CN114044584B

CN114044584B - Method for treating heavy metal leaching wastewater by using multi-walled carbon nanotube crosslinked natural latex adsorbent

Info

Publication number: CN114044584B
Application number: CN202111287442.5A
Authority: CN
Inventors: 李建华; 陆胜勇; 丁佳敏; 朱慧萍; 郭轩豪
Original assignee: Research Institute of Zhejiang University Taizhou
Current assignee: Research Institute of Zhejiang University Taizhou
Priority date: 2021-11-02
Filing date: 2021-11-02
Publication date: 2022-11-04
Anticipated expiration: 2041-11-02
Also published as: WO2023077631A1; CN114044584A; CN115382511A; CN115382511B

Abstract

The invention belongs to the technical field of heavy metal wastewater treatment, and discloses a method for treating heavy metal leaching wastewater by using a multi-walled carbon nanotube crosslinked natural latex adsorbent, which specifically comprises the following steps: preparing elution wastewater, precipitating the elution wastewater, preparing a multi-walled carbon nanotube crosslinked natural latex adsorbent, adsorbing the elution wastewater, breaking a complex of the elution wastewater, adjusting pH, adding precipitate, adding a flocculating agent, and separating the precipitate; leaching the waste water by using a composite leaching solution prepared from 5-50 mmol/L chloride and 20-150mmol/L organic acid to leach the high-concentration heavy metal polluted soil such as lead, cadmium and the like; the wastewater treatment precipitation method has the advantages of obvious technical effect, high efficiency, simple operation, relatively low cost and strong practicability, the removal rate of lead and cadmium in the leaching wastewater can respectively reach 99.94 percent and 99.86 percent, the treated wastewater can be recycled through pH value adjustment, the water quality is purified, and the risk of water pollution is reduced.

Description

Method for treating heavy metal leaching wastewater by using multi-walled carbon nanotube crosslinked natural latex adsorbent

Technical Field

The invention relates to the field of wastewater treatment, in particular to a method for treating heavy metal leaching wastewater by using a multi-walled carbon nanotube crosslinked natural latex adsorbent.

Background

At present, about 548 million hectares of soil in China are in a serious pollution condition, and main pollutants comprise cadmium, lead, arsenic and polycyclic aromatic hydrocarbon, wherein the soil pollution around a nonferrous metal mining area is particularly serious. Activities such as mining and metal smelting in mining areas can cause the soil near the mining areas to suffer serious heavy metal pollution and damage, and pollution sources mainly comprise tailings overflowing from the mining areas, dust discharged in the air, acid mine water entering farmlands along with rivers and the like. Once entering the farmland, the heavy metals not only can seriously damage the functions and the structures of the soil, but also can adversely affect the growth and the development of crops, and seriously can cause the yield reduction and even the extinction of the crops, and on the other hand, the pollution of the heavy metals to the soil can be remained for a long time if the heavy metals are not treated, so that the purification of the polluted soil is necessary.

Wherein chemical leaching is an effective remediation method for treating heavy metal contaminated soil. The chemical leaching mainly comprises the step of enabling reagent components in the leaching agent to react with heavy metals in the soil through chemical reaction to form soluble heavy metal ions or metal complexes, so that the heavy metal components in the soil can be removed quickly and efficiently. However, new heavy metal wastewater is generated by chemical leaching, secondary pollution is caused by improper treatment of the heavy metal wastewater, and even toxicity is possibly caused. Therefore, an efficient treatment method for heavy metal leaching wastewater is urgently needed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a method for treating heavy metal leaching wastewater by using a multi-walled carbon nanotube crosslinked natural latex adsorbent.

