CN111337335A - Cadmium digestion and purification separation method for cadmium-containing iron and organic matter mixed sample - Google Patents
Cadmium digestion and purification separation method for cadmium-containing iron and organic matter mixed sample Download PDFInfo
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- 229910052793 cadmium Inorganic materials 0.000 title claims abstract description 81
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 title claims abstract description 80
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 45
- 230000029087 digestion Effects 0.000 title claims abstract description 29
- 238000000926 separation method Methods 0.000 title claims abstract description 25
- 238000000746 purification Methods 0.000 title claims abstract description 23
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 22
- 239000005416 organic matter Substances 0.000 title claims abstract description 12
- 238000011084 recovery Methods 0.000 claims abstract description 14
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 8
- 238000002360 preparation method Methods 0.000 claims abstract description 5
- 238000002133 sample digestion Methods 0.000 claims abstract description 5
- 239000000126 substance Substances 0.000 claims abstract description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 59
- 239000000243 solution Substances 0.000 claims description 34
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 29
- 229910017604 nitric acid Inorganic materials 0.000 claims description 29
- 238000005342 ion exchange Methods 0.000 claims description 24
- 239000011347 resin Substances 0.000 claims description 21
- 229920005989 resin Polymers 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 19
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 16
- 239000011521 glass Substances 0.000 claims description 16
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 14
- 238000002386 leaching Methods 0.000 claims description 12
- 229910021642 ultra pure water Inorganic materials 0.000 claims description 12
- 239000012498 ultrapure water Substances 0.000 claims description 12
- -1 and meanwhile Substances 0.000 claims description 9
- QJZYHAIUNVAGQP-UHFFFAOYSA-N 3-nitrobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid Chemical compound C1C2C=CC1C(C(=O)O)C2(C(O)=O)[N+]([O-])=O QJZYHAIUNVAGQP-UHFFFAOYSA-N 0.000 claims description 8
- 239000004021 humic acid Substances 0.000 claims description 8
- 238000012360 testing method Methods 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 7
- 229910052598 goethite Inorganic materials 0.000 claims description 7
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 claims description 7
- 239000011780 sodium chloride Substances 0.000 claims description 7
- 238000001704 evaporation Methods 0.000 claims description 6
- 229910052725 zinc Inorganic materials 0.000 claims description 6
- 239000011701 zinc Substances 0.000 claims description 6
- 150000001450 anions Chemical class 0.000 claims description 5
- 150000002500 ions Chemical class 0.000 claims description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 4
- 238000005349 anion exchange Methods 0.000 claims description 4
- 238000004821 distillation Methods 0.000 claims description 4
- 238000002474 experimental method Methods 0.000 claims description 4
- 239000011159 matrix material Substances 0.000 claims description 4
- 230000007935 neutral effect Effects 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 2
- 238000005406 washing Methods 0.000 claims 4
- 239000012266 salt solution Substances 0.000 claims 2
- 238000011049 filling Methods 0.000 claims 1
- 229920006395 saturated elastomer Polymers 0.000 claims 1
- 238000002791 soaking Methods 0.000 claims 1
- 230000001502 supplementing effect Effects 0.000 claims 1
- 238000005303 weighing Methods 0.000 claims 1
- 239000002689 soil Substances 0.000 description 9
- 230000008569 process Effects 0.000 description 5
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005194 fractionation Methods 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000003456 ion exchange resin Substances 0.000 description 2
- 229920003303 ion-exchange polymer Polymers 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- 238000002203 pretreatment Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000013049 sediment Substances 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- DPORRQCIAXYPGF-UHFFFAOYSA-N F.Cl.O[N+]([O-])=O Chemical compound F.Cl.O[N+]([O-])=O DPORRQCIAXYPGF-UHFFFAOYSA-N 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 229910001608 iron mineral Inorganic materials 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000011146 organic particle Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/34—Purifying; Cleaning
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/44—Sample treatment involving radiation, e.g. heat
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Biomedical Technology (AREA)
- Molecular Biology (AREA)
- Engineering & Computer Science (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
The invention relates to a cadmium digestion and purification separation method for a cadmium-containing iron and organic matter mixed sample, which comprises the steps of preparation of an experimental reagent, sample digestion and chemical separation and purification of cadmium. For the sample with cadmium content of 2-294.6ppm, the recovery rate of cadmium is 92.5-108.6%, and the requirement of cadmium isotope determination on Cd separation and purification is completely met.
