Method for manufacturing powder containing iron oxide

Abstract

To provide: powder containing iron oxide having high hydrogen sulfide adsorption capability while effectively using pit wastewater discharged from suspended or abandoned mines; a hydrogen sulfide adsorbent using the powder containing iron oxide; and a method for manufacturing the powder containing iron oxide.SOLUTION: Powder containing iron oxide includes goethite as a main component, and has a volume-based mean particle diameter of 1 μm or more and 50 μm or less, and a specific surface of 80 m2 / g or more and 500 m2 / g or less. S / Fe is 0.05 or less in terms of an element weight ratio.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an iron oxide-containing powder, a hydrogen sulfide adsorbent using the iron oxide-containing powder, and a method for producing the iron oxide-containing powder.

Background Art

[0002] Due to the increase in abandoned mines, the treatment of waste from abandoned mines has become a problem. In abandoned mines, mine wastewater is neutralized and neutralization precipitates are recovered so that water pollution does not occur in the downstream area. Conventionally, these neutralization precipitates have been discarded as industrial waste. However, from the viewpoints of environmental protection and effective use of resources, it is desired to effectively utilize the mine wastewater generated in abandoned mines.

[0003] Patent Document 1 describes a desulfurized water material contained in iron hydroxide produced using mine wastewater discharged from an abandoned mine after mining and a method for producing the same.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Hydrogen sulfide gas is generated in sludge treatment at water purification plants and biomass gas power generation. To treat this hydrogen sulfide gas, a large amount of hydrogen sulfide adsorbents are required. If a higher-performance and less expensive hydrogen sulfide adsorbent can be produced, reduction of the adsorbent replacement work and reduction of the hydrogen sulfide gas treatment cost can be expected. However, the desulfurized water material in the invention described in Patent Document 1 contains a sulfur (S) component in its composition, and there is room for further improvement.

[0006] Therefore, the present invention aims to provide an iron oxide-containing powder mainly composed of goethite, a hydrogen sulfide adsorbent using the iron oxide-containing powder, and a method for producing the iron oxide-containing powder, which can effectively utilize the mine wastewater discharged from abandoned mines and can be used as a hydrogen sulfide adsorbent material.

Means for Solving the Problems

[0007] The gist of the constitution of the iron oxide-containing powder of the present invention, the hydrogen sulfide adsorbent using the iron oxide-containing powder, and the method for producing the iron oxide-containing powder is as follows.

[0008] Containing goethite as a main component, The average particle diameter on a volume basis is 1 μm or more and 50 μm or less, The specific surface area is 80 m 2 / g or more and 500 m 2 / g or less, An iron oxide-containing powder used for a hydrogen sulfide adsorbent.

[0009] In the elemental weight ratio, it is preferable that S / Fe is 0.05 or less, more preferably 0.03 or less, and even more preferably 0.01 or less, for the iron oxide-containing powder described above.

[0010] A hydrogen sulfide adsorbent containing the iron oxide-containing powder described above and having a hydrogen sulfide gas adsorption amount of 350 mg / g or more.

[0011] An iron oxidation step of adding iron-oxidizing bacteria to an iron salt aqueous solution containing divalent Fe ions and a reduced inorganic sulfur compound to obtain a first precipitate containing schwertmannite, An S component removal step of adding NaOH to the first precipitate to obtain a second precipitate containing goethite, and a method for producing an iron oxide-containing powder including the above steps.

[0012] The first precipitate contains 4.0 wt% or more and 8.0 wt% or less of the S component in the elemental weight ratio, for the method for producing the oxide-containing powder described above.

[0013] In the S component removal step, the S component contained in the first precipitate is dissolved and removed to form pores in the iron oxide-containing particles. The method for producing an iron oxide-containing powder according to the above description.

[0014] The NaOH is 0.7 equivalent or more and 2.0 equivalents or less with respect to the S component in the first precipitate. The method for producing an iron oxide-containing powder according to the above description.

[0015] The pH of the aqueous iron salt solution is 2.0 or more and 5.0 or less. The method for producing an iron oxide-containing powder according to the above description.

Advantages of the Invention

[0016] According to the present invention, it is possible to effectively utilize the mine wastewater discharged from the abandoned mine, and it is possible to provide an iron oxide-containing powder mainly composed of goethite that can be used as a hydrogen sulfide adsorbent, a hydrogen sulfide adsorbent using the iron oxide-containing powder, and a method for producing the iron oxide-containing powder.

