Study on purification of refined quartz sand from a quartz sandstone in Sichuan

Quartz sand is very rich in reserves in China, but it is rich in minerals in general. The ore contains many kinds of impurity minerals and the state of impurities is complicated. In addition, the purification of quartz sand is strict on the production equipment, environment and operational factors, and it may be Caused by secondary pollution, objectively led to difficulties in the purification of quartz sand. The dryness of crystal resources and the increasing market demand, and correspondingly stricter quality requirements for their products, require further experimental research on quartz sand deep processing technology to develop high quality quartz sand products to meet high technology. The demand for silicon. The sandstone mine of Xinfeilou Chemical Fertilizer in Jiahe Village, Huangdan Town, Muchuan County, Sichuan Province is rich in mineral resources. According to preliminary investigations by relevant departments, the quartz sandstone ore reserves in this area are 950,000 tons, and the grade of ore SiO2 is generally above 93%. Mining as quartz sand for fertilizers. In order to further improve the utilization value of the quartz sand ore and make it have better economic development and utilization value, on the basis of the research of process mineralogy, the quartz selection exploration test is carried out in order to increase the SiO2 content and reduce the impurities A1203, Fe203 and Ti. The content of the refined quartz sand grade that can be selected by the mine is determined to provide technical support for improving the utilization value of the mine. I. Mineralogy Characteristics of Ore Process (I) The analysis results of multi-element chemical composition of ore chemical composition ore are shown in Table 1.

Table 1 Chemical composition of ore /%

The ore is mainly SiO2, and the other components are very low. Al2O3, K2O and iron are high in content and, in addition, contain a certain amount of CaO, MgO and Na2O, so the main purpose of the purification test is to remove Al2O3, K2O and iron. (II) Composition and content of minerals The polished surface of ore is colorless under the naked eye, and the ore structure is mainly blocky. Identified by microscope, the main mineral quartz, clay minerals impurities, high potassium feldspar mineral of aluminum and iron minerals, iron minerals in a small amount of hematite-containing magnetite (Table 2).

Table 2 Content of main minerals in ore /%

(III) Production form of main minerals Quartz: The main carrier mineral of SiO2 is also the main purpose mineral of the experimental research. Its form and embedding form are relatively simple. The output forms in the ore are mainly the following: (1) Sand Shape: sub-circle-secondary crumb, sorting well, particle support, pore-contact cementation, mostly in the fine-medium grain sand of 0.1 ~ 0.5mm (Figure 1 A). (2) Siliceous agglomerate: Clay recrystallized product. (3) Increase the edge shape: it is the recrystallized product of silicon matter between quartz crumbs, which is secondary to increase the distribution of quartz crumbs around the edges. Clay, K-feldspar: mainly minerals for K2O and Al2O3, K-feldspar is sub-circular-sub-horny crumb, mostly fine-medium-grained sand with a thickness of 0.1-0.5mm; Mainly, partially crystallized into microscopic scale-like hydromica. Hematite: It is an iron mineral in ore that is distributed in the inter-debris pores with 0.002 mm ± particles.

(IV) The grain size of quartz sand is used to provide a basis for formulating a reasonable beneficiation process and determining the appropriate grinding fineness. The grain size of quartz in the ore is statistically analyzed. The results show that the grain size of the sample is more uniform. It is distributed in the category of fine particles (0.417 to 0.104 mm).

In summary, the ore is a fine-medium-grained siliceous quartz sandstone, and the SiO2 content in the ore is only about 93%. As a refined quartz sand raw material, it needs to be purified and used. Clay minerals, potassium feldspar, and particulate iron minerals (hematite, magnetite) produced in the form of intergranular pore interstitials in the ore lead to higher levels of harmful impurities such as Al2O3, K2O and Fe. The grain size of quartz sand in the ore is 0.1-0.5mm, and the fineness of grinding is -0.1m (140 mesh) to ensure that about 60% of the quartz in the ore sample dissociates. Although the ore sample is an optional quartz sandstone ore, the physical properties such as specific gravity of potassium feldspar are similar to those of quartz, and it is difficult to separate from quartz.
Second, the exploration and purification of mineral processing

The mineralogical study of quartz sand ore shows that the minerals in the quartz sandstone are mainly secondary to the cement, and the impurity minerals mainly exist between the surface of the particles and the cracks of the quartz particles. Quartz surface is unclean, distributed with a lot of dusty clay and impurity minerals (Fig. 4), mostly secondary cementation, local clay cementation, very small amount of quartz crystals containing gas-liquid inclusions, other mineral inclusions, but overall The upper quartz crystal is basically pure. The impurities of the ore mainly come from clay minerals, iron minerals, potassium feldspar, and a small amount of clay derived from the submicroscopic distribution of secondary quartz cement and primary quartz particles. Based on this, the process of grading-wiping mud-acid treatment was selected, and the single-factor beneficiation and purification test of the quartz sand was carried out, and the feasibility of magnetic separation and flotation of potassium and aluminum was explored. (1) Grinding particle size In order to determine the appropriate grinding fineness, the quartz was dissociated and recovered without being pulverized, and two groups of grinding fineness tests were carried out, which were respectively crushed to a size of -2 mm. Analysis and grinding fineness test. The results of -2mm sieve particle size analysis showed that the SiO2 grade in the grinding product was 89.23～95.06% under the different particle size conditions, and reached the maximum (95.06%) in the -0.208~+0.104mm particle size, indicating that the sample was very Fine and coarse particle size conditions do not significantly increase the quartz grade (Table 3). Inspecting the -0.208~+0.104mm particle size, the grain size SiO2 is increased to 95.06%, and the total content of Fe, Al and Ti is also the smallest at the grain size, suggesting that the quartz and impurity minerals are largely separated at the grade. For the economics of the grinding process and the classification effect of grinding, choose -0.208~+0.104mm as the suitable grinding size. The sample was prepared by a simple grinding process using a primary crushing-ball milling process to obtain a yield of 53.42% from -0.208 to +0.104 mm (Table 4). Table 3 Sample-2mm sieve particle size chemical analysis results /%
(2) Rubbing and de-sludge test Because the impurities in the ore adhere to the surface of the quartz, the product of -0.208～+0.104mm is treated with water glass as the rubbing agent. The test results show that the original sample is rubbed. After deliming, the grade of SiO2 is greatly improved, and the impurities Fe and Al are also removed (Table 5). However, the concentrate grade (98.01%) obtained by the process still does not reach the good available value grade, and the removal rate of harmful impurities is not high. Therefore, this process is simply selected as the ore dressing process of the mine. Completely purified.