Description
Technical Field
The invention belongs to the field of chemical processes, relates to a digestion, purification and separation technology, and particularly relates to a cadmium digestion, purification and separation method for a cadmium-containing iron and organic matter mixed sample.
Background
Cd pollution is one of the research subjects which are always regarded by the scientific community, so that the pollution source of Cd is found out and controlled from the source, and the method has very important significance for implementing pollution control and changing the current situation of the environment. The distribution rule and the fractionation mechanism of the cadmium isotope in the soil are hindered by the heterogeneity of the soil and the complexity of the multi-component characteristics and the variability of the soil conditions.
The soil contains fine particles of metal (hydr) oxide, natural organic matter and silicate clay minerals, which control the behavior characteristics of cadmium isotopes in the soil, sediments, etc. In practical research, purified humic acid (humic acid) is used to represent organic particles in soil, and synthetic metal oxide (such as iron oxide goethite) is used to represent mineral particles in soil, so that when isotope fractionation caused by adsorption migration behavior of cadmium under the influence of the model minerals (goethite and humic acid) in an ideal state is researched, a simpler and easier-to-operate process can be adopted to pretreat a sample and further determine the cadmium isotope value of the sample.
In the past, aiming at soil, rock and sediment samples, nitric acid-hydrofluoric acid-hydrochloric acid and hydrogen peroxide are mainly used for digestion, and the process is complicated. Before the sample is subjected to the cadmium isotope test analysis, in order to ensure the analysis precision of the sample, the sample to be detected needs to be purified and separated to eliminate the interference of other ions, and the method mainly comprises an ion exchange resin double-column method and an ion exchange resin single-column method. Wherein, the double-column method needs to use acids with different concentrations and types for leaching, and the operation process is complicated; the improved single-column method still needs to adopt hydrochloric acid with different concentrations for multi-step elution, and the Pd removal effect is not ideal.
In conclusion, a pretreatment method for a cadmium isotope test, which is simple in digestion operation process and good in separation effect, needs to be designed based on the existing method.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a cadmium digestion and purification separation method for a cadmium-containing iron and organic matter mixed sample.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
a cadmium digestion and purification separation method for a cadmium-containing iron and organic matter mixed sample comprises the following steps:
(1) preparation of test reagents
During the experiment, all containers (such as a polytetrafluoroethylene digestion tube, a glass anion exchange column, a beaker, a glass rod and the like) are soaked in 5% dilute nitric acid and are cleaned by ultrapure water, and meanwhile, hydrochloric acid and nitric acid are subjected to subboiling secondary distillation and purification, so that the utensils and the reagents have low enough cadmium background values, and the influence on the subsequent cadmium isotope determination is avoided.
The anion resin AG-MP-1M (100-200 mesh, Bio-Rad) was soaked in saturated saline for 12 hours, then washed with dilute saline and then washed with ultrapure water to remove NaCl. Then, the solution is washed by a solution with the volume being 3 times of the volume of the resin and the concentration being 2mol/LHCl, and finally washed by ultrapure water to be neutral, and the solution is filled into glass ion exchange columns by a wet method, wherein each ion exchange column is filled with 3 mL. Specification of glass ion exchange column: the inner diameter is 0.6cm, the length is 15cm, and the top is funnel-shaped (the volume is 30ml) so as to facilitate sample injection. Respectively preparing 1% nitric acid and hydrochloric acid solution of 2mol/L, 0.3mol/L and 0.0012mol/L for later use.
(2) Sample digestion
For a cadmium-containing solid sample containing goethite and/or humic acid, selecting a sample with certain mass (ensuring that the total cadmium content in the solution before leaching is at least 2-3mg/kg) according to the cadmium content in the sample, recording the sample weight, adding 10mL of concentrated nitric acid, and heating on a graphite digestion instrument. Heating was maintained at 80, 100 and 120 ℃ for 2 hours, followed by heating at 150 ℃ for 48 hours, during which the positions of the digestion tubes were changed every 12 hours, and 4mL of concentrated nitric acid was added thereto when the amount of acid in the tubes was less than 2 mL. After 48 hours, cooling the tube to be digested to room temperature, adding 4mL of hydrogen peroxide, removing organic matters, slowly heating to 60, 80 and 120 ℃, keeping the temperature for about 20min until the reaction in the tube is not severe, and then heating to 150 ℃ for 2 hours. The step of adding hydrogen peroxide is repeated once, and the addition amount is changed to 2 mL. After digestion was complete, the solution in the digestion tube was evaporated to dryness and the sample was dissolved with 5mL of 1% nitric acid for further use.
