Celite in order to remove impurities mineral quartz, feldspar detrital minerals, clay minerals, iron oxide mineral and organic matter, so as to enrich and increase the whiteness of diatoms. At present, there are mainly the following diatomite beneficiation methods: scrubbing method, roasting method, acid leaching method, centrifugal sedimentation method, magnetic separation method, and comprehensive purification method.
1, the experimental part
(1) The diatomaceous earth raw material is from Inner Mongolia Huade, and the analysis results are shown in Table 1.
Table 1 Analysis results of Dehua diatomaceous earth in Inner Mongolia
BaiDu/% | SiO 2 | A1 2 O 3 | Fe 2 O 3 | MgO |
64.5 | 78.57 | 8.23 | 3.18 | 0.92 |
CaO | Na 2 O | K 2 O | H 2 O | Loss on ignition |
0.89 | 0.50 | 1.02 | 3.95 | 4.5 |
(2) Experimental method: Take 200 g of diatomaceous earth sample, add water to adjust the slurry and adjust the pH value of the slurry, scrub for a certain time, add a certain amount of dispersant, and continue scrubbing. After the scrubbing, sieve, add a certain amount of sieve water, centrifuge, take the bottom stream, and dry.
Take 20g of the sample after centrifugation and drying in a 500mL three-necked flask, add an appropriate amount of dilute sulfuric acid with a certain concentration, and put it into a constant temperature water bath to raise the temperature to a specified temperature and then acid immerse for a certain period of time. After the completion of the reaction, suction filtration, washing, and drying were carried out. Finally, the chemical element analysis and whiteness determination of the diatomite after acid leaching were carried out.
2, scrubbing - centrifugation process
(1) Scrubbing time
The fixed conditions were a scrub mass fraction of 30%, a pH of 10, a dispersant dosage of 0.5%, a centrifugation time of 5 min, and a centrifugal speed of 2000 r/min. The effects of scrubbing time on the whiteness and iron oxide content of diatomite were discussed. The results are shown in Figure 1.
Fig.1 Effect of scrubbing time on whiteness and iron oxide content of diatomite
It can be seen from Fig. 1 that as the scrubbing time increases, the whiteness of the diatomaceous earth increases, and the iron oxide content gradually decreases. When the scrubbing time was 40 min, the whiteness of the diatomaceous earth was 71.6%, and then the whiteness increased as the scrubbing time increased. Therefore, it is determined that the scrubbing time is 40 min.
(2) Scrub quality score
The fixed conditions were scrubbing time 40 min, pH value 10, dispersant dosage 0.5%, centrifugation time 5 min, centrifugal speed 2000 r/min. The effect of scrub mass fraction on the whiteness and iron oxide content of diatomite was discussed. The results are shown in Figure 2.
Fig. 2 Effect of scrubbing mass fraction on whiteness and iron oxide content of diatomite
It can be seen from Fig. 2 that as the scrub mass fraction increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. When the scrub mass fraction is 30%, the whiteness of the diatomaceous earth is 71.6%, and then the whiteness decreases as the scrub mass fraction increases. Thus, the scrub quality score was determined to be 30%.
(3) Dispersant dosage
The fixed conditions were scrubbing time of 40 min, pH value of 10, scrub mass fraction of 30%, centrifugation time of 5 min, and centrifugation speed of 2000 r/min. The effect of the amount of dispersant on the whiteness and iron oxide content of diatomite was discussed. The results are shown in Fig. 3.
Fig. 3 Effect of dispersant dosage on whiteness and iron oxide content of diatomite
It can be seen from Fig. 3 that as the amount of the dispersant increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. When the amount of the dispersant is 0.5%, the whiteness of the diatomaceous earth is 71.6%, and then the whiteness increases tend to be gentle as the amount of the dispersant increases. Therefore, the amount of the dispersant was determined to be 0.5%.
(4) pH value
The fixed condition is scrubbing time 40 min, scrub mass fraction 30%, dispersant dosage 0.5%, centrifugation time 5 min, centrifugal speed 2000 r/min. The effect of pH on the whiteness and iron oxide content of diatomite was discussed. The results are shown in Fig. 4.
