Full-spectrum titration detection method for total iron content in ore

Abstract

The invention belongs to the technical field of chemical mineral detection, and particularly relates to a full-spectrum titration detection method for total iron content in ore. According to the method, after ore sample decomposition is completed, a stannous chloride solution, a sodium tungstate solution, a titanium trichloride solution, a dilute potassium dichromate solution, sulfur-phosphorus mixed acid, a sodium diphenylaminesulfonate solution indicator and a potassium dichromate standard solution are sequentially added into sample liquid, and the whole titration process is measured through a visible light full-spectrum titrator. And presetting a titration condition change point to mark the change of the titration condition, and calculating the total iron content in the ore by taking the volume value corresponding to the full-spectrum titration color change parameter of the titration of the potassium dichromate standard solution as the volume value of the titration end point.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical mineral detection, and in particular relates to a full-spectrum titration detection method for total iron content in an ore. Background Art

[0002] Iron is one of the most widely distributed metal elements on earth, with an average content of 5% in the earth's crust. There are more than 300 known iron minerals in nature, and the main one with industrial utilization value is magnetite (Fe 3 O 4 Contains 72.4% iron), hematite (Fe 2 O 3 Contains 70.0% iron), siderite (FeCO 3 Iron content 48.2%), limonite (Fe 2 O 3 ·nH 2 O contains 48% to 62.9% iron). Ore is the main raw material of the steel industry. Ore is the basic raw material of the steel industry and can be smelted into pig iron, wrought iron, ferroalloy, carbon steel, alloy steel, special steel, etc. The ore used for blast furnace ironmaking requires that its total iron TFe (total iron content) is ≥50%. The iron grade of the mined raw ore is generally only 20% to 40%. Through mineral processing and enrichment, the grade of the ore can be increased to 50% to 65%.

[0003] The stannous chloride-titanium chloride reduction potassium dichromate volumetric method is a common method for detecting the total iron content in ores. This method is mentioned in GB / T6730.5 and GB / T6730.66. This method refers to ISO 2597-1:2006 and uses HgCl 2 Oxidation of excess SnCl 2 In fact, the stannous chloride-titanium chloride reduction potassium dichromate volumetric method is not satisfactory in terms of accuracy. The main reason is that potassium dichromate is used to determine iron. + The acidity of each determination must be kept consistent to ensure that the repeatability limit and reproducibility limit are small. Although the photometric instrument is used to determine the titration end point, the systematic error is eliminated. However, the principle of the photometric method is a fixed wavelength measurement method that complies with the Lambert-Beer law. Due to the limitation of the specified wavelength, it cannot adapt to the wavelength deviation caused by the matrix and the processing process, and its application is limited. In addition, the visual determination of the titration end point brings about systematic errors, especially in the pre-reduction stage, that is, when the excess reducing agent is oxidized with dilute potassium dichromate, the error is even greater.

[0004] For example, "GB / T 6730.5-2022 Iron ore—Determination of total iron content—Titrimetric methods after titanium(Ⅲ)chloride reduction" (Ironores—Determination of total iron content—Titrimetric methods after titanium(Ⅲ)chloride reduction [ISO 2597-2:2019, Iron ores—Determination of total iron content—Part 2: Titrimetric methods after titanium(Ⅲ)chloride reduction, MOD]) was proposed by the China Iron and Steel Association and is under the jurisdiction of the National Technical Committee for Ores and Direct Reduced Iron Standardization (SAC / TC317). It will take effect on November 1, 2022 under the State Administration for Market Regulation and the National Standardization Administration. The principle is that for samples containing no more than 0.05% vanadium, acid decomposition is used, that is, hydrochloric acid is used to dissolve the sample, the filtered residue is burned, and then treated with hydrofluoric acid and sulfuric acid, melted with potassium pyrosulfate, the leached molten material is combined with the main solution, and oxidized with potassium permanganate solution; for samples containing more than 0.05% vanadium, the melting-filtration method is used, that is, alkali is melted, the cooled molten material is leached with water, filtered, the precipitate is washed with sodium hydroxide solution, and then dissolved and precipitated with hydrochloric acid. Most of the iron in the dissolved sample is reduced by stannous chloride, and the remaining iron is reduced by titanium trichloride; then the excess reducing agent is oxidized with dilute potassium dichromate solution, and the reduced iron is titrated with potassium dichromate solution using sodium diphenylamine sulfonate as an indicator. Therefore, the completion of each titration stage is marked by color change.

[0005] However, this kind of measurement method based on visual color change has the following four uncertain errors: ① The eye is a sensor. Due to the different structures and development levels of natural people, the perception threshold of color is different. Different people have different feelings and their own understanding of the language to describe the color of the "titration end point". Different people understand the color of the "titration end point" differently, resulting in the "guessing" of the color titration analysis results. ② The evaluation conditions for observing color have strict and detailed regulations. Different standards have different regulations, which are difficult for laboratories to meet one by one. The color of the same reaction process under different color evaluation conditions will produce different color perception results. ③ Traceability is a necessary condition for modern measurement technology. What is seen in the visual titration process is the feeling of the full spectrum of visible light "imagined" in the brain. To describe this feeling in language is to use an adjective that only the observer knows. It cannot be quantified, preserved, communicated, reproduced or traced. So far, the most critical traceability problem in chemical analysis has not been solved. ④ For more than a hundred years, the sensory determination method has been unable to provide reliable detection limit, quantitative limit, linear range and other parameters necessary for modern metrology, and its methodological defects cannot be met.

