Adsorption coagulation method for efficiently treating wastewater containing chromium and nickel

Abstract

The application relates to the technical field of wastewater treatment, and discloses an adsorption coagulation method for efficiently treating chromium-nickel-containing wastewater, which comprises the following steps: NaOH modified powder activated carbon preparation: (1) 20g of NaOH is dissolved in 100ml of deionized water to prepare a 5mol / L NaOH solution; (2) 10g of powder activated carbon is placed in the solution prepared in (1), and after immersion, magnetic stirring is carried out for 2h; the solid material is repeatedly washed and filtered, and the SH-PAC material is obtained by drying at 60 DEG C for 24h; powder activated carbon adsorption combined with flocculation is used to remove chromium and nickel. The application provides an adsorption coagulation method for efficiently treating chromium-nickel-containing wastewater; the application uses an economical, reliable and mature treatment method, reduces dosing, does not change the pH of raw water, removes two kinds of heavy metals (nickel and chromium) in a short time, and enables treated wastewater to reach the groundwater quality standard.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and more particularly to an efficient adsorption-coagulation method for treating chromium- and nickel-containing wastewater. Background Technology

[0002] In recent years, my country's industrial enterprises have developed rapidly. Due to industrial restructuring and urban land use adjustments, some electroplating, leather tanning, chemical, and steel enterprises have relocated and transformed. The relocated sites and surrounding areas contain high concentrations of heavy metal ions in the groundwater and soil, making them difficult to directly utilize in existing areas and posing a threat to urban residents' lives and the environment. Heavy metals adhere to the soil, accumulating over time and exceeding standards, damaging soil structure and physicochemical properties, affecting plant growth, causing loss of soil microbial communities, and disrupting the local ecological balance. In agricultural areas, heavy metal pollution affects the growth of agricultural products, leading to reduced grain yields and other problems, causing serious economic losses. With the progress of biological cycles, heavy metal pollution will further expand, threatening human health. A survey shows that 74% of key industrial enterprises in Bao'an District, Shenzhen, totaling 330, are heavily polluted with heavy metals, especially chromium and nickel, due to various reasons. Trace amounts of Cr(VI) can corrode human skin, causing "chromium sores." Furthermore, Cr(VI) is carcinogenic and deadly; once it enters the human body, it seriously endangers life and health, with an ingestion of 1.5-1.6g being fatal. Nickel pollution can enter the human body through various pathways, inducing apoptosis and inhibiting proliferation, leading to corresponding functional disorders and adverse effects on human health. Therefore, exploring effective control and efficient removal methods for heavy metals such as chromium and nickel in water is of great significance for protecting the natural environment and ensuring the health of organisms.

[0003] In recent years, researchers have mainly used methods such as chemical precipitation, conventional adsorption, ion exchange, and coagulation / flocculation to remove heavy metal pollution from water. While these methods can remove heavy metals from wastewater, they also have corresponding drawbacks:

[0004] (1) Chemical precipitation method

[0005] Commonly used chemical substances such as sulfides and hydroxides combine with metal ions to form insoluble or sparingly soluble substances, which are then separated to remove heavy metal ions from the water. However, this method involves chemical reactions that produce mineral salts, causing secondary pollution. Furthermore, the use of alkaline substances is costly, and the selectivity for heavy metal ions is poor.

[0006] (2) Ion exchange method

[0007] Currently, ion exchange using synthetic resins is an effective method for treating polluted wastewater. It involves exchanging ions in the resin with metal ions to remove heavy metals from the wastewater. However, the use of synthetic resins significantly impacts the heavy metal removal efficiency, can severely damage the resin during use, and is difficult to recycle.

[0008] (3) Membrane separation method

[0009] This technology utilizes pressure and membrane separation efficiency to remove metal ions, effectively improving the ability to treat polluted wastewater. Common types include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. A significant problem with membrane treatment is membrane fouling, which can lead to a series of issues such as decreased membrane flux, increased membrane resistance, and reduced product water quality. Furthermore, membrane treatment typically also means incurring higher economic costs.

[0010] (4) Adsorption method

[0011] Traditional adsorption methods have the advantages of high efficiency, economy and simplicity, but targeted adsorbents still need further research and development. Most new adsorbents are still in the experimental stage, with problems such as small processing capacity and long cycle.

[0012] (5) Coagulation method

[0013] Coagulation sedimentation is a simple process that does not require complex and expensive equipment and technology and has a wide range of applications. However, coagulation sedimentation requires a long hydraulic retention time, which is not conducive to saving energy and reducing energy consumption. On the other hand, it is not suitable for treating high-concentration wastewater. In the treatment of wastewater with high pollutant content, it is necessary to combine it with other technologies.

[0014] To address the aforementioned problems, this application proposes an efficient adsorption-coagulation method for treating chromium- and nickel-containing wastewater. Summary of the Invention

[0015] (a) Purpose of the invention

[0016] To address the technical problems existing in the background art, this invention proposes an efficient adsorption coagulation method for treating chromium and nickel-containing wastewater. This invention uses an economical, reliable, and technically mature treatment method that reduces the amount of chemicals used, does not change the pH of the raw water, and removes both nickel and chromium, two heavy metals, in a short time, so that the treated wastewater can meet the groundwater quality standards.