Brief Description of the Drawings

[0017]

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Mode for Carrying Out the Invention

[0018] Hereinafter, with reference to the drawings, the iron oxide-containing powder according to the present embodiment, the hydrogen sulfide adsorbent using the iron oxide-containing powder, and the method for producing the iron oxide-containing powder will be described. The embodiments shown below are specifically described to better understand the gist of the invention, and do not limit the present invention unless otherwise specified.

[0019] (Iron Oxide-Containing Powder) The iron oxide-containing powder according to the present embodiment contains goethite as a main component. The average particle diameter of the iron oxide-containing powder on a volume basis is 1 μm or more and 50 μm or less. The specific surface area of the iron oxide-containing powder is 80 m 2 / g or more and 500 m 2 / g or less. The hydrogen sulfide adsorbent according to the present embodiment contains this iron oxide-containing powder.

[0020] If the average particle diameter of the iron oxide-containing powder on a volume basis is less than 1 μm, it is likely to scatter, and the working environment deteriorates significantly. Further, if it exceeds 50 μm, a dense granule cannot be formed when performing the granulation process, and it cannot be used as an adsorbent in practice. If the specific surface area of the iron oxide-containing powder is less than 80 m 2 / g, the adsorption ability of hydrogen sulfide is low, and if it exceeds 500 m 2 / g, the adsorption rate is too fast, and a long-term stable adsorption ability cannot be maintained. The iron oxide-containing powder according to the present embodiment has an appropriate particle diameter for use as a hydrogen sulfide adsorbent and at the same time has a large specific surface area.

[0021] Hereinafter, aspects such as the composition and particle size distribution of the iron oxide-containing powder containing goethite as a main component according to the present invention will be described.

[0022] (Average Particle Diameter and Specific Surface Area) The particle size distribution of the iron oxide-containing powder according to this embodiment is measured using a laser diffraction particle size distribution measuring device. The average particle diameter is evaluated by the cumulative 50% particle diameter based on volume (hereinafter referred to as D50). At this time, the D50 of the iron oxide-containing powder according to this embodiment is 1 μm or more and 50 μm or less, preferably 5 μm or more and 20 μm or less.

[0023] Also, the specific surface area is measured by the BET one-point method. The specific surface area of the iron oxide-containing powder according to this embodiment is 80 m 2 / g or more and 500 m 2 / g or less, preferably 100 m 2 / g or more and 400 m 2 / g or less. By setting both D50 and the specific surface area within the above numerical ranges, an effect of efficiently adsorbing hydrogen sulfide gas can be expected.

[0024] (Element weight ratio) The element weight ratio of the iron oxide-containing powder according to this embodiment is determined from the analysis results by ICP emission spectrometry. The iron oxide-containing powder according to this embodiment contains α-iron oxyhydroxide [α-FeO(OH)] as a main component, and may also contain a trace amount of calcium oxide (CaO) and the like derived from anti-wastewater. The iron oxide-containing powder according to this embodiment contains at least 70 wt% or more of iron oxide, preferably 90 wt% or more. Also, the ratio of the weight of the S component to the weight of the Fe component (S / Fe) is preferably 0.05 or less, more preferably 0.03 or less, and even more preferably 0.01 or less.

[0025] Also, the iron oxide-containing powder according to this embodiment may contain inevitable elements such as trace impurities contained in anti-wastewater and other raw materials and impurities derived from manufacturing equipment. In the present invention, "goethite" shall include those having the same crystal structure as iron oxyhydroxide [α-FeO(OH)] and having a trace amount of other elements dissolved therein.

[0026] (Hydrogen sulfide adsorbent) A hydrogen sulfide adsorbent is an adsorbent that physically or chemically adsorbs hydrogen sulfide. The hydrogen sulfide adsorbent according to this embodiment contains the above-described iron oxide-containing powder and chemically adsorbs hydrogen sulfide. The hydrogen sulfide adsorbent may combine an inorganic plasticizer, an organic binder, and a fibrous reinforcing material with the iron oxide-containing powder. Further, additives may be mixed or molded as necessary.

[0027] As the inorganic plasticizer, preferably kaolin (Al4Si4O 10 (OH)8) or talc (Mg3Si4O 10 (OH)2) may be used. As the organic binder, preferably polyvinyl alcohol (PVA) or methyl cellulose may be used. As the fibrous reinforcing material, preferably pulp or cellulose may be used. These inorganic plasticizers, organic binders, and fibrous reinforcing materials may be of one type or a combination of multiple types may be added.

[0028] The above kneaded product may be formed into granules or pellets. Thereby, the handleability as a hydrogen sulfide adsorbent is improved. When forming the kneaded product into pellets, for example, an extrusion granulator may be used. By using an extrusion granulator, the kneaded product is extruded from a die and formed into a cylindrical shape, and this is cut to a predetermined length to obtain a pelletized desulfurized hydrogen material.