[0006] The above-mentioned defects of artificial sensory color titration technology are increasingly unable to meet the urgent needs of modern detection technology for rapidity, accuracy, automation and intelligence. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a full-spectrum titration detection method for the total iron content in an ore in order to solve the problems existing in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A full-spectrum titration detection method for total iron content in ore comprises the following steps: after decomposing the ore sample, adding stannous chloride solution, sodium tungstate solution, titanium trichloride solution, dilute potassium dichromate solution, sulfur-phosphorus mixed acid, sodium diphenylamine sulfonate solution indicator and potassium dichromate standard solution to the sample liquid in sequence, measuring the entire titration process by a visible light full-spectrum titrator, presetting a titration condition change point to mark the change of the titration condition, and taking the volume value corresponding to the full-spectrum titration color change parameter of the potassium dichromate standard solution titration as the titration endpoint volume value, and calculating the total iron content in the ore.

[0010] It is worth noting that the principle of the visible light full spectrum titration method (visible spectral titration technology, VSTT) is to use a sensor to obtain the data of the visible light range change during the whole reaction process, establish a rectangular coordinate system with the reagent amount, and use the signal peak on the color change titration curve as the maximum change value of the titration end point of this step, which corresponds to the volume of the added reagent. The visible light full spectrum titration method has the advantages of overcoming the above four defects, meeting the methodological requirements, clear titration end point signal, and not interfering with the reaction process, and has a very broad application prospect. At present, there are no domestic and foreign reports on the measurement of total iron content in ore using the VSTT method.

[0011] The reagent configuration used in the detection method disclosed in the present invention is:

[0012] Water: distilled water in accordance with GB / T 6682 or water of equivalent purity.

[0013] 0.1 mol / L iron standard solution: Slowly add 75 mL of hydrochloric acid solution (1+1) to 5.58 g of pure iron with a purity greater than 99.9%, heat until dissolved, slowly add 5 mL of hydrogen peroxide solution (1+9) after cooling, heat to boiling until excess hydrogen peroxide is decomposed and chlorine is removed, and then cool and dilute to 1000 mL with water.

[0014] 100g / L stannous chloride solution: 100g stannous chloride crystals (SnCl 2 ·2H2 O) in 200 mL of hydrochloric acid (ρ1.19 g / mL), heat in a water bath until dissolved, cool and dilute to 1 L with water, and store in a brown glass bottle containing a small amount of tin particles.

[0015] 250g / L sodium tungstate solution: Dissolve 25g sodium tungstate in water, add 5mL phosphoric acid (ρ1.7g / mL), and then dilute to 100mL with water.

[0016] 15g / L titanium trichloride solution: dilute 1 volume of titanium trichloride solution (about 15% titanium trichloride solution) with 9 volumes of hydrochloric acid solution (1+1), and make up to 1000mL with water.

[0017] 0.25g / L potassium dichromate solution: Dissolve 0.25g potassium dichromate in water, dilute and make up to 1000mL.

[0018] Sulfur-phosphorus mixed acid: inject 200 mL of phosphoric acid (ρ1.7 g / mL) into about 500 mL of water, add 300 mL of sulfuric acid solution (1+1) and mix well, cool to room temperature, and dilute to 1 L with water.

[0019] 2g / L sodium diphenylamine sulfonate indicator solution: 0.2g sodium diphenylamine sulfonate (C 6 H 5 NHC 6 H 4 SO 3 Na) was dissolved in water, diluted, fixed to 100 mL, and stored in a brown glass bottle.

[0020] 0.01667 mol / L potassium dichromate standard solution: 4.904 g of potassium dichromate (reference reagent) that was previously dried at 140°C-150°C for 2 h and cooled to room temperature in a desiccator was dissolved in water, diluted, and fixed to 1000 mL.

[0021] Hydrogen peroxide (30%, v / v).

[0022] ammonia.

[0023] Ammonia solution (5+95).

[0024] Hydrochloric acid solution (1+1).

[0025] Hydrochloric acid solution (1+50).

[0026] Furthermore, the detection method specifically includes:

[0027] I. Parameters and test program settings of full spectrum titrator;

[0028] II. Select the instrument blank correction procedure and correct the instrument blank value to L *=100±0.5, a * =0±0.5, b * =0±0.5;

[0029] III. Blank sample titration: According to the determination method set in step I, add 1.00mL of the blank sample with a concentration of 0.1mol / L iron standard solution, and measure it. The volume of potassium dichromate standard solution consumed at the titration endpoint is recorded as V. 0 , calculate the volume V of potassium dichromate standard solution consumed by the titrated sample in the blank test after adding the iron standard solution 白 , V 白 =V 0 -1.00;

[0030] IV. Sample measurement: According to the determination procedure set in step I, the sample pre-treated solution is measured, and the volume of potassium dichromate standard solution consumed at the titration endpoint is recorded as V 样 ;

[0031] V. Calculate the total iron content in the sample, mass fraction ω, the formula is:

[0032]

[0033] Where:

[0034] V 样 ——The volume of potassium dichromate standard solution consumed by the titrated sample, in mL;

[0035] V 白 ——The volume of potassium dichromate standard solution consumed by the titrated sample in the blank test after the iron standard solution is added, in mL;

[0036] m——mass of the sample, in g;

[0037] A——The hygroscopic moisture content (mass fraction) of the sample measured according to GB / T 6730.3, in %.

[0038] Furthermore, the setting parameters of the full spectrum titrator in step I include:

[0039] Spectral range 380nm~780nm, △λ5nm, measurement period 150ms, integration time 200ms, optical path 10.0mm, titration rate adjustable, stirring speed 150rpm~350rpm, CLIP 0.5, room temperature.

