JP2641239B2 - Silver adsorbent and method of using the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a silver adsorbent for use in a number of silver-related applications, such as silver recovery and purification, and the manufacture of silver compounds, and methods of using the same. Things.

(Conventional technology and its problems) As a conventional adsorbent having a property of adsorbing silver,
Activated carbon, kaolin diatomaceous earth, bone charcoal and the like are used as inorganic adsorbents, and ion exchange resins and chelate exchange resins are used as organic types.

The former is often based on physical adsorption, and is less likely to deteriorate even if the processing solution contains a strong alkali, a strong acid, or an oxidizing agent, but has the drawback of low adsorption capacity and distribution ratio.

The latter is adsorbed by chemisorption and has a higher distribution ratio than the former, but the adsorption capacity is as large as several tens of grams per resin because the functional groups are bonded to the resin base material. is not. Further, a strong alkali or strong acid solution, or a solution containing an oxidizing agent or the like has a disadvantage that undesirable phenomena such as deterioration and swelling of the resin occur.

Furthermore, when an aqueous solution of silver and another coexisting metal is treated, it is very difficult to selectively adsorb only silver due to the influence of coexisting metal ions.

(Object of the Invention) The present invention has been made in view of such problems,
Offers an inorganic silver adsorbent that has strong selectivity for silver ions, has an adsorption capacity about 10 times that of the conventional one, and has little deterioration in handling, and a method of using the same. Things.

(Means for Solving the Problems) The present inventors have conducted research to solve the above-mentioned problems, and have accomplished the present invention. Adsorbents silver according to the invention, characterized in that comprising a titanium oxide represented by the rational formula _{X 2 O · 4TiO 2 · nH} 2 O, its use is rational formula X ₂
O · 4TiO ₂ · nH replace X of titanium oxide represented by ₂ O with hydrogen, it is characterized in that for use in silver adsorbed as hydrated titanium oxide.

(Operation) The operation of the present invention will be described below.

Adsorbents silver according to the invention, rational formula _{X 2 O · 4TiO 2 · nH} 2 O
And a compound represented by the following formula, wherein X in the exponential formula of the titanium oxide is any one of potassium, sodium, and ammonium.

When silver is adsorbed, the titanium oxide of the adsorbent is replaced in advance with X represented by the chemical formula X ₂ O.4TiO ₂ .nH ₂ O by hydrogen to obtain a hydrated titanium oxide (chemical formula H ₂ O.4TiO ₂ · nH ₂ O) (1 formula)
Used for silver adsorption.

Silver adsorption is based on hydrated titanium oxide substituted with hydrogen
Reaction of H ₂ O ・ 4TiO ₂・ nH ₂ O) with silver ion (Ag ⁺ ) (2
Equation).

X ₂ O ・ 4TiO ₂・ nH ₂ O ＋ HNO ₃ → H ₂ O ・ 4TiO ₂・ nH ₂ O ＋ XNO ₃ … 1
Formula H ₂ O.4TiO ₂ .nH ₂ O + Ag ⁺ → Ag ₂ O.4TiO ₂ .nH ₂ O + H ⁺ ... Formula 2 The elution of the adsorbed silver is preferably carried out with an appropriate concentration of acid, and most preferably nitric acid. (Equation 3). This is because elution with nitric acid also serves as a regeneration step as hydrated titanium oxide, and silver can be adsorbed as it is or after washing with water. Elution can also be carried out with an aqueous solution of a suitable concentration such as sodium nitrate, potassium nitrate, ammonium nitrate, sodium hydroxide, potassium hydroxide, ammonium water, etc.
Formula), it is necessary to perform a regeneration treatment of the adsorbent.