[0029] The iron oxide-containing powder according to this embodiment has an appropriate particle size for use as a hydrogen sulfide adsorbent and at the same time has a large specific surface area. Therefore, the hydrogen sulfide adsorbent according to this embodiment can come into contact with hydrogen sulfide gas over a wide contact area.

[0030] In addition, the iron oxide-containing powder has large particle diameters of the particles constituting the powder, and the region of the voids formed during filling also becomes large. Therefore, in the hydrogen sulfide adsorbent, the resistance when hydrogen sulfide gas passes through the iron oxide-containing powder is small. Thus, even at low pressures, the hydrogen sulfide gas can sufficiently make solid-gas contact with the surface of the iron oxide-containing powder. In this way, the hydrogen sulfide gas is efficiently adsorbed onto the iron oxide-containing powder and stored as iron sulfide. The adsorption capacity of the hydrogen sulfide adsorbent according to this embodiment can be evaluated by a static adsorption test. The hydrogen sulfide adsorption capacity of the hydrogen sulfide adsorbent according to this embodiment is 350 mg / g or more, and preferably 400 mg / g or more.

[0031] (Hydrogen sulfide adsorption capacity) As methods for measuring the hydrogen sulfide adsorption capacity in the hydrogen sulfide adsorbent, there are two types: a dynamic adsorption capacity measurement method and a static adsorption capacity measurement method. In the present invention, the static adsorption capacity measurement method is used.

[0032] In the dynamic adsorption capacity measurement method, a hydrogen sulfide adsorbent sample is filled in a column or the like, a control valve, a flow meter, a cylinder of hydrogen sulfide gas, etc. are connected to the column, and a ribbon heater or the like is used to keep the column at a constant temperature at a predetermined temperature. Then, hydrogen sulfide gas at a constant concentration is flowed at a constant flow rate to adsorb hydrogen sulfide onto the hydrogen sulfide adsorbent sample. For example, a gas bag is connected to the outlet side, and the hydrogen sulfide gas concentration of the gas collected in the gas bag is measured using gas chromatography or the like at regular intervals. The breakthrough point is confirmed from this concentration change, and the adsorption capacity per unit mass of the adsorbent is calculated from the ventilation time, the concentration, and the amount of the adsorbent used.

[0033] In the static adsorption capacity measurement method shown in Fig. 5, after drying the raw material of the hydrogen sulfide adsorbent sample 1 with a constant temperature dryer or the like, it is lightly crushed to adjust the size, and the material passing through a mesh with a predetermined mesh size is used as the evaluation hydrogen sulfide adsorbent sample 1. First, a predetermined amount of the hydrogen sulfide adsorbent sample 1 is taken and placed in a sealed container 2 (a vacuum desiccator in this example) and sealed. This desiccator is preliminarily equipped with a thermometer 3, a pressure gauge 4, a communication pipe 5 connecting the sealed container 2 and the outside, a gas outlet, a gas inlet, and a control valve 6 for controlling its opening / closing and flow rate. The state after evacuating the air in the desiccator with a vacuum pump 7 or the like is shown in Fig. 5(A). Next, as shown in Fig. 5(B), hydrogen sulfide gas with a predetermined concentration is enclosed using a syringe 8. Then, the entire desiccator is placed in a constant temperature dryer or the like, the temperature is kept constant, and after a predetermined time has elapsed, as shown in Fig. 5(C), the gas in the desiccator is extracted using the syringe 8. Finally, the extracted gas is measured using a detector 9 such as gas chromatography, and the state is shown in Fig. 5(D). Considering the amount of the enclosed gas and the weight of the adsorbent used, the adsorption capacity per unit mass of the adsorbent is calculated based on the concentration difference between the hydrogen sulfide gas with the predetermined concentration initially enclosed and the hydrogen sulfide concentration of the gas finally extracted. The hydrogen sulfide gas used in each measurement method is generally assumed to be for hydrogen sulfide gas countermeasures in sewage treatment plants where hydrogen sulfide adsorbents are often used, and a gas with a concentration of about several thousand ppm is used.

[0034] (Method for producing iron oxide-containing powder) Fig. 1 shows a flowchart of the method for producing the iron oxide-containing powder according to this embodiment. The iron oxide-containing powder according to this embodiment includes an iron salt aqueous solution preparation step S1 of obtaining an iron salt aqueous solution containing divalent Fe ions and a reduced inorganic sulfur compound, an iron oxidation step S2 of adding iron-oxidizing bacteria to the iron salt aqueous solution to obtain a first precipitate containing schwertmannite, an S component removal step S3 of adding NaOH to the first precipitate to obtain a second precipitate containing goethite, and a recovery step S4 of solid-liquid separating and washing the second precipitate, and can be produced by a method including these steps.

