CN102976467A - Treating method of electroplating wastewater - Google Patents

Abstract

The invention discloses a method for treating electroplating wastewater in the field of environmental pollution control. The electroplating wastewater is filtered to remove solid particles, the ions that may exist therein are analyzed according to the production process, metal cations are added or various electroplating wastewater are mixed to make the concentration of divalent ions It is 2~4 times of the concentration of trivalent ions; quickly add 50%~70% NaOH solution dropwise to the electroplating wastewater until the pH value reaches 8~10, and stir rapidly at 300~400rpm for 60~120 minutes during the dropwise addition , metal ions generate hydrotalcite through co-precipitation; precipitate and separate the generated hydrotalcite, add hydrochloric acid or sulfuric acid, and adjust the pH to 7; use metal ions in electroplating wastewater to prepare hydrotalcite with a wide range of applications through simple steps , realize waste utilization, and can remove heavy metals in electroplating wastewater, and the synthesized hydrotalcite can be used as an adsorption material and continue to be used for environmental governance.

Description

A kind of treatment method of electroplating wastewater

technical field

The invention relates to the development of new technologies for environmental pollution control, in particular to a treatment method for electroplating wastewater.

Background technique

Wastewater and waste liquid discharged from electroplating factories (or workshops), such as rinsing water for plated parts, waste bath liquid, equipment cooling water and flushing ground water, etc., the water quality varies with the production process, and often contains oil and various metal ions. , often contain Cr ⁶⁺ , Cd ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ , Fe ²⁺ and other heavy metals; electroplating wastewater is mostly toxic and harmful. For example, cyanide can cause acute poisoning of humans and animals and cause death, and long-term effects of low concentrations can also cause chronic poisoning. Cadmium can cause pathological changes in the kidneys and cause itai disease. Hexavalent chromium can cause lung cancer, gastrointestinal disorders, and anemia, and can accumulate in bones, spleen, and liver. Therefore, electroplating wastewater must be strictly controlled and properly disposed of.

There are many electroplating wastewater treatment processes: resin exchange was popular in the 1970s, electrolysis, chemical methods and air flotation in the 1980s. Electrolysis method: high energy consumption, high power consumption and iron consumption, too much sludge generated for high-concentration chromium-containing wastewater, unsuitable, and unsatisfactory treatment of cyanide-containing wastewater, so cyanide-containing wastewater must use chemical methods. Chemical agents and air flotation method: use chemical redox neutralization, and use air flotation to separate mud and water. Due to the large proportion of electroplating sludge and various organic additives in wastewater, the air flotation separation is not complete in actual use, and the operation Management is inconvenient. By the end of the 1990s, the application of air flotation was less and less. Chemical agents and precipitation: This method is the earliest applied method, after more than 30 years of actual use and comparison of different treatment processes. At present, it has returned to the earliest and most effective treatment process. Most foreign countries also use this method in electroplating treatment. However, after a long time of actual solid-liquid separation operation, sludge will turn up in the sedimentation tank, and it is difficult to ensure that the effluent is stable and up to standard. The biological treatment process developed in recent years: a small amount of water with a single type of plating has a high operating effect, and many large projects are very unstable. Because the water quality and quantity are difficult to maintain, microorganisms are difficult to adapt to changes in water temperature, species, concentration of heavy metal ions, and pH value. A large number of microorganisms die instantly, environmental pollution accidents occur, and it is not easy to cultivate bacteria.

Layered Double Hydroxides (LDH for short), also known as hydrotalcite, is an important class of inorganic functional materials. Its unique layered structure and the tunable variability of layer elements and interlayer anions have attracted widespread attention. The introduction of new guest anions into the layer through ion exchange can cause corresponding changes in the layered structure and composition, so it can be prepared A large class of functional materials with special properties. Hydrotalcite materials belong to anionic layered compounds. Layered compounds refer to a class of compounds with a layered structure and interlayer ions that are exchangeable. Utilizing the intercalation and exchangeability of layered compounds under the action of strong polar molecules, Some functional guest substances are introduced into the interlayer space and the distance between the layers is stretched to form layer pillar compounds.

