阅读说明：本技术 吸附剂的制造方法、吸附剂及处理方法 (Method for producing adsorbent, adsorbent and treatment method ) 是由 金熙濬 坂本太毅 于 2018-06-01 设计创作，主要内容包括：本发明的吸附剂的制造方法其特征是包括让白云石类与包括溶解状态的磷化合物的溶液接触的吸附工序,及对与上述溶液接触过的上述白云石类进行烧成的烧成工序。上述吸附工序,优选进行条件的pH值为2以上12以下。另外,上述烧成工序,优选进行条件为300℃以上1000℃以下。依据本发明可提供即使在高氢离子浓度指数(pH值)的状态下,也可有效地去除重金属的吸附剂,并提供可制造该吸附剂的吸附剂的制造方法,另外还提供可从被处理物中有效地去除重金属的处理方法。(The method for producing an adsorbent of the present invention is characterized by comprising an adsorption step of bringing dolomite into contact with a solution containing a phosphorus compound in a dissolved state, and a firing step of firing the dolomite which has been brought into contact with the solution. The adsorption step is preferably carried out under conditions of a pH of 2 to 12. The firing step is preferably carried out at a temperature of 300 ℃ to 1000 ℃. According to the present invention, it is possible to provide an adsorbent which can effectively remove a heavy metal even in a state of a high hydrogen ion concentration index (pH value), a method for producing the adsorbent, and a method for treating an object to be treated to effectively remove a heavy metal.)

1. A method for producing an adsorbent, comprising:

an adsorption step in which a dolomite is brought into contact with a solution containing a phosphorus compound in a dissolved state, and a phosphorus component is adsorbed onto the dolomite; and

and a firing step of firing the dolomite in contact with the solution.

2. The method for producing the adsorbent according to claim 1, wherein the dolomite is dolomite hydroxide.

3. The method for producing the adsorbent according to claim 1 or 2, wherein the dolomite is dolomite.

4. The method for producing the adsorbent according to any one of claims 1 to 3, wherein the adsorption step is performed under a condition of a pH value of 2 or more and 12 or less.

5. The method for producing an adsorbent according to any one of claims 1 to 4, wherein the firing step is performed at 300 ℃ to 1000 ℃.

6. The method for producing the adsorbent according to any one of claims 1 to 5, further comprising a hydration step of hydrating the calcined product.

7. The method for producing the adsorbent according to any one of claims 1 to 6, wherein a sludge ash source is used as the phosphorus compound.

8. The method for producing the adsorbent according to any one of claims 1 to 7, wherein the adsorption ratio of phosphate ions is 0.1 to 20 parts by mass with respect to 100 parts by mass of the dolomite.

9. An adsorbent comprising a dolomite and phosphate ions, wherein at least a part of the phosphate ions are chemically bonded to at least one of Ca and Mg constituting the dolomite to form at least one of a calcium phosphate compound and a magnesium phosphate compound.

10. The adsorbent according to claim 9, wherein the elution amount of phosphate ions is 100ppm or less when 1g of the adsorbent is mixed with 10m L of water at 25 ℃ and the elution amount of phosphate ions is 30% or more of the adsorption amount when 1g of the adsorbent is mixed with 10m L1N of hydrochloric acid at 25 ℃.

11. The adsorbent according to claim 9 or 10, having a BET specific surface area of 10m²Over 1000 m/g²The ratio of the carbon atoms to the carbon atoms is less than g.

12. The adsorbent according to any one of claims 9 to 11, wherein the average pore diameter is 1nm or more and 200nm or less.

13. A treatment method characterized by bringing an adsorbent produced by the production method according to any one of claims 1 to 8 into contact with an object to be treated containing a heavy metal to remove the heavy metal contained in the object to be treated.

14. A treatment method characterized by bringing an object to be treated containing a heavy metal into contact with the adsorbent according to any one of claims 9 to 12 to remove the heavy metal contained in the object to be treated.

15. The treatment method according to claim 13 or 14, wherein the adsorbent is brought into contact with the object to be treated at a pH of 5 or more.

Technical Field

The invention relates to a manufacturing method of an adsorbent, the adsorbent and a treatment method.

Background

In water used in factories or mines, many contaminants such as heavy metals are included. If such contaminated water is to be discharged, it is necessary to remove the contaminants sufficiently.

Further, well water and the like that contaminate soil may also contain contaminants such as heavy metals, and when used as domestic water such as drinking water, it is necessary to sufficiently remove the contaminants.

Conventionally, a large amount of adsorbent has been used for removing contaminants (for example, patent document 1). However, when an adsorbent is used for treatment in an alkaline liquid (for example, in a liquid having a hydrogen ion concentration index (pH) of 10 or more), it is difficult to sufficiently adsorb heavy metals or to dissolve the adsorbed heavy metals again, thereby making it difficult to sufficiently remove contaminants.

Disclosure of Invention

Technical problem to be solved by the invention

An object of the present invention is to provide an adsorbent which can effectively remove heavy metals even in a state of high hydrogen ion concentration index (pH); and a method for producing the adsorbent, which can produce the adsorbent; also disclosed is a treatment method whereby a heavy metal can be efficiently removed from a material to be treated.