In order to solve the problems, the invention adopts the following technical scheme:

a method for treating heavy metal leaching wastewater by using a multi-walled carbon nanotube crosslinked natural latex adsorbent comprises the following steps:

step 1: leaching the heavy metal contaminated soil by using a leaching agent to obtain heavy metal leaching waste liquid; wherein the eluent is a compound eluent prepared by mixing chloride and organic acid;

step 2: taking the leaching waste liquid, and standing and precipitating the leaching waste liquid for 0-3 h;

and step 3: transferring the supernatant of the precipitation of the leaching waste liquid, and adding an adsorbent prepared by crosslinking multi-walled carbon nano tubes with natural latex; the adding proportion is that 0.1g to 1.5g of adsorbent is added to every 100ml of leaching waste liquid;

and 4, step 4: adding an adsorbent, stirring for 5-60 min, and centrifuging by a centrifuge after stirring;

and 5: transferring the supernatant after centrifugal separation, adding a decomplexer, and stirring; the addition proportion of the decomplexer is that 0.1ml to 4ml of the decomplexer is added into every 50ml of the decomplexer; stirring for 5-60 min to complete the vein breaking treatment;

step 6: regulating the pH value of the waste liquid after the decomplexation to 9-11.5;

and 7: adding a precipitator into the waste liquid, wherein the adding proportion of the precipitator is 1 g-10 g/L; adding the precipitator, and then placing the mixture into a constant-temperature oscillator for oscillation, wherein the oscillation time is 5-40 min;

and 8: adding a flocculating agent into the waste liquid in a proportion of 1 to 25g/L; after adding the flocculating agent, placing the mixture into a constant-temperature oscillator for oscillation, wherein the oscillation time is 5-40 min;

and step 9: and (4) centrifugally separating the waste liquid obtained in the step (8) by a centrifugal machine to obtain liquid meeting the discharge standard, and ending the step.

Further, the preparation of the adsorbent made of the multi-walled carbon nanotube crosslinked natural latex in the step 3 comprises the following steps:

step 31: transferring 100-200 ml of deionized water, placing the deionized water in a container, adding 1-3 g of dispersing agent, and ultrasonically stirring the mixture for 5-30 min at room temperature;

step 32: adding 1 g-3 g of multi-carbon-wall nanotubes in a small amount for multiple times, and ultrasonically stirring at room temperature for 20 min-50 min;

step 33: adding 30-70 g of natural latex in a small amount for multiple times, and ultrasonically stirring for 10-30 min at room temperature;

step 34: drying the mixture to constant weight through a constant-temperature drying box to obtain an adsorbent;

step 35: placing the dried adsorbent in a muffle furnace for roasting and carbonizing;

step 36: the carbonized adsorbent is ground by a mortar and sieved by a 100-mesh sieve.

Further, in the step 35, the carbon is roasted and carbonized for 1 to 3 hours in a muffle furnace at the temperature of 700 to 800 ℃.

Further, the complex breaking agent in the step 5 is 30% hydrogen peroxide.

Further, in the step 6, pH adjustment is carried out through an alkali solution; the concentration of the alkali solution is 0.1-0.3 mol/L.

Further, the precipitating agent in the step 7 is sodium phosphate.

Further, the flocculant in the step 8 is polyacrylamide.

Further, the rotation speed of the centrifuge in the step 4 and the step 9 is 4000rpm.

Further, the compound eluting agent in the step 1 comprises 5-50 mmol/L of chloride and 20-150mmol/L of organic acid; the chloride includes ferric chloride and calcium chloride, and the organic acid includes citric acid, malic acid and tartaric acid.

Further, the process of leaching the heavy metal contaminated soil specifically comprises the following steps:

step 11: naturally drying the heavy metal contaminated soil, selecting gravel and a straw stick, grinding, and sieving with a 50-mesh sieve;

step 12: moistening the sieved soil with water;

step 13: adding an eluting agent for mixed elution, wherein the mass ratio of the volume of the added eluting agent to the soil is 2-3L/kg during elution;

step 14: standing the washed soil, and removing a supernatant;

step 15: repeating the step 13 to the step 14, and circulating for 1 to 3 times to obtain the demetallized soil;

step 16: adding distilled water to dilute the residual solution, wherein the volume of the added distilled water is 2-3L/kg of the mass ratio of the added distilled water to the soil;

and step 17: standing the diluted soil, and removing a supernatant;

step 18: and (5) repeating the step 16 to the step 17, circulating for 1 to 3 times, and ending the step.