[0040] Furthermore, the test method set in step I is:

[0041] 1) Place the sample solution to be tested in the detection position of the visible light full spectrum titrator;

[0042] 2) First titration: After adding stannous chloride solution to the preset full spectrum titration color change parameter signal value, stop the titration step;

[0043] 3) Second titration: After adding 0.5 mL of 250 g / L sodium tungstate solution, stop the titration step;

[0044] 4) The third titration: After adding titanium trichloride solution to the preset full spectrum titration color change parameter signal value, stop the titration step and cool to room temperature;

[0045] 5) Fourth titration: After adding dilute potassium dichromate solution to the preset full spectrum titration color change parameter signal value, stop the titration step;

[0046] 6) Fifth titration: After adding 30 mL of sulfur-phosphorus mixed acid, stop the titration step;

[0047] 7) Sixth titration: After adding a certain amount of sodium diphenylamine sulfonate solution, stop the titration step;

[0048] 8) Seventh titration: After adding potassium dichromate standard solution to the preset full spectrum titration color change parameter signal value, stop the titration and record the volume of potassium dichromate standard solution consumed at the titration endpoint.

[0049] Furthermore, the full spectrum titration color change parameters include chromaticity value parameters, color change peak parameters of the color change curve S and color change curve S J The color change peak parameters.

[0050] 8. Furthermore, the chromaticity value parameter includes lightness L * Value, red-green quality index a * Value, yellow-blue index b * Value, chroma C * ab Value, hue angle h ab Value and color difference △E value;

[0051] The color change peak parameters of the color change curve S include the color change curve S s and color change curve S △s .

[0052] It is worth noting that the calculation formula of the full spectrum titration color change parameter involved in the present invention includes:

[0053] Lightness value L * Calculation formula:

[0054]

[0055] Among them, when (i.e. 0.0088565),

[0056] when (i.e. 0.0088565),

[0057] Red-green color index value a * Calculation formula:

[0058]

[0059] Among them, when (i.e. 0.0088565),

[0060] when (i.e. 0.0088565),

[0061] Among them, when (i.e. 0.0088565),

[0062] when (i.e. 0.0088565),

[0063] Yellow-blue color index value b * Calculation formula:

[0064]

[0065] Among them, when (i.e. 0.0088565),

[0066] when (i.e. 0.0088565),

[0067] Among them, when (i.e. 0.0088565),

[0068] when (i.e. 0.0088565), Chroma value C * ab Calculation formula:

[0069]

[0070] Hue angle h ab Calculation formula:

[0071]

[0072] Where:

[0073] L * ——Psychological lightness coordinate value of the sample in CIELAB color space (also called lightness value);

[0074] a * ——Psychological chromaticity coordinate value of the sample in CIELAB color space (also known as red-green color index value);

[0075] b * ——Psychological chromaticity coordinate value of the sample in the CIELAB color space (also known as the yellow-blue color index value);

[0076] C * ab ——Chroma value of the sample in CIELAB color space;

[0077] h ab ——The hue angle value of the sample in the CIELAB color space, unit: °;

[0078] X 10 ——Color stimulus value X among CIE 1964 standard colorimetric observers;

[0079] Y 10 ——Color stimulus value Y among CIE 1964 standard colorimetric observers;

[0080] Z 10 ——Color stimulus value Z among CIE 1964 standard colorimetric observers.

[0081] Color difference △E calculation formula 1:

[0082]

[0083] Where:

[0084] △L * ——are the brightness differences of sample 1 and sample n in the CIELAB color space;

[0085] △a * ——are the red-green color index differences of sample 1 and sample n in the CIELAB color space;

[0086] △b * ——respectively are the yellow-blue index differences of sample 1 and sample n in the CIELAB color space.

[0087] Color difference △E calculation formula 2:

[0088]

[0089] Where:

[0090] △L * ——are the brightness differences of sample 1 and sample n in the CIELAB color space;

[0091] △C * ab ——are the chroma differences between sample 1 and sample n in the CIELAB color space;

[0092] △h ab ——are the hue angle differences between sample 1 and sample n in the CIELAB color space, in radians (°).

[0093] Color change curve S of full spectrum titration s Calculation formula 1:

[0094]

[0095] Where:

[0096] S s —Color change curve of full spectrum titration (when the measurement value J takes the current amount);

[0097] n—1,2,3,…;

[0098] x—1,2,3,…;

[0099] y—2,3,4,…;

[0100] M—Lightness L of the chromaticity value in CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b * Value and its derived parameter chroma C * ab Value, hue angle h ab Value and color difference △E value;

[0101] J—titration process time t parameter, pulse signal f parameter, reagent volume v parameter, reagent concentration c parameter, pH value and hydrogen ion concentration c [H+] One of the parameters.

[0102] Color change curve S of full spectrum titration △s The calculation method is:

[0103]

[0104] Where:

[0105] S △s —Color change curve of full spectrum titration (when the measured value J takes the difference of the current amount);

[0106] n—1,2,3,…;

[0107] m—1,2,3,…;

[0108] x—1,2,3,…;

[0109] y—2,3,4,…;

[0110] M—Lightness L of the chromaticity value in CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b * Value and its derived parameter chroma C * ab Value, hue angle h ab Value and color difference △E value;

[0111] J—titration process time t parameter, pulse signal f parameter, reagent volume v parameter, reagent concentration c parameter, pH value and hydrogen ion concentration c [H+] A parameter value in a parameter.

