Of manganese ore generally high phosphorus content, the phosphorus manganese [/ ω (Mn) ω ( P)] at an average of about 0.1, while the metallurgical ores claim ω (P) / ω (Mn ) <0.003 ratio. Among the explored deposits, manganese ore with a high phosphorus content [ω(P)/ω(Mn)>0.005] accounts for 49.59% of the total reserves. Phosphorus in manganese ore is mainly present in the form of apatite or collophosphate. Phosphorus minerals have fine particle size, or are closely symbiotic with energy minerals, or exist in the form of isomorphism. It is difficult to separate monomers.

In recent years, more and more research has been carried out on the outdoor process of manganese ore removal at home and abroad. The research methods mainly include high gradient magnetic separation, ammonia leaching, extra-furnace dephosphorization, and manganese ore. High-gradient magnetic separation method has problems of excessive power consumption, serious equipment wear, and automatic agglomeration of fine particles. It still stays in the small test stage according to the immersion method; the cost of dephosphorization outside the furnace is too high; the black manganese ore method has serious corrosion problems. They have failed to fundamentally solve the problem of phosphorus-reducing phosphorus. Therefore, researchers have proposed a new idea of ​​using microbial dephosphorization and made great progress. The advantages of microbial technology are low investment, low energy consumption, low cost and environmental friendliness. Studies have shown that a variety of bacteria, fungi, actinomycetes have a phosphorus solubilizing effect. Many researchers have succeeded in phosphating phosphate rock in the laboratory.

The strain used in this experiment is a strain with better dephosphorization effect in the soil samples of different plant roots in Xiangtan Manganese Mine. It has been transformed into a high-yield strain by UV, and the demineralization test of pyrolusite has been carried out, and good results have been obtained.

First, experimental materials and methods

(1) Soil collection and pretreatment

The soil samples were taken from the root surface of the plant in Xiangtan Manganese Mine, Hunan Province, 15 to 20 cm deep, placed in a previously sterilized Erlenmeyer flask, and the strain was isolated within 24 hours.

(2) Mineral samples

The ore sample was taken from a manganese mine in Yongzhou City, Hunan Province, crushed and ground to a particle size of less than 0.1 mm. In the ore sample, ω(P)/ω(Mn)=0.0109 is a high-phosphorus manganese ore. The results of multi-element chemical analysis of ore samples are shown in Table 1.

Table 1 Results of multi-element chemical analysis of ore samples

(three) medium

In addition to Chad's solid medium, bovine inner peptone medium and PKO solid medium, a phosphorus-rich medium (sucrose 30 g, sodium nitrate 2 to 3 g, dibasic hydrogen phosphate 1 g, sulfuric acid iron 0.01) was also prepared. g, potassium chloride 0.5g, manganese sulfate 0.5g, 1000mL of distilled water) and phosphorus deficiency + Cas (PO _{4) 2} medium (glucose 10g, calcium chloride 0.2g, magnesium sulfate 0.5g, ammonium sulfate 2.0g, KCl 0.2 g, 0.9 g of tricalcium phosphate, 1000 mL of distilled water). The above medium was adjusted to pH 7.0.

(4) Test methods

1, strain separation

The strain was isolated by dilution plate separation, medium-based medium and annual meat paste peptone medium. The soil samples were prepared into dilutions of various concentrations of 10 ^-3 , 10 ^-4 , 10 ^-5 , 10 ^-6 , and 10 ^-7 . A solution having a dilution of 10 ^-5 to 10 ^-7 was inoculated to the medium, and cultured at 30 ° C in a constant temperature biochemical incubator.

2. Screening of phosphate solubilizing bacteria

The screening is divided into two steps: a flat screen and a shake flask.

The initial screening uses the dissolved phosphorus circle method. The pure strain obtained by isolation was inoculated on PKO solid medium and placed in a 30 ° C incubator for 7-15 days to observe the presence or absence of dissolved phosphorus rings, and according to the ratio of the diameter of the phosphate ring (D) to the diameter of the colony (d). Preliminary determination of dephosphorization capacity. The dephosphorization isolate was inoculated on a slant medium and stored for later use.

When rescreening, the spores on the inclined surface of the test tube were washed with sterile water, and counted by a blood ball counting plate, and the concentration of the bacterial liquid was adjusted to about 10 ⁸ /mL. 1 mL of the bacterial suspension was inoculated into PKO liquid medium, placed on a shaker at a speed of 150 r/min, and cultured at 28 ° C for 5 days. The obtained bacterial liquid was separated in a 9000r/min centrifuge for 15 minutes, and the supernatant was aspirated, and its effective phosphorus content was determined by molybdenum antimony anti-spectrophotometry.

3. Simulated manganese ore dephosphorization

The test strain was inoculated into the Chach's body medium, then inoculated into the phosphorus-rich medium, placed in a shaker, and activated twice at 30 ° C, 150 r / min speed, 2d each time, spare.

1 mL of the activated strain was inoculated to a conical flask containing 100 mL of a phosphorus-deficient medium containing 0.090 g of calcium phosphate and 0.2612 g of MnO ₂ (MnO ₂ ) according to ω(P)/ω(Mn)=0.0109. In the aerobic culture at a temperature of 150 ° C/min at 30 ° C, the changes in pH and phosphorus concentration were examined.

4, UV mutagenesis

The strain P69 with the best effect in the simulated manganese ore dephosphorization test was used as the strain.

