Process for purifying natural powder quartz to 4N high-purity fine-grained quartz sand

Abstract

The application belongs to the field of non-metallic mineral deep processing, and particularly relates to a process for preparing and processing 4N high-purity fine-grained quartz sand from natural fine quartz. The technical scheme of the application comprises the following steps: (1) screening the fine quartz; (2) removing iron minerals by magnetic separation; (3) adjusting the pH of the slurry to 2.0-3.0 by HF, and performing two-stage reverse flotation on the magnetic separation product by using dodecylamine and sodium dodecylsulfonate as two kinds of anion and cation collectors; (4) adjusting the pH of the slurry to 11-12 by NaOH, and performing positive flotation by using dodecylamine and sodium oleate as two kinds of anion and cation collectors, CaCl2 as a quartz activator, and 0.05-0.1 mmol / L chloro-triethylene glycol as a synergist; (5) calcining and water quenching; and (6) heating and leaching for 2-6 h by using a mixed acid of H2SO4+HCl+HNO3+HF, so that high-purity quartz sand with a SiO2 content of more than 99.99% can be finally obtained. The application provides an economic and efficient method for high-value utilization of fine quartz.

Description

Technical Field

[0001] This invention belongs to the field of deep processing of non-metallic minerals, specifically relating to a process for preparing and processing 4N grade high-purity fine-grained quartz sand using natural powdered quartz. Background Technology

[0002] Natural quartz powder is a loosely structured, weathered residual ore formed from microcrystalline siliceous rock through intense weathering. The deposits are mostly large or super-large, with stable strata, shallow burial, planar distribution, and loose structure, making them easy to mine via open-pit mining. They are widely distributed in Jiangxi, Guizhou, and Hunan provinces of my country. The most significant characteristic of natural quartz powder is its high SiO2 content and fine particle size, which eliminates the need for crushing and grinding processes, greatly reducing purification costs. Quartz powder is typically processed to a purity of 2N–3N (SiO2 content approximately 99%–99.9%) and can be used in metallurgy, glass, cement, ceramics, and chemical industries.

[0003] Studies have found that flotation is an effective method for purifying fine-grained quartz powder, but the key to its feasibility lies in the flotation reagent formulation. Du Jie et al. (patent number CN201910724769.0) disclosed a beneficiation and purification method for incompletely weathered quartz powder, involving a scrubbing-screening-selective flocculation-reverse flotation process. The reverse flotation uses sulfuric acid as a pH adjuster, water glass as a dispersant, and a mixture of mixed amines and kerosene as a collector, ultimately yielding a purified product with a SiO2 content of only 99.2%. Zheng Shuilin et al. (application number: CN201811063854.9) disclosed a chemical purification method that involves calcining natural quartz powder with ammonium salts, followed by washing and leaching. Zheng Shuilin et al. (application number: CN201811063854.9) also disclosed a purification method using polyphosphate scrubbing-screening-centrifugation, which can obtain a quartz product with a SiO2 content of 99.5%. Wu Zhaoyang et al. (China Nonmetallic Minerals Industry Guide, 2011.4) used a process of scrubbing-desliming-magnetic separation-flotation-acid washing-calcination to purify powdered quartz to the 3N level purity. The flotation collector, a mixture of sodium dodecyl sulfonate and coconut oil-based propylene diamine, can increase the SiO2 content to 99.33%.

[0004] In conventional quartz flotation, commonly used fatty acid and amine collectors suffer from poor dispersibility and selectivity, affecting the separation efficiency of quartz and gangue minerals. Currently, there are two main methods for improving the performance of fatty acid collectors: one is to modify the collector molecule by introducing polar functional groups such as halogen, sulfonic acid, and carboxyl groups; the other is to improve the selectivity of the collector by using combination reagents based on the synergistic effect between reagents.