Table 5 Grinding - Strong Magnetic Separation - Desliming - Acid Treatment Process Test Results /%

(3) Acid treatment test Because the acidic medium has good leaching power for Fe, Al, K, etc., it has no effect on Si. For this reason, the possibility of impurity removal under strong acid environment is explored for the sample. Take -0.208 ~ +0.104mm grain-level rub-off sample, after chemical analysis, according to 20g group, divided into four groups, respectively, with different proportions of mono-acid and mixed acid for strong acid treatment, at room temperature (17 ~ 20 ° C The pH value was adjusted to 1.8 to 2.0, the treatment time was 30 minutes and 60 minutes, and the sample was washed and leached to a pH value of about 7.0. The test results are shown in Table 6.

Table 6 Acid treatment test results /%

From the results of Table 6, it can be seen that the sample is treated with a monoacid (sulfuric acid), and a refined quartz sand having a SiO2 grade of 99% or more and a harmful impurity such as Al2O3 and TFe2O3 is greatly reduced, and the impurity removal rate is remarkably increased as the treatment time is increased; Although hydrofluoric acid (HF) has a certain etch on SiO2, it has been proved by experiments that under the same conditions, the mixed acid treatment with HF is better than monoacid, and a reasonable balance can be obtained between the improvement of SiO2 and the reduction of Al2O3 and TFe2O3. . (IV) Feasibility of removing iron and removing potassium Considering that some iron minerals can be removed by magnetic separation before acid treatment, acid consumption can be reduced. For samples of ore-0.208～+0.104mm, Wuhan Rock Grinding Equipment Manufacturing Co., Ltd. is used. The /YC-Φ300 permanent magnet magnetic separator performs strong magnetic separation under the condition of magnetic field strength of 3000 Gauss. The chemical analysis of the magnetic separation concentrate confirmed that the removal rate of iron is extremely low, mainly because the iron mineral is encapsulated in other minerals in the form of particles (0.002 mm±), which cannot be effectively dissociated at the level, so at this level The use of strong magnetic separation can not achieve the purpose of effective iron removal. The impurities K and Al in the ore are mainly derived from a small amount of potassium feldspar and clay. After washing the sludge, the K and Al contained in some clays can be removed to further remove such impurities. The particle size after deliming treatment is -0.208~+ The 0.104mm sample was subjected to flotation process exploration test to separate the feldspar and quartz by flotation. The flotation test was carried out by adding a collector under normal temperature (18-20 °C) acidic environment. The instrument was a 0.5L-XFDIII single tank flotation machine of Jilin Province Prospecting Machinery Factory.

The test results show that although the flotation process can be used, quartz and potassium feldspar can be separated, but the sorting effect is not satisfactory. According to previous research data, F-flotation has a good effect on the separation of K-feldspar and quartz, but considering the problem of F emission, this article does not explore the F-containing flotation process; and because the flotation will increase the mine's Processing costs, so no more in-depth testing of the flotation process parameters. III. CONCLUSIONS AND RECOMMENDATIONS (I) The quartz sand beneficiation purification method and process are generally considered from the three aspects of the occurrence of impurity minerals in the ore, the ore dressing cost of the purification process, and the industrial use of the fine sand products. Under the premise, the process should be as simple as possible, low cost and easy to implement in industry. (2) The ore is an optional quartz sandstone ore. Through a reasonable and simple process, the SiO2 in the ore can be purified to more than 99%. The mixed acid treatment effect of adding HF is obviously superior to that of monoacid (sulfuric acid), but the problem of F emission in the leachate needs to be considered. (3) As the raw material of micro-silica powder, the ore is selected to meet the requirements of “grinding grade-wipe-cleaning mud”; as refined quartz sand for general industrial use (SiO2≥99.0～99.5%, Fe2O3≤0.02～0.015%), It is recommended to use the “grinding classification-wipe-lime-monoacid treatment” process to meet the quality requirements of fine sand; as high-purity quartz sand (SiO2≥99.5～99.9%, Fe2O3≤0.005%) or fused silica sand (SiO2> 99.9～99.95%, Fe2O3<5～25×10-6, Al2O3<20～30×10-6) and other high-tech sand raw materials, it is necessary to further study the flotation and acid leaching process conditions for quartz sand again. Purification. After preliminary tests, under the premise of abandoning the flotation process, the fine-tuned process parameters of “grinding classification-wiping sludge-strong magnetic separation-strong acid treatment” can make the SiO2 grade to 99.9% and above, but whether there is economy. Benefits need to be determined through technical and economic evaluation. (IV) The single factor exploration and purification test results have met the requirements of refined quartz sand, but as a prerequisite for development and application, the optimum conditions of each parameter in the process should be tested to seek reasonable technical and economic balance process conditions.

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