CN101445952A - Purifying treatment method for waste silver electrolyte - Google Patents

Abstract

The invention discloses a purifying treatment method for waste silver electrolyte. The method aims to hydrolyze and precipitate impurity ions of copper and bismuth in the waste silver electrolyte through ammonia water neutralization and precipitation and separation, so as to purify silver electrolyte and improve quality and reclaiming ratio of silver powder. The method comprises the following method: A, ammonia water neutralization, namely, injecting the waste silver electrolyte containing silver, copper and bismuth ions into a neutralizing tank for mechanically stirring, adding ammonia water during stirring to neutralize, controlling pH value of the waste electrolyte to be 5 to 6, and hydrolyzing and precipitating the copper ions and the bismuth ions in the waste electrolyte; and B, precipitation and separation, namely, firstly stopping stirring, keeping the hydrolyzed waste electrolyte standing for at least 24 hours in the neutralizing tank or a precipitation tank to carry out precipitation and separation, returning the precipitated solution to be used as electrolyte, and conveying precipitated dregs after being washed and filtered to a converter for smelting. The method is mainly used for removing the impurity ions of copper and bismuth in the waste silver electrolyte.

Description

Purifying treatment method for waste silver electrolyte

Technical field

The present invention relates to a kind of purifying treatment method for waste silver electrolyte.More particularly, relate to a kind of method that copper, bismuth foreign ion are removed in hydrolysis from waste silver electrolyte.

Background technology

The processing of waste silver electrolyte is that silver is smelted an important step in producing, and directly the quality of silver powder is separated out in influence.On the one hand electrolytic solution is by after certain production time in silver-colored electrolysis production, and impurity wherein is as Cu ²⁺(bivalent cupric ion), Bi ³⁺Impurity such as (trivalent bismuth ions) is accumulation constantly, and the quality of silver powder is separated out in influence, must regularly handle; The processing that silver-colored on the other hand electrolysis contains the impurity such as Cu, Bi in the nitric acid waste electrolyte all is to adopt the pyrolysated method to handle all the time, this method adopts the straight fire of gas heating to concentrate, nitric acid is decomposed efflux a large amount of oxynitride obnoxious flavour of generation, though through the nitric acid tail gas treatment system, but poor effect causes the severe contamination to environment.And need expend a large amount of water and coal gas, steam, the treatment time is longer, handles the time that once electrolytic liquid approximately needs a week.

Summary of the invention

The object of the present invention is to provide a kind of purifying treatment method for waste silver electrolyte, this method is by adding ammoniacal liquor under room temperature and mechanical stirring, control the pH value of waste liquid in waste silver electrolyte, making the Cu in this waste liquid ²⁺And Bi ³⁺Hydrolytic precipitation gets off and is removed, and Ag ⁺Then stay behind the hydrolytic precipitation in the liquid and return silver-colored electrolyzer, remove the purpose that impurity improves the quality of cathode silver and the rate of recovery thereby reach.

For achieving the above object, technical solution of the present invention is: will contain Ag ⁺, Cu ²⁺, Bi ³⁺Deng waste silver electrolyte inject in the neutralizing well, under room temperature and churned mechanically condition, add the ammoniacal liquor neutralization, the pH value of control waste liquid, hydrolysis removes Bi in the scope of 3.5-4.5 ³⁺, in the scope of 5.0-6.0, remove Cu ²⁺, liquid leaves standstill and carried out precipitate and separate at least in 24 hours after the hydrolysis, and post precipitation liquid returns does the silver electrolyte use, and precipitation slag then send the converter melting after washing, filtration.

Though also can add the pH value that NaOH (caustic alkali) adjusts solution in waste silver electrolyte, the NaOH adition process promptly generates bolarious silver suboxide precipitation, causes a large amount of losses of precious metal silver, and its chemical equation is as follows:

2AgNO ₃+2NaOH＝2NaNO ₃+Ag ₂O↓+H ₂O

Because it is very fast to add NaOH neutralization reaction speed, the difficult control of its add-on, though the impurity hydrolytic precipitation is more complete in the liquid of neutralization back, Ag in the solution ⁺(silver ions) also is hydrolyzed thereupon and precipitates, Ag in the liquid of neutralization back ⁺Loss is bigger.So, should not select NaOH to adjust the pH value of solution.

The ammoniacal liquor neutralization is to utilize the degree of stability of material in the aqueous solution to depend primarily on the pH value of solution, this basic theory of the activity alpha of current potential E and reaction, difference according to the activity of pH value, current potential and the reaction of each impurity in the electrolytic solution, regulate the pH value of electrolytic solution, make impurity in electrolytic solution hydrolytic precipitation and being removed in its corresponding pH value scope.Relevant Me-H ₂O is E ⁰-pH ⁰Numerical value sees Table 1.

Relevant Me-the H of table 1 ₂O is E ⁰-pH ⁰Numerical value

As can be known from Table 1, select the pH value in 4.6-6.32 scopes, can make BiO in the solution ⁺, Cu ²⁺Ion converts Cu (OH) to ₂, Bi ₂O ₃Precipitate and isolate etc. solid-state goods and materials, and Ag ⁺Still stay in the solution, reduce BiO in the solution thereby reach ⁺, Cu ²⁺The purpose of ionic concn plays the effect of cleaning waste electrolyte.

Because silver ammino ion and ammoniacal copper complex ion are similar with weak electrolyte in the aqueous solution, there are complex ion and form its central ion, the dissociation equilibrium between the ligand:

The stability constant of the common complex ion of table 2

As known from Table 2: silver ammino ion Ag (NH ₃) ₂ ⁺Stability constant 1.6 * 10 ⁷Than ammoniacal copper complex ion Cu (NH ₃) ₂ ⁺Stability constant 7.4 * 10 ¹⁰Little, Cu (NH is described ₃) ₂ ⁺Than Ag (NH ₃) ₂ ⁺More stable.According to the while equilibrium principle, when pH value in the solution is 4.6-6.32, Cu (NH ₃) ₂ ⁺Under can not the situation of stable existence, Ag (NH ₃) ₂ ⁺Also can not stable existence.Explanation adopts the technology of ammonia treatment waste silver electrolyte can not have Ag (NH once more ₃) ₂ ⁺Negative impact.And pH value can not the stable existence ammoniacal copper complex ion in the scope of 4.6-6.32 in the solution, and copper will be with CuO, Cu ₂The form of O exists.When explanation added ammoniacal liquor in silver salt solution, the copper in the waste silver electrolyte can be cleaned away.

The invention is characterized in following steps:

The neutralization of A, ammoniacal liquor is that the waste silver electrolyte with argentiferous, copper, bismuth ion injects in the churned mechanically neutralizing well, adds ammoniacal liquor while stirring and neutralizes, and the pH value of controlling above-mentioned waste liquid is 5-6, makes cupric ion and bismuth ion hydrolytic precipitation in the waste liquid;

B, precipitate and separate are to stop earlier stirring, again with the waste liquid after the said hydrolyzed in neutralizing well or settling bath, leave standstill and carried out precipitate and separate at least in 24 hours, post precipitation liquid returns makes silver electrolyte usefulness, precipitation slag is then through washing, be sent to the converter melting after filtering.

Described mechanical stirring speed is 20-22 rev/min.

The invention has the beneficial effects as follows: 1, waste silver electrolyte is handled and is given off a large amount of nitric acid tail gas when adopting the primary thermolysis process, pollution to environment is very serious, can not adapt to environmental protection requirement, now adopt ammonia liquor neutralization process Processing Ag electrolysis waste solution, there has not been the discharging of nitric acid tail gas, the execute-in-place environment is greatly improved, and has eliminated atmospheric pollution.2, improve preceding every month processing once electrolytic waste liquid 12M ³Need about 10 days consuming time, expend coal gas approximately: 120000 cubes, the electrolysis waste solution that improves the same quantity of aftertreatment only needed about 3-4 days, needed ammoniacal liquor 600-700 liter, did not need to consume coal gas.Do not adopt thermolysis process, every month reduces nitric acid and consumes about 1 ton.

Year is saved gas consumption: 12 * 120000m ³* 0.4 yuan/m ³=59.25 (ten thousand yuan)

Year save nitric acid consumption: 12t * 2480 yuan/t=2.9 (ten thousand yuan)

Year increases ammoniacal liquor consumption: 12 * 700 liters * 1.77 yuan/liter=14868 yuan

Year economic benefit is approximately: 59.25+2.9-1.4868 ≈ 60.6 (ten thousand yuan)

Description of drawings

Accompanying drawing is a process flow sheet of the present invention.

Embodiment

Below in conjunction with accompanying drawing the present invention and embodiment thereof are described in further detail.

Referring to accompanying drawing, the invention is characterized in following steps:

The neutralization of A, ammoniacal liquor is that the waste silver electrolyte with argentiferous, copper, bismuth ion injects in the churned mechanically neutralizing well, adds ammoniacal liquor while stirring and neutralizes, and the pH value of controlling above-mentioned waste liquid is 5-6, makes cupric ion and bismuth ion hydrolytic precipitation in the waste liquid;

B, precipitate and separate are to stop earlier stirring, again with the waste liquid after the said hydrolyzed in neutralizing well or settling bath, leave standstill and carried out precipitate and separate at least in 24 hours, post precipitation liquid returns makes silver electrolyte usefulness, precipitation slag is then through washing, be sent to the converter melting after filtering.

Described mechanical stirring speed is 20-22 rev/min.

Below tabulation provides each embodiment:

Waste silver electrolyte neutralization precipitation industrial implementation example data

The technological process of each embodiment is all identical, and example 2 is to adopt NaoH to make neutralizing agent, so Ag ⁺Loss bigger, containing Ag in the precipitation slag is 35%, should not adopt.PH value is to use artificial controlled in the scope of 5-6 by precision test paper, uncontrollable exact value, and stirring velocity also is to use artificial controlled in 20-22 rev/min scope by step-down gear.

Ammoniacal liquor adopts " starry sky board " 2500ml/ bottled, molecular formula: NH ₃, molecular weight: 17.03, content 25.0-28.0%, the place of production: Zhuzhou Inst. of Chemical Industry, Hunan Prov. produces.

Precision test paper adopts " trying three boards ", two kinds of pH value 3.8-5.4 and 5.4-7.0, and the place of production: Chinese Shanghai three likes to think reagent company limited (former Shanghai reagent three factories).

Claims (2)

1. purifying treatment method for waste silver electrolyte is characterized in that following steps:

The neutralization of A, ammoniacal liquor is that the waste silver electrolyte with argentiferous, copper, bismuth ion injects in the churned mechanically neutralizing well, adds ammoniacal liquor while stirring and neutralizes, and the pH value of controlling above-mentioned waste liquid is 5-6, makes cupric ion and bismuth ion hydrolytic precipitation in the waste liquid;

B, precipitate and separate are to stop earlier stirring, again with the waste liquid after the said hydrolyzed in neutralizing well or settling bath, leave standstill and carried out precipitate and separate at least in 24 hours, post precipitation liquid returns makes silver electrolyte usefulness, precipitation slag is then through washing, be sent to the converter melting after filtering.

2. by the described cleaning method of claim 1, it is characterized in that described mechanical stirring speed is 20-22 rev/min.