CN114920381A - Method for removing heavy metal ions by ultrasonic-assisted vulcanization precipitation method - Google Patents

Abstract

The invention discloses a method for removing heavy metal ions by an ultrasonic-assisted sulfide precipitation method, which introduces ultrasonic waves into the process of treating waste acid wastewater by a sulfide precipitation method. By adjusting ultrasonic parameters, the uniformity of the vulcanization reaction environment is effectively controlled, and the problem of overhigh local concentration in a reactor is avoided, so that the supersaturation degree of the solution is reduced and the solution is more uniformly distributed, the explosive homogeneous nucleation phenomenon of sulfide precipitation is inhibited, and a large amount of fine particles are prevented from being generated; in addition, the ultrasonic wave enables the precipitated particles to oscillate violently, mutual collision among the particles is aggravated, the particles are promoted to be gathered into larger particles, and favorable conditions are provided for subsequent solid-liquid separation. The method is simple and easy to implement, provides favorable chemical and physical environments for nucleation and growth of metal precipitation particles, and also provides reference for efficiently recovering valuable metal resources of the waste acid smelting wastewater by a sulfide precipitation method.

Description

Method for removing heavy metal ions by ultrasonic-assisted sulfide precipitation method

technical field

The invention belongs to the field of heavy metal sewage treatment, and more particularly relates to a method for removing heavy metal ions in wastewater by an ultrasonic-assisted sulfide precipitation method.

Background technique

Industrial processes such as printing, electroplating, and metal smelting will generate a large amount of wastewater containing heavy metals. If it is directly discharged into the water environment, it will cause a series of negative impacts on the environment and organisms. The removal of heavy metal ions and the recovery of valuable resources in non-ferrous metal smelting polluted acid wastewater has always been a key and difficult point in the process of industrial environmental protection.

In the process of heavy metal wastewater treatment, the sulfide precipitation method has many advantages such as wide adaptability to pH range, fast reaction rate, stable sulfide generated, and high recycling value. It is widely used in the process of sewage acid treatment. However, because the solubility of sulfide is too low, a great degree of supersaturation will occur at the moment when the heavy metal ions are in contact with the sulfide precipitant, resulting in explosive homogeneous nucleation, resulting in a large number of very fine particles, which is not conducive to subsequent further separation operations. In addition, if the vulcanization reaction rate is too fast, the supersaturation distribution in the reactor will be uneven, and the reaction rate will be uneven. These are the fundamental reasons for the large amount of slag produced by the precipitation method and the low recovery efficiency of valuable metals. Therefore, how to provide suitable nucleation and growth conditions for the growth of sulfide precipitated particles, and how to improve the sedimentation performance of the precipitated material by increasing the sulfide precipitate particles or changing the surface properties of the particles, so as to further improve the solid-liquid separation efficiency is the The key to the treatment of heavy metal wastewater by sulfide precipitation.

SUMMARY OF THE INVENTION

The present invention aims to solve the technical problems existing in the prior art. For this reason, the object of the present invention is to provide a method for removing heavy metal ions by ultrasonic-assisted sulfidation precipitation method for the problems such as difficulty in separating metal precipitates, large amount of slag, waste of valuable resources and the like in the process of foul acid sulfide precipitation method. Ultrasonic treatment is introduced in the process of heavy metal ion sulfide precipitation to improve the reaction environment and optimize the reaction performance, so that the generated precipitated particles have better sedimentation performance, thereby improving the solid-liquid separation efficiency.

In the method, sodium sulfide solution or hydrogen sulfide is mixed with a heavy metal-containing solution to react, and then filtered and separated.

In the described method, the ultrasonic treatment time is 0-40 min, preferably: 4-8 min, more preferably 5 min.

In the method, the power of ultrasonic treatment is 40-100W, preferably: 60-100W, more preferably 100W.

In the described method, the temperature of ultrasonic treatment is 10-55°C, preferably 25-30°C, more preferably 25°C.

In the method, the heavy metal-containing solution contains non-ferrous metal smelting polluted acid wastewater.

In the method, the pH value of the solution containing heavy metals is in the range of 1-3, preferably pH 2.

In the method, the heavy metal comprises: copper, arsenic, and zinc, preferably the heavy metal is copper.

The invention simulates the preparation of non-ferrous metal smelting polluted acid wastewater (acidic solution containing heavy metal copper ions), and provides a method for removing heavy metal ions by an ultrasonic-assisted sulfide precipitation method, comprising the following steps:

(1) configure a certain molar concentration of copper sulfate solution and sodium sulfide solution;

(2) adjust the initial pH value of copper sulfate solution with concentrated sulfuric acid or sodium hydroxide solution;

(3) in the ultrasonic environment, the sodium sulfide solution and the copper sulfate solution are mixed in equimolar amounts to react;

(4) After a certain time of reaction, take a certain amount of suspension sample for laser particle size analysis;

(5) carry out suction filtration separation for the remaining suspension in step (4), wash the filter cake with deionized water, dry the filter cake to constant weight, obtain metal sulfide precipitation powder by grinding, and analyze it under a scanning electron microscope its shape and structure.