Technical scheme for solving technical problem

The above object is achieved by the present invention described below.

The method for producing an adsorbent of the present invention is characterized by comprising an adsorption step of bringing a dolomite into contact with a solution containing a dissolved phosphorus compound to adsorb a phosphorus component onto the dolomite and a firing step of firing the solution; the firing step is to fire the dolomite in contact with the solution.

In the method for producing the adsorbent of the present invention, the dolomite is preferably dolomite hydroxide.

In the method for producing the adsorbent of the present invention, the dolomite is preferably dolomite.

In the method for producing an adsorbent of the present invention, the adsorption step is preferably carried out under conditions of a pH of 2 to 12.

In the method for producing an adsorbent of the present invention, the firing step is preferably carried out under conditions of 300 ℃ to 1000 ℃.

In the method for producing an adsorbent of the present invention, it is preferable that a hydration step of hydrating be further included after the firing step.

In the method for producing the adsorbent of the present invention, a sludge ash-derived material is preferably used as the phosphorus compound.

In the method for producing the adsorbent of the present invention, the adsorption ratio of phosphate ions is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the dolomite.

The adsorbent of the present invention is characterized by comprising a dolomite and phosphate ions, wherein at least a part of the phosphate ions are chemically bonded to at least one of Ca and Mg constituting the dolomite to form at least one of a calcium phosphate compound and a magnesium phosphate compound.

In the adsorbent of the present invention, it is preferable that the elution amount of phosphate ions when 1g of the adsorbent is mixed with 10m L of water at 25 ℃ is 100ppm or less, and the elution amount of phosphate ions when 1g of the adsorbent is mixed with 10m L1N of hydrochloric acid at 25 ℃ is 30% or more of the adsorption amount.

In the adsorbent of the present invention, a BET specific surface area of 10m is preferred²Over 1000 m/g²The ratio of the carbon atoms to the carbon atoms is less than g.

In the adsorbent of the present invention, the average pore diameter is preferably 1nm or more and 200nm or less.

The treatment method of the present invention is characterized by bringing the adsorbent produced by the production method of the present invention into contact with an object to be treated containing a heavy metal to remove the heavy metal contained in the object to be treated.

The treatment method of the present invention is characterized by bringing the adsorbent of the present invention into contact with a treatment object containing a heavy metal to remove the heavy metal contained in the treatment object.

In the treatment method of the present invention, the adsorbent is preferably brought into contact with the object to be treated at a pH of 5 or more.

Effects of the invention

According to the present invention, it is possible to provide an adsorbent which can effectively remove a heavy metal even in a state of a high hydrogen ion concentration index (pH value), a method for producing the adsorbent, and a method for treating an object to be treated to effectively remove a heavy metal.

Drawings

Fig. 1 is a graph showing the results of X-ray diffraction (XRD) of the adsorbent of example 1.

FIG. 2 is a graph showing the pore distribution of the adsorbent of example 3.

FIG. 3 shows the pore distribution of the adsorbent of comparative example 2.

FIG. 4 is a graph showing the removal rate of arsenic in the range of pH 10 to 14 when standard solutions containing arsenic, nickel, cadmium, lead and chromium each in an amount of 2000ppb were treated with the adsorbents of examples 1 to 5 and comparative examples 1 and 2.

Fig. 5 is a graph showing the relationship between the pH value and the removal rate of arsenic when a standard solution (single solution) containing 2000ppb of arsenic and substantially no other heavy metals was treated using the adsorbent of example 3, and the relationship between the pH value and the removal rate of arsenic when a standard solution (mixed solution) containing 2000ppb of each of arsenic, nickel, cadmium, lead and chromium was treated using the adsorbent of example 3.

FIG. 6 is a graph showing the removal rate of chromium at a pH value in the range of 10 to 14 when standard solutions containing arsenic, nickel, cadmium, lead and chromium each in an amount of 2000ppb were treated with the adsorbents of examples 1 to 5 and comparative examples 1 and 2.

Detailed Description

[ method for producing adsorbent ]

First, a method for producing the adsorbent of the present invention will be described.

The method for producing an adsorbent of the present invention comprises an adsorption step of bringing a dolomite into contact with a solution containing a phosphorus compound in a dissolved state to adsorb a phosphorus component onto the dolomite and a firing step of firing the solution; the firing step is to fire the dolomite in contact with the solution.

Thus, a method for producing an adsorbent capable of efficiently removing heavy metals even in a high hydrogen ion concentration index (pH) state can be provided. In particular, an adsorbent capable of efficiently removing heavy metals can be produced at low cost with high productivity.

In addition, the production method of the present invention can produce an adsorbent which can remove arsenic, which has been difficult to remove particularly at a high removal rate, and which can also remove arsenic at a high removal rate.

< adsorption step >

An adsorption process: the dolomites are contacted with a solution comprising a phosphorus compound in dissolved form. Thereby, the phosphorus component included in the solution is adsorbed onto the dolomite.

Examples of the dolomite used in the present step include: dolomite, dolomite hydroxide (including digested dolomite and dolomitic lime mud), light burned dolomite, and dolomite clinker, and can be selected from one or more of them.