[0112] Color change curve S J The calculation method is:

[0113]

[0114] Where:

[0115] S J —Full spectrum titration endpoint curve parameter value;

[0116] S a —Lightness L of the chromaticity value in the CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b * Value and its derived parameter chroma C * ab Value, hue angle h ab Any one of the value and color difference △E value;

[0117] S b —With S a Lightness L of chromaticity values ​​in different CIELAB color uniformity space * Value, red-green quality index a * Value, yellow-blue index b * Value and its derived parameter chroma C * ab Value, hue angle h ab Value and color difference △E

[0118] Any value.

[0119] Furthermore, the sample pretreatment method in step IV is selected from acid decomposition or melt-filtration.

[0120] The present invention replaces the visual manual titration analysis process of the National Standard of the People's Republic of China "GB / T 6730.5-2022 Iron ore determination of total iron content - Part 2: Titrimetric methods after titanium (III) chloride reduction, MOD" (ISO 2597-2:2019, Iron ores - Determination of total iron content - Part 2: Titrimetric methods after titanium (III) chloride reduction, MOD) with the visible light full spectrum titration technology of the visible light full spectrum titrator, solving the chronic disease of manual titration analysis technology for more than 200 years. In addition, the full spectrum titration detection method for total iron content in ore disclosed in the present invention can be seamlessly connected with the titration method specified in the national standard, and the precision is better than the national standard. While realizing continuous automatic detection, it is also conducive to the effective integration of full spectrum titration technology within the original national standard framework, which helps the digital upgrade of the titration detection method and effectively improves the work efficiency of the detection of total iron content in ore.

[0121] Compared with the prior art, the beneficial technical effects of the present invention are:

[0122] 1. The present invention adopts visible light full spectrum detection calculation, and uses real color measurement to express the color and its changes with a digital color change titration curve, and identifies the titration end point of each stage by the established color change curve and the mutation peak on the color change curve.

[0123] 2. The present invention marks the titration endpoints at different stages with the mutation peaks of the color change curve parameters, realizes the digital, graphical and automatic identification of the titration endpoint, and realizes the intelligent identification and control of multi-color change experiments by combining automation technology;

[0124] 3. The present invention establishes the corresponding relationship between the color parameter value measured by the visible light full spectrum titration technology and the amount of reagent added, realizing the traceability and transfer of the value.

[0125] 4. The greatest innovation of the present invention is that the visible light full spectrum titration technology provides the minimum detection limit and quantitative limit parameters of the detection method, which makes up for the methodological defects of manual sensory titration. BRIEF DESCRIPTION OF THE DRAWINGS

[0126] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0127] Figure 1 is the brightness L of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention * curve.

[0128] Figure 2 is the red-green color index a of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention * and yellow-blue quality index b * .

[0129] Figure 3 The chroma C of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention * ab curve.

[0130] Figure 4 is the hue angle h of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention ab curve.

[0131] Figure 5 The color difference △E curve of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention.

[0132] Figure 6 The chromaticity diagram (L * -a * ).

[0133] Figure 7 The chromaticity diagram (L * -b * ).

[0134] Figure 8 The chromaticity diagram (a) of the full spectrum parameters of the ore total iron content reduction-titration step in Example 1 of the present invention * -b * ).

[0135] Fig. 9 The chromaticity diagram and parameter values ​​of the full spectrum titration of the total iron content reduction-titration step of the ore in Example 1 of the present invention.

[0136] Fig.10 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention JL*-a* .

[0137] Fig.11 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention JL*-b* .

[0138] Fig.12 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention JL*-C*ab .

[0139] Fig.13 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention JL*-hab .

[0140] Fig.14 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention JL*-△E .

[0141] Fig.15 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Ja*-b* .

[0142] Fig.16 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Ja*-b* (Enlarged image).

[0143] Fig.17 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Ja*-C*ab .

[0144] Fig.18 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Ja*-C*ab (Enlarged image).

[0145] Fig.19 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Ja*-hab .

[0146] Fig. 20 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Ja*-△E .

[0147] Fig.21is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Jb*-C*ab .

[0148] Fig. 22 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Jb*-C*ab (Enlarged image).

[0149] Fig.23 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Jb*-hab .

[0150] Fig.24 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Jb*-hab (Enlarged image).

[0151] Fig.25 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Jb*-△E .

[0152] Fig.26 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention JC*ab-hab .

[0153] Fig. 27 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention JC*ab-△E .

[0154] Fig.28 is the color change curve parameter S of the full spectrum titration of the ore total iron content reduction-titration step in Example 1 of the present invention Jhab-△E . DETAILED DESCRIPTION

[0155] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0156] The present invention belongs to the technical field of chemical mineral detection, and specifically relates to a full-spectrum titration detection method for total iron content in an ore. After the ore sample is decomposed, the method sequentially adds stannous chloride solution, sodium tungstate solution, titanium trichloride solution, dilute potassium dichromate solution, sulfur-phosphorus mixed acid, sodium diphenylamine sulfonate solution indicator and potassium dichromate standard solution to the sample liquid, measures the entire titration process by a visible light full-spectrum titrator, presets a titration condition change point to mark the change of the titration condition, and uses the volume value corresponding to the full-spectrum titration color change parameter of the potassium dichromate standard solution titration as the titration endpoint volume value to calculate the total iron content in the ore.

