomethyluracil is used as an adsorption functional group, dialdehyde is used as a connecting arm, and imine is produced by the 5-aminomethyluracil and the amino foam respectively with dialdehyde in a water phase environment, and then the 5-aminomethyluracil functionalized foam is synthesized. In the method, 5-amine methyl uracil is firmly grafted on the surface of foam plastic in a covalent bond mode, the yield is high, but the 5-amine methyl uracil is expensive, and a complex structure formed by a 5-amine methyl uracil functional group and gold is unstable, so that gold in a sample cannot be accurately measured. Meanwhile, the invention breaks the foam plastic into 100-200 mu m fine particles, then carries out functional modification and then is put into an adsorption column for adsorption, but the polyurethane foam has strong electrostatic repulsion after breaking, is difficult to assemble the column, and limits the application range.
The present invention differs from the literature (Ding shuai Xue et al, analytical methods, 2016,8,29-39) which mentions that cytosine is grafted onto the surface of polyurethane foam by glutaraldehyde as a functional group using glutaraldehyde as a linking arm to prepare a cytosine-functionalized foam. However, cytosine is expensive, limiting its production applications in geological laboratories. Meanwhile, the polyurethane foam plastic is crushed into powder and then synthesized and prepared, and finally the powder is filled into an adsorption column to enrich trace gold in a geological sample, and the polyurethane foam has strong electrostatic repulsion after being crushed, so that the polyurethane foam plastic is difficult to fill the column, and the application range of the polyurethane foam plastic is limited.
The invention is different from the method for synthesizing the amino foam plastic proposed in the literature (Wang Gongyue and the like, rock and mineral test and 2016,35,4,409-414), because the preparation of the amino foam plastic is a routine operation means of a laboratory, generally, acid heating reflux, boiling, soaking and other modes are adopted to carry out hydrolysis reaction on the foam plastic, so as to promote the fracture of carbamate bonds on the surface and generate the foam plastic with exposed amino groups, and the purpose is to improve the adsorption performance of the foam plastic and remove impurities on the surface of the foam plastic. In the invention, the foam plastic is subjected to hydrolysis reaction, so that a large amount of amino groups are generated on the surface of the foam plastic, and an organic reaction intermediate is formed, thereby being convenient for better participating in the chemical reaction of the grafted functional groups.
In addition, a method for directly measuring gold, platinum and palladium in a geochemical sample has been proposed in the literature (Huang Zhenyu et al, rock-mine test, 2001). In the method, after a sample is dissolved by aqua regia, cooling, constant volume and standing are carried out, and then supernatant is directly separated and measured by ICP-MS. The method is simple and quick, but is only suitable for a sample with simple composition, and for a complex sample, a large amount of coexisting ions in a solution to be detected cause serious mass spectrum interference on gold, platinum and palladium, and the interference needs to be subtracted through complex mathematical correction.
Therefore, through the characteristics description of the embodiment and the corresponding method, the proper organic reaction conditions and the proper reagent dosage are determined through scientific and reasonable experimental design, so that the grafting load rate of the organic functional groups on the surface of the foam plastic can be greatly improved, the organic functional groups are firmly grafted on the surface of the foam plastic, the adsorption capacity of the foam plastic on gold, platinum and palladium is improved, the material reagent cost is saved, the use of the organic reagent is reduced, and the environmental pollution influence is reduced.