Further, in the step (1), the initial concentrations of the copper sulfate solution and the sodium sulfide solution are 0.1 mol/L and 0.2 mol/L, respectively.

Further, in the step (2), the initial pH value of the copper sulfate solution is adjusted to 2.

Further, the ultrasonic environment in the step (3) includes: ultrasonic time 0-40min, preferably 5min, ultrasonic power 40-100W, preferably 100W, and ultrasonic temperature 10-55°C, preferably 25°C.

Further, in the step (5), the filter cake is dried in an oven at 60-80° C. for 12-24 hours.

The beneficial effects obtained by adopting the scheme of the present invention are:

The invention proposes a method for removing heavy metal ions by an ultrasonic-assisted sulfide precipitation method. Ultrasonic waves are introduced into the process of treating polluted acid wastewater by the sulfide precipitation method for the first time. By adjusting the ultrasonic parameters, the uniformity of the vulcanization reaction environment is effectively improved, and the efficiency of the vulcanization precipitation reaction is improved. This method avoids the problem of high local concentration in the reactor, so that the supersaturation of the solution is reduced and the distribution is more uniform, and finally the explosive homogeneous nucleation of the sulfide precipitation is suppressed; It aggravates the mutual collision between particles and promotes them to aggregate into larger particles, which provides convenience for the subsequent solid-liquid separation. The method is simple and easy to operate, safe and clean, and has high treatment efficiency. At the same time, it provides favorable conditions for the nucleation and growth of precipitated particles in terms of chemical reaction environment and physical sedimentation performance, promotes the separation and recovery of valuable metals, and improves the precipitation of sulfides. The treatment efficiency of smelting acid wastewater by the method.

Description of drawings

Fig. 1 is the scanning electron microscope picture of the CuS precipitation particles obtained under different ultrasonic time conditions in Example 1;

Fig. 2 is the scanning electron microscope image of CuS precipitated particles obtained under different ultrasonic power conditions in Example 2;

Fig. 3 is the scanning electron microscope image of CuS precipitated particles obtained under different ultrasonic temperature conditions in Example 3;

FIG. 4 is a particle size distribution diagram and a scanning electron microscope image of the CuS precipitated particles obtained under the condition of no ultrasound in the comparative example.

Detailed ways

The present invention will be further described below with reference to the embodiments. The technical solutions in the embodiments of the present invention are clearly and completely described, and obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1: Different time (5, 10, 20, 30min), power 100W, temperature 25°C;

Measure four groups of 200 mL copper sulfate solutions (pH=2) with a concentration of 0.1 mol/L into four 500 mL beakers with a graduated cylinder, and put the beakers into the ultrasonicator. Then measure 4 groups of 100mL sodium sulfide solution with a concentration of 0.2mol/L, pour them into 4 beakers respectively, and start timing when all the sodium sulfide solutions are poured. The ultrasonic power of the ultrasonic machine was set to 100 W and the ultrasonic temperature was 25 °C, and the 4 groups were ultrasonicated for 5 min, 10 min, 20 min and 30 min respectively. After the ultrasonication was completed, 50 mL samples of the suspension were taken and sent to a laser particle size analyzer for particle size detection. It was determined that the median diameter (D50) of the four groups of copper sulfide precipitated particles treated with different ultrasonic times was 6.42 μm, 5.12 μm, 5.54 μm, and 5.85 μm in turn, and the remaining precipitates were filtered and washed with deionized water. , and dried in an oven at 60 °C for 24 h, and finally ground into powder and sent to a scanning electron microscope to scan and analyze its morphology.

The ultrasonic-assisted vulcanization precipitation method is used to obtain the largest particle size under the condition of ultrasonic 5min. If the ultrasonic time is too long, the mechanical effect of ultrasonic will be strengthened, and then the particles will be broken and the agglomeration between particles will be destroyed. It can be seen from the scanning electron microscope image that the agglomeration effect of the precipitated particles after 5 min of ultrasound is more obvious than that of the other three groups (as shown in Figure 1).

Example 2: Different power (40, 60, 80, 100W), time 5min, temperature 25°C;

Measure four groups of 200 mL copper sulfate solutions (pH=2) with a concentration of 0.1 mol/L with a graduated cylinder and pour them into four 500 mL beakers respectively, and put the beakers into the ultrasonicator. Then 4 groups of 100 mL sodium sulfide solutions with a concentration of 0.2 mol/L were measured and poured into the 4 groups of beakers respectively, and the timing was started at the moment when the reaction started. The ultrasonic temperature was set to 25°C, and the four groups of reactions were ultrasonicated for 5 min at ultrasonic powers of 40W, 60W, 80W, and 100W, respectively. After sonication, 50 mL samples were taken and sent to a laser particle size analyzer for particle size detection. It was determined that the median diameter (D50) of the four groups of copper sulfide precipitated particles treated with different ultrasonic powers was 5.83 μm, 6.32 μm, 6.39 μm and 6.42 μm in turn. The remaining precipitates were filtered and washed with deionized water. And dried in an oven at 60 °C for 24 h, and finally ground into powder and sent to a scanning electron microscope to scan and analyze its morphology.

