CN110607450B

CN110607450B - Method for recovering palladium in printed circuit board by selective leaching precipitation

Info

Publication number: CN110607450B
Application number: CN201911034979.3A
Authority: CN
Inventors: 张承龙; 周永杰; 王瑞雪; 马恩; 白建峰; 王景伟
Original assignee: Shanghai Polytechnic University
Current assignee: Shanghai Polytechnic University
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2021-03-30
Anticipated expiration: 2039-10-29
Also published as: CN110607450A

Abstract

The invention discloses a method for recovering palladium in a printed circuit board by selective leaching precipitation. The method takes waste circuit boards and components as raw materials, an anhydrous organic solvent-bromide system is added for selective leaching reaction, the reaction time is 30-90min, the leaching is finished and then the filtering is carried out, a selective precipitator is added into the filtered leaching solution to precipitate palladium in the leaching solution, and the purification and enrichment of the palladium are realized.

Description

Method for recovering palladium in printed circuit board by selective leaching precipitation

Technical Field

The invention relates to a method for recovering palladium in a printed circuit board by selective leaching precipitation, belonging to the technical field of metal recovery and solid waste recycling.

Background

The population of China is large, the generation amount of electronic wastes is huge, the quantity of the electronic wastes is increased along with the acceleration of the updating and upgrading time of electronic products, the Li jin professor makes a conservative estimate on the market of the electronic wastes in China, the generation amount of the electronic wastes is expected to reach 1000 ten thousand tons every year by 2020, and the generation amount of the electronic wastes reaches 2000-2500 ten thousand tons every 2040 years. The treatment of electronic waste has become an urgent problem to be solved all over the world, and printed wiring boards are used in almost all electronic and electrical products, so the treatment of printed wiring boards is the key point for the treatment and utilization of electronic waste. It is reported that about 1300g of silver, 490g of gold and 99g of palladium are contained in a liquid crystal display panel of a 1t computer. The circuit board contains 450g/t of gold, 450g/t of silver, 110g/t of palladium and 30g/t of platinum. The economic value is very considerable.

On the one hand, gold is an important "strategic resource" as a worldwide currency due to the unique physical and chemical properties of noble metals, and palladium is also widely used in industrial applications such as automotive parts, chemical catalysts, electronic parts and materials, and the like. On the other hand, precious metals are scarce resources and have a small reserve, and only a few tenths of grams to tens of grams of platinum group metals are obtained by smelting 1t of platinum group metal ores. The environmental pollution is large during smelting, and palladium is easy to enter a biosphere through the absorption of plant roots after entering the environment, thereby threatening the health of human beings. There is a need to enhance the recovery of precious metals from waste resources. The method for recovering noble metals comprises a pyrogenic process and a wet process, wherein the basic principle of the pyrogenic process is to strip off non-metallic substances by high-temperature heating, and the recovery rate of the noble metals in the method reaches over 90 percent, but the method also has many defects, such as large energy consumption, large generation amount of waste gas and waste residue, and complex subsequent separation procedure due to the fusion of all metals. The wet extraction technology for noble metal palladium mainly utilizes strong acid and corrosive reagents to leach metals in electronic wastes, and utilizes the characteristic that ammonium chloropalladate or dichlorodiamminepalladium is easy to selectively precipitate to separate and purify after acid dissolution, and the method has the advantages of single flow, low yield, high palladium impurity content and unsuitability for recovering a low-palladium-content solution. In addition, there are a concentration roasting method, a copper/iron substitution method, and an activated carbon adsorption method. The concentration roasting method and the copper/iron replacement method are complex to operate, toxic gas is easy to generate, palladium contains more impurities, the activated carbon adsorption method needs pretreatment, desorption and regeneration, and the adsorption efficiency of the palladium is low.

Therefore, a leaching system for selectively dissolving out palladium in the circuit board is explored, and a process for selectively precipitating palladium is worth researching.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a method for selectively leaching, precipitating and recovering palladium in a printed circuit board. According to the method, the palladium in the printed circuit board is selectively leached by using an anhydrous organic solvent-bromide system, and then the palladium ions are selectively precipitated by using a selective precipitator, so that the high-selectivity leaching of the palladium in the printed circuit board is realized.

The invention adopts an anhydrous organic solvent-bromide system to selectively leach palladium in the circuit board, selectively dissolves the palladium into palladium ions, mainly utilizes the system to have a leaching rate superior to other metals in the printed circuit board, and reduces the dissolution of base metals; the precipitation of palladium is realized by adding selective precipitator into the leaching solution to achieve the effect of separation and selection, and the technical scheme of the invention is as follows:

the invention provides a method for recovering palladium in a printed circuit board by selective leaching precipitation, which comprises the following steps:

adding waste printed circuit board powder into an anhydrous polar aprotic solvent according to the solid-liquid mass-volume ratio of 1: 5-1: 20g/ml, then adding bromide salt, carrying out a leaching experiment for 30-90min, filtering to obtain a leaching solution and filter residues after leaching is finished, adding a selective precipitator into the leaching solution, wherein the concentration of the precipitator is 0.01-0.5mol/L, the volume ratio of the precipitator solution to the leaching solution is 1: 1-1: 5, precipitating palladium ions in the leaching solution, filtering to obtain crude palladium, and further refining to obtain high-purity palladium sponge.