[0157] The present invention replaces the visual manual titration analysis process of the National Standard of the People's Republic of China "GB / T 6730.5-2022 Iron ore determination of total iron content - Part 2: Titrimetric methods after titanium (III) chloride reduction, MOD" (ISO 2597-2:2019, Iron ores - Determination of total iron content - Part 2: Titrimetric methods after titanium (III) chloride reduction, MOD) with the visible light full spectrum titration technology of the visible light full spectrum titrator, solving the chronic disease of manual titration analysis technology for more than 200 years. In addition, the full spectrum titration detection method for total iron content in ore disclosed in the present invention can be seamlessly connected with the titration method specified in the national standard, and the precision is better than the national standard. While realizing continuous automatic detection, it is also conducive to the effective integration of full spectrum titration technology within the original national standard framework, which helps the digital upgrade of the titration detection method and effectively improves the work efficiency of the detection of total iron content in ore.

[0158] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0159] Example 1: Acid decomposition of ore samples (vanadium < 0.05%, and copper < 0.1%)

[0160] 1.1. Sample collection and preparation:

[0161] The particle size of the sample should be less than 100 μm. If the sample contains high content of combined water or oxidizable substances, the particle size should be less than 160 μm.

[0162] 1.2 Reagents, instruments and equipment

[0163] Visible light full spectrum titrator (VSTAI): G2304-10X, Qinhuangdao Water Bear Technology Co., Ltd.

[0164] Unless otherwise specified, the single-marked volumetric flasks and single-marked pipettes used shall comply with the requirements of GB / T 12806 and GB / T 12808.

[0165] Corundum crucible, capacity 25mL~30mL.

[0166] Burette, Class A, in accordance with GB / T 12805.

[0167] Platinum crucible, capacity 25mL~30mL, with lid.

[0168] Weighing spoon, made of non-magnetic material or demagnetized stainless steel.

[0169] The high temperature furnace is suitable for controlling the temperature in the range of 500℃~800℃.

[0170] Balance, graduation value: 0.0001g.

[0171] 1.3 Instrument and program settings

[0172] 1.3.1. The setting conditions of the full spectrum titrator are as follows: spectral range 380nm~780nm, △λ5nm, measurement period 150ms, integration time 200ms, optical path 10.0mm, titration rate adjustable, stirring speed 150rpm~350rpm, CLIP0.5, room temperature.

[0173] 1.3.2. Titration procedure The first titration step is to pump 2 to add 100 g / L stannous chloride solution until the color change curve parameter S of the preset visible light full spectrum titration method is reached. Ja*-b* After the peak, the titration step was stopped.

[0174] 1.3.3. The second titration step is to add 0.5 mL of 250 g / L sodium tungstate solution and then stop the titration step.

[0175] 1.3.4. The third titration step is to add a titanium chloride solution with a concentration of 15 g / L until the preset parameter b * =-28±2, stop the third titration step and cool to room temperature.

[0176] 1.3.5. The fourth titration step is to add a dilute potassium dichromate solution with a concentration of 0.25 g / L until the color change curve parameter S of the preset visible light full spectrum titration method is Jhab-△E After the peak, the titration step was stopped.

[0177] 1.3.6. The fifth titration step is to add 30 mL of sulfur-phosphorus mixed acid and then stop the titration step.

[0178] 1.3.7. The sixth titration step is to dropwise add 0.25 mL of sodium diphenylamine sulfonate solution with a concentration of 2 g / L, and then stop the titration step.

[0179] 1.3.8. The seventh titration step is to add a potassium dichromate standard solution with a concentration of 0.01667 mol / L until the color change curve parameter S of the preset visible light full spectrum titration method is Ja*-b* The peak value is the titration endpoint, and the volume of potassium dichromate standard solution consumed is recorded.

[0180] 1.4. Select the instrument blank correction procedure and correct the instrument blank value to L * =100±0.5,a * =0±0.2, b * =0±0.2;

[0181] 1.5. Transfer the blank sample to the reactor of the visible light spectrometer titrator, add 1.00 mL of the iron standard solution with a concentration of 0.1 mol / L, and titrate according to the titration method in 1.3 to obtain the volume V of the potassium dichromate standard solution consumed at the titration endpoint. 0 , calculate the blank value V of the measured sample 白 =0.1mL;

[0182] 1.6. Sample pretreatment and measurement calculation:

[0183] 1.6.1. Use a weighing spoon to weigh 0.40 g of the sample (accurate to 0.0002 g) into a 250 mL beaker, moisten it with a small amount of water, add 30 mL of hydrochloric acid, cover it with a watch glass, and slowly heat the solution without boiling to decompose the sample in order to prevent the ferric chloride from volatilizing.

[0184] 1.6.2. Rinse the watch glass with running water and dilute to 50 mL with warm water. Filter the insoluble residue with medium-speed filter paper. Clean the beaker wall with a wiper and wash the beaker 3 times with warm hydrochloric acid solution (1+50). Wash the residue with warm hydrochloric acid solution (1+50) until the yellow ferric chloride is no longer visible. Then wash with warm water 6 to 8 times. Collect the filtrate and washings in a 400 mL beaker.

[0185] 1.6.3. Place the filter paper and the residue in a platinum crucible with a capacity of 25 mL to 30 mL, dry, incinerate the filter paper, and finally burn at 750°C to 800°C. Cool the crucible, add 4 drops of sulfuric acid solution (1+1) to moisten the residue, add 5 mL of hydrofluoric acid, and heat slowly to remove silicon dioxide and sulfuric acid (until all sulfur trioxide white smoke is emitted).

[0186] 1.6.4. Add 2g of finely powdered potassium pyrosulfate to the cooled crucible, cover the crucible, heat slowly first, then heat at high temperature until the melt is clear (melting at 650℃ for about 5min), cool, put the crucible and the crucible cover into the original 250mL beaker, add about 25mL of water and 5mL of hydrochloric acid in sequence, and dissolve the melt by warming. Wash out the crucible and the crucible cover, and combine the solution with the main solution.