The invention has the beneficial effects that:

heavy metal ions in the leaching waste liquid are adsorbed by the adsorbent and are subjected to treatment such as complex breaking, precipitation, flocculation and the like, so that the leaching waste liquid reaches the discharge standard, and secondary pollution to the surrounding environment is avoided;

the adsorbent is prepared by crosslinking the natural latex and the multi-carbon wall nanotube, so that heavy metal ions in the leaching waste liquid can be efficiently adsorbed, the heavy metal ions and the leaching waste liquid are fully separated, and the treatment effect of the leaching waste liquid is ensured;

the pH value of the leaching waste liquid is adjusted to be 9-11.5, so that the problem of high pH value of the existing waste water treatment technology is avoided, and the problem of water body environmental pollution is solved.

Drawings

Fig. 1 is a block diagram of an embodiment of the present invention.

Detailed Description

The following embodiments of the present invention are provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the features in the following embodiments and examples may be combined with each other without conflict.

It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

The first embodiment is as follows:

as shown in fig. 1, a method for treating heavy metal leaching wastewater by using a multi-walled carbon nanotube cross-linked natural latex adsorbent comprises the following steps:

and 3, step 3: transferring the supernatant of the precipitation of the leaching waste liquid, and adding an adsorbent prepared by crosslinking multi-walled carbon nano tubes with natural latex; the adding proportion is that 0.1g to 1.5g of adsorbent is added to every 100ml of leaching waste liquid;

and 7: adding a precipitator into the waste liquid, wherein the adding proportion of the precipitator is 1 g-10 g/L; adding the precipitator, and then placing the mixture into a constant temperature oscillator for oscillation, wherein the oscillation time is 5-40 min;

and 8: adding a flocculating agent into the waste liquid in a proportion of 1 to 25g/L; after the flocculating agent is added, placing the mixture into a constant temperature oscillator for oscillation, wherein the oscillation time is 5-40 min;

The compound eluent in the step 1 comprises 5-50 mmol/L of chloride and 20-150mmol/L of organic acid, wherein the chloride comprises ferric trichloride, calcium chloride and the like, and the organic acid comprises citric acid, malic acid, tartaric acid and the like; the soil polluted by heavy metals is mainly soil containing cadmium and lead; in this example, 20mmol/L ferric chloride and 50mmol/L citric acid were used to prepare the eluent. The process for leaching the heavy metal contaminated soil specifically comprises the following steps:

step 12: wetting the screened soil with water;

step 14: standing the washed soil, and removing a supernatant;

step 15: repeating the steps 13-14, and circulating for 1-3 times to obtain the demetallized soil;

and step 17: standing the diluted soil, and removing a supernatant;

In step 12, the washing process is carried out at room temperature.

And the supernatant in the step 14 and the step 17 is the leaching waste liquid.

In the step 3, the preferable ratio range of the dosage of the adsorbent is 0.5-1.5 g/100ml. In this case 1g/100ml. The preparation of the adsorbent prepared by the multi-wall carbon nano tube crosslinked natural latex comprises the following steps:

step 31: transferring 100-200 ml of deionized water, placing the deionized water in a container, adding 1-3 g of dispersing agent, and ultrasonically stirring for 5-30 min at room temperature;

step 34: drying the mixture to constant weight in a constant-temperature drying oven at the temperature of 50-100 ℃ to obtain an adsorbent;

step 35: placing the dried adsorbent in a muffle furnace, and roasting and carbonizing for 1-3 h at the temperature of 700-800 ℃;

In the step 31, the preferred volume range of the deionized water is 100-150 ml, the preferred mass range of the dispersing agent is 1-2 g, and the preferred duration of ultrasonic stirring is 5-20 min. In the example, 135mL of deionized water is taken, 1.8g of dispersing agent is added, and ultrasonic stirring is carried out for 20min at room temperature; the dispersing agent is one of Arabic gum or sodium polyphosphate.