Among these, by using dolomite hydroxide, it is possible to form chemical bonds between the phosphate ions and Ca and/or Mg constituting the dolomite more preferably in the subsequent firing step.

Further, by using dolomite, the range of selection of dolomite as a raw material is wide, and conditions such as particle size and pore size of the dolomite can be appropriately adjusted. In addition, since the raw material is cheaper, it is advantageous from the viewpoint of further reducing the production cost of the adsorbent.

The dolomite used in the present step (i.e., the dolomite as a raw material) is generally porous.

In this way, the surface area per unit mass (or per unit volume) of the adsorbent can be increased, and the removal efficiency of the heavy metal can be further improved. Further, the specific surface area can be increased by the firing step.

The average pore diameter of the dolomite as a raw material is not particularly limited, but is preferably 1nm to 200nm, more preferably 2nm to 100nm, and still more preferably 5nm to 30 nm.

Thus, the efficiency of removing heavy metals from the adsorbent can be further improved while the durability of the adsorbent is ensured. Further, the average pore diameter can be adjusted by, for example, firing conditions in the firing step.

In the adsorption step, at least a part of the phosphorus compound (i.e., the phosphorus component adsorbed to the dolomite) in contact with the dolomite needs to be dissolved in the solvent, and for example, the other part of the phosphorus compound may be in a state of being dispersed in the solution. That is, the solvent constituting the above solution may also function as a dispersion medium.

The solvent is preferably an aqueous solution containing at least water, and may contain a solvent other than water. The solvent may contain components other than the phosphorus compound as a solute or a dispersoid.

In the present step, examples of the phosphorus compound to be brought into contact with the dolomite include: phosphoric acid and salts thereof (e.g., ammonium phosphate, diammonium phosphate, ammonium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, calcium dihydrogen phosphate, etc.), phosphorous acid and salts thereof, peroxyphosphoric acid and salts thereof, phosphonic acid and salts thereof, phosphinic acid and salts thereof, phosphorus oxide such as phosphorus pentoxide, phosphorus halide such as phosphorus pentachloride, phosphorus halide such as phosphorus oxychloride, calcium phosphide such as calcium monophosphide, tricalcium diphosphide, etc., and the like.

Among them, phosphoric acid and salts thereof are preferable.

In this manner, in the firing step, it is more preferable that the phosphate ions and Ca and Mg constituting the dolomite be chemically bonded to each other.

Further, the adsorbent can be produced economically and preferably by dissolving phosphorus contained in the sludge ash in the form of phosphate ions in an acid or alkaline solution and then chemically bonding the phosphorus to Ca and/or Mg constituting the dolomite.

The concentration of the phosphorus compound in the solution is preferably 0.01 to 80 mass%, more preferably 0.1 to 10 mass%, and still more preferably 1 to 2 mass%.

Thus, the amount of the phosphorus compound which cannot be adsorbed to the dolomite residue can be suppressed, and the amount of the phosphorus compound adsorbed to the dolomite can be increased, whereby the heavy metal removal efficiency of the adsorbent can be further improved.

Any phosphorus compound can be used, and examples thereof include: synthetic products, mineral-derived substances, activated sludge-derived substances, steel slag-derived substances, etc., preferably sludge ash-derived substances.

In this way, the use of the sludge ash source substance of the industrial waste as phosphorus, which is a valuable resource, is preferable from the viewpoint of efficient use of resources and reduction of industrial waste. In addition, it is also preferable from the viewpoint of reducing the cost of the adsorbent.

The ratio of the dolomite and the phosphorus compound is not particularly limited, and the amount of the phosphorus compound adsorbed on the dolomite is preferably 0.1 to 20 parts by mass, more preferably 1 to 2 parts by mass, in terms of phosphate ion content, for 100 parts by mass (%) of the dolomite and 100 parts by mass (%) of the dolomite.

Thus, the amount of the phosphorus compound which cannot be adsorbed to the dolomite residue can be suppressed, and the amount of the phosphorus compound adsorbed to the dolomite can be increased, thereby saving phosphorus which is more expensive than dolomite. Furthermore, the heavy metal removal efficiency of the adsorbent can be further improved.

In this step, the pH of the mixture containing the dolomite and the solution of the phosphorus-containing compound is preferably carried out under conditions of 2 to 12, more preferably 4 to 8.

Thus, the phosphorus compound can be more effectively adsorbed to the dolomite, and the heavy metal removal efficiency of the adsorbent can be further improved.

In this step, it is preferable to stir the mixture while stirring the mixture.

Thus, the phosphorus compound can be more effectively brought into contact with the dolomite, and the phosphorus compound can be more effectively adsorbed to the dolomite. In particular, the phosphorus compound can be more effectively adsorbed to the dolomite in the pores of the dolomite. As a result, the heavy metal removal efficiency of the adsorbent can be further improved.

For mixing the above mixture, various stirring apparatuses and various mixing apparatuses can be used.

The treatment time in this step (i.e., the contact time between the dolomite and the solution containing the dissolved phosphorus compound) is preferably 1 minute to 180 minutes, and more preferably 10 minutes to 60 minutes.

