Method for detecting fluorescent substances in talc raw ore

Abstract

The invention belongs to the technical field of talc, and provides a method for detecting fluorescent substances in talc raw ore, which comprises the following steps: S1, carrying out ball milling on the talc raw ore in a ball mill, sieving to obtain sieved powder, and adding deionized water into the sieved powder to obtain slurry; s2, adding the slurry into the mixture to enable the pH value of the slurry to be 5, stirring, and standing in a water bath for 2-3 hours to obtain a first precipitate; s3, adding a thiourea-ascorbic acid solution into the first precipitate to obtain a second precipitate; and S4, carrying out secondary ball milling on the second precipitate, and spreading the second precipitate in an enamel plate to detect whether the talc raw ore contains the fluorescent substances or not. The hydrochloric acid can dissolve quartz and mica to avoid generation of background fluorescence or quenching effect, and the nonionic surfactant polyethylene glycol can be adsorbed on the surface of the mineral to reduce interfacial tension, so that the hydrochloric acid is easier to infiltrate tiny pores, the pit defect caused by local over-corrosion is reduced, the pickling uniformity is improved, and the detection sensitivity is improved.

Description

Technical Field

[0001] This invention belongs to the field of talc raw ore detection technology, specifically relating to a method for detecting fluorescent substances in talc raw ore. Background Technology

[0002] Talc is used as a filler in the paper industry to improve the smoothness, opacity, and printability of paper. In the manufacture of tissue paper, the use of small amounts of talc is common, primarily to eliminate resin, prevent contamination of production equipment, and avoid defects such as pinholes in the paper.

[0003] Non-fluorescent paper typically refers to paper that has not had optical brighteners added during the manufacturing process. Optical brighteners are chemical substances that absorb ultraviolet light and emit blue-violet fluorescence, making paper appear whiter and brighter.

[0004] However, some consumers may prefer to choose paper without fluorescent whitening agents for health or environmental reasons, as fluorescent whitening agents may have potential health effects, especially with long-term exposure or ingestion.

[0005] Therefore, the manufacturing process of fluorescent-free paper requires strict control over the raw materials used, ensuring they do not contain fluorescent substances. Thus, the detection of fluorescent substances in talc is particularly important. Currently, when detecting fluorescent substances in raw talc ore, no pretreatment is performed. This results in background fluorescence or quenching effects from the complex mineral matrix (quartz, mica, etc.) within the talc ore. Simultaneously, the rough surface of the raw talc ore induces light scattering, masking or distorting the target fluorescent signal and reducing detection sensitivity. Summary of the Invention

[0006] To address the problems existing in the background art, the present invention provides a method for detecting fluorescent substances in raw talc ore.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for detecting fluorescent substances in raw talc ore, comprising the following steps: S1. Place 10g of raw talc ore in a ball mill and mill it for a period of time. Then, sieve it to obtain sieved powder. Add the sieved powder to deionized water to obtain a slurry. S2. Add the slurry obtained in S1 to the mixture to make the pH value of the slurry 5, stir for 30 min, and then place it in a water bath at 60℃ for 2-3 h to obtain the first solid. Filter to obtain the first solid, and wash the first solid to obtain the first precipitate. The mixture includes hydrochloric acid, polyethylene glycol and water. S3. Add 50 mL of thiourea-ascorbic acid solution to the precipitate obtained in S2, then let it stand for 1-2 h, filter to obtain the second solid, wash and dry the second solid to obtain the second precipitate; S4. After the second precipitate is ball-milled for a period of time, the sample is passed through a 7mm sieve and spread evenly in an enamel dish. In a dark and sealed environment, it is irradiated with a 365nm fluorescence detector. Visually inspect whether the raw talc ore in the enamel dish contains fluorescent substances.

[0008] Furthermore, in S1, the ball milling time is 30-35 min, the ball mill speed is 750-800 r / min, the screen particle size is 7 mm, and the slurry mass concentration is 20%.