Ag ₂ O ・ 4TiO ₂・ nH ₂ O ＋ 2HNO ₃ → H ₂ O ・ 4TiO ₂・ nH ₂ O ＋ 2AgNO ₃
… 3 formulas Ag ₂ O ・ 4TiO ₂・ nH ₂ O ＋ 2KNO ₃ → K ₂ O ・ 4TiO ₂・ nH ₂ O ＋ 2AgNO ₃
… 4 formulas K ₂ O ・ 4TiO ₂・ nH ₂ O ＋ 2HNO ₃ → H ₂ O ・ 4TiO ₂・ nH ₂ O ＋ 2KNO ₃ …
Formula 5 The concentration of the eluent varies depending on the dissolution conditions. However, when nitric acid is used as the eluent, the concentration is 0.1 N or more, preferably 1
It is more than specified. When the other eluents are used, they are almost the same, and the pH may be adjusted as needed.

In addition, acids other than nitric acid such as hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid and sodium chloride, sodium sulfate, sodium carbonate, sodium hydrogen sulfate, sodium phosphate, sodium hydrogen phosphate, sodium acetate, potassium chloride,
Potassium sulfate, potassium carbonate, potassium hydrogen sulfate, potassium phosphate, potassium hydrogen phosphate, potassium acetate, ammonium chloride, ammonium sulfate, ammonium carbonate,
Silver can be eluted with an alkali metal salt that does not contain nitric acid, such as ammonium hydrogen sulfate, ammonium phosphate, ammonium hydrogen phosphate, and ammonium acetate, but silver chloride and other insoluble salts may form in the eluent, or the solubility may be insufficient. Therefore, care must be taken in selecting an eluent other than nitric acid, nitrate, and alkali hydroxide.

When salts or alkali hydroxides were used as the eluent, the adsorbent could not be reused unless the adsorbent was regenerated, so that the regeneration was performed with an acid having an appropriate concentration, preferably 1N or more. It can be reused as an adsorbent later (formula 5).

By the above action, the silver adsorbent according to the present invention can adsorb and desorb silver.

The silver adsorbent according to the present invention has an advantage that the amount of silver adsorbed per adsorbent is larger than that of the conventional one.
This is titanium oxide (H ₂ O ・ 4TiO ₂・ H ₂ O: molecular weight 337.6)
2 moles of silver (molecular weight: 107.87) is adsorbed theoretically to 1 mole, and becomes Ag ₂ O · 4TiO ₂ · H ₂ O (molecular weight: 551.3). Therefore, titanium oxide (H ₂ O · 4TiO _{This is because} the theoretical amount of silver absorbed per 1 kg of ₂ · H ₂ O) is 639 g. In actual application, the limit of the silver adsorption amount is up to about two-thirds of the theoretical value, titanium oxide _{(H 2 O · 4TiO 2 ·} H 2 O) 1kg
Up to about 400 g of silver can be adsorbed per unit weight of the silver adsorbent according to the present invention due to the large number of functional groups per unit weight.

In addition, conventional inorganic adsorbents are often based on physical adsorption, and have the drawback that the adsorbed amount is small.However, the silver adsorbent of the present invention utilizes an ion exchange reaction. And the characteristic feature of conventional inorganic adsorbents: "the processing liquid is hardly deteriorated even if it contains a strong alkali, a strong acid, or an oxidizing agent".

Further, it has excellent separation characteristics between silver and other metals, and can selectively adsorb silver. This is thought to be due to the fact that the functional group of the titanium oxide is monovalent by hydrogen substitution and the valence of silver is also monovalent, and that other metals are mostly polyvalent except for alkali metals. I can say that.

As the silver adsorbent according to the present invention, a powder of X ₂ O.4TiO ₂ .nH ₂ O may be used as it is, but it is more convenient to process it into granules because handling becomes easier. When the particles are processed into particles, a binder or an extender may be added or the particles may be made porous, and X ₂ O.4TiO ₂ .nH ₂ O may be contained in the adsorbent.

 Examples of the present invention will be described below.

Example 1 Potassium titanate (K ₂ O.4TiO ₂ ) was placed in one beaker.
Take 5 g, add 300 ml of dilute nitric acid (3N), replace potassium in potassium titanate with hydrogen, and add hydrated titanium oxide (H _{2
O · 4TiO 2 · H 2 O} ) and the. This was packed in a cylindrical column having a capacity of 300 ml, and a silver adsorption operation was performed.