Thus, the reduction in productivity of the adsorbent can be effectively prevented, and the heavy metal removal efficiency of the adsorbent can be further improved.

The treatment temperature in this step is preferably 0 ℃ to 100 ℃, more preferably 10 ℃ to 80 ℃, and still more preferably 20 ℃ to 60 ℃.

Thus, the energy required for producing the adsorbent can be reduced, and the phosphorus compound can be more effectively adsorbed to the dolomite, and the process can be efficiently performed in a short time.

In the adsorption step, phosphorus is adsorbed to the dolomite in an aqueous solution in which the phosphorus component is dissolved, and then solid-liquid separation is performed (solid-liquid separation step).

Further, the phosphorus-adsorbed dolomite, which is the solid obtained in the solid-liquid separation step, may be subjected to a drying treatment (drying step).

The treatment temperature in the drying step is not particularly limited, but is preferably 300 ℃ or lower, and more preferably 70 ℃ to 300 ℃.

Then, the dolomite is adsorbed to the dried phosphorus, and the following firing step is performed. The firing process will be described in detail below.

< firing Process >

A firing process: the dolomite (i.e., the dolomite adsorbing the phosphorus component) brought into contact with the solution is fired.

In this manner, the phosphoric acid component is fixed to the adsorbent (i.e., the dolomite as the raw material), and the adsorption capacity of the heavy metal is improved as compared with the dolomite as the raw material. Particularly, the heavy metal adsorption capacity under alkaline conditions is remarkably improved.

Further, at least one of Ca and Mg constituting the dolomite forms chemical bonds (particularly ionic bonds) with P by firing to form at least one of a calcium phosphate compound and a magnesium phosphate compound, and the desorption of a phosphorus component when the adsorbent comes into contact with the object to be treated is effectively prevented in a wide pH range (particularly, a range of pH 5 or more), and excellent adsorption ability can be stably exhibited.

In addition, not only heavy metals but also F (fluorine) can be removed.

In addition, the phosphorus component can be dissolved appropriately in a low pH range (for example, a range of pH 3 or less), and the heavy metal adsorbed to the adsorbent can be eluted appropriately. In this way, the adsorbent and the heavy metal can be appropriately separated, and for example, the heavy metal can be appropriately reused. Particularly, it is advantageous for adsorbing noble metals (i.e., Au, Ag, Pt, Pd, Rh, Ir, Ru, Os), and rare metals (e.g., Cr, Mn, Co, Ni, Mo, W, Bi, etc.).

The above-described advantageous effects are obtained by adsorbing and immobilizing the phosphorus component on the adsorbent (i.e., dolomite) in the firing step, and cannot be obtained by merely mixing the dolomite with the phosphorus compound and bringing the solid into contact with the solid. More specifically, for example, in an aqueous solution containing phosphorus, the dolomite and the phosphorus compound are brought into contact with each other alone, and the reactivity is poor, and if the treatment object is treated under high-concentration alkaline conditions without performing the firing step, the elution of the phosphoric acid component is likely to occur, and the effect of improving the heavy metal removal efficiency cannot be stably obtained.

Examples of the calcium phosphate compound include: calcium phosphate (Ca (H)₂PO₄)₂And hydrate thereof), anhydrous calcium hydrogen phosphate (CaHPO)₄) HydroxyapatiteStone (HAP) (Ca)₁₀(PO₄)₆(OH)₂) And the like include phosphate ions and calcium ions.

Examples of the magnesium phosphate compound include: magnesium phosphate hydrate (Mg)₃(PO₄)₂And hydrate thereof), magnesium hydrogen phosphate hydrate ((MgHPO)₄)₂And hydrates thereof), magnesium pyrophosphate (Mg)₂P₂O₇) And the like include phosphate ions and magnesium ions.

The treatment temperature (maximum firing temperature) in the firing step is preferably 300 ℃ to 1000 ℃ inclusive, and more preferably 400 ℃ to 800 ℃ inclusive.

Thus, the energy required for producing the adsorbent can be reduced, and chemical bonding between the phosphate ions and Ca and/or Mg constituting the dolomite can be more effectively formed, so that the process can be efficiently performed in a short time.

The treatment time in the firing step (for example, heating time at a temperature of 200 ℃ or higher) is not particularly limited, but is preferably 0.3 to 10 hours, more preferably 1 to 5 hours, and still more preferably 2 to 3 hours.

Thus, the reduction in productivity of the adsorbent can be effectively prevented, and the heavy metal removal efficiency of the adsorbent can be further improved.

The heating in the firing step may be performed while keeping a substantially constant temperature, or may be performed while keeping a plurality of different stages of temperatures. The heating in the firing step may be performed at a substantially constant temperature rise rate or a substantially constant temperature fall rate, or at least one of the temperature rise rate at the time of temperature rise and the temperature fall rate at the time of temperature fall may be changed with time.