The general chemical structure formula of hydrotalcite is: [M ²⁺ _1-x M ³⁺ x (OH) ₂ ] ^x+ [(A ^n- ) _x/n mH ₂ O], where M ²⁺ is Mg ²⁺ , Ni ²⁺ , Mn ²⁺ , Zn ²⁺ , Ca ²⁺ , Fe ²⁺ , Cu ²⁺ and other divalent metal anions; M ³⁺ is Al ³⁺ , Cr ³⁺ , Fe ³⁺ , Co ³⁺ and other trivalent metal anions Metal anions; ^An- is an anion, such as CO ₃ ^2- , NO ₃ ^- , Cl ^- , OH ^- , SO ₄ ^2- , PO ₄ ^3- , C ₆ H ₄ (COO) ₂ ^2- and other inorganic and organic ions As well as complex ions, when the inorganic anions between layers are different, the interlayer spacing of hydrotalcite is different. At the same time, after hydrotalcite adsorbs pollutants, the interlayer spacing will also increase to accommodate more pollutants.

At present, the synthesis methods of hydrotalcite materials mainly include salt-alkali method, salt-oxide method and ion exchange method, and induced hydrolysis method, hydrothermal method, heat treatment and rehydration method are also derived. The most commonly used method is the co-precipitation method, which is prepared by co-precipitating the mixed solution of metal ions forming the hydrotalcite layer under the action of alkali at a certain temperature. The method is simple and easy to operate, and is a commonly used preparation method. In this method, a certain amount of divalent metal ions and trivalent metal ions need to be used, which increases the investment from an economic point of view; The production of waste water has been increased, and new problems have been raised for environmental governance.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art in the treatment of electroplating wastewater, and provide a treatment method for electroplating wastewater with low energy consumption, no pollution and high efficiency. the

The technical scheme that the present invention adopts is to comprise the following steps successively:

1) Filter the electroplating wastewater to remove solid particles, analyze the ions that may exist in it according to the production process, add metal cations or mix various electroplating wastewater, so that the concentration of divalent ions is 2 to 4 times that of trivalent ions;

2) Quickly add 50%~70% NaOH solution [B1] to the electroplating wastewater until the pH value reaches 8~10, and stir rapidly at 300~400 rpm for 60~120 minutes during the dropwise addition, and the metal ions pass through the total Precipitation produces hydrotalcite;

3) Separate the generated hydrotalcite precipitate, add hydrochloric acid or sulfuric acid, and adjust the pH to 7.

The advantage of the present invention is that the metal ions in the electroplating wastewater are used to prepare hydrotalcites with a wide range of applications through simple steps, realize waste utilization, and remove heavy metals in the electroplating wastewater at the same time, and the synthesized hydrotalcites can be used as adsorption materials. for environmental governance.

Detailed ways

Filter the electroplating wastewater to remove solid particles, analyze the ions that may exist in it according to the production process, add appropriate metal cations, or mix various electroplating wastewater to ensure that the concentration of divalent ions is 2 to 4 times that of trivalent ions. If only For divalent metal cations, add a small amount of trivalent metal cations, such as relatively cheap Al ³⁺ , Fe ^{3+ ,} etc.; if there are only trivalent metal cations, add a small amount of divalent metal cations, such as relatively cheap Mg ²⁺ , Fe ²⁺ , etc. If there are already divalent metal cations and trivalent metal cations, check the concentration to ensure that the concentration of divalent ions is 2 to 4 times the concentration of trivalent ions.

Quickly add 50%~70% NaOH solution [B2] to the electroplating wastewater until the pH value reaches 8~10. During the dropwise addition, stir rapidly at 300~400 rpm for 60~120 minutes, and the metal ions pass through coprecipitation , generate hydrotalcite, precipitate and separate the generated hydrotalcite, the pollutants in the washing wastewater will be removed with the precipitation, and finally add hydrochloric acid or sulfuric acid to adjust the pH to about 7.

Further provide 4 embodiments of the present invention below:

Example 1

Filter the electroplating wastewater to remove solid particles. According to the analysis of the production process, it contains Ni ²⁺ and Cu ²⁺ . Add a small amount of Al ³⁺ to make the concentration of divalent ions twice the concentration of trivalent ions; Adjust the pH value to 8 with 70% NaOH solution, stir rapidly at 400 rpm for 120 minutes during the dropwise addition, and precipitate and separate. .

The water quality of the treated wastewater was measured. After analyzing the metal ions Ni ²⁺ , Cu ²⁺ and Al ³⁺ in the electroplating wastewater, the removal rates were 97.2%, 98.1%, and 95.3%, respectively.

