CN110790427A

CN110790427A - Treatment and recovery process of alkaline etching wastewater

Info

Publication number: CN110790427A
Application number: CN201911107728.3A
Authority: CN
Inventors: 刘为峰
Original assignee: Jiangsu Fangshiyuanlue Technology Consulting Co Ltd
Current assignee: Jiangsu Fangshiyuanlue Technology Consulting Co Ltd
Priority date: 2019-11-13
Filing date: 2019-11-13
Publication date: 2020-02-14

Abstract

A treatment and recovery process of alkaline etching wastewater sequentially comprises the recovery of copper and the reuse of tail liquid; the copper recovery comprises the following steps: pumping the alkaline etching wastewater into a reduction recovery tank by a pump, feeding water until the water reaches a pre-liquid-full line of the reduction recovery tank, adding sodium hydroxide to adjust the pH value of the reduction recovery tank, wherein the pH value is 11-12, and adding glucose into the reduction recovery tank for pre-reduction, wherein the pre-reduction time is 10-30 min; standing for precipitation, performing solid-liquid separation to obtain tail liquid with small suspended solid concentration, discharging the tail liquid, washing the precipitate with water, and drying to obtain the elemental copper. The process for treating and recycling the alkaline etching wastewater is simple, realizes zero discharge of sewage, recycles copper and magnesium ammonium phosphate crystals, has high recycling rate and extremely high economic and environmental benefits, and the treated alkaline etching wastewater has clear water quality and wide prospect.

Description

Treatment and recovery process of alkaline etching wastewater

Technical Field

The invention belongs to the technical field of environmental protection, and particularly relates to a treatment and recovery process of alkaline etching wastewater.

Background

In recent years, with the rapid development of the electronic information industry, printed circuit boards (PCB for short) have also been rapidly developed as the supporting industry, and the demand is increasing. Printed circuit technology has been increasingly being implemented and used on a large scale since the mid-50 of the 20 th century. The PCB industry in China is gradually developed, and in 2006, China surpasses Japan for the first time, becomes the largest PCB manufacturing big country in the world and keeps the status for a long time.

Although the rapid development of the PCB industry drives the economic development of China, the problems of various environmental pollutions brought by the rapid development of the PCB industry are more and more serious. In the manufacture of printed circuit boards, etching is one of the indispensable processes. A large amount of waste liquid generated in the etching process contains complex components such as copper ions, ammonia water, chloride and the like. When the concentration of copper ions is gradually increased to a specific range, the copper ions become waste liquid, and particularly serious damage is brought to the human environment. Generally, the copper content is about 100-160 g/L, and the ammonia Nitrogen (NH)₃And NH₄ ⁺) The content is about 150 to 200 g/L. After the waste liquid is subjected to copper recycling by the traditional method, the ammonia nitrogen concentration in the waste liquid is still very high and is about 10-50 g/L. If the etching cleaning waste liquid can be effectively recycled, the problem of current related copper supply shortage can be relieved, and environmental hazards brought by the copper supply shortage can be reduced.

Therefore, the waste etching cleaning liquid cannot be directly discharged, and must be reasonably and effectively recycled and harmlessly treated. Heretofore, the etching cleaning waste liquid is generally simply treated by conventional methods such as adsorption method, extraction method, precipitation method and liquid film separation, but these methods still have many disadvantages, such as easy secondary pollution, high treatment cost, undesirable effect and the like.

Chinese patent application No. CN201310491934.5 discloses a method for treating waste etching solution and a treatment device thereof, wherein acidic waste etching solution and alkaline waste etching solution are mixed; adjusting the pH value of the mixed etching waste liquid and heating the etching waste liquid to perform neutralization reaction; separating the precipitate and the filtrate; and adding a flocculating agent into the filtrate to flocculate suspended particles and colloidal arsenic in the filtrate, the steps are complicated, the treatment cost is high, the effect is not ideal, and the method is not beneficial to popularization.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects, the invention aims to provide a treatment and recovery process of alkaline etching wastewater, which realizes zero discharge of sewage, recovers copper and magnesium ammonium phosphate crystals, has high recovery rate and has extremely high economic benefit and environmental benefit.