For the liquid sample containing iron and other ions, a certain volume of solution is measured according to the cadmium content and is evaporated to dryness, and 5mL of 1% nitric acid is used for dissolving the sample for later use.
(3) Chemical separation and purification of cadmium
This part is mainly leached with acids of different concentrations, including:
1) eluting the ion exchange column with 2mol/L hydrochloric acid (20mL), and balancing the resin to convert the resin into a hydrochloric acid system;
2) transferring 1-2mL of the sample obtained in the step (2) to an ion exchange column;
3) eluting the ion exchange column with 2mol/L hydrochloric acid (10mL) again to remove matrix elements (such as iron) in the resin;
4) leaching with 0.3mol/L hydrochloric acid (30mL) to remove most of lead and part of zinc elements;
5) leaching with 0.0012mol/L hydrochloric acid (20mL) to separate cadmium element;
6) and evaporating the leached solution to dryness, dissolving the solution again by using 5mL of 1% nitric acid, taking 3mL of the solution for measuring the cadmium content, and calculating the separation recovery rate of the cadmium.
The invention has the advantages and positive effects that:
aiming at cadmium-containing iron minerals and organic matter systems, iron oxide and organic matter can be effectively digested by only using nitric acid and hydrogen peroxide in the digestion process, and the invention provides the pretreatment method for the determination of the cadmium isotope, which has the advantages of simple purification and separation process and good separation effect. For the sample with cadmium content of 2-294.6ppm, the recovery rate of cadmium is 92.5-108.6%, and the requirement of cadmium isotope determination on Cd separation and purification is completely met.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
Example one
The method for digesting, purifying and separating the cadmium in the cadmium-containing aqueous solution sample comprises the following specific steps:
(1) preparation of test reagents
During the experiment, all containers (such as a polytetrafluoroethylene digestion tube, a glass anion exchange column, a beaker, a glass rod and the like) are soaked in 5% dilute nitric acid and are cleaned by ultrapure water, and meanwhile, hydrochloric acid and nitric acid are subjected to subboiling secondary distillation and purification, so that the utensils and the reagents have low enough cadmium background values, and the influence on the subsequent cadmium isotope determination is avoided. The anion resin AG-MP-1M (100-200 mesh, Bio-Rad) was soaked in saturated saline for 12 hours, then washed with dilute saline and then washed with ultrapure water to remove NaCl. Then, the solution is washed by a solution with the volume being 3 times of the volume of the resin and the concentration being 2mol/LHCl, and finally washed by ultrapure water to be neutral, and the solution is filled into glass ion exchange columns by a wet method, wherein each ion exchange column is filled with 3 mL. Specification of glass ion exchange column: the inner diameter is 0.6cm, the length is 15cm, and the top is funnel-shaped (the volume is 30ml) so as to facilitate sample injection. Preparing 1% nitric acid, 2, 0.3 and 0.0012mol/L hydrochloric acid solution for later use.
(2) Sample digestion
The cadmium-containing solution sample is manually prepared by a standard solution, the cadmium and iron contents In different concentration ranges are set, and different other ions including Al, Ca, Cr, Cu, In, Mg, Mn, Mo, Ni, Pb, Pd, Sn and Zn are added. Wherein the content of cadmium is 2-3ppm, the content of iron is 2-1500ppm, and the content of other ions is 2 ppm. The aqueous sample was evaporated to dryness and then dissolved in 5mL of 1% nitric acid for further use.
(3) Chemical separation and purification of cadmium
This part is mainly leached with acids of different concentrations, including:
1) eluting the ion exchange column with 2mol/L hydrochloric acid (20mL), and balancing the resin to convert the resin into a hydrochloric acid system;
2) transferring 2mL of the sample obtained in the step (2) to an ion exchange column;
3) eluting the ion exchange column with 2mol/L hydrochloric acid (10mL) again to remove matrix elements (such as iron) in the resin;
4) leaching with 0.3mol/L hydrochloric acid (30mL) to remove most of lead and part of zinc elements;
5) leaching with 0.0012mol/L hydrochloric acid (20mL) to separate cadmium element;
6) and evaporating the eluted solution to dryness, dissolving the evaporated solution again by using 5mL of 1% nitric acid, taking 3mL of the solution for measuring the cadmium content, and calculating the separation recovery rate (shown in table 1) of cadmium, namely the cadmium recovery rate is 99.9-108.6% in the cadmium recovery rate, and the iron recovery rate is 99.1-109.4%. Although the separation and purification process has no ideal effect on the removal of Zn, Pd and Sn, the system related by the invention only relates to Cd and Fe, so that the influence on the measured value of the cadmium isotope is small, and the recovery rate of other elements is 88.1-107.3%.