In the step 32, the preferable mass range of the multi-carbon wall nanotube is 1g to 2g, and the preferable duration of the ultrasonic stirring is 20min to 40min. In this example, 1.6g of multi-walled carbon nanotubes were taken and ultrasonically stirred for 30min.

In the step 33, the preferable mass range of the natural rubber latex is 40g to 60g. In this example, the mass of the added natural rubber latex was 50g, and the mixture was ultrasonically stirred for 25min.

In the step 35, the preferable time range of roasting and carbonizing is 1-2 h. In this example, the carbonized material was calcined in a muffle furnace at 750 ℃ for 1.5 hours.

In the step 4, the stirring time after the adsorbent is added is 20min-60min. In this example, the stirring time was 40min, and after completion of the stirring, the mixture was centrifuged at 4000rpm for 10min in a centrifuge.

In the step 5, the complex breaking agent is 30% hydrogen peroxide, and the preferred range of the complex breaking agent is that 0.5-3.5 mL of 30% hydrogen peroxide is added into every 50mL of solution, and the mixture is stirred for 10-50 min. In this example, stirring was carried out at room temperature for 30min with magnetic stirring.

In the step 6, the pH value is adjusted by an alkali solution, and the concentration of the alkali solution is 0.1-0.3 mol/L. The pH value of the waste liquid after being regulated is preferably between 9.5 and 10.5. In this example, na (OH) solution was used as the alkali solution, and the pH was adjusted to 10.

In the step 7, the precipitant is sodium phosphate in this example, and the preferable ratio range of the addition amount of the precipitant is 2 to 9g/L. In this case, the ratio of the precipitant is 5g/L, and the mixture is shaken at 25 ℃ for 30min after the precipitant is added.

In the step 8, the flocculating agent is polyacrylamide in the example, the flocculating agent is added according to the proportion of 5-25 g/L, the vibration environment temperature of the constant temperature oscillator is 15-30 ℃, and the vibration time is 10-40 min. In the example, the proportion of the flocculating agent is 5g/L, and the flocculating agent is added and then shaken for 15min at the temperature of 25 ℃.

In the step 9, the centrifugal rotating speed range of the centrifugal machine is 2500-5000 rpm. The centrifuge speed of the centrifuge is 4000rpm in this example, and the centrifuge time is 15min.

In the implementation process, a plurality of parts of soil of a farmland polluted by heavy metals under a mine in a certain place are taken, wherein the lead content of the soil is 661mg/kg, the cadmium content of the soil is 13mg/kg, and the mass of each part of soil is set to be 200g. Firstly, completing one-time leaching of one part of soil by 400ml of compound leaching agent of 20mmol/L ferric chloride and 50mmol/L citric acid; in the steps 1-9, 10g/L of adsorbent, 1mL of 30% hydrogen peroxide, 0.2mol/L of NaOH concentration, 5g/L of sodium phosphate and 5g/L of polyacrylamide are added until the leaching of soil and the treatment of leaching wastewater are completed. Heavy metal ions in the leaching waste liquid are adsorbed by the adsorbent, and are subjected to treatment such as complex breaking, precipitation, flocculation and the like, so that the leaching waste liquid reaches the discharge standard, and secondary pollution to the surrounding environment is avoided; the adsorbent is prepared by crosslinking natural latex and the multi-carbon wall nanotube, and can efficiently adsorb heavy metal ions in the elution waste liquid, so that the heavy metal ions and the elution waste liquid are fully separated, and the treatment effect of the elution waste liquid is ensured; the pH value of the leaching waste liquid is adjusted to be 9-11.5, so that the problem of high pH value of the existing waste water treatment technology is avoided, and the problem of water body environmental pollution is solved.