More specifically, for example, in the firing step, the temperature is raised at a predetermined temperature raising rate (i.e., a first temperature raising rate), and when the temperature reaches the predetermined temperature (i.e., the first temperature), the first temperature is held for a predetermined time (i.e., a first holding time) (i.e., the temperature raising rate is set to zero); then, the temperature is raised at a predetermined temperature raising rate (i.e., a second temperature raising rate) different from the first temperature raising rate, and the second temperature is held (i.e., the temperature raising rate is set to zero) for a predetermined time (i.e., a second holding time) when the predetermined temperature (i.e., the second temperature) is reached; then, the temperature is decreased at a predetermined temperature decrease rate (i.e., a first temperature decrease rate), and the third temperature is maintained (i.e., the temperature increase rate is set to zero) only for a predetermined time (i.e., a third maintenance time) when the predetermined temperature (i.e., the third temperature) is reached; then, the temperature is lowered at a predetermined temperature lowering rate (i.e., a second temperature lowering rate) different from the first temperature lowering rate.

The first temperature may be, for example, 100 ℃ to 300 ℃.

The second temperature may be, for example, a maximum firing temperature.

The third temperature may be, for example, 100 ℃ to 300 ℃.

The first holding time may be, for example, 10 minutes to 4 hours.

The second holding time may be, for example, 30 minutes to 5 hours.

The third holding time may be, for example, 10 minutes to 4 hours.

The first temperature rise rate may be set to, for example, 5 ℃/min to 20 ℃/min.

The second temperature rise rate may be, for example, 10 ℃/min to 40 ℃/min.

The first temperature decrease rate may be set to, for example, 2 ℃/min to 15 ℃/min.

The first temperature decrease rate may be set to, for example, 5 ℃/min to 20 ℃/min.

The firing step may be performed in any atmosphere, and is preferably performed in air.

Thus, the sintering process can adopt equipment with a simpler structure, the atmosphere composition does not need to be adjusted, and the like, and the productivity of the adsorbent can be improved. In addition, even when a phosphorus compound other than phosphoric acid (including phosphate) is used as a raw material, the calcium phosphate compound can be efficiently formed by adjusting the oxidation number of phosphorus in this step.

< hydration step >

A hydration step: the calcined material obtained in the above calcination step may be used as it is as an adsorbent, or may include a hydration step for hydrating the calcined material after the calcination step.

In this way, the chemical stability of the adsorbent can be improved. In addition, the hydrophilicity of the adsorbent is increased, and for example, when the treated material to be treated with the adsorbent contains water, the affinity between the adsorbent and the treated material (for example, wettability with respect to the treated material of the adsorbent) can be further increased. As a result, for example, the object to be treated can appropriately enter the pores in the adsorbent, and the heavy metal removal efficiency of the adsorbent is further improved.

The hydration step may be performed by contacting the calcined material with water, and for example, the calcined material may be immersed in a liquid containing water, or the calcined material may be sprayed with an aqueous solution containing water.

According to the method for producing an adsorbent of the present invention, an adsorbent capable of effectively removing heavy metals even in a high hydrogen ion concentration index (pH) state can be efficiently produced in a simple manner.

In the production method of the present invention, the ease of adsorption of various heavy metals can be adjusted by adjusting the production conditions, more specifically, the ratio of the dolomite-like phosphorus compound to the dolomite-like phosphorus compound, the heat treatment conditions in the firing step, and the like. Thus, for example, the selectivity for a specific heavy metal can be improved, and the method can be applied to recovery, purification, and the like of the specific heavy metal.

[ adsorbent ]

Next, the adsorbent of the present invention will be explained.

The adsorbent of the present invention is characterized by comprising a dolomite and phosphate ions, wherein at least a part of the phosphate ions are chemically bonded (particularly ionically bonded) to at least one of Ca and Mg constituting the dolomite to form at least one of a calcium phosphate compound and a magnesium phosphate compound.

Thus, an adsorbent can be provided which can effectively remove heavy metals even in a state of high hydrogen ion concentration index (pH value).

In particular, the adsorbent of the present invention can remove arsenic, which has been difficult to remove particularly at a high removal rate, at a high removal rate.

The adsorbent of the present invention can be produced by any method, and the adsorbent of the present invention can be efficiently produced by using the above-mentioned production method for the adsorbent of the present invention.

The adsorbent of the present invention preferably has a large part of phosphate ions chemically bonded to Ca and/or Mg constituting the dolomite.

More specifically, the amount of phosphate ion elution when 1g of the adsorbent and 10m of L of water are mixed at 25 ℃ is preferably 100ppm or less, more preferably 50ppm or less, and still more preferably 30ppm or less.

If these conditions are satisfied, phosphorus is more stably immobilized in the adsorbent, and heavy metals can be stably removed with excellent efficiency even when the adsorbent is used for a long time or a large amount of the object to be treated is treated (i.e., when a large amount of the object to be treated is brought into contact with the adsorbent).

Further, the elution amount of phosphate ions when the adsorbent and water are mixed can be obtained by the following method: for example, the measurement is performed after mixing the adsorbent and water and stirring for 1 hour.

The fact that the phosphate ions chemically bind to Ca and/or Mg constituting the dolomite can be confirmed by the following method: for example, when the adsorbent is contacted with water as described above and then contacted with a low pH liquid, the elution amount of phosphate ions is greatly increased.