[0017] (II) Technical Solution

[0018] To address the above problems, this invention provides an efficient adsorption-coagulation method for treating chromium- and nickel-containing wastewater, comprising the following steps:

[0019] Preparation of NaOH-modified powdered activated carbon:

[0020] (1) Dissolve 20g of NaOH in 100mL of deionized water to prepare a 5mol / L NaOH solution;

[0021] (2) Place 10g of powdered activated carbon in the solution prepared in (1), impregnate and stir magnetically for 2h, wash repeatedly and filter to obtain solid material, dry at 60℃ for 24h to obtain SH-PAC material;

[0022] Powdered activated carbon adsorption combined with flocculation for the removal of chromium and nickel:

[0023] (1) Prepare 1L of the target concentration pollutant solution and place it in a stirring tank;

[0024] (2) Add SH-PAC at a Ni(II) to SH-PAC mass ratio of 1:200, followed by 10 mg / L PFS and stirring;

[0025] (3) Add reducing agent and stir according to the mass ratio of Cr(VI) to FeSO4 of 1:20;

[0026] (4) Add 6 mg / L PAM to start the flocculation program and begin the coagulation experiment;

[0027] (5) After flocculation, allow the sediment to settle for 5 minutes, take the supernatant and filter it through a 0.45 μm filter membrane, and measure the concentration of the remaining pollutants using an atomic absorption spectrometer;

[0028] The flocculation process involves stirring in stages.

[0029] Preferably, NaOH-modified powdered activated carbon is used to prepare SH-PAC, and the prepared SH-PAC is used in combination with coagulant PFS and flocculant PAM to remove Ni(II) and Cr(VI).

[0030] Preferably, during the staged stirring process of flocculation:

[0031] The first stage, with a rotation speed of 450 r / min and a duration of 30 s, begins with the addition of the drug at the start of operation;

[0032] The second stage, with a rotation speed of 100 r / min and a duration of 2 min;

[0033] The third stage, with a rotation speed of 85 r / min and a time of 2.5 min;

[0034] The fourth stage, with a rotation speed of 70 r / min and a time of 3.5 min;

[0035] The fifth stage was conducted at a rotation speed of 50 r / min for 5.5 min.

[0036] Preferably, in (2) of the powdered activated carbon adsorption combined with flocculation for the removal of chromium and nickel:

[0037] Stir at 400 rpm for 15 minutes.

[0038] Preferably, in (3) of the powdered activated carbon adsorption combined with flocculation for the removal of chromium and nickel:

[0039] Stir at 400 rpm for 3 minutes.

[0040] The above-described technical solution of the present invention has the following beneficial technical effects:

[0041] The method utilizes readily available activated carbon materials, which are modified and then combined with flocculation to control heavy metal pollution. The adsorbent material is easy to prepare and has high stability. The treatment time for pollutants is short, the treatment process does not require pH adjustment, the amount of reagents added is small, reducing the possibility of secondary pollution, the energy consumption is low, the treatment cost is low, the operation is convenient, the removal effect of pollutants is significant, and the concentration of heavy metals after treatment is effectively controlled. Attached Figure Description

[0042] Figure 1 This is a scanning electron microscope image of the SH-PAC of the present invention.

[0043] Figure 2 This is the X-ray diffraction pattern of the SH-PAC of the present invention.

[0044] Figure 3 This is a diagram illustrating the effect of the present invention in removing chromium and nickel contaminants.

[0045] Figure 4 This is a flowchart of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0047] The technical solution adopted by this invention to solve the existing problems mainly consists of two steps: first, treating polluted wastewater by adding NaOH-modified powdered activated carbon (SH-PAC), which can adsorb Ni(II) in 15 minutes; second, adding a reducing agent and a flocculant to remove the remaining activated carbon particles and Cr(III) after the pretreatment. After adding PAM to aid coagulation, the floc particles increase in size, and complete sedimentation can be achieved within 5 minutes after flocculation, shortening the sedimentation time after flocculation.

[0048] like Figure 1-4 As shown, the present invention proposes an efficient adsorption-coagulation method for treating chromium-nickel-containing wastewater, comprising the following steps:

[0049] (1) Dissolve 20g of NaOH in 100mL of deionized water to prepare a 5mol / L NaOH solution;

[0050] (2) Place 10g of powdered activated carbon in the solution prepared in (1), impregnate and stir magnetically for 2h, wash repeatedly and filter to obtain solid material, dry at 60℃ for 24h to obtain SH-PAC material;

[0051] Furthermore, the prepared SH-PAC was used in combination with coagulant PFS and flocculant PAM to remove Ni(II) and Cr(VI).