[0187] 1.6.5. Add about 0.25 mL of 25 g / L potassium permanganate solution and heat the solution below the boiling point. Maintain the solution at this temperature for 5 minutes to oxidize organic matter and arsenic, and continue to evaporate to about 150 mL without boiling.

[0188] 1.6.6. Keep the sample solution at 90℃~95℃ and clean the watch glass and the inner wall of the beaker with a small amount of hot water.

[0189] 1.6.7. Weigh 4.006g of sample according to the above operation, and place the treated sample solution on the measuring position of G2304-10X Visible Light Full Spectrum Titrator (VSTAI).

[0190] 1.6.8. The first titration step of the titration procedure is to pump 2 to add 100 g / L stannous chloride solution to reduce iron (III) until the color change curve parameter S of the preset visible light full spectrum titration method is reached. Ja*-b* After the peak, the titration step was stopped.

[0191] 1.6.9. The second titration step is to add 0.5 mL of 250 g / L sodium tungstate solution and then stop the titration step.

[0192] 1.6.10. The third titration step is to add a titanium chloride solution with a concentration of 15 g / L until the preset parameter L * =55±5, stop the third titration step and cool to room temperature.

[0193] 1.6.11. The fourth titration step is to add a dilute potassium dichromate solution with a concentration of 0.25 g / L until the color change curve parameter S of the preset visible light full spectrum titration method is Jhab-△E After the peak, the titration step was stopped.

[0194] 1.6.12. The fifth titration step is to add 30 mL of sulfur-phosphorus mixed acid and then stop the titration step.

[0195] 1.6.13. The sixth titration step is to dropwise add 0.25 mL of 2 g / L sodium diphenylamine sulfonate solution and stop the titration step.

[0196] 1.6.14. The seventh titration step is to add a potassium dichromate standard solution with a concentration of 0.01667 mol / L until the color change curve parameter S of the preset visible light full spectrum titration method is Ja*-b* The peak value is the titration endpoint. The volume of potassium dichromate standard solution consumed by the titrated sample is 40.24 mL, recorded as (V 样 ).

[0197] 1.6.15. The eighth titration step is to adjust the volume V of the potassium dichromate standard solution consumed in the seventh titration step according to the measured sample amount and the volume V of the potassium dichromate standard solution consumed in the seventh titration step. 样 and the sample blank value V 白 The total iron content in the sample was calculated to be 55.96%.

[0198] The measured data at the endpoint of each titration step are shown in Table 1.

[0199] Table 1

[0200]

[0201]

[0202] Example 2: Acid decomposition of ore samples (vanadium < 0.05%, and copper ≥ 0.1%)

[0203] 2.1. Sample collection and preparation:

[0204] The particle size of the sample should be less than 100 μm. If the sample contains high content of combined water or oxidizable substances, the particle size should be less than 160 μm.

[0205] 2.2 Reagents, instruments and equipment

[0206] Visible light full spectrum titrator (VSTAI): G2304-10X, Qinhuangdao Water Bear Technology Co., Ltd.

[0207] Platinum crucible, capacity 25mL~30mL, with lid.

[0208] Weighing spoon, made of non-magnetic material or demagnetized stainless steel.

[0209] The high temperature furnace is suitable for controlling the temperature in the range of 500℃~800℃.

[0210] Balance, graduation value: 0.0001g.

[0211] 2.3. Instrument and parameter setting

[0212] 2.3.1. The setting conditions of the full spectrum titrator are as follows: spectral range 380nm~780nm, △λ5nm, measurement period 150ms, integration time 200ms, optical path 10.0mm, titration rate adjustable, stirring speed 150rpm~350rpm, CLIP0.5, room temperature;

[0213] 2.3.2. Titration procedure The first titration step is to pump 2 to add 100 g / L stannous chloride solution until the color change curve parameter S of the preset visible light full spectrum titration method is reached. Ja*-△E After the peak, stop the titration step;

[0214] 2.3.3, the second titration step is to add 0.5mL of 250g / L sodium tungstate solution, and then stop the titration step;

[0215] 2.3.4. The third titration step is to add a titanium chloride solution with a concentration of 15 g / L until the preset parameter a * = After the range of -7.3±3, stop the third titration step and cool for a few minutes;

[0216] 2.3.5. The fourth titration step is to add a dilute potassium dichromate solution with a concentration of 0.25 g / L until the color change curve parameter S of the preset visible light full spectrum titration method is Jha*-b* After the peak, stop the titration step;

[0217] 2.3.6. The fifth titration step is to add 30 mL of sulfur-phosphorus mixed acid and then stop the titration step;

[0218] 2.3.7, the sixth titration step is to add 0.25 mL of sodium diphenylamine sulfonate solution with a concentration of 2 g / L, and then stop the titration step;

[0219] 2.3.8. The seventh titration step is to add a potassium dichromate standard solution with a concentration of 0.01667 mol / L until the color change curve parameter S of the preset visible light full spectrum titration method is Ja*-hab The peak value is the titration endpoint, and the volume of potassium dichromate standard solution consumed by the titrated sample is recorded as (V 样 );

[0220] 2.3.9. The eighth titration step is to adjust the volume V of the potassium dichromate standard solution consumed in the seventh titration step according to the measured sample volume. 0 Calculate the total iron content in the sample;

[0221] 2.4. Select the instrument blank correction procedure and correct the instrument blank value to L * =100±0.5,a * =0±0.2, b * =0±0.2;

[0222] 2.5. Transfer the reagent blank sample to the visible light spectrometer titrator reactor and add 1.00 mL of iron standard solution with a concentration of 0.1 mol / L. Measure the sample blank value V according to the above titration steps. 白 is 0.1mL.