[0009] Furthermore, in the mixture of S2, the mass fraction of polyethylene glycol is 3-5%, the mass fraction of hydrochloric acid is 7-8%, and the remainder is water.

[0010] Further, in S2, the first solid is washed with deionized water until it becomes neutral, thus obtaining the first precipitate.

[0011] Furthermore, in the thiourea-ascorbic acid solution S3, the volume fraction of thiourea is 5%, and the volume fraction of ascorbic acid is 5%. Furthermore, in S3, the second solid is washed with deionized water until neutral, and then placed in a drying oven and dried at 85-90℃ for 2-3 hours.

[0012] Furthermore, in S4, the ball milling time is 25-30 minutes, and the ball mill speed is 750-800 r / min.

[0013] This application has the following beneficial effects: 1. After the raw talc ore is ground in a ball mill, the talc ore particles are refined by impact with steel balls, which reduces the roughness of the talc ore surface, reduces the phenomenon of target fluorescence signal being masked or distorted, and improves detection sensitivity. At the same time, it breaks the embedding relationship between quartz / mica and talc, releases the encapsulated fluorescent substances, and further improves detection sensitivity.

[0014] 2. Hydrochloric acid can dissolve quartz and mica, thus avoiding the occurrence of background fluorescence or quenching effects. The nonionic surfactant polyethylene glycol can be adsorbed on the mineral surface, reducing interfacial tension, making it easier for hydrochloric acid to wet micropores, reducing pit defects caused by local over-etching, improving pickling uniformity, and giving talc powder better flowability. Hydrochloric acid and polyethylene glycol also work together to improve detection sensitivity.

[0015] 3. Thiourea-ascorbic acid synergistic washing: Thiourea, as a soft Lewis base, preferentially complexes Cu. 2+ Pb 2+Heavy metal ions block the metal-fluorophore energy transfer pathway; ascorbic acid will... 3+ Reduced to Fe 2+ It also forms a soluble ferrous complex, which avoids the ·OH free radicals generated by the Fenton reaction from quenching the fluorescence and improves the detection sensitivity. Detailed Implementation

[0016] The present application will be further described in detail below with reference to the embodiments.

[0017] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0018] Example 1: A method for detecting fluorescent substances in raw talc ore, comprising the following steps: S1. Place 10g of raw talc ore in a ball mill and mill for a period of time. Then, sieve the ore to obtain sieved powder. Add the sieved powder to deionized water to obtain a slurry. The ball milling time is 30min, the ball mill speed is 750r / min, the sieve particle size is 7mm, and the slurry mass concentration is 20%.

[0019] S2. Add the slurry obtained in S1 to the mixture to adjust the pH of the slurry to 5, stir for 30 minutes, and then let it stand in a water bath at 60°C for 2 hours to obtain the first solid. Filter the first solid to obtain the first precipitate. The mixed acid includes hydrochloric acid, polyethylene glycol, and water; the mass fraction of polyethylene glycol is 3%, the mass fraction of hydrochloric acid is 7%, and the remainder is water. The polyethylene glycol used is polyethylene glycol with a molecular weight of 600. Wash the first solid with deionized water until neutral to obtain the first precipitate.

[0020] S3. Add 50 mL of thiourea-ascorbic acid solution to the precipitate obtained in S2, then let it stand for 1 h, filter to obtain a second solid, wash and dry the second solid to obtain a second precipitate; the volume fraction of thiourea in the thiourea-ascorbic acid solution is 5%, and the volume fraction of ascorbic acid is 5%. Wash the second solid with deionized water until neutral, then place it in a drying oven and dry at 85℃ for 2 h.

[0021] S4. After ball milling the second precipitate for 25 minutes, pass the sample through a 7mm sieve, spread it evenly in an enamel dish, and irradiate it with a 365nm fluorescence detector in a dark, sealed environment. Visually inspect the talc ore in the enamel dish for fluorescent substances. The ball mill speed is 750 r / min.