[0005] In quartz flotation, synergists do not possess collecting ability, but they can serve as auxiliary agents to alter the interaction between the collector and quartz minerals, thereby enhancing the flotation separation process. They also offer significant advantages such as low reagent consumption and simple operation. Existing research mainly focuses on desilication of iron ore via reverse flotation and phosphate rock, with reported synergists primarily falling into two categories: nonionic surfactants (Tween 20, Tween 80, octylphenol polyoxyethylene ether, octyldecyl alcohol polyoxyethylene ether) and anionic surfactants (such as SDS, SDBS, etc.). However, there are currently few reports on synergists used in quartz purification, especially in the purification of fine-grained quartz powder. To effectively develop and utilize these high-grade siliceous resources, developing an economical and efficient flotation process enhancement technology is imperative. Summary of the Invention

[0006] To address the problem of substandard use of high-quality fine-grained quartz resources, this invention provides a combined process of classification-magnetic separation-flotation-leaching to purify and process 4N grade high-purity fine-grained quartz sand. The process flow is as follows: Figure 1 As shown. The technical solution for achieving the objective of this invention includes the following steps:

[0007] (1) By sieving the powdered quartz sample and directly removing the intermediate particle size material with the highest impurity content of 37-100μm, a product with SiO2 content of over 99% can be obtained.

[0008] (2) Under the conditions of slurry concentration of 10-30% and magnetic field strength of 1-1.5T, a wet high-intensity magnetic separator or an electromagnetic high-gradient magnetic separator is used to perform two-stage magnetic separation on the screened rough concentrate to remove magnetic impurity minerals.

[0009] (3) In a single-cell flotation machine, the pH of the pulp is adjusted to 2.0-3.0 using HF, i.e. hydrofluoric acid. Under the conditions of pulp concentration of 10-30% and main machine speed of 1700-2100 r / min, two cationic and anionic collectors, dodecylamine and sodium dodecyl sulfonate, are used to perform two-stage reverse flotation on the magnetic concentrate to remove feldspar impurities.

[0010] (4) In a single-cell flotation machine, the pH of the pulp is adjusted to 11-12 with NaOH, and two anionic and cationic collectors, dodecylamine and sodium oleate, are used. CaCl2 is used as a quartz activator, and 0.05mM-0.1mM molar concentration of triethylene chloride is added as an synergist to remove mica, kaolinite and amphibole impurities by positive flotation. The flotation concentrate is washed with ultrapure water 5-10 times and dried to obtain 3N grade quartz sand.

[0011] (5) Weigh a certain mass of flotation concentrate and put it into a quartz crucible. Place it in a muffle furnace at 800-1100℃ and calcine for 1-2 hours. Then quickly take out the calcined material and place it in ultrapure water to expose the inclusions on the quartz surface. Wash the calcined product with ultrapure water 5-10 times.

[0012] (6) The product after water quenching is heated and stirred at about 90°C for 2-6 hours to remove the leachate. The product is then washed with ultrapure water 5-10 times and dried to obtain high-purity quartz sand with a SiO2 content of over 99.99%.

[0013] The natural powdered quartz is a fine-grained siliceous mineral raw material with quartz as the main mineral.

[0014] The aforementioned triethylene chloride glycol (CTG) has the chemical formula C6H. 13 ClO3, molecular structure as follows Figure 2 As shown. The features and beneficial effects of the present invention are:

[0015] A process for preparing 4N-grade high-purity fine-grained quartz sand using natural quartz powder involves a purification process of natural quartz powder ore, including screening, strong magnetic separation, reverse flotation, enhanced direct flotation with synergists, calcination-water quenching, and heated acid leaching. This process yields high-purity quartz sand with an SiO2 content of over 99.99%. The process utilizes the chlorination effect of triethylene glycol on fatty acid collectors after screening and strong magnetic separation to significantly improve the collector's ability and selectivity for quartz minerals, resulting in a flotation product with a purity reaching the 3N7 level.

[0016] The synergist triethylene chloride involved in this invention has advantages such as low price, stable properties, and no pollution. Furthermore, when used at a concentration of less than 0.1 mM, it does not cause pollution problems related to metal ions or organic matter in the quartz purification system. This method has advantages such as small dosage, cleanliness and environmental friendliness, low cost, and good enhancement indicators. It provides a new approach for subsequent deep purification and preparation of high-value quartz products, and can be used to produce high-purity quartz powder, silica micropowder, glass fiber, silicon-based modified materials, etc. It also has certain reference value for the development and utilization of other fine-grained quartz mineral resources. Attached Figure Description

[0017] Figure 1 A flowchart illustrating the purification and processing technology of natural powdered quartz;

[0018] Figure 2 This is the molecular structure diagram of triethylene chloride;

[0019] Figure 3 XRD analysis diagram of raw quartz powder;

[0020] Figure 4 This is a flow chart of the flotation separation process. Detailed Implementation Plan

[0021] Example

[0022] (1) Representative powdered quartz ore samples were collected from Pingxiang City, Jiangxi Province. The samples were grayish-white and had a loose, clay-like appearance. No crushing was required; they were lightly crushed into a uniform powder and used as the raw ore for testing. The multi-element analysis results of the raw ore are shown in Table 1; the X-ray diffraction analysis results are shown in... Figure 3 As shown.