Fig. 4 Effect of scrubbing pH on whiteness and iron oxide content of diatomite
It can be seen from Fig. 4 that as the pH value increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. At a pH of 10, the whiteness of the diatomaceous earth was 71.6%, and then the whiteness increased as the pH value increased. Therefore, it is determined that the scrub pH is 10.
(5) Centrifugation time
The fixed conditions were scrubbing time 40 min, scrub mass fraction 30%, dispersant dosage 0.5%, scrub pH 10, and centrifugal speed 2000 r/min. The effects of centrifugation time on the whiteness and iron oxide content of diatomite were investigated. The results are shown in Fig. 5.
Fig. 5 Effect of centrifugation time on whiteness and iron oxide content of diatomite
It can be seen from Fig. 5 that as the centrifugation time increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. When the centrifugation time was 5 min, the whiteness of the diatomaceous earth was 71.6%, and then the whiteness decreased as the centrifugation time increased. Therefore, the scrubbing centrifugation time was determined to be 5 min.
(6) Centrifugal speed
The fixed conditions were scrubbing time 40 min, scrub mass fraction 30%, scrub pH 10, and centrifugation time 5 min. The effects of centrifugal speed on diatomaceous earth whiteness and iron oxide content were investigated. The results are shown in Fig. 6.
Fig.6 Effect of centrifugal speed on whiteness and iron oxide content of diatomite
It can be seen from Fig. 6 that as the centrifugal speed increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. When the centrifugal speed was 2000 r/min, the whiteness of the diatomaceous earth was 71.6%, and then the whiteness decreased as the centrifugal rotation speed increased. Therefore, it was determined that the scrubbing centrifugal speed was 2000 r/min.
3. Acid leaching process
(1) Sulfuric acid concentration
The fixing conditions were an acid immersion temperature of 98 ° C, an acid leaching time of 4 h, and a liquid-solid ratio of 3:1 (mL/g). The effect of sulfuric acid concentration on the whiteness and iron oxide content of diatomite was discussed. The results are shown in Fig. 7.
Fig. 7 Effect of acid leaching concentration on whiteness and iron oxide content of diatomite
It can be seen from Fig. 7 that as the concentration of sulfuric acid increases, the whiteness of diatomaceous earth increases gradually, and the content of iron oxide decreases. When the sulfuric acid concentration is 5 ml/L, the whiteness of the diatomaceous earth is 82.4%, and then the whiteness increases tend to be gentle as the sulfuric acid concentration increases. Therefore, the sulfuric acid concentration was determined to be 5 ml/L.
(2) Acid immersion time
The fixed conditions were acid immersion temperature of 98 °C, sulfuric acid concentration of 5 ml/L, and liquid-solid ratio of 3:1 (mL/g). The effect of acid leaching time on diatomaceous earth whiteness and iron oxide content was investigated. 8.
Fig. 8 Effect of acid leaching time on whiteness and iron oxide content of diatomite
It can be seen from Fig. 8 that as the acid leaching time increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. When the acid leaching time was 4h, the diatomaceous earth whiteness was 82.4%, and then the whiteness increased toward the gradual as the acid leaching time increased. Therefore, the acid immersion time was determined to be 4 h.
(3) Acid immersion liquid to solid ratio
The fixed conditions were acid immersion temperature 98 °C, sulfuric acid concentration 5 ml/L, and acid leaching time 4 h. The influence of liquid-solid ratio on diatomaceous earth whiteness and iron oxide content was investigated. The results are shown in Fig. 9.
Fig. 9 Effect of acid immersion liquid to solid ratio on whiteness and iron oxide content of diatomite
It can be seen from Fig. 9 that as the liquid-solid ratio increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. When the liquid-solid ratio is 2.5:1 (mL/g), the whiteness of diatomaceous earth is 82.4%, and then the whiteness increases as the liquid-solid ratio increases. Therefore, the liquid-solid ratio was determined to be 2.5:1 (mL/g).
(4) Acid immersion temperature
The fixed conditions were sulfuric acid concentration of 5ml/L, acid leaching time of 4h, and liquid-solid ratio of 3:1 (mL/g). The effect of acid immersion temperature on diatomaceous earth whiteness and iron oxide content was investigated. 10.