The purpose of the invention is realized by the following technical scheme:

a treatment and recovery process of alkaline etching wastewater is characterized by sequentially comprising the steps of copper recovery and tail liquid reuse; the copper recovery comprises the following steps:

(1) pre-reduction: pumping the alkaline etching wastewater into a reduction recovery tank by a pump, feeding water until the water reaches a pre-liquid-full line of the reduction recovery tank, adding sodium hydroxide to adjust the pH value of the reduction recovery tank, wherein the pH value is 11-12, and adding glucose into the reduction recovery tank for pre-reduction, wherein the pre-reduction time is 10-30 min;

(2) reduction: adding a dispersing agent and a reducing agent into the reduction recovery tank for reduction, adding a Na2C03 solution to adjust the pH value of inlet water, wherein the pH value is 9-10, the reaction temperature is 70-80 ℃, and the reaction time is 10-20 min;

(3) separation, water washing and solid drying: standing for precipitation, performing solid-liquid separation to obtain tail liquid with small suspended solid concentration, discharging the tail liquid, washing the precipitate with water, and drying to obtain the elemental copper.

The alkaline etching waste liquid contains a large amount of copper ions, and if the alkaline etching waste liquid can be effectively recycled, the environmental pollution can be avoided, the waste can be changed into valuable, the product can be developed, and the economic benefit can be generated. At present, copper ions in the alkaline etching waste liquid can be recycled to produce basic copper carbonate, copper sulfate, copper chloride, copper oxide, copper powder and other products.

The treatment and recovery process of the alkaline etching wastewater comprises the recovery of copper and the reuse of tail liquid. The copper recovery adopts a liquid phase reduction method, and the liquid phase reduction method has the advantages of low investment, low production cost, simple and convenient operation, short reaction period, easy reaction control, easy realization of industrial production and better application prospect. The method for recycling copper from the alkaline etching waste liquid mainly comprises the steps of firstly adding glucose under the strong alkaline condition, reducing Cu2+ into Cu2O by the glucose, and then reducing a pre-reduction product Cu2O into elemental copper by adopting a reducing agent and a dispersing agent, so that the copper is convenient to recycle. The cost for treating the alkaline etching waste liquid mainly comes from two aspects of reagent consumption and power consumption, and the income of the simple substance copper obtained by recovering the copper exceeds the cost for treating the alkaline etching waste liquid, so that the method has certain economic benefit.

Further, in the treatment and recovery process of the alkaline etching wastewater, the concentration of glucose in the step (2) is 1.20-1.30 mol/L.

Further, in the above treatment and recovery process of alkaline etching wastewater, the dispersant in the step (2) is polyvinyl pyrrolidone copper.

Further, in the above treatment and recovery process of alkaline etching wastewater, the reducing agent in step (2) is thiourea dioxide, and the ratio of the molar concentration of thiourea dioxide to the molar concentration of copper ions in the alkaline etching wastewater is 3: 2.

Further, in the above treatment and recovery process of alkaline etching wastewater, the recycling of the tail liquid sequentially comprises the recovery of copper ions in the tail liquid, the recovery of ammonia nitrogen in the tail liquid, and the treatment of the remaining tail liquid; the recovery of copper ions in the tail liquid comprises the following steps:

(1) water inflow: pumping the tail liquid into a micro-electrolysis cell, feeding water until the micro-electrolysis cell is filled with liquid in advance, and adding hydrochloric acid to adjust the pH value of the micro-electrolysis cell, wherein the pH value is 2-3;

(2) reaction: adding iron powder into the micro-electrolytic cell at the rotating speed of 150 r/min, the reaction temperature of 25-30 ℃ and the reaction time of 90-100 min;

(3) water outlet: standing for precipitation, performing solid-liquid separation to obtain primary tail liquid, discharging the primary tail liquid, washing the precipitate with water, and drying to obtain the copper.

The alkaline etching waste liquid contains a large amount of copper ions and high-concentration ammonia nitrogen, and the concentration of the ammonia nitrogen is generally 150-200 g/L. After the waste liquid is subjected to copper recovery, urea is generated in the reduction process of the copper recovery, the concentration of the urea reaches 6-8 g/L, and the concentration of ammonia nitrogen in tail liquid is about 10-50 g/L. Therefore, the tail liquid must be recovered.