More specifically, when 1g of the adsorbent and 10m L1N hydrochloric acid were mixed at 25 ℃, it was confirmed that the elution amount of phosphate ions was significantly increased.

The elution amount of phosphate ions when 1g of the adsorbent and 10m L1N hydrochloric acid are mixed at 25 ℃ is preferably 30% or more, more preferably 60% or more, and still more preferably 80% of the total amount of phosphorus contained in the adsorbent (i.e., the adsorption amount).

Under the conditions that the heavy metal removal capacity can be satisfied, more phosphorus can be fixed in the adsorbent, and particularly excellent heavy metal removal capacity can be obtained. Therefore, even when the adsorbent is used for a long time or a large amount of the object to be treated is treated (that is, when a large amount of the object to be treated is brought into contact with the adsorbent), heavy metals can be stably removed with excellent efficiency.

The elution amount of phosphate ions when the adsorbent is mixed with 1N hydrochloric acid can be obtained by the following method: for example, the adsorbent and 1N hydrochloric acid are mixed and stirred for 1 hour before measurement.

The adsorbent is typically a porous body.

In this way, the surface area per unit mass (or per unit volume) of the adsorbent can be increased, and the removal efficiency of the heavy metal can be further improved.

The average pore diameter of the adsorbent is not particularly limited, but is preferably 1nm to 200nm, more preferably 2nm to 100nm, and still more preferably 5nm to 30 nm.

Thus, the efficiency of removing heavy metals from the adsorbent can be further improved while the durability of the adsorbent is ensured.

The BET specific surface area of the adsorbent is not particularly limited, but is preferably 10m²More than g. As long as at 40m²Over 1000 m/g²Sufficient heavy metal removal efficiency can be obtained below/g.

Thus, the heavy metal removal efficiency of the adsorbent can be further improved.

The shape and size of the adsorbent are not particularly limited, and when the adsorbent is in the form of particles, the average particle diameter is preferably 0.5 μm to 20000 μm, more preferably 1 μm to 500 μm, and still more preferably 50 μm to 300 μm.

In this way, the surface area of the particles per unit mass (or per unit volume) of the adsorbent can be increased, the phosphorus component can be uniformly adsorbed to the adsorbent, the effect of preventing unintended aggregation of the particulate adsorbent can be obtained, and the flowability of the adsorbent and the ease of handling can be improved. In addition, the filling property of the container (i.e., the ease of filling and the following property to the shape of the container) can be improved, and the container can be easily molded into a desired shape.

[ adsorbent treatment method ]

Next, the adsorbent treating method of the present invention will be explained.

The treatment method of the present invention is characterized by bringing the adsorbent of the present invention into contact with a treatment object containing a heavy metal, and removing the heavy metal contained in the treatment object.

Thus, a treatment method capable of efficiently removing a heavy metal from a treatment object can be provided.

The form of the object to be treated in the case of performing the treatment method of the present invention is not particularly limited, and the object to be treated generally has fluidity, and examples thereof include: liquid (including paste and slurry) and/or gas.

In particular, the form of the object to be treated is preferably liquid. Thus, the treated material can be appropriately brought into contact with the adsorbent (for example, appropriately entered into the pores possessed by the adsorbent), and the heavy metal can be more effectively removed.

When the adsorbent is brought into contact with the object to be treated, the pH (hydrogen ion concentration index) of the mixture of the adsorbent and the object to be treated is preferably 5 or more, more preferably 10 or more, and still more preferably 11 or more and 14 or less.

Thus, the heavy metal removal efficiency of the adsorbent can be further improved. In particular, while the conventional adsorbents tend to have a significantly reduced heavy metal removal efficiency in the high pH range as described above, the adsorbents of the present invention have a particularly excellent heavy metal removal efficiency in the high pH range as described above. That is, when the adsorbent is used at a high pH as described above, the effect of the present invention can be more remarkably exhibited.

In particular, when the heavy metal to be removed is Pb (lead), the pH value of the adsorbent in contact with the object to be treated is preferably 5 or more, when the heavy metal to be removed is Cd (cadmium), the pH value of the adsorbent in contact with the object to be treated is preferably 8 or more, and when the heavy metal to be removed is a heavy metal other than Pb and Cd, the pH value of the adsorbent in contact with the object to be treated is preferably 10 or more.

The object to be treated may be any object as long as it is possible to include the heavy metal to be removed, and examples thereof include: industrial or laboratory, power plant, building demolition site, mine wastewater, combustion ash of sewage sludge, and liquids including these, well water, and the like.

The object to be treated may be any object including the possibility of heavy metals to be removed, regardless of whether or not heavy metals are actually included.

However, the content of the heavy metal in the object to be treated (however, if a plurality of heavy metals are included, the total of these heavy metals) is not particularly limited, but is preferably 0.001ppm to 100,000ppm, more preferably 0.01ppm to 10,000 ppm.

Thus, the removal rate (i.e., adsorption rate) of heavy metals can be particularly improved, and the content of heavy metals in the treated material after treatment can be particularly reduced. That is, the present invention can exert the effects more remarkably.