Fig. 10 Effect of acid leaching temperature on whiteness and iron oxide content of diatomite
It can be seen from Fig. 10 that as the acid leaching temperature increases, the whiteness of the diatomaceous earth increases gradually, and the iron oxide content gradually decreases. When the acid immersion temperature was 98 ° C and the diatomaceous earth whiteness was 82.4%, it was confirmed that the acid immersion temperature was 98 °C.
In summary, the optimized mineral processing conditions of Huade diatomite are: scrubbing time 40min, scrub mass fraction 30%, scrub dispersant dosage 0.5%, scrub pH 10, centrifugation time 5min, centrifugation speed 2000r/min, acid leaching The temperature was 98 ° C, the acid leaching time was 4 h, the sulfuric acid concentration was 5 ml/L, and the liquid-solid ratio was 2.5:1 (mL/g).
4, diatomite soil characterization results
(1) Chemical composition and phase
The chemical composition analysis and whiteness determination of the diatomite concentrate obtained by the above-mentioned optimized process conditions showed that the SiO2 content was 92.83%, the Fe2O3 content was 0.48%, the A12O3 content was 3.28%, and the whiteness was 82.4%. The SiO2 content of diatomite soil is greatly improved, Fe2O is also effectively removed, and the whiteness is over 80%. High-quality diatomite is obtained through the above-mentioned beneficiation process. The X-ray diffraction pattern of the diatomite obtained by the treatment under superior conditions is shown in Fig. 11.
Figure 11 X-ray diffraction pattern of diatomite
It can be seen from Fig. 11 that the original diatom soil contains clay minerals such as hydromica and kaolin , and detrital minerals such as quartz and feldspar. After scrubbing-acid leaching combined with beneficiation, clay minerals are effectively removed, and the contents of quartz and feldspar are also significantly reduced.
(2) Microscopic morphology
The SEM analysis of the Huade ore and concentrate was carried out separately, and the results are shown in Fig. 12.
It can be seen from Fig. 12 that the diatom particles in the diatomite ore are mainly disc algae, some of the pores are blocked by debris impurities, the pore structure of the diatom is fuzzy, and the content of impurities such as clastic minerals and clay is high; compared with the original ore The surface debris of the fine soil was basically removed, and the tunnel was effectively cleared. The content of impurities in diatom concentrate is reduced, and the pore structure characteristics are effectively improved.
(3) Energy spectrum analysis
EDS spectrum analysis was carried out by selecting diatomite ore and intact diatoms in the concentrate, and the distribution of diatom surface elements (Si, Al, Fe) was quantitatively analyzed by surface scanning. The results are shown in Fig. 13.
The chemical composition of diatom is mainly SiO2, and the constituent elements are mainly Si and O. The impurities on the surface of diatom particles are mainly clay minerals. The representative elements are A1 elements. The A1 elements are widely distributed, and the surface and periphery of diatom particles exist. There are some iron filing minerals on the surface of the diatom, the representative element is Fe element, the Fe impurity is evenly distributed, and the Fe material is contained in the shell and the surrounding. After the ore dressing, the surface of the diatom has not detected Fe element, and the Al element is also basically removed, and the Si content is greatly improved.
5 Conclusion
(1) diatomite physical-chemical combined beneficiation optimization process conditions: scrubbing time 40min, scrub mass fraction 30%, scrub dispersant dosage 0.5%, scrub pH value 10, centrifugation time 5min, centrifugation speed 2000r/min; acid The immersion temperature was 98 ° C, the acid leaching time was 4 h, the sulfuric acid concentration was 5 ml/L, and the liquid-solid ratio was 2.5:1 (mL/g).
(2) Through beneficiation and purification, the whiteness of diatomaceous earth increased from 64.5% to 82.4%, and the silica content increased from 78.57% to 92.83%.
(3) Scrubbing centrifugal and acid leaching treatment process can effectively remove clay minerals, impurities such as quartz and feldspar, and significantly increase diatom content.
The data were organized into the study of self-chemical diatomite ore dressing technology.
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