[0022] Comparative Example 1: The difference between this comparative example and Example 1 is that the raw talc ore was not treated with S1, S2, and S3. Specifically, 10g of raw talc ore was ball-milled for 25 minutes, and the sample was passed through a 7mm sieve and spread evenly in an enamel dish. In a dark, sealed environment, the sample was irradiated with a 365nm fluorescence detector, and the presence of fluorescent substances in the raw talc ore in the enamel dish was visually observed. The ball mill speed was 750r / min.

[0023] Comparative Example 2: The difference between this comparative example and Example 1 is that polyethylene glycol is removed from the mixture in S2. Specifically: S2: The slurry obtained in S1 is added to the mixture to make the pH of the slurry 5, stirred for 30 minutes, and then placed in a water bath at 60°C for 2 hours to obtain a first solid. The first solid is filtered and washed to obtain a first precipitate. The mixed acid includes hydrochloric acid and water; the mass fraction of hydrochloric acid is 7%, and the remainder is water. The first solid is washed with deionized water until neutral to obtain the first precipitate.

[0024] Comparative Example 3: The difference between this comparative example and Example 1 is that step S3 is deleted. Specifically, it is as follows: A method for detecting fluorescent substances in raw talc ore includes the following steps: S1. Place 10g of raw talc ore in a ball mill and mill for a period of time. Then, sieve the ore to obtain sieved powder. Add the sieved powder to deionized water to obtain a slurry. The ball milling time is 30min, the ball mill speed is 750r / min, the sieve particle size is 7mm, and the slurry mass concentration is 20%.

[0025] S2. Add the slurry obtained in S1 to the mixture to adjust the pH of the slurry to 5, stir for 30 minutes, and then let it stand in a water bath at 60°C for 2 hours to obtain the first solid. Filter the first solid to obtain the first precipitate. The first solid is then washed to obtain the first precipitate. The mixed acid includes hydrochloric acid, polyethylene glycol, and water; the mass fraction of polyethylene glycol is 3%, the mass fraction of hydrochloric acid is 7%, and the remainder is water. Wash the first solid with deionized water until neutral to obtain the first precipitate.

[0026] S4. After ball milling the first precipitate for 25 minutes, pass the sample through a 7mm sieve, spread it evenly in an enamel dish, and irradiate it with a 365nm fluorescence detector in a dark, sealed environment. Visually inspect the talc ore in the enamel dish for fluorescent substances. The ball mill speed is 750 r / min. Experimental examples: Samples obtained from Example 1 and Comparative Examples 1-3.

[0027] Experimental items: background noise level and fluorescence signal intensity. The experimental results are shown in Table 1.

[0028] Table 1. Background noise and fluorescence signal intensity of talc samples from the test examples, as detected by a fluorescence detector. Background noise / cps Fluorescence signal intensity (target peak intensity) / cps Example 1 200 6500 Comparative Example 1 1800 1200 Comparative Example 2 1000 2600 Comparative Example 3 900 2700 Results Analysis: Analysis of Example 1 and Comparative Examples 1-3, combined with Table 1, shows that, by comparing Comparative Example 1 and Example 1, the background noise obtained by the fluorescence detector in Comparative Example 1 is greater than that in Example 1, and the fluorescence signal intensity obtained by the fluorescence detector in Comparative Example 1 is less than that in Example 1.

[0029] Comparing Comparative Example 1, Comparative Example 2 and Example 1, it can be seen that the background noise obtained by the fluorescence detector in Comparative Example 2 is greater than that in Example 1 but less than that in Comparative Example 1, and the fluorescence signal intensity obtained by the fluorescence detector in Comparative Example 2 is less than that in Example 1 but greater than that in Comparative Example 1.