[0035] FIG. 2 shows a detailed flowchart of the method for manufacturing an iron oxide-containing powder according to the present embodiment. Hereinafter, each step in the case of manufacturing an iron oxide-containing powder using mine wastewater as a raw material will be described with reference to FIG. 2.

[0036] (Iron salt aqueous solution preparation step S1) In the iron salt aqueous solution preparation step S1, an iron salt aqueous solution suitable for use in the iron oxidation step S2 using iron-oxidizing bacteria described later is prepared. The iron salt aqueous solution preparation step S1 includes a mine wastewater recovery step S11 and an arsenic removal step S12.

[0037] The mine wastewater recovery step S11 is a step of recovering mine wastewater as a raw material for the iron salt aqueous solution.

[0038] In the mine wastewater recovery step S11, as a raw material for the iron salt aqueous solution, mine wastewater discharged from a closed mine may be recovered and used. Examples of the closed mine include mines of iron sulfide ore. The mine wastewater of the iron sulfide ore mine contains a reduced inorganic sulfur compound and divalent Fe ions. The mine wastewater may contain divalent Fe ions in an amount of 0.01 g / L or more. Further, the pH of the mine wastewater may be sulfuric acid acidity of 2.5 or more and 5.0 or less. Due to the inclusion of the reduced inorganic sulfur compound and divalent Fe ions, divalent Fe ions can be oxidized to trivalent Fe ions using iron-oxidizing bacteria described later. From the viewpoint of effective utilization of resources, it is preferable to use mine wastewater as a raw material for the iron salt aqueous solution, but the raw material is not particularly limited as long as it chemically satisfies the above conditions.

[0039] The arsenic removal step S12 is a step of removing arsenic from the raw material of the iron salt aqueous solution obtained in the mine wastewater recovery step S11.

[0040] In the arsenic removal step S12, first, NaOH and an inorganic flocculant (trade name: Bioferric) are added to the mine wastewater obtained in the mine wastewater recovery step S11. Thereby, arsenic contained in the mine wastewater is removed. At this time, it is preferable to set the pH to 3.0 or more and 4.0 or less. Thus, an iron salt aqueous solution suitable for use in the iron oxidation step S2 using iron-oxidizing bacteria is obtained.

[0041] (Iron oxidation step S2) In the iron oxidation step S2, divalent Fe ions in the aqueous iron salt solution are oxidized to obtain a primary precipitate containing schwertmannite. The iron oxidation step S2 includes a bacterial reaction step S21, a bacterial recovery step S22, and a primary precipitate recovery step S23.

[0042] The bacterial reaction step S21 is a step of oxidizing divalent Fe ions contained in the aqueous iron salt solution to trivalent Fe ions by iron-oxidizing bacteria.

[0043] In the bacterial reaction step S21, in the bacterial reaction tank, divalent Fe ions contained in the aqueous iron salt solution are oxidized to trivalent Fe ions by iron-oxidizing bacteria. And a primary precipitate containing schwertmannite [Fe8O8(OH)6(SO4)·nH2O] is obtained. Examples of the iron-oxidizing bacteria used in the bacterial reaction tank include Acidithiobacillus ferrooxidans and Ferrovum myxofaciens.

[0044] In the bacterial reaction step S21, the pH of the aqueous iron salt solution in the bacterial reaction tank is preferably 2.0 or more and 5.0 or less, more preferably 2.3 or more and 4.0 or less, and even more preferably 2.3 or more and 3.0 or less. If the pH is less than 2.0, the function of the iron-oxidizing bacteria to oxidize divalent Fe ions may not work effectively, which is not preferable. If the pH exceeds 5.0, although it is advantageous from the viewpoint of iron oxidation, the amount of NaOH added to the anti-wastewater for pH adjustment will increase, and the cost of wastewater treatment will increase, so it is not preferable.

[0045] In this way, by adjusting the pH to an appropriate range, the divalent Fe ions in the aqueous iron salt solution are sufficiently oxidized. Therefore, the hydraulic retention time (HRT) in the bacteria reaction tank can be set to about 1.5 hours. If the hydraulic retention time is too long, there is a problem that the equipment becomes large. Within the range where sufficient time for the oxidation treatment can be ensured, it is preferable to shorten the hydraulic retention time. The hydraulic retention time is defined as (the effective volume of the bacteria reaction tank) / (the inflow rate of the aqueous iron salt solution per hour).