Although the embodiments suitable for the present invention have been described above, the scope of the present invention is not limited thereto.

For example, the adsorbent of the present invention is not limited to the one produced by the above method, as long as it contains dolomite and phosphate ions, and at least a part of the phosphate ions chemically bind to at least one of Ca and Mg constituting the dolomite to form at least one of a calcium phosphate compound and a magnesium phosphate compound.

The method for producing the adsorbent of the present invention may include steps other than the above-described steps (for example, a pretreatment step, an intermediate treatment step, a post-treatment step, and the like). For example, the firing step may be followed by a step of pulverizing or crushing the fired product, or a classification step. Further, the method may further include a molding step of molding the adsorbent into a predetermined shape.

In the above embodiment, the embodiment including the hydration step after the firing step is described as a typical example, and the method for producing the adsorbent of the present invention may not include the hydration step.

Specific examples of the present invention will be described in detail below, but the scope of the present invention is not limited to these examples

(1) Manufacture of adsorbents

(example 1)

First, 100m L hydrochloric acid adjusted to 1 mol/L was put into a 300m L conical flask and heated to 80 ℃.

After the completion of the stirring, solid-liquid separation was carried out, and the separated liquid phase (i.e., filtrate) was volume-scaled with a 500m L-capacity bottle, and the concentration of the phosphorus compound in the scaled solution was determined by molybdenum blue photometry, whereby the dissolution rate of phosphorus was 90% by mass.

Next, a 1 mol/L aqueous solution of sodium hydroxide was added to the solution to adjust the pH to 7.

Next, the pH-adjusted solution of the phosphorus compound was cooled to room temperature (25 ℃ C.), and 5g of separately prepared porous dolomite having an average pore size of 10 to 20nm was added to 500m L of the solution, and the mixture was stirred for 1 hour to allow the dolomite to adsorb the phosphorus compound (adsorption step).

After the completion of the stirring, solid-liquid separation is performed, and a firing treatment is applied to the dolomite having adsorbed the phosphorus compound (firing step). And (3) firing treatment: firstly, heating from room temperature to 200 ℃ at a heating rate of 10 ℃/min, and then keeping the temperature of 200 ℃ constant for 2 hours; secondly, heating to 800 ℃ (the highest firing temperature) at a heating rate of 20 ℃/minute, and keeping the temperature of 800 ℃ (the highest firing temperature) constant for 2 hours; secondly, cooling to 200 ℃ at a cooling speed of 5 ℃/min, and keeping the temperature of 200 ℃ for 2 hours; then, the temperature is reduced to room temperature at a temperature reduction rate of 10 ℃/min.

Next, the fired material obtained above was immersed in water to be hydrated, and then subjected to solid-liquid separation and natural drying. Then, the resultant was ground and ground in a grinding bowl to obtain a powdery adsorbent.

Further, the liquid phase (i.e., filtrate) after adsorbing the phosphorus compound to the dolomite was subjected to volume calibration using a 1000m L capacity bottle, and then the concentration of the phosphorus compound in the calibrated solution was determined by molybdenum blue photometry.

(example 2)

An adsorbent was produced in the same manner as in example 1, except that the maximum firing temperature under the firing treatment conditions was changed to 900 ℃.

(example 3)

An adsorbent was produced in the same manner as in example 1, except that the maximum firing temperature under the firing treatment conditions was changed to 700 ℃.

(example 4)

An adsorbent was produced in the same manner as in example 1, except that the maximum firing temperature under the firing treatment conditions was changed to 600 ℃.

(example 5)

An adsorbent was produced in the same manner as in example 1, except that the maximum firing temperature under the firing treatment conditions was changed to 400 ℃.

Comparative example 1

In this comparative example, dolomite used as a raw material in example 1 was used as it was as an adsorbent.

Comparative example 2

In this comparative example, dolomite hydroxide was used as it was as an adsorbent.

In addition, BET specific surface area data are the results of measurement using a specific surface area meter (TriStarII 3020, manufactured by Micromeritics Inc.) in each of the above examples, the average particle size of the adsorbent in each of the above examples is a value in the range of 200nm to 300nm, the pH of the mixture including dolomite and a solution of a phosphorus-containing compound in the adsorption step in each of the above examples is 6 or less, in each of the above examples, 1g of the adsorbent is mixed with 10m L of water at 25 ℃, the elution amount of phosphate ions measured after stirring for 1 hour is 10ppm or less, solid-liquid separation is performed, 1g of the adsorbent is mixed with 10m L1N hydrochloric acid at 25 ℃, and the elution amount of phosphate ions after stirring for 1 hour is 80% or more of the total amount of phosphorus contained in the adsorbent.

Further, the adsorbents of the above examples were analyzed for their components by X-ray diffraction (XRD), and it was confirmed that each of the adsorbents contained a calcium phosphate compound (i.e., calcium phosphate, anhydrous calcium hydrogen phosphate, and hydroxyapatite). As a representative, the result of X-ray diffraction (XRD) of the adsorbent of example 1 is shown in fig. 1.

Further, pore distributions of the adsorbents of example 3 and comparative example 2 are shown in fig. 2 and 3.