[0223] 2.6. Sample pretreatment and measurement calculation:

[0224] 2.6.1. Weigh 0.3985 g of sample into a 250 mL beaker, moisten with a small amount of water, add 30 mL of hydrochloric acid, cover with a watch glass, and slowly heat the solution without boiling to decompose the sample in order to prevent the ferric chloride from volatilizing.

[0225] 2.6.2. Rinse the watch glass with running water and dilute to 50 mL with warm water. Filter the insoluble residue with medium-speed filter paper. Clean the beaker wall with a wiper and wash the beaker 3 times with warm hydrochloric acid solution (1+50). Wash the residue with warm hydrochloric acid solution (1+50) until the yellow ferric chloride is no longer visible. Then wash with warm water 6 to 8 times. Collect the filtrate and washings in a 400 mL beaker.

[0226] 2.6.3. Place the filter paper and the residue in a platinum crucible with a capacity of 25 mL to 30 mL, dry, incinerate the filter paper, and finally burn at 750°C to 800°C. Cool the crucible, add 4 drops of sulfuric acid solution (1+1) to moisten the residue, add 5 mL of hydrofluoric acid, and heat slowly to remove silicon dioxide and sulfuric acid (until all sulfur trioxide white smoke is emitted).

[0227] 2.6.4. Add 2g of finely powdered potassium pyrosulfate to the cooled crucible, cover the crucible, heat slowly first, then heat at high temperature until the melt is clear (melting at 650℃ for about 5min), cool, put the crucible and the crucible cover into the original 250mL beaker, add about 25mL of water and 5mL of hydrochloric acid in sequence, and dissolve the melt by warming. Wash out the crucible and the crucible cover, and combine the solution with the main solution.

[0228] 2.6.5. Add about 0.25 mL of 25 g / L potassium permanganate solution and heat the solution below the boiling point. Maintain the solution at this temperature for 5 minutes to oxidize organic matter and arsenic, and continue to evaporate to about 150 mL without boiling.

[0229] 2.6.6. Add 5 mL of hydrogen peroxide (30%, v / v) to the test solution, heat the solution without boiling, and maintain it at this temperature for 5 minutes.

[0230] 2.6.7. Neutralize with ammonia water until precipitation occurs, with an excess of 10 mL, boil and wait for the precipitation to settle.

[0231] 2.6.8. Filter with quick filter paper and wash the precipitate with ammonia solution (5+95) 8 to 9 times.

[0232] 2.6.9. Dissolve the precipitate in a 400 mL beaker with 20 mL of hydrochloric acid solution (1+1) and wash with hot hydrochloric acid solution (1+50) until the filter paper becomes colorless.

[0233] 2.6.10. Add water to the filtrate to a volume of about 150 mL and bring to a near-boiling state. Use a small amount of hot water to clean the watch glass and the inner wall of the beaker. Place the sample solution in the measuring position of the G2304-10X Visible Light Full Spectrum Titrator (VSTAI).

[0234] 2.6.11. Titration procedure The first titration step is to pump 2 to add 100g / L stannous chloride solution until the color change curve a of the preset visible light full spectrum titration method is reached. * =-2±1, and b * =4±1 value, stop the titration step.

[0235] 2.6.12. The second titration step is to add 0.5 mL of 250 g / L sodium tungstate solution and then stop the titration step.

[0236] 2.6.13. The third titration step is to add a titanium chloride solution with a concentration of 15 g / L until the preset parameter C * ab =27±5, stop the third titration step and cool for a few minutes.

[0237] 2.6.14. The fourth titration step is to add a dilute potassium dichromate solution with a concentration of 0.25 g / L until the color change curve parameter S of the preset visible light full spectrum titration method is JC*ab-hab After the peak, the titration step was stopped.

[0238] 2.6.15. The fifth titration step is to add 30 mL of sulfur-phosphorus mixed acid and then stop the titration step.

[0239] 2.6.16. The sixth titration step is to dropwise add 0.25 mL of sodium diphenylamine sulfonate solution with a concentration of 2 g / L, and then stop the titration step.

[0240] 2.6.17. The seventh titration step is to add a potassium dichromate standard solution with a concentration of 0.01667 mol / L until the color change curve parameter S of the preset visible light full spectrum titration method is Ja*-△E The peak value is the titration endpoint, and the volume of potassium dichromate standard solution consumed by the titrated sample is V 样 =39.726mL.

[0241] 2.6.18. The eighth titration step is to adjust the volume V of the potassium dichromate standard solution consumed in the seventh titration step according to the measured sample amount and the volume V of the potassium dichromate standard solution consumed in the seventh titration step. 样 and the sample blank value V 白Calculated total iron content in the sample = 55.5%.

[0242] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are used to further illustrate the beneficial effects of the full-spectrum titration detection method for total iron content in ore disclosed in the present invention, but they should not be construed as limitations on the present invention. The properties of the methods obtained by other experiments conducted by technicians in this field based on the above-mentioned invention content and the applications based on the above-mentioned properties are also deemed to fall within the protection scope of the present invention.