The bromide salt is one or more of anhydrous potassium bromide, anhydrous sodium bromide and anhydrous copper bromide.

The feeding ratio of the bromide salt to the anhydrous polar aprotic solvent is 1: 4-3: 2 mol/L.

The aprotic polar solvent is one or more of dimethyl sulfoxide, hexamethylphosphoric triamide, N-dimethylformamide, N-dimethylacetamide and N, N-methylpyrrolidone.

The precipitant is selected from one or two of dimethylglyoxime and sodium butylxanthate.

When the precipitant is dimethylglyoxime, the reaction is carried out at normal temperature, and the precipitation time is 40-60 min; and when the precipitator is sodium butyl xanthate, reacting at the temperature of 70-80 ℃, wherein the precipitation time is 40-60 min.

The technical principle of the invention is shown in the following equation:

leaching out

Precipitated Pd²⁺+2C₄H₈N₂O₂＝＝＝(C₄H₇N₂O₂)₂Pd↓+2H⁺

Pd²⁺+2C₄H₉OCSSNa＝＝＝(C₄H₉O)₂Pd↓+2Na⁺

Compared with the prior art, the invention has the advantages that: the method has the advantages of simple process, good selectivity, high recovery rate, mild reaction conditions, short reaction time and low cost, avoids using a large amount of toxic and harmful solvents such as strong acid and the like, reduces leaching and precipitation of other metals, and reduces the difficulty in treatment and recovery of subsequent metals.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and examples.

Example 1

The content (%) of each metal measured by experiments by using pins in waste computer CPUs as raw materials is shown in Table 1:

TABLE 1

The extraction process is shown in figure 1: 1g of pin is weighed and put into 10ml of N, N-dimethylformamide solvent containing 1mol/L of anhydrous copper bromide for leaching for 90 min. And (3) filtering after leaching is finished, adding 10ml of dimethylglyoxime ethanol solution with the concentration of 0.2mol/L into the leaching solution, precipitating palladium ions in the leaching solution, and filtering to obtain dimethylglyoxime palladium after precipitation is finished for 60min at normal temperature, wherein the leaching rate of palladium is 85 percent, and the precipitation rate of palladium is 98.5 percent.

Example 2

The content (%) of each metal in the waste computer CPU substrate used as a raw material is shown in table 2:

TABLE 2

The extraction process is shown in figure 1: 1g of computer substrate particles crushed to 100 meshes is taken and put into 20ml of N, N-dimethylacetamide solvent containing 1mol/L of anhydrous copper bromide, and leaching is carried out for 90 min. And (3) filtering after leaching is finished, adding 20ml of dimethylglyoxime ethanol solution with the concentration of 0.1mol/L into the leaching solution, precipitating palladium ions in the leaching solution, and filtering to obtain dimethylglyoxime palladium after precipitation is finished for 60min at normal temperature, wherein the leaching rate of palladium is 80% and the precipitation rate of palladium is 97%.

Example 3

The content (g/Kg) of each metal in the multilayer ceramic capacitor as a raw material is experimentally found in Table 3:

TABLE 3

The extraction process is shown as 1, the materials are ball-milled and sieved for standby use with 200 meshes, 1g of the ground materials are put into 20ml of N, N-dimethylformamide solvent containing 1.5mol/L of anhydrous copper bromide, the leaching time is 90min, the filtration is carried out after the leaching is finished, the leaching rate of palladium is 84%, 16ml of butyl xanthic acid solution with the concentration of 0.1mol/L is added into the leaching solution, the reaction temperature is 75 ℃, the precipitation reaction time is 60min, the palladium xanthate is obtained through filtration, and the palladium precipitation rate is 98.1%.

Claims

1. A method for recovering palladium in a printed circuit board by selective leaching precipitation is characterized by comprising the following specific steps:

adding waste printed circuit board powder into an anhydrous polar aprotic solvent according to the solid-liquid mass-volume ratio of 1: 5-1: 20g/ml, then adding bromide salt, carrying out a leaching experiment for 30-90min, filtering to obtain a leaching solution and filter residue after leaching is finished, adding a precipitator solution into the leaching solution, wherein the concentration of the precipitator solution is 0.01-0.5mol/L, the volume ratio of the precipitator solution to the leaching solution is 1: 1-1: 5, precipitating palladium ions in the leaching solution, and filtering to obtain crude palladium; wherein: the precipitant is selected from one or two of dimethylglyoxime and butyl sodium xanthate.

2. The method of claim 1, wherein the bromide salt is one or more of potassium bromide, sodium bromide, and copper bromide.

3. The method according to claim 1, wherein the charge ratio of the brominated salt to the anhydrous polar aprotic solvent is 1:4 to 3:2 mol/L.

4. The method according to claim 1, wherein the polar aprotic solvent is selected from any one or more of dimethylsulfoxide, hexamethylphosphoric triamide, N-dimethylformamide, N-dimethylacetamide, or N, N-methylpyrrolidone.

5. The method according to claim 1, wherein when the precipitant is dimethylglyoxime, the reaction is carried out at normal temperature for 40-60 min; and when the precipitator is sodium butyl xanthate, reacting at the temperature of 70-80 ℃, wherein the precipitation time is 40-60 min.