[0023] Table 1. Multi-element analysis results (%) of the raw ore

[0024]

[0025]

[0026] (2) The raw ore was screened using 37μm and 100μm standard sieves (see Table 2). The +37μm sieve was directly subjected to tailings treatment to obtain a screened concentrate with SiO2 content of 99.62%, Al2O3 content of 0.051%, and Fe2O3 content of 0.063%.

[0027] Table 2. Sieving results (%) of powdered quartz samples

[0028] >100μm 11.65 99.52 11.64 0.043 5.84 0.06 10.19 37~100μm 7.61 98.79 7.55 0.51 45.24 0.13 14.43 ~37μm 80.74 99.64 80.81 0.052 48.93 0.064 75.37 total 100.00 99.56 100.00 0.086 100.00 0.069 100.00

[0029] (3) The screened rough concentrate was subjected to magnetic separation to remove impurities under the conditions of feed concentration of 30% and magnetic field strength of 1T and 1.5T respectively, and magnetic rough concentrate with SiO2 content of 99.61% and Fe2O3 content of 0.021% was obtained.

[0030] (4) Take 50g of mineral sample into a 500mL flotation cell, add deionized water, stir for 3min, add NaOH or HF to adjust the pH of the pulp, then add collector, activator, and synergist in sequence, stirring for 3min after each addition, and then flotation for 3min. The flotation process is as follows: Figure 4 As shown, the flotation reagent system and flotation results are shown in Tables 3 and 4, respectively.

[0031] Table 3 Comparison of flotation reagent systems for three different flotation schemes

[0032]

[0033] Table 4 Comparison of flotation results for three different flotation schemes

[0034]

[0035] After two stages of reverse flotation purification, the effects of using sodium oleate alone (a fatty acid collector), sodium oleate with conventional synergist SDS, and sodium oleate with novel synergist CTG on the purification of powdered quartz in an alkaline positive flotation system were compared under the same experimental conditions. The results showed that sodium oleate alone produced the worst flotation performance, with a SiO2 content of 99.77% and a recovery rate of only 56.52% in the flotation concentrate. The addition of conventional synergist SDS increased the recovery rate of the flotation concentrate to 81.06% and reduced the SiO2 content to 99.69%. The combination of CTG and sodium oleate yielded a flotation concentrate with a SiO2 content as high as 99.97% and a recovery rate of 83.86%, while reducing the Al2O3 content in the flotation concentrate to 0.015%, significantly better than the combination of SDS and sodium oleate. The synergistic effect of CTG was significant.

[0036] Under alkaline conditions, CTG introduces highly chemically active polar functional groups such as chlorine and ethoxy groups, which can chlorinate the fatty acid collector sodium oleate, significantly improving the collecting performance and selectivity of sodium oleate. Its mechanism of action is as follows: (1) The chlorination effect of CTG increases the polarity of the hydrophilic end of sodium oleate, which greatly improves its solubility and dispersibility in the slurry compared with sodium oleate alone, thereby increasing the activity of the reagent and increasing the probability of its contact and interaction with quartz minerals, thus significantly improving the reagent's ability to collect quartz; (2) Triethylene chloroglycol and sodium oleate are co-adsorbed on the mineral surface, effectively avoiding the interaction between the collector and the slurry, improving the selectivity of the collector, and thus enhancing the separation effect of impurities, showing a significant synergistic effect.

[0037] (5) Weigh a certain mass of flotation concentrate from Scheme 3, place it in a quartz crucible, and calcine it in a muffle furnace at a temperature of 1000℃ for 2 hours. After calcination, quickly pour the sample into ultrapure water for water quenching. The "calcination-water quenching" process exposes mineral and fluid inclusions in the quartz due to thermal stress, and also allows elements such as Al, Li, Na, and K in the crystal lattice to accumulate on the quartz surface under high-temperature phase transformation, which is beneficial for subsequent leaching to remove impurities.