The recycling of the tail liquid sequentially comprises the recovery of copper ions in the tail liquid, the recovery of ammonia nitrogen in the tail liquid and the treatment of the residual tail liquid. Wherein, the recovery of copper ions in the tail liquid adopts a micro-electrolysis method, a certain amount of scrap iron is added into the tail liquid, and a micro-battery is formed through the inherent potential difference between iron and carbon. Under acidic conditions, these fine cells produce an electrochemical reaction in an aqueous solution with high-potential carbon as a cathode and low-potential iron as an anode, and low-potential divalent copper ions are replaced by the high-potential iron and reduced to metallic copper to precipitate. The copper ions in the tail liquid are recovered, so that the complete recovery of the copper ions in the alkaline etching wastewater is basically realized.

Further, in the above treatment and recovery process of alkaline etching wastewater, the mass ratio of the iron filings and the tail liquid in the step (2) is 2%.

Further, the process for treating and recovering the alkaline etching wastewater comprises the following steps of:

(1) water inflow: pumping the primary tail liquid into a chemical precipitation tank, feeding water until the chemical precipitation tank is full of liquid in advance, and adding sodium hydroxide to adjust the pH value of the chemical precipitation tank, wherein the pH value is 9.5-10;

(2) chemical precipitation: adding a precipitator into the chemical precipitation tank, wherein the reaction temperature is 25-28 ℃, and the reaction time is 25-30 min;

(3) water outlet: standing for precipitation, performing solid-liquid separation to obtain a secondary tail liquid, discharging the secondary tail liquid to obtain magnesium ammonium phosphate crystals, and drying and recovering.

The recovery of ammonia nitrogen in the tail liquid adopts a chemical precipitation method, the recovery effect of ammonia nitrogen in the primary tail liquid is good, the concentration of urea in the primary tail liquid can be reduced, and magnesium ammonium phosphate crystals with a rhombus structure are obtained, and the magnesium ammonium phosphate crystals have high purity, uniform distribution and good economic benefit.

Further, in the treatment and recovery process of the alkaline etching wastewater, the precipitant is magnesium salt, and the molar ratio of Mg2+, NH4+, PO 43-in the magnesium salt is 1.5: 1: 1.5.

further, the above treatment and recovery process of alkaline etching wastewater, the treatment of the residual tail liquid, comprises the following steps:

(1) water inflow: pumping the secondary tail liquid into an electrochemical reactor by a pump, feeding water until a liquid line of the electrochemical reactor is filled in advance, taking a ruthenium iridium titanium plate as an anode and a stainless steel polar plate as a cathode, adjusting the distance between the polar plates to be 2 cm, and adjusting the pH value to be 11;

(2) electrochemical reaction: starting the electrochemical reactor, adding NaCl, wherein the current density is 60 mA/cm2, and the reaction time is 260-265 min;

(3) water outlet: if the concentrations of ammonia nitrogen and urea do not reach the relevant standard values, the three tail liquids of the electrochemical reaction are subjected to biochemical treatment; and if the ammonia nitrogen and urea concentration reaches the relevant standard value, discharging.

The treatment of the residual tail liquid adopts an electrochemical method, so that ammonia nitrogen in the solution can be removed, and the urea can be converted into N₂And CO₂And the like, thereby removing urea and realizing zero emission of sewage.

Compared with the prior art, the invention has the following beneficial effects: the treatment and recovery process for the alkaline etching wastewater has the advantages of reasonable step arrangement, simple process, good effect, low operation cost, high efficiency, zero sewage discharge, recovery of copper and magnesium ammonium phosphate crystals, high recovery rate, waste recycling, no toxic and harmful byproducts generated in the treatment process, no pollution, high economic benefit and environmental benefit and wide application prospect.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the following embodiments and specific experimental data, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The following example provides a treatment and recovery process of alkaline etching wastewater.