Claims (8)

1. A separation, enrichment and determination method of gold, platinum and palladium in a geochemical sample is characterized by comprising the following main steps:
(1) The preparation of the blocky thiocarbamic foam plastic comprises the following steps:
firstly, placing a cube-shaped polyurethane foam plastic block into a position of 10-15%V/V) Boiling in hydrochloric acid for 2-3 h, washing with water to neutrality, and drying at 50 ℃ to obtain the amino foam plastic;
adding 50-60 mL of anhydrous ethanol and 10-12 pieces of amino foam into a 250mL three-neck flask with a magnetic stirring device, dropwise adding 15-20 mL of carbon disulfide into a water bath at 30-40 ℃, and preserving heat for 30-40 min at 35-40 ℃ after the dropwise adding is finished; then, dropwise adding 10-15 mL of 50% (m/V) sodium hydroxide solution, preserving heat for 30-40 min, continuously dropwise adding 5-10 mL of 50% (m/V) sodium hydroxide solution, preserving heat for 1-1.5 h at 35-40 ℃ after the dropwise adding is finished, alternately washing to be neutral by using absolute ethyl alcohol and distilled water, and drying at 50 ℃ to obtain blocky thiocarbamic acid functionalized foam plastic, and placing the blocky thiocarbamic acid functionalized foam plastic in a brown bottle for standby;
(2) Adding 15-20 mL of concentrated hydrochloric acid and 3-4 g of potassium chlorate into a 250mL conical flask, plugging a rubber plug with a catheter, inserting the catheter into a beaker containing 300-400 mL of water, and absorbing generated chlorine until the chlorine is saturated, thereby obtaining saturated chlorine water serving as a sample decomposition solvent;
(3) Accurately weighing 10.0g of geochemical sample, heating in a square porcelain boat, roasting for 1.5-2 h from low temperature rise to 650 ℃, taking out, cooling, transferring into a 250mL polyethylene plastic bottle, wetting the sample with water, adding 20-25 mL saturated chlorine water prepared in the step (2), fully shaking the sample, screwing a bottle cap, oscillating for 2-3 h at a ventilation position, taking down, and standing to obtain digestion mixed solution;
(4) Adding water into the digestion mixed solution obtained in the step (3), shaking uniformly, and then adding a piece of thiocarbamic acid functionalized foam plastic for static oscillation enrichment; taking out the enriched thiocarbamic acid foam plastic blocks, cleaning sediment and squeezing out water;
(5) Ashing the thiocarbamic acid foam plastic block enriched in the step (4) from low temperature, and using 2mL of the obtained product to achieve 50% after the ashing is completedV/V) Performing aqua regia thermal extraction, cooling, fixing the volume, and standing for testing;
(6) And (3) measuring by adopting an inductive coupling plasma mass spectrometry method.
2. The method for separating, enriching and determining gold, platinum and palladium in a geochemical sample according to claim 1, wherein the method comprises the following steps: and (3) in the step (1), the side length of the square block-shaped polyurethane foam plastic block is 0.8-1 cm.
3. The method for separating, enriching and determining gold, platinum and palladium in a geochemical sample according to claim 1, wherein the method comprises the following steps: the block thiocarbamic acid functional foam plastic which is preserved is prepared in the step (1) and is soaked in clear water for 20-30 min before being used.
4. The method for separating, enriching and determining gold, platinum and palladium in a geochemical sample according to claim 1, wherein the method comprises the following steps: the geochemical sample in step (3) was prepared according to the protocol of DZ/T0130.2-2006 with a sample size of 0.075 mm.
5. The method for separating, enriching and determining gold, platinum and palladium in a geochemical sample according to claim 1, wherein the method comprises the following steps: in the step (4), 100-110 mL of water is added into the digestion mixed solution, a piece of thiocarbamic acid functional foam plastic is added after shaking, shaking is carried out for 50-60 min, and then the enriched thiocarbamic acid foam plastic block is taken out.
6. The method for separating, enriching and determining gold, platinum and palladium in a geochemical sample according to claim 1, wherein the method comprises the following steps: the oscillating speed of the oscillator used in the step (4) is 100r/min.
7. The method for separating, enriching and determining gold, platinum and palladium in a geochemical sample according to claim 1, wherein the method comprises the following steps: the analysis isotopes of gold, platinum and palladium in the step (6) are respectively 197 Au、 106 Pd、 195 Pt, using 115 In and 185 re double internal standard correction.
8. The method for separating, enriching and determining gold, platinum and palladium in a geochemical sample according to claim 1, wherein the method comprises the following steps: the method comprises the steps of selecting the first-level standard substances GBW07288 and GBW07289 of the national geochemistry, respectively measuring for 5 times in parallel, taking an average value, and examining the enrichment accuracy of the blocky thiocarbamic acid functionalized foam plastic; for trace gold platinum palladium in the geochemical sample, when the obtained final measured value is identical with the identification value, the enrichment method is proved to meet the measurement requirement of trace gold platinum palladium in the geochemical sample.
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