[0046] The bacteria recovery step S22 is a step of recovering bacteria after the completion of the bacteria reaction step S21.

[0047] In the bacteria recovery step S22, the aqueous iron salt solution that has undergone the bacteria reaction step S21 is transferred to a bacteria recovery tank. Then, in the bacteria recovery tank, the bacteria can be precipitated and the precipitated bacteria can be returned to the bacteria reaction tank.

[0048] The first precipitate recovery step S23 is a step of recovering the first precipitate containing schwertmannite that has been oxidized in the bacteria reaction step S21.

[0049] In the first precipitate recovery step S23, the residual liquid containing the first precipitate is transferred to an iron coagulation tank, and the first precipitate containing schwertmannite [Fe8O8(OH)6(SO4)·nH2O] is recovered in the iron coagulation tank. The first precipitate may be recovered in a slurry state. At this time, solid-liquid separation may be performed, and for example, the filter press method can be mentioned. In this way, the first precipitate may be recovered as a slurry or a water-containing cake. The first precipitate can also be further dried to a powder state. Also, the first precipitate recovered in this way contains the S component in the range of 4.0 wt% or more and 8.0 wt% or less in terms of elemental weight ratio.

[0050] (S component removal step S3) In the S component removal step S3, the S component is removed from the first precipitate to obtain a second precipitate containing goethite. The S component removal step S3 includes a first precipitate transfer step S31, an alkali treatment step S32, and a second precipitate recovery step S33.

[0051] In the first precipitate transfer step S31, first, the first precipitate containing schwertmannite obtained in the iron oxidation step S2 is transferred to a reaction tank prepared with an alkali solution such as NaOH. Here, the first precipitate may be transferred in a water-containing state.

[0052] In the alkali treatment step S32, goethite is obtained from schwertmannite. Specifically, the S component of schwertmannite [Fe8O8(OH)6(SO4)·nH2O] contained in the first precipitate is removed to obtain goethite [FeO(OH)]. An alkali solution is used for removing the S component, for example, NaOH is used.

[0053] At this time, when the amount of NaOH required to remove 1 mol of the S component contained in the first precipitate is defined as 1 equivalent, the addition amount of NaOH is preferably 0.7 equivalent or more and 2.0 equivalents or less. Here, the mechanism for removing the S component by NaOH is assumed to be S 2- +2NaOH→NaS2+2OH - If it is less than 0.7 equivalent, the S component is not sufficiently removed. If it is more than 2.0 equivalents, in addition to the specific surface area becoming small and the adsorption capacity decreasing, the amount of chemicals used increases, which also causes problems in terms of cost. In either case, it is not preferable for use as a hydrogen sulfide adsorbent.

[0054] The second precipitate recovery step S33 is a step of recovering the second precipitate containing goethite by an arbitrary method. Similar to the first precipitate recovery step S23, it can be recovered in a slurry state.

[0055] (Recovery step S4) The recovery step S4 is a step of obtaining the final iron oxide-containing powder from the second precipitate obtained in the S component removal step S3. The recovery step S4 includes a solid-liquid separation step S41 and a water washing step S42.

[0056] The solid-liquid separation step S41 is a step of separating the obtained second precipitate into solid and liquid by any method. The method of solid-liquid separation is carried out by any method.

[0057] The water washing step S42 is a step of washing the solid-liquid separated second precipitate. In the water washing step S42, it is advisable to wash thoroughly to remove the residual liquid of NaOH and the iron salt aqueous solution from the second precipitate as much as possible. By drying the second precipitate after water washing, an iron oxide-containing powder mainly composed of goethite can be obtained. The drying method of the second precipitate is not limited as long as it does not break the crystal structure of goethite. For example, it may be dried using a natural convection constant temperature dryer, a forced convection constant temperature dryer, or the like. If the drying temperature is too high, the iron oxide-containing powder mainly composed of goethite may be transformed into hematite or other iron oxides. Therefore, the temperature during drying is preferably 120 °C or lower.

[0058] The iron oxide-containing powder produced through this S component removal step S3 has an appropriate particle size for use as a hydrogen sulfide adsorbent and at the same time has a large specific surface area. Although the mechanism is not necessarily clear, the inventors expect that the following phenomena occur in the S component removal step S3. The crystal structure of schwertmannite [Fe8O8(OH)6(SO4)·nH2O] has a tunnel structure based on a double chain of Fe octahedrons (FeO3(OH)3) that surrounds (SO4) 2- ions. And in the first precipitate that has undergone the S component removal step S3 according to this embodiment, while the tunnel structure mainly composed of this Fe is maintained, only the (SO4) 2- portion in the crystal structure is removed. As a result, the region where SO4 2- ions are removed becomes voids, and pores are formed in the particles of the second precipitate. Therefore, the second precipitate that has undergone the S component removal step S3 has no significant change in particle size distribution compared to the first precipitate, but the specific surface area increases dramatically.