Example two:

the embodiment is obtained by improving the first embodiment, wherein a plurality of parts of soil of a farmland polluted by heavy metals under a mine in a certain place are taken, wherein the lead content of the soil is 812mg/kg, the cadmium content of the soil is 33mg/kg, and the mass of each part of soil is set to be 200g.

Step S1: leaching the heavy metal contaminated soil by using a leaching agent to obtain heavy metal leaching waste liquid; wherein the eluent comprises 20mmol/L ferric chloride and 100mmol/L citric acid;

step S2: taking the leaching waste liquid, and standing and precipitating the leaching waste liquid for 3 hours;

and step S3: transferring the precipitate supernatant of the leaching waste liquid, and adding an adsorbent prepared by crosslinking multi-walled carbon nanotubes and natural latex; the adding proportion is that 1.5g of adsorbent is added into every 100ml of leaching waste liquid;

and step S4: adding the adsorbent, stirring for 40min, and centrifuging at 4000rpm for 10min;

step S5: transferring the supernatant after centrifugal separation, adding 30% hydrogen peroxide, and stirring by magnetons; stirring for 30min to complete the vein breaking treatment;

step S6: regulating the pH value of the waste liquid after the decomplexation to 10;

step S7: adding sodium phosphate into the waste liquid, wherein the adding proportion of the sodium phosphate is 8g/L; adding sodium phosphate, and placing into a constant temperature oscillator for oscillation, wherein the set temperature is 25 ℃, and the oscillation time is 25min;

step S8: adding polyacrylamide into the waste liquid in a proportion of 10g/L; after adding the polyacrylamide, placing the polyacrylamide into a constant-temperature oscillator for oscillation, wherein the set temperature is 25 ℃, and the oscillation time is 15min;

step S9: and (5) centrifuging the waste liquid obtained in the step (S8) for 15min at 4000rpm by using a centrifugal machine to obtain liquid meeting the discharge standard, and ending the step.

The waste liquid treated in the first and second examples was emitted by inductively coupled plasma

The contents of Pb and Cd in the treated solution were measured by a spectrometer (ICP-OES Agilent 710) and the results are shown in Table 1:

TABLE 1 leacheate heavy metal removal Rate

The above description is only a specific example of the present invention and should not be construed as limiting the invention in any way. It will be apparent to persons skilled in the relevant art(s) that, having the benefit of this disclosure and its principles, various modifications and changes in form and detail can be made without departing from the principles and structures of the invention, which are, however, encompassed by the appended claims.

Claims

1. A method for treating heavy metal leaching wastewater by using a multi-walled carbon nanotube cross-linked natural latex adsorbent is characterized by comprising the following steps: step 1: leaching the heavy metal contaminated soil by using a leaching agent to obtain heavy metal leaching waste liquid; wherein the eluent is a compound eluent prepared by mixing chloride and organic acid; the soil is cadmium and lead-containing soil;

step 2: taking elution waste liquid, and standing and precipitating the elution waste liquid for 0 to 3 hours;

and step 3: transferring the supernatant of the precipitation of the leaching waste liquid, and adding an adsorbent prepared by crosslinking multi-walled carbon nano tubes with natural latex; the adding proportion is that 0.1g to 1.5g of adsorbent is added to every 100ml of elution waste liquid;

the preparation of the adsorbent prepared from the multi-walled carbon nanotube crosslinked natural latex in the step 3 comprises the following steps:

step 31: transferring 100 to 200ml of deionized water, putting the deionized water into a container, adding 1g to 3g of dispersing agent, and ultrasonically stirring the mixture for 5 to 30min at room temperature; the dispersing agent is one of Arabic gum or sodium polyphosphate;