TABLE 1 test results of pretreatment of cadmium-containing aqueous solution samples
Example two
The method for digesting, purifying and separating cadmium in samples containing cadmium goethite and humic acid comprises the following specific steps:
(1) preparation of test reagents
During the experiment, all containers (such as a polytetrafluoroethylene digestion tube, a glass anion exchange column, a beaker, a glass rod and the like) are soaked in 5% dilute nitric acid and are cleaned by ultrapure water, and meanwhile, hydrochloric acid and nitric acid are subjected to subboiling secondary distillation and purification, so that the utensils and the reagents have low enough cadmium background values, and the influence on the subsequent cadmium isotope determination is avoided. The anion resin AG-MP-1M (100-200 mesh, Bio-Rad) was soaked in saturated saline for 12 hours, then washed with dilute saline and then washed with ultrapure water to remove NaCl. Then, the solution is washed by a solution with the volume being 3 times of the volume of the resin and the concentration being 2mol/LHCl, and finally washed by ultrapure water to be neutral, and the solution is filled into glass ion exchange columns by a wet method, wherein each ion exchange column is filled with 3 mL. Specification of glass ion exchange column: the inner diameter is 0.6cm, the length is 15cm, and the top is funnel-shaped (the volume is 30ml) so as to facilitate sample injection. Preparing 1% nitric acid, 2, 0.3 and 0.0012mol/L hydrochloric acid solution for later use.
(2) Sample digestion
The cadmium content of the solid sample containing the cadmium goethite and the humic acid is within 23.8-294.6ppm, the iron content is within 1.14-2.73%, and the solid organic carbon content is within 40.3 g/kg. Two soil standards SRM2711 and SRM2711a were included, the former having cadmium and iron contents of 41.7. + -. 0.25ppm and 2.89. + -. 0.06%, respectively, and the latter 54.1. + -. 0.5ppm and 2.82. + -. 0.04%, respectively. 0.3-0.4g of sample is weighed into a polytetrafluoroethylene tube, 10mL of concentrated nitric acid is added, and then the sample is heated on a graphite digestion instrument. Heating was maintained at 60, 80, 100 and 120 ℃ for 2 hours, followed by heating at 150 ℃ for 48 hours, during which the positions of the digestion tubes were changed every 12 hours, and 4mL of concentrated nitric acid was added thereto when the amount of acid in the tubes was less than 2 mL. After 48 hours, cooling the tube to be digested to room temperature, adding 4mL of hydrogen peroxide, removing organic matters, slowly heating to 40, 60, 80 and 120 ℃, keeping the temperature for about 20 minutes until the reaction in the tube is not severe, and then heating to 150 ℃ for 2 hours. The step of adding hydrogen peroxide is repeated once, and the addition amount is changed to 2 mL. After digestion, the solution in the digestion tube was evaporated to dryness, and 5mL of 1% nitric acid was used to dissolve the sample, and the cadmium and iron contents were determined for use.
(3) Chemical separation and purification of cadmium
This part is mainly leached with acids of different concentrations, including:
1) eluting the ion exchange column with 2mol/L hydrochloric acid (10-20mL), and balancing the resin to convert the resin into a hydrochloric acid system;
2) transferring 1-3mL of the sample obtained in the step (2) to an ion exchange column;
3) eluting the ion exchange column with 2mol/L hydrochloric acid (10mL) again to remove matrix elements (such as iron) in the resin;
4) leaching with 0.3mol/L hydrochloric acid (30mL) to remove most of lead and part of zinc elements;
5) leaching with 0.0012mol/L hydrochloric acid (20-25mL) to separate cadmium element;
6) and evaporating the leached solution to dryness, dissolving the solution again by using 5mL of 1% nitric acid, taking 3mL of the solution for measuring the cadmium content, and calculating the separation recovery rate of cadmium, wherein the result is shown in Table 2. The cadmium recovery rate is more than 92.5 percent, and the iron recovery rate is more than 92.1 percent
TABLE 2 pretreatment test results for goethite and humic acid samples containing cadmium
No | Sample number | Cd content/ppm | Fe content/%) | Percent Cd recovery/%) | Fe recovery/% |
1 | B0-5 | 61.5 | 1.37 | 99.2 | 95.1 |
2 | B25-30 | 23.8 | 1.39 | 92.5 | 92.1 |
3 | H0-5 | 190.3 | 1.37 | 101.7 | 95.8 |
4 | H25-30 | 58.1 | 1.49 | 102.0 | 95.4 |
5 | I0-5 | 216.4 | 1.50 | 103.5 | 94.5 |
6 | I25-30 | 111.0 | 1.25 | 102.1 | 93.1 |
7 | J0-5 | 294.6 | 1.26 | 105.9 | 98.1 |
8 | J25-30 | 51.1 | 1.34 | 98.0 | 95.4 |
9 | K0-5 | 147.1 | 1.14 | 100.1 | 92.6 |
10 | K25-30 | 48.7 | 1.43 | 98.5 | 95.1 |
11 | 2711 | 41.0 | 2.73 | 95.6 | 93.3 |
12 | 2711a | 50.5 | 2.77 | 95.9 | 97.1 |
Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the embodiments disclosed.