Example 1

Copper recovery

The copper recovery comprises the following steps:

(1) pre-reduction: pumping the alkaline etching wastewater into a reduction recovery tank by a pump, feeding water until the liquid is filled in the reduction recovery tank in advance, adding sodium hydroxide to adjust the pH value of the reduction recovery tank, wherein the pH value is 11-12, adding glucose into the reduction recovery tank, and carrying out pre-reduction, wherein the concentration of the glucose is 1.20-1.30 mol/L, and the pre-reduction time is 10-30 min;

(2) reduction: adding polyvinyl pyrrolidone copper and thiourea dioxide into the reduction recovery tank for reduction, wherein the ratio of the molar concentration of the thiourea dioxide to the molar concentration of copper ions in the alkaline etching wastewater is 3:2, and adding Na₂CO₃Adjusting the pH value of inlet water by the solution, wherein the pH value is 9-10, the reaction temperature is 70-80 ℃, and the reaction time is 10-20 min;

The operation effect is as follows: and taking the tail liquid and the untreated alkaline etching wastewater, and measuring the concentration of copper ions in the tail liquid and the untreated alkaline etching wastewater by adopting an atomic absorption method to obtain the recovery rate of copper. The recovery rate of the copper can reach 98.9-99.2% by determination.

Example 2

The recycling of the tail liquid sequentially comprises the recovery of copper ions in the tail liquid, the recovery of ammonia nitrogen in the tail liquid and the treatment of the residual tail liquid.

The recovery of copper ions in the tail liquid comprises the following steps:

(2) reaction: adding iron powder into the micro-electrolytic cell, wherein the mass ratio of the iron filings to the tail liquid is 2%, the rotating speed is 150 r/min, the reaction temperature is 25-30 ℃, and the reaction time is 90-100 min;

The operation effect is as follows: the copper ions in the tail liquid are recovered, so that the complete recovery of the copper ions in the alkaline etching wastewater is basically realized.

Example 3

The recovery of ammonia nitrogen in the tail liquid comprises the following steps:

(2) chemical precipitation: adding a precipitator into the chemical sedimentation tank, wherein the precipitator is magnesium salt, and Mg in the magnesium salt² ⁺、NH⁴⁺、PO₄ ^3-In a molar ratio of 1.5: 1: 1.5, the reaction temperature is 25-28 ℃, and the reaction time is 25-30 min;

The operation effect is as follows: and (3) recovering ammonia nitrogen in the tail liquid, namely recovering the ammonia nitrogen in the primary tail liquid, wherein the recovery rate of the ammonia nitrogen is 88-90%, the concentration of urea in the primary tail liquid is reduced to 2-3 g/L, and magnesium ammonium phosphate crystals with a rhombus structure are obtained, and the magnesium ammonium phosphate crystals are high in purity and uniform in distribution.

Example 4

The treatment of the residual tail liquid comprises the following steps:

The operation effect is as follows: the tertiary tail liquid reaches a relevant standard value.

The preferred embodiments of the present invention have been described in detail with reference to the examples, but the present invention is not limited to the details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination between the embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the idea of the present invention.

Claims

1. A treatment and recovery process of alkaline etching wastewater is characterized by sequentially comprising the steps of copper recovery and tail liquid reuse; the copper recovery comprises the following steps:

2. The process for treating and recycling alkaline etching wastewater according to claim 1, wherein the concentration of glucose in the step (2) is 1.20-1.30 mol/L.

3. The process for treating and recovering alkaline etching waste water according to claim 1, wherein the dispersant in the step (2) is copper polyvinylpyrrolidone.

4. The process for treating and recycling alkaline etching wastewater according to claim 1, wherein the reducing agent in the step (2) is thiourea dioxide, and the ratio of the molar concentration of thiourea dioxide to the molar concentration of copper ions in the alkaline etching wastewater is 3: 2.

5. The process for treating and recycling alkaline etching wastewater according to claim 1, wherein the recycling of the tail solution comprises the steps of recycling copper ions in the tail solution, recycling ammonia nitrogen in the tail solution and treating the residual tail solution in turn; the recovery of copper ions in the tail liquid comprises the following steps:

6. The process for treating and recovering alkaline etching wastewater according to claim 5, wherein the mass ratio of the iron filings and the tail liquid in the step (2) is 2%.

7. The process for treating and recycling alkaline etching wastewater according to claim 5, wherein the recycling of ammonia nitrogen in the tail liquid comprises the following steps:

8. The process for treating and recovering the alkaline etching wastewater according to claim 7, wherein the precipitant is magnesium salt, and the molar ratio of Mg2+, NH4+ and PO 43-in the magnesium salt is 1.5: 1: 1.5.

9. the process for treating and recycling alkaline etching wastewater according to claim 5, wherein the treatment of the residual tail solution comprises the following steps: