CN100390310C

CN100390310C - Method for recovering silver from low silver contained industrial waste water

Info

Publication number: CN100390310C
Application number: CNB2006101246146A
Authority: CN
Inventors: 肖珲; 郑春到; 赵鹭娜; 欧阳辉; 刘昌勇; 梁亚群; 胡建辉
Original assignee: JIANGXI COPPER CORP GUIYE BRANCH
Current assignee: JIANGXI COPPER CORP GUIYE BRANCH
Priority date: 2006-09-22
Filing date: 2006-09-22
Publication date: 2008-05-28
Anticipated expiration: 2026-09-22
Also published as: CN1928133A

Abstract

One process of recovering silver from silver-containing industrial waste water includes the following steps: adding Pb grain into the industrial waste water and stirring for 1 hr to react said replace partial Ag; eliminating unreacted Pb grain and adding iodide salt to convert Ag into insoluble silver iodide; adding iodide into sodium sulfide solution via stirring to obtain silver sulfide precipitate for recovery and converting iodine into sodium iodide for reuse. One other process includes the following steps: adding potassium iodide or sodium iodide into the industrial waste water to obtain silver iodide precipitate and adding sodium sulfite simultaneously to raise the silver precipitating efficiency; and adding the silver iodide into sodium sulfide solution. The former is suitable for industrial waste water with lower silver content of 8-40 mg/L, and the later for that with silver content of 40-270 mg/L. The processes are low in cost and simple in operation.

Description

Method for recovering silver from low-silver-content industrial wastewater

Technical Field

The invention relates to the field of metallurgical industry, in particular to a method for recovering silver from low-silver-content industrial wastewater.

Background

When the chlorination pretreatment process is adopted to remove impurities in the copper anode slime, a small amount of silver enters the wastewater, the average silver content of the silver is about 170mg/L, and the silver contains 17-20 g/L, As 10-19 g/L of Cu, 0.4-39 g/L of Sb0.5-27 g/L, Cl 18-21 g/L of H and₂SO₄60-170 g/L. The silver in the wastewater is difficult to recover due to complex impurity components and large fluctuation. According to the reports of related data, silver dissolved in industrial wastewater is mainly in the form of chloride complexIn the conventional recovery process, the dissolved silver is replaced with an active metal such as zinc powder or iron powder. Because the wastewater contains a large amount of arsenic, the highly toxic arsenic hydride is easily generated; the test also shows that the cost is incredible because the silver consumption is more than 100 g per one g of replacement. The silver is directly deposited by iodide salt, the consumption is 3-5 times of the theoretical amount, although part of iodide salt can be recycled, the cost is also difficult to accept.

Disclosure of Invention

The invention aims to provide a method for recovering silver from low-silver-content industrial wastewater, which has the advantages of low production cost, simple process and convenient operation.

The method for recovering silver from low-silver-content industrial wastewater comprisesthe following steps of (the silver content of the low-silver-content industrial wastewater is 8-40 mg/L): 1. adding lead particles into the industrial wastewater at the temperature of 30-60 ℃ to perform stirring reaction for more than 1 hour, so that part of silver is replaced firstly; 2. removing unreacted lead particles, and adding iodide salt to carry out silver precipitation so as to convert silver into insoluble silver iodide; 3. adding silver iodide into sodium sulfide solution, stirring to recover silver in the form of silver sulfide precipitate, and converting iodine into sodium iodide for reuse.

The basic chemical reaction is as follows:

Pb+2AgCl＝2Ag+PbCl₂

(AgCl₄)^3-+I^-→Agl+4Cl^-

AgI+Na₂S→Ag₂S+2NaI

the method for recovering silver from low-silver-content industrial wastewater comprises the following steps of (the industrial wastewater with low silver content contains 40-270 mg/L of silver): 1. adding potassium iodide or sodium iodide into industrial wastewater to precipitate silver to obtain silver iodide, and simultaneously adding sodium sulfite to improve the silver precipitation efficiency of adding potassium iodide or sodium iodide by utilizing the reducibility of sodium sulfite; 2. the method is characterized in that silver iodide is added into a sodium sulfide solution, so that silver is recovered in a form of silver sulfide precipitation, iodine is converted into sodium iodide again for reuse, and the iodine consumption is reduced by 30-50% compared with the method of directly adding iodide salt.

The basic chemical reaction is as follows:

(AgCl₄)^3-+I^-→AgI+4Cl^-

Sb⁵⁺+2I^-＝Sb³⁺+I₂

I₂+Na₂SO₃+H₂O＝Na₂SO₄+2HI

AgI+Na₂S→Ag₂S+2NaI

the method for recovering silver from low-silver-content industrial wastewater has the advantages of low production cost, simple process and convenient operation.

Detailed Description

Example 1: in 3 liters of solution containing 13mg/L of silver, 0.31 g of crude lead is added to replace the silver, so that the silver content of the solution is reduced to 9mg/L, the precipitation rate of the silver is 30.76 percent, 0.22 g of KI is added to precipitate the silver, the solution after silver precipitation contains 2mg/L of silver, and the cumulative precipitation rate of the silver is 84.62 percent.

Example 2: 3 g of sodium sulfite and 0.80 g of KI are added into 3 liters of solution containing 95mg/L of silver to precipitate the silver, the solution after silver precipitation contains 6mg/L of silver, and the precipitation rate of the silver is 93.68 percent.

Example 3: in 3 liters of solution containing 83mg/L of silver, after 1 gram of sodium sulfite, 0.31 gram of KI is added for silver precipitation, the solution after silver precipitation contains 28mg/L of silver, and the precipitation rate of the silver is 66.27 percent.

Example 4: in 3 liters of solution containing 45mg/L of silver, after 6 grams of sodium sulfite, 0.42 grams of KI is added for silver precipitation, the solution after silver precipitation contains 12mg/L of silver, and the cumulative precipitation rate of the silver is 73.33 percent.

Example 5: in 3 liters of solution containing 83mg/L of silver, after 9 grams of sodium sulfite, 0.25 grams of KI is added for silver precipitation, and the solution is aged for 36 hours, wherein the silver content of the solution after silver precipitation is 1mg/L, and the cumulative precipitation rate of the silver is 98.80 percent.

Claims

1. A method for recovering silver from low silver-containing industrial wastewater is characterized in that: it comprises the following steps:

(1) adding lead particles into industrial wastewater containing 8-40 mg/L of silver at 30-60 ℃ to perform stirring reaction for more than 1 hour, so that part of silver is replaced first;

(2) removing unreacted lead particles, and adding iodide salt to carry out silver precipitation so as to convert silver into insoluble silver iodide;

(3) adding silver iodide into sodium sulfide solution, stirring to recover silver in the form of silver sulfide precipitate, and converting iodine into sodium iodide for reuse.

2. A method for recovering silver from low silver-containing industrial wastewater is characterized in that: it comprises the following steps:

(1) adding potassium iodide or sodium iodide into industrial wastewater containing 40-270 mg/L of silver to precipitate silver to obtain silver iodide, and simultaneously adding sodium sulfite;

(2) and adding silver iodide into the sodium sulfide solution to recover silver in the form of silver sulfide precipitate, and converting iodine into sodium iodide for reuse.