[0052] II. Experimental steps for removing chromium and nickel using powdered activated carbon adsorption combined with flocculation:

[0053] (1) Prepare 1L of the target concentration pollutant solution and place it in a stirring tank;

[0054] (2) Add SH-PAC at a mass ratio of Ni(II) to SH-PAC of 1:200, followed by 10 mg / L PFS, and stir at 400 r / min for 15 min;

[0055] (3) Add reducing agent at a mass ratio of Cr(VI) to FeSO4 of 1:20 and stir at 400 r / min for 3 min;

[0056] (4) Add 6 mg / L PAM to start the flocculation program and begin the coagulation experiment;

[0057] (5) After flocculation, allow the sediment to settle for 5 minutes. Take the supernatant and filter it through a 0.45 μm filter membrane. Measure the concentration of the remaining pollutants using an atomic absorption spectrometer.

[0058] III. The stirring procedure for the flocculation process is designed as follows:

[0059] (1) First stage, rotation speed 450r / min, time 30s, add medicine at the start of operation;

[0060] (2) Second stage, rotation speed 100 r / min, time 2 min;

[0061] (3) The third stage, with a rotation speed of 85 r / min and a time of 2.5 min;

[0062] (4) Fourth stage, rotation speed 70 r / min, time 3.5 min;

[0063] (5) Fifth stage, rotation speed 50 r / min, time 5.5 min.

[0064] The flocculation process takes 14 minutes and effectively aggregates the SH-PAC particles that adsorb Ni(II) and the reduced Cr(III) into large flocs, achieving good removal. No additional reagents are added during the entire process, and pH adjustment is unnecessary. The pH of the treated water sample remains within the groundwater pH range, allowing for direct discharge.

[0065] In this invention, wastewater containing chromium and nickel pollution was selected as the treatment object. The removal effect of target metal ions under different systems was studied. The results showed that the experimental scheme achieved a 100% removal rate of Cr(VI) and an 83% removal rate of Ni(II).

[0066] In this invention, readily available activated carbon material is modified and then combined with flocculation to control heavy metal pollution. The adsorption material is easy to prepare and has high stability. The pollutant treatment time is short, the treatment process does not require pH adjustment, the amount of reagent added is small, reducing the possibility of secondary pollution, the energy consumption is low, the treatment cost is low, the operation is convenient, the pollutant removal effect is significant, and the heavy metal concentration is effectively controlled after treatment.

[0067] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An efficient adsorption-coagulation method for treating chromium-nickel-containing wastewater, characterized in that, Includes the following steps: Preparation of NaOH-modified powdered activated carbon: (1) Dissolve 20g of NaOH in 100mL of deionized water to prepare a 5mol / L NaOH solution; (2) Place 10g of powdered activated carbon in the solution prepared in (1), impregnate and stir magnetically for 2h, wash repeatedly and filter to obtain solid material, dry at 60℃ for 24h to obtain SH-PAC material; Powdered activated carbon adsorption combined with flocculation for the removal of chromium and nickel: (1) Prepare 1L of the target concentration pollutant solution and place it in a stirring tank; (2) Add SH-PAC at a Ni(II) to SH-PAC mass ratio of 1:200, followed by 10 mg / L PFS and stirring; (3) Add reducing agent and stir according to the mass ratio of Cr(VI) to FeSO4 of 1:20; (4) Add 6 mg / L PAM to start the flocculation program and begin the coagulation experiment; (5) After flocculation, allow the sediment to settle for 5 minutes, take the supernatant and filter it through a 0.45 μm filter membrane, and measure the concentration of the remaining pollutants using an atomic absorption spectrometer; The flocculation process involves stirring in stages.

2. The adsorption coagulation method for efficiently treating wastewater containing chromium and nickel according to claim 1, characterized by, NaOH-modified powdered activated carbon was used to prepare SH-PAC. The prepared SH-PAC was then used in combination with coagulant PFS and flocculant PAM to remove Ni(II) and Cr(VI).

3. The adsorption coagulation method for efficiently treating wastewater containing chromium and nickel according to claim 2, characterized by, During the staged stirring process of flocculation: The first stage, with a rotation speed of 450 r / min and a duration of 30 s, begins with the addition of the drug at the start of operation; The second stage, with a rotation speed of 100 r / min and a duration of 2 min; The third stage, with a rotation speed of 85 r / min and a time of 2.5 min; The fourth stage, with a rotation speed of 70 r / min and a time of 3.5 min; The fifth stage was conducted at a rotation speed of 50 r / min for 5.5 min.

4. The adsorption-coagulation method for efficiently treating chromium-nickel-containing wastewater according to claim 3, characterized in that, In (2) of the combined process of powdered activated carbon adsorption and flocculation for the removal of chromium and nickel: Stir at 400 rpm for 15 minutes.

5. The adsorption-coagulation method for efficiently treating chromium-nickel-containing wastewater according to claim 4, characterized in that, In (3) of the combined process of powdered activated carbon adsorption and flocculation for the removal of chromium and nickel: Stir at 400 rpm for 3 minutes; In the removal of chromium and nickel by powdered activated carbon adsorption combined with flocculation, (5) is as follows: Filtered through a 0.45μm filter membrane.

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