Example

[0059] Hereinafter, examples of the iron oxide-containing powder and its manufacturing method will be described. In preliminary studies, when the D50 of the iron oxide-containing powder was less than 1 μm on a volume basis, it was prone to scattering, and the working environment could deteriorate significantly. On the other hand, when the iron oxide-containing powder exceeded 50 μm, it was sometimes impossible to produce a dense granule during the granulation process. Therefore, the ranges where D50 was less than 1 μm and 50 μm or more were excluded from the study of the manufacturing method of the hydrogen sulfide adsorbent. Also, when the specific surface area of the iron oxide-containing powder was less than 80 m 2 / g, the adsorption ability of hydrogen sulfide was clearly low, and when it exceeded 500 m 2 / g, perhaps due to the adsorption rate being too fast, it was sometimes impossible to maintain a stable adsorption ability over the long term. Therefore, it was excluded from the comparison of the performance of the hydrogen sulfide adsorbent.

[0060] (Example 1) First, as the aqueous iron salt solution, the waste water from the Koga mine's pyrite mine containing a reducing inorganic sulfur compound and divalent Fe ions was used. This waste water contained 0.8 g / L or more and 1.1 g / L or less of divalent Fe ions. Also, the pH was sulfuric acid acidic with a pH of 2.5 or more and 3.0 or less. To this waste water, NaOH was added to adjust the pH to 3.6 or more and 3.9 or less. An inorganic flocculant (trade name: Bioferric, main component: ferric polysulfate) was added to the waste water after pH adjustment to remove arsenic in the waste water. Then, the arsenic-removed waste water was transferred to a bacteria reaction tank. In the bacteria reaction tank, the divalent Fe ions contained in the waste water were oxidized to trivalent Fe ions by iron-oxidizing bacteria. The pH of the waste water in the bacteria reaction tank was adjusted to 2.5. The hydraulic retention time (HRT) in the bacteria reaction tank at this time was set to 1.62 hours. Thereafter, the waste water in the bacteria reaction tank was transferred to a bacteria recovery tank to recover the bacteria (iron-oxidizing bacteria), and then transferred to an iron flocculation tank. Then, solid-liquid separation was performed by a filter press to recover the first precipitate containing schwertmannite [Fe8O8(OH)6(SO4)·nH2O].

[0061] Next, NaOH was added to the recovered first precipitate, i.e., the first precipitate containing Schubertite obtained in the iron oxidation step, and the mixture was stirred. At this time, the addition amount of NaOH with respect to the S component contained in the first precipitate was 1.2 equivalents, and the stirring time was 3 hours.

[0062] The obtained second precipitate was subjected to solid-liquid separation by a filter press and washed with water. The second precipitate after washing with water was dried to obtain an iron oxide-containing powder.

[0063] For the iron oxide-containing powder thus obtained, the specific surface area, particle size distribution, and identification of the crystal structure by X-ray diffraction (XRD) measurement were performed.

[0064] The particle size distribution of the iron oxide-containing powder was measured using a laser diffraction particle size distribution analyzer (Microtrac MT3300 manufactured by Nikkiso Co., Ltd.). When the cumulative 50% particle size (D50) based on volume was determined as the average particle diameter, it was 7.8 μm. The obtained particle size distribution is shown in FIG. 6. In addition, SEM observation images of the iron oxide-containing powder observed by a scanning electron microscope (JSM-7800F manufactured by JEOL) are shown in FIGS. 7 and 8. From the observation image at 50,000 times the state of the particle surface in Example 1 of FIG. 8, it was found that the iron oxide-containing powder is composed of secondary particles consisting of primary particles having a characteristic needle-like crystal shape in goethite.

[0065] The specific surface area of the iron oxide-containing powder was measured by the BET one-point method using a specific surface area measuring device (Macsorb HM-Model 1210 manufactured by Mountech Co., Ltd.). As a result, the specific surface area of the iron oxide-containing powder was 232.6 m 2 / g.

[0066] The X-ray diffraction measurement of the iron oxide-containing powder was performed by the powder X-ray diffraction method (XRD) using a powder X-ray diffractometer (LabX XRD-6100 manufactured by Shimadzu Corporation), with a CuKα ray as the radiation source, a tube voltage of 40 kV, a tube current of 30 mA, and a measurement range of 2θ = 20° to 70°. As a result of this X-ray diffraction measurement, it was confirmed that the obtained iron oxide-containing powder was goethite. The X-ray diffraction spectrum obtained by the X-ray diffraction measurement is shown in Fig. 4 together with the X-ray diffraction spectrum measured in the first precipitate for comparison.