Silver nitric acid solution (silver concentration: 3.2g /, pH = 2.8)
At a speed of 2, the liquid was passed through the lower part of the column packed with the hydrated titanium oxide to perform the adsorption operation of silver. 13.2 After passing through, the concentration of silver in the passing solution became 0.1 g /, so the passing was stopped.

The adsorption amount of silver was as high as 422 g / kg of hydrated titanium oxide.

The column after the adsorption of silver was washed with 1 pure water at SV = 20, then the silver was eluted with 500 ml of 6N nitric acid, the adsorbent was regenerated, and the column was washed with 500 ml of washing water and mixed. Thus, a silver eluent 1 (Ag: 41.8 g /) was obtained.

The above-mentioned acidic solution of silver nitrate was passed through the column again, and was passed until the concentration of silver in the passing solution reached about 0.1 g /.

The operation of silver adsorption → silver elution / adsorbent regeneration → washing → (silver adsorption) was repeated 50 times by the above method, but no decrease in adsorbent capacity was observed.

(Example 2) In a 3 beaker, 10 g / solution of silver nitrate 1 (pH = 5,
Ag: 6.35g /) and hydrated titanium oxide (H ₂ O ・ 4TiO ₂・ H ₂ O) 10
g was mixed and stirred for 20 minutes to adsorb silver. 4.2 g of silver was adsorbed on the hydrated titanium oxide, and the pH of the liquid after the adsorption became 1.5. After filtering and washing the hydrated titanium oxide after adsorbing silver, the hydrated titanium oxide and nitric acid (1+
1) 200 ml was mixed and stirred for 20 minutes.
5% eluted. After standing for 1 hour, the supernatant was removed, and 200 ml of nitric acid (1 + 1) was further added. After mixing and stirring for 20 minutes, most of the remaining 5% silver was eluted.

(Conventional example) 100 ml (about 90 g) of a cation exchange resin was packed in a cylindrical column having a capacity of 300 ml, and a silver adsorption operation was performed.

Silver nitric acid solution (silver concentration: 3.2g /, pH = 2.8)
At a speed of 2, the solution was passed through the lower part of the column packed with the above-mentioned cation exchange resin to perform the adsorption operation of silver. At the passage of 1.2, the passing of the liquid was stopped because the concentration of silver in the passing liquid became 0.1 g /.

The adsorption amount of silver was 38.4 g per cation exchange resin, which was lower than that in Example 1.

(Example 3) An acidic solution of silver containing copper, iron and nickel (Ag: 0.73 g /
, Cu: 1.02 g /, Fe: 0.51 g /, Ni: 0.67 g /, pH = 1.
0) 20 of 5 and 25 g of hydrated titanium oxide (H ₂ O ・ 4TiO ₂・ H ₂ O)
The mixture was stirred for minutes to adsorb silver. After standing for 1 hour, the supernatant was analyzed and the silver was 0.01 g /, copper,
The concentrations of iron and nickel did not change.

(Effect of the Invention) The silver sorbent according to the present invention is about
It has 10 times the capacity and has features such as selectivity to silver and little deterioration. Further, it has a feature that it can be easily adsorbed and regenerated as in the case of the conventional cation exchange resin, and thus greatly contributes to the industry.

Claims (2)

(57) [Claims] 1. A titanium oxide represented by the chemical formula X ₂ O.4TiO ₂ .nH ₂ O, wherein X includes a titanium oxide in which one of sodium, potassium and ammonium is contained. Silver adsorbent. 2. The titanium oxide-containing silver adsorbent of claim 1 represented by the chemical formula X ₂ O.4TiO ₂ .nH ₂ O, wherein X of said titanium oxide is replaced with hydrogen, and hydration is performed. A method for using a silver adsorbent, which is used for adsorption of silver as titanium oxide.