[0038] (6) The water-quenched sample was washed, dried, and cooled repeatedly with ultrapure water before being used as a leaching sample. A certain amount of leaching sample was placed in a clean polytetrafluoroethylene beaker, and a mixed acid mixture of H2SO4 (0.25 mol / L), HCl (0.5 mol / L), HNO3 (0.25 mol / L), and HF (0.5 mol / L) was added. Leaching was carried out for 4 hours at a pulp concentration of 10%, a temperature of 90℃, and a stirring speed of 300 rpm. After leaching, the leachate was removed, the leaching concentrate was taken out, and the product was washed repeatedly with ultrapure water 5-10 times before drying. The final quantitative analysis results of impurity elements in the purified product are shown in Table 5. The results showed that the SiO2 content of the leaching concentrate reached 99.992%, and the total impurity content was 78.74 μg / g.

[0039] Table 5. Multi-element analysis results of the leaching concentrate (μg / g)

[0040] content 17.50 27.81 0.25 6.42 2.75 1.48 0 13 8.415 0.134 0.645 0 0

Claims

1. A process for purifying and processing natural powdered quartz into 4N grade high-purity fine-grained quartz sand, characterized in that, The process includes: S1 involves sieving the powdered quartz sample to remove impurities; S2 uses a wet high-intensity magnetic separator or an electromagnetic high-gradient magnetic separator to perform magnetic separation on the screened rough concentrate under certain conditions of slurry concentration and magnetic field strength. In the S3 single-cell flotation machine, the pH of the pulp is adjusted to 2.0-3.0 using HF (hydrofluoric acid). Under the conditions of pulp concentration of 10-30% and main machine speed of 1700-2100 r / min, two cationic and anionic collectors, dodecylamine and sodium dodecyl sulfonate, are used to perform two-stage reverse flotation on the magnetic concentrate to remove feldspar impurities. In a single-cell flotation unit, the pH of the pulp was adjusted to 11-12 using NaOH, and two cationic and anionic collectors, dodecylamine and sodium oleate, were employed for S4. As a quartz activator, 0.05mM to 0.1mM triethylene chloride is added as a synergist for positive flotation to remove mica, kaolinite, and amphibole impurities. The flotation concentrate is washed 5 to 10 times with ultrapure water and dried to obtain 3N grade quartz sand. The chemical formula of the triethylene chloride is [insert chemical formula here]. The molecular structure is ； S5 Weigh a certain mass of flotation concentrate and put it into a quartz crucible. After calcining in a high-temperature muffle furnace, quickly take out the calcined material and place it in ultrapure water to expose the inclusions on the quartz surface. Then wash the calcined product with ultrapure water. S6 adopts The mixed acid is used to leach the water-quenched product by heating and stirring for 2-6 hours. After removing the leachate, the leached product is washed with ultrapure water and dried to obtain the desired product. High-purity quartz sand products with a content of 99.99% or higher.

2. The process for purifying and processing natural quartz powder into 4N grade high-purity fine-grained quartz sand as described in claim 1, characterized in that, The impurities removed in S1 are materials with a particle size between 37 and 100 μm.

3. The process for purifying and processing natural powdered quartz into 4N grade high-purity fine-grained quartz sand as described in claim 1, characterized in that, Under the conditions of a slurry concentration of 10-30% and a magnetic field strength of 1-1.5T, the screened rough concentrate is subjected to two-stage magnetic separation to remove magnetic impurity minerals.

4. The process for purifying and processing natural quartz powder into 4N grade high-purity fine-grained quartz sand as described in claim 1, characterized in that, S5 describes weighing a certain mass of flotation concentrate and placing it in a quartz crucible. After calcining in a muffle furnace at 800-1100℃ for 1-2 hours, the calcined material is quickly removed and placed in ultrapure water to expose the inclusions on the quartz surface. The calcined product is then washed with ultrapure water 5-10 times.

5. The process for purifying and processing natural quartz powder into 4N grade high-purity fine-grained quartz sand as described in claim 1, characterized in that, S6 describes the use of The product after water quenching is leached with a mixed acid at 90℃ with stirring for 2–6 hours. The leachate is then removed, and the leached product is washed 5–10 times with ultrapure water and dried to obtain the desired product. High-purity quartz sand products with a content of 99.99% or higher.

6. The process for purifying and processing natural quartz powder into 4N grade high-purity fine-grained quartz sand as described in claim 1, characterized in that, The natural powdered quartz is a fine-grained siliceous mineral raw material with quartz as the main mineral.

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