[ TABLE 1]

TABLE 1

(2) Evaluation of

First, a standard solution a and a standard solution B were prepared.

Standard solution a: including an arsenic (As) content of 2000ppb, virtually exclusive of other heavy metals, pH 13;

and standard solution B: comprises 2000ppb of each of arsenic (As), nickel (Ni), cadmium (Cd), lead (Pb) and chromium (Cr),

pH＝13。

then, 0.1g of the adsorbent in each of the above examples and comparative examples was added to 50m L of standard solution A, and the mixture was stirred for 1 hour, followed by solid-liquid separation, and the content of arsenic in the liquid phase was determined by ICP mass Spectrometry (Inductively Coupled plasma Mass Spectrometry), and the removal rate of the adsorbent was calculated from the content value.

Similarly, 0.1g of the adsorbent in each of the above examples and comparative examples was added to 50m L of standard solution B, and the mixture was stirred for 1 hour, followed by solid-liquid separation, and the content of each heavy metal in the liquid phase was determined by ICP mass spectrometry, and the removal rate of the adsorbent was calculated from the content.

A summary of these results is shown in table 2.

[ TABLE 2 ]

TABLE 2

Table 2 shows that, in the present invention, heavy metal arsenic can be removed (i.e., adsorbed) at a high removal rate (i.e., adsorption rate). In particular, even in a high pH state where it has been difficult to remove heavy metals at a high removal rate, heavy metals can be effectively removed. Similarly, in the present invention, heavy metals other than arsenic (nickel (Ni), cadmium (Cd), lead (Pb), and chromium (Cr)) can be removed (i.e., adsorbed) at a high removal rate (i.e., adsorption rate).

In contrast, in each comparative example, satisfactory results were not obtained.

Further, the adsorbents of the above examples and comparative examples were evaluated in the same manner as described above except that each of the liquids prepared in the same manner as the standard liquid a was prepared with the pH value varying in the range of 10 to 14 as the standard liquid, and as a result, in each of the examples, arsenic, which is a heavy metal, was removed (adsorbed) at a high removal rate (adsorption rate), as compared with each of the comparative examples, the removal rate for each of the heavy metals was low.

The relationship between the pH value and the arsenic removal rate when standard solutions containing arsenic, nickel, cadmium, lead and chromium each in an amount of 2000ppb were treated with the adsorbents of examples 1 to 5 and comparative examples 1 and 2 is shown in FIG. 4.

Further, the adsorbents of the above examples and comparative examples were evaluated in the same manner as described above except that each of the liquids prepared in the same manner as the standard liquid B was prepared with the pH value varying in the range of 10 to 14 as the standard liquid, and as a result, in the examples, arsenic, which is a heavy metal, was removed (adsorbed) at a high removal rate (adsorption rate), as compared with the comparative examples, in which the removal rate for each of the heavy metals was low. In addition, the adsorbents of the above examples can remove heavy metals other than arsenic at a high removal rate, as with arsenic.

The relationship between the pH value and the removal rate of arsenic when the standard solution (single solution) containing 2000ppb of arsenic and substantially not containing other heavy metals was treated with the adsorbent of example 3, and the relationship between the pH value and the removal rate of arsenic when the standard solution (mixed solution) containing 2000ppb of each of arsenic, nickel, cadmium, lead and chromium was treated with the adsorbent of example 3 are shown in fig. 5.

The removal rates of chromium in the range of pH 10 to 14 when standard solutions containing arsenic, nickel, cadmium, lead and chromium each in an amount of 2000ppb were treated using the adsorbents of examples 1 to 5 and comparative examples 1 and 2 are shown in FIG. 6.

Further, as the phosphorus compound used for producing the adsorbent, an adsorbent was produced in the same manner as described above except that the treatment of treating the sludge ash with an acid to elute it was changed to the treatment of treating the sludge ash with an alkali to elute it, and the evaluation was carried out in the same manner as described above, and as a result, the same result as described above was obtained.

Industrial applicability of the invention

The method for producing an adsorbent of the present invention comprises an adsorption step of bringing a dolomite into contact with a solution containing a dissolved phosphorus compound to adsorb a phosphorus component onto the dolomite and a firing step of firing the solution; the firing step is to fire the dolomite in contact with the solution. Therefore, it is possible to provide a method for producing an adsorbent which can efficiently remove a heavy metal even in a high hydrogen ion concentration index (pH) state. The adsorbent of the present invention comprises dolomite and phosphate ions, and at least a part of the phosphate ions are chemically bonded to at least one of Ca and Mg constituting the dolomite to form at least one of a calcium phosphate compound and a magnesium phosphate compound. Therefore, an adsorbent that can effectively remove heavy metals even in a state of high hydrogen ion concentration index (pH value) can be provided. In the treatment method of the present invention, the adsorbent according to the present invention is brought into contact with an object to be treated containing a heavy metal, and the heavy metal contained in the object to be treated is removed. Therefore, a treatment method capable of effectively removing heavy metals from the object to be treated can be provided. As described above, the method for producing an adsorbent for heavy metals, the adsorbent, and the treatment method of the present invention are industrially applicable.