[0243] Comparative Example 1

[0244] The total iron content in the ore was manually titrated in accordance with the visual manual titration analysis process of the National Standard of the People's Republic of China "GB / T 6730.5-2022 Iron ore—Determination of total iron content—Part 2: Titrimetric methods after titanium(Ⅲ)chloride reduction, MOD" (ISO 2597-2:2019, Iron ores—Determination of total iron content—Part 2: Titrimetric methods after titanium(Ⅲ)chloride reduction, MOD).

[0245] The same ore sample was measured according to the method of Example 1 and Comparative Example 1, and the results are shown in Table 2.

[0246] Table 2 Comparison test results

[0247]

[0248] It can be seen that the relative standard deviation of the full spectrum titration detection method for the total iron content in the ore disclosed in Example 1 is 0.175%, and the relative standard deviation of the manual titration method disclosed in Comparative Example 1 is 0.481%. The precision of the full spectrum titration detection method is better than that of the manual titration method. Therefore, the full spectrum titration detection method for the total iron content in the ore disclosed in the present invention realizes continuous measurement of the whole process, and does not need to continue titrating after manual judgment at each color change point, and can replace the manual titration method to realize continuous automatic measurement.

[0249] In addition, the full-spectrum titration detection method for total iron content in ore disclosed in the present invention can be seamlessly connected with the titration standard specified in the national standard, and the precision is better than the manual titration method. While realizing continuous automated detection, this is conducive to the effective integration of full-spectrum titration technology within the original national standard framework, and helps the digital upgrade of titration detection methods, effectively improving the work efficiency of titration of total iron content in ore.

[0250] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A full-spectrum titration detection method for total iron content in ore, after the ore sample is decomposed, stannous chloride solution, sodium tungstate solution, titanium trichloride solution, dilute potassium dichromate solution, sulfur-phosphorus mixed acid, sodium diphenylamine sulfonate solution indicator and potassium dichromate standard solution are added to the sample liquid in sequence, characterized in that: The entire titration process is automatically measured by a visible light full-spectrum titrator, and the titration condition change point is preset to indicate the change of titration conditions. The volume value corresponding to the full-spectrum titration color change parameter of potassium dichromate standard solution titration is used as the titration endpoint volume value to calculate the total iron content in the ore.

2. The full spectrum titration detection method for total iron content in ore according to claim 1, characterized in that: The detection method specifically comprises: I. Parameters and test program settings of full spectrum titrator; II. Select the instrument blank correction procedure and correct the instrument blank value to L * =100±0.5, a * =0±0.5, b * =0±0.5; III. Blank sample titration: According to the determination method set in step I, a blank sample is measured by adding 1.00 mL of a 0.1 mol / L iron standard solution. The volume of potassium dichromate standard solution consumed at the titration endpoint is recorded as V0. The volume of potassium dichromate standard solution consumed by the titrated sample of the blank test after adding the iron standard solution is calculated as V. 白 , V 白 =V0-1.00; IV. Sample measurement: According to the determination procedure set in step I, the sample pre-treated solution is measured, and the volume of potassium dichromate standard solution consumed at the titration endpoint is recorded as V 样 ; V. Calculate the total iron content in the sample, mass fraction ω, the formula is: Where: V 样 ——The volume of potassium dichromate standard solution consumed by the titrated sample, in mL; V 白 ——The volume of potassium dichromate standard solution consumed by the titrated sample in the blank test after the iron standard solution is added, in mL; m——mass of the sample, in g; A——The hygroscopic moisture content (mass fraction) of the sample measured according to GB / T 6730.3, in %.

3. The full spectrum titration detection method for total iron content in ore according to claim 2, characterized in that: The setting parameters of the full spectrum titrator in step I include: Spectral range 380nm~780nm, △λ5nm, measurement period 150ms, integration time 200ms, optical path 10.0mm, titration rate adjustable, stirring speed 150rpm~350rpm, CLIP 0.5, room temperature.

4. The full spectrum titration detection method for total iron content in ore according to claim 2, characterized in that: The test procedure set in step I is: 1) Place the sample solution to be tested in the detection position of the visible light full spectrum titrator; 2) First titration: After adding stannous chloride solution to the preset full spectrum titration color change parameter signal value, stop the titration step; 3) Second titration: After adding 0.5 mL of 250 g / L sodium tungstate solution, stop the titration step; 4) The third titration: After adding titanium trichloride solution to the preset full spectrum titration color change parameter signal value, stop the titration step and cool to room temperature; 5) Fourth titration: After adding dilute potassium dichromate solution to the preset full spectrum titration color change parameter signal value, stop the titration step; 6) Fifth titration: After adding 30 mL of sulfur-phosphorus mixed acid, stop the titration step; 7) Sixth titration: After adding 0.25 mL of 2 g / L sodium diphenylamine sulfonate solution, stop the titration step; 8) Seventh titration: After adding potassium dichromate standard solution to the preset full spectrum titration color change parameter signal value, stop the titration and record the volume of potassium dichromate standard solution consumed at the titration endpoint.

5. The full spectrum titration detection method for total iron content in ore according to claim 4, characterized in that: The full spectrum titration color change parameters include chromaticity value parameters, color change peak parameters of the color change curve S and color change curve S J The color change peak parameters.

6. The full spectrum titration detection method for total iron content in ore according to claim 5, characterized in that: The chromaticity value parameters include lightness L * Value, red-green quality index a * Value, yellow-blue index b * Value, chroma C * ab Value, hue angle h ab Value and color difference △E value; The color change peak parameters of the color change curve S include the color change curve S s and color change curve S △s .

7. The full spectrum titration detection method for total iron content in ore according to claim 2, characterized in that: The sample pretreatment method in step IV is selected from acid decomposition or melt-filtration.

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