Using the ultrasonic-assisted vulcanization precipitation method, the particle size of the obtained particles increases with the increase of ultrasonic power within the set range. It can also be seen from the scanning images that the precipitated crystals obtained under the four conditions are regular in shape and have good agglomeration effect (as shown in Figure 2).

Example 3: Different temperatures (10, 25, 40, 55°C), time 5min, power 100W;

Measure four groups of 200 mL copper sulfate solutions (pH=2) with a concentration of 0.1 mol/L with a graduated cylinder and pour them into four 500 mL beakers respectively, and put the beakers into the ultrasonicator. Then 4 groups of 100 mL sodium sulfide solutions with a concentration of 0.2 mol/L were measured and poured into the 4 groups of beakers respectively, and the timing was started at the moment when the reaction started. The ultrasonic power was set to 100 W, and the 4 groups of reactions were ultrasonicated for 5 min at ultrasonic temperatures of 10 °C, 25 °C, 40 °C, and 55 °C, respectively. After sonication, 50 mL samples were taken and sent to a laser particle size analyzer for particle size detection. It was determined that the median diameter (D50) of the four groups of copper sulfide precipitated particles treated with different ultrasonic powers was 5.07 μm, 6.42 μm, 6.16 μm and 5.81 μm in turn. The remaining precipitates were filtered and washed with deionized water. And dried in an oven at 60 °C for 24 h, and finally ground into powder and sent to a scanning electron microscope to scan and analyze its morphology.

Using the ultrasonic-assisted vulcanization precipitation method, the particle size of the obtained particles first increased and then decreased with the increase of ultrasonic temperature. If the temperature is too low, the vulcanization reaction rate will be limited; if the temperature is too high, the cavitation of ultrasonic waves will be significant, which will promote the explosive increase of crystal nuclei and produce a large number of fine particles. It can be seen from the SEM image that, especially under the condition of ultrasonic temperature of 25°C, the resulting crystal surface is smooth and not easy to agglomerate (Fig. 3).

Comparative example: time (5min), no ultrasound

Measure 200mL of copper sulfate solution (pH=2) with a concentration of 0.1mol/L in a measuring cylinder and pour it into a 500mL beaker, and then measure 100mL of sodium sulfide solution with a concentration of 0.2mol/L, pour it into the beaker, and the reaction begins. Time starts in an instant. After 5 min of reaction, a 50 mL sample was taken and sent to a laser particle size analyzer for particle size detection. The median particle size (D50) of the copper sulfide precipitated particles was determined to be 2.93 μm. The remaining precipitates were filtered by suction, washed with deionized water, dried in an oven at 60 °C for 24 hours, and finally ground into powder and sent for scanning. Scanning and analysis of its morphology by electron microscope.

Comparing the copper sulfide precipitates obtained under ultrasonic and no ultrasonic conditions, it can be found that after the introduction of ultrasonic waves, the particle size of the obtained particles is significantly increased, and the stability and dispersibility of the crystals are better (Fig. 4).

It should be emphasized that the examples described in the present invention are illustrative rather than restrictive, so the present invention is not limited to the examples described in the specific implementation manner, and all the examples obtained by those skilled in the art according to the technical solutions of the present invention Other embodiments that do not depart from the spirit and scope of the present invention, whether modified or replaced, also belong to the protection scope of the present invention.

Claims (8)

1. a method for removing heavy metal ions by ultrasonic-assisted sulfide precipitation method, is characterized in that, in heavy metal ion sulfide precipitation process, introduce ultrasonic wave, improve reaction environment, optimize reaction performance. 2. method according to claim 1, is characterized in that, sodium sulfide solution or hydrogen sulfide gas is mixed with the solution containing heavy metal to react, and gained precipitation is separated by filtration. 3. The method according to claim 1 or 2, wherein the ultrasonic treatment time is 10-40 min, preferably: 4-8 min, more preferably 5 min. 4. The method according to claim 1 or 2, wherein the power of the ultrasonic treatment is 40-100W, preferably: 60-100W, more preferably 100W. 5. The method according to claim 1 or 2, wherein the temperature of the ultrasonic treatment is 10-55°C, preferably 25-30°C, more preferably 25°C. 6. The method according to claim 1, wherein the heavy metal-containing solution specifically refers to non-ferrous metal smelting polluted acid wastewater. 7. The method according to claim 1 or 6, characterized in that, the pH value of the solution containing heavy metals is in the range of 1-3, preferably pH 2. 8. The method of claim 1, wherein the heavy metals comprise copper, arsenic and zinc.

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