step 32: adding 1g to 3g of multi-carbon-wall nanotubes in a small amount for multiple times, and ultrasonically stirring at room temperature for 2 min to 50min;

step 33: adding 30g to 70g of natural latex in a small amount for multiple times, and ultrasonically stirring at room temperature for 10 to 30min;

step 35: placing the dried adsorbent in a muffle furnace for roasting and carbonization;

in the step 35, roasting and carbonizing for 1 to 3 hours in a muffle furnace at the temperature of 700 to 800 ℃;

step 36: grinding the carbonized adsorbent by a mortar, and sieving by a 100-mesh sieve;

and 4, step 4: adding an adsorbent, stirring for 5min to 60min, and centrifuging by using a centrifuge after stirring is finished;

and 5: transferring the supernatant after centrifugal separation, adding a decomplexer, and stirring; the proportion of the added vein-breaking agent is that 0.1ml to 4ml of vein-breaking agent is added into every 50ml of vein-breaking agent; stirring for 5min to 60min to complete the vein breaking treatment;

step 6: adjusting the pH value of the waste liquid after the envelope breaking to be 9-11.5;

and 7: adding a precipitator into the waste liquid, wherein the adding proportion of the precipitator is 1 g-10 g/L; adding the precipitator, and then placing the precipitator into a constant temperature oscillator for oscillation, wherein the oscillation time is 5min to 40min;

and 8: adding a flocculating agent into the waste liquid in a proportion of 1g to 25g/L; after the flocculating agent is added, placing the mixture into a constant temperature oscillator for oscillation, wherein the oscillation time is 5min to 40min;

2. The method for treating heavy metal leaching wastewater by using the multi-walled carbon nanotube cross-linked natural latex adsorbent as claimed in claim 1, wherein the complex breaking agent in the step 5 is 30% hydrogen peroxide.

3. The method for treating heavy metal leaching wastewater by using the multi-walled carbon nanotube cross-linked natural latex adsorbent as claimed in claim 1, wherein in the step 6, pH adjustment is performed by using an alkali solution; the concentration of the alkali solution is 0.1-0.3 mol/L.

4. The method for treating heavy metal leaching wastewater by using the multi-walled carbon nanotube cross-linked natural latex adsorbent as claimed in claim 1, wherein the precipitant in the step 7 is sodium phosphate.

5. The method for treating heavy metal leaching wastewater by using the multi-walled carbon nanotube cross-linked natural latex adsorbent as claimed in claim 1, wherein the flocculant in the step 8 is polyacrylamide.

6. The method for treating heavy metal leaching wastewater by using the multi-walled carbon nanotube cross-linked natural latex adsorbent as claimed in claim 1, wherein the rotation speed of the centrifuge in the steps 4 and 9 is 4000rpm.

7. The method for treating heavy metal leaching wastewater by using the multi-walled carbon nanotube cross-linked natural latex adsorbent as claimed in claim 1, wherein the composite leaching agent in the step 1 comprises 5-50 mmol/L of chloride and 20-150mmol/L of organic acid; the chloride includes ferric chloride and calcium chloride, and the organic acid includes citric acid, malic acid and tartaric acid.

8. The method for treating heavy metal leaching wastewater by using the multi-walled carbon nanotube cross-linked natural latex adsorbent as claimed in claim 7, wherein the process for leaching the heavy metal contaminated soil specifically comprises the following steps:

step 12: moistening the sieved soil with water;

step 13: adding an eluting agent for mixed elution, wherein the volume of the added eluting agent is 2-3L/kg of the mass ratio of the added eluting agent to the soil;

step 14: standing the washed soil, and removing a supernatant;

step 15: repeating the steps 13 to 14, and circulating 1~3 times to obtain the demetallized soil;

and step 17: standing the diluted soil, and removing a supernatant;

step 18: and (5) repeating the steps 16-17, circulating 1~3 times, and ending the steps.