Claims (3)
1. A cadmium digestion and purification separation method for a cadmium-containing iron and organic matter mixed sample is characterized by comprising the following steps: the method comprises the following steps:
(1) preparation of test reagents
All containers used in the experimental period are soaked in 5 percent dilute nitric acid and are cleaned by ultrapure water, and meanwhile, hydrochloric acid and nitric acid are subjected to azeotropic secondary distillation and purification;
soaking the used anion resin in saturated salt solution for 12 hours, then washing with dilute salt solution, then washing with ultrapure water to remove NaCl, then washing with HCl solution with the volume being 3 times that of the resin and the concentration being 2mol/L, finally washing with ultrapure water to be neutral, filling into glass ion exchange columns by a wet method, wherein each ion exchange column is filled with 3 mL;
respectively preparing 1% nitric acid and hydrochloric acid solution of 2mol/L, 0.3mol/L and 0.0012mol/L for later use.
(2) Sample digestion
For a cadmium-containing solid sample containing goethite and/or humic acid, selecting the sample according to the cadmium content in the sample, ensuring that the total cadmium content in the solution before leaching is at least 2-3mg/kg, recording the sample weighing amount, adding 10mL of concentrated nitric acid, and heating on a graphite digestion instrument;
keeping heating at 80, 100 and 120 ℃ for 2h respectively, then heating at 150 ℃ for 48h, exchanging the positions of the digestion tubes every 12h, and supplementing 4mL of concentrated nitric acid when the acid amount in the tubes is less than 2 mL;
after 48h, cooling the pipe to be digested to room temperature, adding 4mL hydrogen peroxide, removing organic matters, slowly heating to 60, 80 and 120 ℃, keeping the temperature for 20min, and then heating to 150 ℃ for 2 h;
repeating the step of adding hydrogen peroxide once, wherein the addition amount is changed to 2mL, evaporating the solution in the digestion tube after digestion is finished, and dissolving a sample with 5mL of 1% nitric acid for later use;
measuring a certain volume of solution for a liquid sample containing iron and other ions according to the cadmium content, evaporating to dryness, and dissolving the sample with 5mL of 1% nitric acid for later use;
(3) chemical separation and purification of cadmium
1) Leaching the ion exchange column by using 2mol/L hydrochloric acid and 20mL, and balancing the resin to convert the resin into a hydrochloric acid system;
2) transferring 1-2mL of the sample obtained in the step (2) to an ion exchange column;
3) eluting the ion exchange column again by using 2mol/L hydrochloric acid and 10mL to remove matrix elements in the resin;
4) leaching and removing most of lead and part of zinc elements by using 0.3mol/L hydrochloric acid of 30 mL;
5) leaching with 0.0012mol/L hydrochloric acid of 20mL to separate cadmium element;
6) and evaporating the leached solution to dryness, dissolving the solution again by using 5mL of 1% nitric acid, taking 3mL of the solution for measuring the cadmium content, and calculating the separation recovery rate of the cadmium.
2. The cadmium digestion and purification separation method for the cadmium-containing iron and organic matter mixed sample according to claim 1, characterized in that: the vessels used during the experiment included a polytetrafluoroethylene digestion tube, a glass anion exchange column, a beaker, a glass rod.
3. The cadmium digestion and purification separation method for the cadmium-containing iron and organic matter mixed sample according to claim 1, characterized in that: the anion resin is AG-MP-1M, 100-mesh and 200-mesh, and the specification of a glass ion exchange column is as follows: the inner diameter is 0.6cm, the length is 15cm, the top is funnel-shaped, and the capacity is 30 ml.
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