[0067] Also, the composition of the obtained iron oxide-containing powder can be measured by any method, but in this example, composition analysis was performed using an ICP emission spectroscopic analyzer (SPS3520 manufactured by Hitachi High-Technologies Corporation). As the analysis results, Ca, Fe, and S are extracted and shown in Table 1. In Example 1, the elemental weight ratio of the S component was less than 0.01 wt%, which is the detection lower limit.

[0068] (Evaluation of hydrogen sulfide adsorption capacity) The adsorption amount of hydrogen sulfide gas as a hydrogen sulfide adsorbent of the iron oxide-containing powder thus obtained was measured by the static adsorption capacity measurement method shown in Fig. 5. First, a hydrogen sulfide adsorbent sample 1 was enclosed in a sealed container 2 together with hydrogen sulfide gas. Then, after one month had passed, the hydrogen sulfide concentration in the sealed container 2 was measured using gas chromatography with a detector 9. The adsorption amount of hydrogen sulfide gas was 440 (mg / g).

[0069] (Example 2) The same treatment as in Example 1 was carried out except that the stirring time in the iron oxidation step was set to 6 hours, and an iron oxide-containing powder according to Example 2 was obtained. The measurement results of each physical property value are shown in Table 1. As a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite. The measured X-ray diffraction spectrum is shown in Fig. 4.

[0070] (Example 3) The same procedures as in Example 1 were carried out except that the stirring time in the iron oxidation step was set to 24 hours, and an iron oxide-containing powder according to Example 3 was obtained. The measurement results of each physical property value are shown in Table 1. In Example 3, the elemental weight ratio of the S component was less than 0.01 wt%, which is the detection lower limit. As a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite. The measured X-ray diffraction spectrum is shown in FIG. 4.

[0071] (Example 4) The same procedures as in Example 1 were carried out except that the stirring time in the iron oxidation step was set to 72 hours, and an iron oxide-containing powder according to Example 4 was obtained. The measurement results of each physical property value are shown in Table 1. As a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite. The measured X-ray diffraction spectrum is shown in FIG. 4.

[0072] (Example 5) The same procedures as in Example 1 were carried out except that the amount of NaOH added in the iron oxidation step was 0.9 equivalents and the stirring time was 3 hours, and an iron oxide-containing powder according to Example 5 was obtained. The measurement results of each physical property value are shown in Table 1. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0073] (Example 6) The same procedures as in Example 1 were carried out except that the amount of NaOH added in the iron oxidation step was 0.9 equivalents and the stirring time was 6 hours, and an iron oxide-containing powder according to Example 6 was obtained. The measurement results of each physical property value are shown in Table 1. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0074] (Example 7) The same treatment as in Example 1 was carried out except that the addition amount of NaOH in the iron oxidation step was 0.9 equivalent and the stirring time was 24 hours, and an iron oxide-containing powder according to Example 7 was obtained. The measurement results of each physical property value are shown in Table 1. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0075] (Example 8) The same treatment as in Example 1 was carried out except that the addition amount of NaOH in the iron oxidation step was 0.9 equivalent and the stirring time was 72 hours, and an iron oxide-containing powder according to Example 8 was obtained. The measurement results of each physical property value are shown in Table 1. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0076] (Example 9) The same treatment as in Example 1 was carried out except that the addition amount of NaOH in the iron oxidation step was 1.8 equivalents and the stirring time was 3 hours, and an iron oxide-containing powder according to Example 9 was obtained. The measurement results of each physical property value are shown in Table 1. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0077] (Example 10) The same treatment as in Example 1 was carried out except that the addition amount of NaOH in the iron oxidation step was 1.8 equivalents and the stirring time was 6 hours, and an iron oxide-containing powder according to Example 10 was obtained. The measurement results of each physical property value are shown in Table 1. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0078] (Example 11) The same treatment as in Example 1 was carried out except that the addition amount of NaOH in the iron oxidation step was 1.8 equivalents and the stirring time was 24 hours, and an iron oxide-containing powder according to Example 11 was obtained. The measurement results of each physical property value are shown in Table 1. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0079] (Example 12) The same treatment as in Example 1 was carried out except that the addition amount of NaOH in the iron oxidation step was 1.8 equivalents and the stirring time was 72 hours, and an iron oxide-containing powder according to Example 12 was obtained. The measurement results of each physical property value are shown in Table 1. In Example 12, the elemental weight ratio of the S component was less than 0.01 wt%, which is the detection lower limit. Although the X-ray diffraction spectrum is not shown, as a result of performing X-ray diffraction measurement on the obtained iron oxide-containing powder in the same manner as in Example 1, it was confirmed that it was goethite.