Example 2

Filter the electroplating wastewater to remove solid particles. According to the analysis of the production process, it contains Fe ³⁺ and Al ³⁺ . Add a small amount of Mg ²⁺ to make the concentration of divalent ions 4 times that of trivalent ions; 50% NaOH solution to adjust the pH value to 10, stir rapidly at 300 rpm for 60 minutes when adding dropwise, precipitate and separate, the pollutants in the washing wastewater will be removed with the precipitation, and finally add hydrochloric acid or sulfuric acid to adjust the pH to about 7 .

The water quality of the treated wastewater was measured. After analyzing the metal ions Fe ³⁺ , Al ³⁺ and Mg ²⁺ in the electroplating wastewater, the removal rates were 97.1%, 98.5% and 97.3%, respectively.

Example 3

Mix a variety of electroplating wastewater to remove solid particles, analyze the presence of Ni ²⁺ , Cu ²⁺ , Fe ³⁺ and Al ³⁺ according to the production process, and the concentration of divalent ions is three times that of trivalent ions. Quickly add 60% NaOH solution in the solution to adjust the pH value to 9, stir rapidly at 300 rpm for 80 minutes during the dropwise addition, precipitate and separate, and the pollutants in the washing wastewater will be removed along with the precipitation, and finally add hydrochloric acid or sulfuric acid to adjust pH to around 7.

The water quality of the treated wastewater was measured. After analyzing the metal ions Ni ²⁺ , Cu ²⁺ , Fe ³⁺ and Al ³⁺ in the electroplating wastewater, the removal rates were 97.3%, 96.9%, 97.4% and 97.1%, respectively.

Add the hydrotalcite powder into the dye wastewater containing 25 mg/L acid scarlet, the volume of treated wastewater corresponding to each gram of hydrotalcite is about 1 L, and stir rapidly for 60 minutes; the reaction product stays in the sedimentation tank for 30 minutes, and the solid-liquid After separation, the concentration of the supernatant was measured by an ultraviolet-visible spectrophotometer, and the removal rate of pollutants was 98.7%.

Example 4

Mix a variety of electroplating wastewater to remove solid particles, and analyze the presence of Ni ²⁺ , Cu ²⁺ , Zn ²⁺ and Al ³⁺ according to the production process, and the concentration of divalent ions is 4 times that of trivalent ions. Quickly add 60% NaOH solution in the solution to adjust the pH value to 9, stir rapidly at 300 rpm for 120 minutes during the dropwise addition, and precipitate and separate, the pollutants in the washing wastewater will be removed along with the precipitation, and finally add hydrochloric acid or sulfuric acid to adjust pH to around 7.

The water quality of the treated wastewater was measured. After analyzing the metal ions Ni ²⁺ , Cu ²⁺ , Zn ²⁺ and Al ³⁺ in the electroplating wastewater, the removal rates were 97.6%, 97.9%, 98.2% and 97.8%, respectively.

Add the hydrotalcite powder into the waste water containing 25 mg/L dye Golden Orange II, the volume of the treated waste water per gram of hydrotalcite is about 1 L, stir rapidly for 60 minutes; the reaction product stays in the sedimentation tank for 30 minutes, solidifies The liquid was separated, and the concentration of the supernatant was measured by an ultraviolet-visible spectrophotometer. The removal rate of pollutants was 98.3%.

The total volume here is not necessarily, according to the amount of water, the initial pH of the water and the amount of metal ions, but the final pH is 8~10.

The total volume here is not necessarily, according to the amount of water, the initial pH of the water and the amount of metal ions, but the final pH is 8~10.

Claims (2)

1. the treatment process of an electroplating wastewater is characterized in that as follows:

1) electroplating wastewater filter is removed solid particulate, according to the ion that analysis of Production Technology wherein may exist, added metallic cation or multiple electroplating wastewater is mixed, making divalent ion concentration is 2 ~ 4 times of trivalent ion concentration;

2) drip fast 50% ~ 70% NaOH solution in the electroplating wastewater, until till pH value to 8 ~ 10, during dropping under 300 ~ 400 rpm rapid stirring 60～120 minutes, metal ion generates hydrotalcite by co-precipitation;

3) with the hydrotalcite precipitate and separate that generates, add hydrochloric acid or sulfuric acid, regulate pH to 7.

2. the treatment process of a kind of electroplating wastewater according to claim 1 is characterized in that: in the step 1), if only have divalent metal in the electroplating wastewater, then add trivalent metal cation; If only have trivalent metal cation, then add divalent metal.