[0030] Comparing Comparative Example 1, Comparative Example 3 and Example 1, it can be seen that the background noise obtained by the fluorescence detector in Comparative Example 3 is greater than that in Example 1 but less than that in Comparative Example 1, and the fluorescence signal intensity obtained by the fluorescence detector in Comparative Example 3 is less than that in Example 1 but greater than that in Comparative Example 1.

[0031] This is because after the raw talc ore is ground in a ball mill, the impact of steel balls refines the talc ore particles, reduces the surface roughness of the talc ore, reduces the phenomenon of target fluorescence signal being masked or distorted, and improves detection sensitivity; at the same time, it disrupts the embedding relationship between quartz / mica and talc, releases the encapsulated fluorescent substances, and further improves detection sensitivity.

[0032] Hydrochloric acid can dissolve quartz and mica, thus avoiding the occurrence of background fluorescence or quenching effects. The nonionic surfactant polyethylene glycol can be adsorbed on the mineral surface, reducing interfacial tension, making it easier for hydrochloric acid to wet micropores, reducing pit defects caused by local over-etching, improving pickling uniformity, giving talc powder better flowability, and improving detection sensitivity.

[0033] Thiourea-ascorbic acid synergistic washing; thiourea, as a soft Lewis base, preferentially complexes Cu. 2+ Pb 2+ Heavy metal ions block the metal-fluorophore energy transfer pathway; ascorbic acid will... 3+ Reduced to Fe 2+ It also forms a soluble ferrous complex, which avoids the ·OH free radicals generated by the Fenton reaction from quenching the fluorescence and improves the detection sensitivity.

[0034] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0035] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for detecting fluorescent substances in raw talc ore, characterized in that, Includes the following steps: S1. Place 10g of raw talc ore in a ball mill and mill it for a period of time. Then, sieve it to obtain sieved powder. Add the sieved powder to deionized water to obtain a slurry. S2. Add the slurry obtained in S1 to the mixture to make the pH value of the slurry 5, stir for 30 min, and then place it in a water bath at 60℃ for 2-3 h to obtain the first solid. Filter to obtain the first solid, and wash the first solid to obtain the first precipitate. The mixed acid includes hydrochloric acid, polyethylene glycol and water. S3. Add 50 mL of thiourea-ascorbic acid solution to the first precipitate obtained in S2, then let it stand for 1-2 hours, filter to obtain the second solid, wash and dry the second solid to obtain the second precipitate. S4. After the second precipitate is ball-milled a second time, the sample that passes through a 7mm sieve is spread evenly in an enamel dish. In a dark and sealed environment, it is irradiated with a 365nm fluorescence detector, and the talc ore in the enamel dish is visually inspected to see if it contains fluorescent substances.

2. The method for detecting fluorescent substances in raw talc ore according to claim 1, characterized in that, In S1, the ball milling time is 30-35 minutes, the ball mill speed is 750-800 r / min, the screen particle size is 7 mm, and the slurry mass concentration is 20%.

3. The method for detecting fluorescent substances in raw talc ore according to claim 1, characterized in that, In the S2 mixture, the mass fraction of polyethylene glycol is 3-5%, the mass fraction of hydrochloric acid is 7-8%, and the remainder is water.

4. The method for detecting fluorescent substances in raw talc ore according to claim 1, characterized in that, In S2, the first solid is washed with deionized water until it becomes neutral, thus obtaining the first precipitate.

5. The method for detecting fluorescent substances in raw talc ore according to claim 1, characterized in that, In the S3 thiourea-ascorbic acid solution, the volume fraction of thiourea is 5% and the volume fraction of ascorbic acid is 5%.

6. The method for detecting fluorescent substances in raw talc ore according to claim 1, characterized in that, In S3, the second solid is washed with deionized water until neutral, and then placed in a drying oven and dried at 85-90℃ for 2-3 hours.

7. The method for detecting fluorescent substances in raw talc ore according to claim 1, characterized in that, In S4, the ball milling time is 25-30 minutes, and the ball mill speed is 750-800 r / min.