[0080] (Comparative Example 1) In Example 1, the same treatment as in Example 1 was carried out except that the S component removal step was not performed on the first precipitate and it was dried, and an iron oxide-containing powder according to Comparative Example 1 was obtained. The evaluation results are shown in Table 1 as Comparative Example 1, and the measurement results of the particle size distribution are shown in FIG. 6 together with the results of Example 1.

[0081] (Conventional Example 1) The evaluation results of a commercially available product (manufactured by Nippon Limonite Co., Ltd., desulfurized water material "Limonic") using limonite, which has been conventionally used as a hydrogen sulfide adsorbent for iron oxide, are shown in Table 1 as Conventional Example 1.

[0082]

Table 1

[0083] From the results of Examples 1 to 12 shown in Table 1 and Figure 3, when NaOH was 0.9 equivalent or more in the S component removal step, the elemental weight ratio S / Fe was 0.03 or less in all cases. And when NaOH was 1.2 equivalent or more in the S component removal step (Examples 1 to 4 and Examples 9 to 12), the elemental weight ratio S / Fe was 0.01 or less, and it was found that almost all of the S components in the first precipitate could be removed. Note that the S component removal rate shown in Figure 3 is 1 - (S component after S component removal step / Fe component after S component removal step) / (S component before S component removal step / Fe component before S component removal step). Also, the XRD measurement results of Examples 1 to 4 were compared with the XRD measurement results of Comparative Example 1 and shown in Figure 4. When NaOH was 1.2 equivalents in the S component removal step, it was found that the schwertmannite of the precipitate had changed to goethite.

[0084] And as shown in Table 1 and Figures 6 to 10, from the comparison between the iron oxide-containing powder of Example 1 and the iron oxide-containing powder of Comparative Example 1, it can be seen that although there is no significant change in the particle size before and after the S component removal step, the specific surface area has increased dramatically. Further observing the SEM image of Figure 10 here, it can be seen that the particle size of about 10 μm confirmed in the measurement of the particle size distribution is a secondary particle. And it can be seen that the particles of Example 1 are formed from primary particles that form acicular particles. From this, in the S component removal step, it is expected that the aggregated structure constituting the secondary particles is not affected, and it acts only on the S component of the primary particles, and the schwertmannite has changed to goethite. As a result, the void part from which the S component has been removed becomes a new surface, the specific surface area increases dramatically, and it is considered that the hydrogen sulfide adsorption ability is improved.

[0085] As described above, it is possible to effectively utilize the mine wastewater discharged from abandoned mines, and it is possible to provide an iron oxide-containing powder mainly composed of goethite that can be used as a hydrogen sulfide adsorbent, a hydrogen sulfide adsorbent using the iron oxide-containing powder, and a method for producing the iron oxide-containing powder.

Industrial Applicability

[0086] The present invention can be applied to iron oxide-containing powder, a hydrogen sulfide adsorbent using the iron oxide-containing powder, and a method for producing the iron oxide-containing powder.

Explanation of Signs

[0087] 1 Hydrogen sulfide adsorbent sample 2 Sealed container 3 Thermometer 4 Pressure gauge 5 Communication pipe 6 Control valve 7 Vacuum pump 8 Syringe 9 Detector

Claims

1. An iron oxidation step of adding iron-oxidizing bacteria to an aqueous iron salt solution containing divalent Fe ions and a reduced inorganic sulfur compound to obtain a first precipitate containing schwertmannite; A method for producing an iron oxide-containing powder, comprising an S component removal step of adding NaOH to the first precipitate to obtain a second precipitate containing goethite.

2. The method for producing an iron oxide-containing powder according to claim 1, wherein the first precipitate contains an S component in an elemental weight ratio of 4.0 wt% or more and 8.0 wt% or less.

3. The method for producing an iron oxide-containing powder according to claim 1 or 2, wherein in the S component removal step, the S component contained in the first precipitate is dissolved and removed to form pores in the iron oxide-containing particles.

4. The method for producing an iron oxide-containing powder according to any one of claims 1 to 3, wherein the NaOH is 0.7 equivalent or more and 2.0 equivalents or less with respect to the S component in the first precipitate.

5. The method for producing an iron oxide-containing powder according to any one of claims 1 to 4, wherein the pH of the aqueous iron salt solution is 2.0 or more and 5.0 or less.

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