(1) Preparation of bacterial suspension. After the P69 strain was activated, the lawn was washed with an appropriate amount of physiological saline, poured into a conical flask containing glass beads, and the bacteria were broken by vigorous shaking, centrifuged (3000 r/min) for 20 min, and the supernatant was discarded. The body was washed twice with sterile physiological saline, and finally a suspension of the bacteria was prepared, and the cell count plate was directly counted under a microscope to adjust the concentration of the bacterial solution to 10 ⁸ /mL.

(2) UV treatment. Turn on the 15W UV light switch and warm up for 20 minutes. Under sterile conditions, pipette 6ml of the above bacterial suspension into a 9cm sterile culture dish, then put a sterile magnetic stir bar, then place it under the UV lamp 30cm, the irradiation time respectively It is 2, 4, 6 min.

Under the red light, the treated bacterial suspension was diluted to 10 ^-5 , 10 ^-6 , 10 ^-7 , coated on PKO inorganic phosphorus medium, and each concentration of the bacterial solution was coated with 3 plates while taking no The UV-treated diluted bacterial solution was applied to a plate as a control. Wrap in a newspaper, avoid light, and incubate in a constant temperature incubator at 28 ° C for 48 h.

(3) Screening. The screening (primary and rescreening) methods for mutagenized strains are the same as in 1.4.2.

5. Demineralization of pyrolusite

30 mL of the mutagenized P-2-8 broth was inoculated into a conical flask containing 150 mL of soft manganese ore pulp phosphate-deficient medium (the mass of the solids was 20%), and the same method was used.

Second, the results and discussion

(1) Flat screening

The strain was cultured in a 30 ° C incubator in a PKO solid medium to obtain 9 strains of fungal strains having a significant melting ring of phosphorus. The D/d range in 7 to 15 days is shown in Table 2, and the colony characteristics are shown in Table 3.

Table 2 D/d range of 9 strains of dephosphorization bacteria on solid medium

Table 3 Characteristics of 9 strains of colonies

(2) shake flask rescreening

1 mL of a bacterial suspension having a concentration of 10 ⁸ /mL was inoculated into a PKO liquid medium, placed on a shaker at a speed of 150 r/min, and cultured at 28 ° C for 5 days. The results are shown in Table 4.

Table 4 Liquid culture results

The results of primary screening and rescreening showed that the D/d value of P69 ranged from 1.12 to 2.30, and the increase of dissolved phosphorus in liquid medium was 15.012 mg/L. Both values ​​were the largest among the 9 strains of phosphate solubilizing bacteria. P69 has the largest dephosphorization ability.

(3) Simulating manganese ore dephosphorization

The pH values ​​of the strains after 5 days and 10 days of culture are shown in Fig. 1, and the effect of phosphorus solubilization is shown in Fig. 2.

Figure 1 Effect of different phosphorus solubilizing strains on the pH value of the solution

Figure 2 Phosphorus solubilization effect of different strains

It can be seen from Fig. 1 and Fig. 2 that the pH of the culture strains decreased after 5 days of culture, and the pH of the culture medium of P71, P79, P98, P113 and P115 increased to a certain extent, P69, P79, P95 cultured. The liquid Pha is unchanged, and the pH of P117 is lowered. When cultured for 5 days, the rate of P for the strain decreased to about 50%, and the rate of dephosphorylation of P69 was the highest, which was 52.2%.

(4) In addition to mutagenesis

1, the first screening

UV-induced mutagenesis of P69 resulted in a total of 29 strains, of which P-2-8 (No. 8 in the 2 min mutagenesis group) had the best effect on phosphorus solubilization. After 15 days of mutagenesis, its D/d value increased from 1.12 to 2.30 to 1.47 to 4.33, and the comparison with the original strain is shown in Fig. 3.

Figure 3 Comparison of D/d changes on solid medium

It can be seen from Fig. 3 that from the 6th day, the D/d value of the strain after the mutagenesis was significantly improved, and the D/d value of P-2-8 was the highest, reaching 4.33.

2, rescreening

The phosphorus content of the mutagenized strain was measured, and the liquid culture results of the dephosphorized bacteria after mutagenesis are shown in Table 5.

Table 5 Comparison of liquid culture results of dephosphorization bacteria after mutagenesis

It can be seen from Table 5 that after the mutagenesis, the amount of phosphorus solubilized by the strain was 24.05 mg/100 mL, which was significantly larger than that of the starting strain P69 (15.01 mg/100 mL). The amount of phosphorus solubilized by the mutagenized strain was increased by about 60.2% compared with the amount of phosphorus dissolved by the starting strain.

(5) Demineralization of pyrolusite

Figure 4 shows the test results of dephosphorization of pyrolusite by P-2-8 and P69. It can be seen that the dephosphorization rate of P-2-8 increases with time, increasing from 12.3% on the 3rd to 74.6% on the 15th, which is 2.25 times that of the original strain P69, which is 33.2%. After dephosphorization, the mass fraction of phosphorus in manganese ore decreased from 0.19% to 0.048%, and ω(P)/ω(Mn) decreased from 0.0109 to 0.0028. The ore after dephosphorization met the metallurgical requirements.

Third, the conclusion

(1) A total of 9 strains with phosphorus-dissolving effect were screened from the soil samples taken from the Xiangtan manganese ore mining area. The nine strains were used to simulate the demineralization of manganese ore. The dephosphorization effect of P69 was the best, and the dephosphorization rate was 52.2%.

(2) Using the strain P69 as the starting strain for UV mutagenesis, the strain P-2-8 with significantly improved dephosphorization effect was obtained. Dephosphorization test of pyrolusite with P-2-8, the dephosphorization rate was 74.6%, the mass fraction of phosphorus in manganese ore after dephosphorization was 0.048%, and ω(P)/ω(Mn) was 0.0028, which met the metallurgical requirements.

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