A method for resourceful treatment of heavy metal wastewater

Abstract

The application provides a resourceful treatment method of heavy metal wastewater, and belongs to the technical field of wastewater treatment. The application selects cheap and easily obtained biomass as raw material for capturing heavy metal ions, so that the biomass is better utilized, the pollution to the environment is reduced to a certain extent, and the biochar prepared from the biomass plays a role in promoting precipitation and adsorbing precipitation in the hydrothermal capture of heavy metal ions due to the special physicochemical properties of the biochar, so that the precipitation rate and removal rate of the heavy metal ions in the wastewater are more than 99%, and the wastewater can be discharged or reused up to the standard. In the process of the hydrothermal reaction of the heavy metal wastewater, the alkali carbonate precipitation reaction is carried out, the heavy metal ions in the original wastewater generate alkali carbonate precipitates and are collected on the biochar, and the alkali carbonate-biochar compound can be easily separated from water. The obtained alkali carbonate-biochar compound can be subjected to simple electrolysis or thermal treatment, so that the heavy metal is recycled and used with high added value. The process is clean and efficient, the method is novel, and the practicality is strong.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a resource treatment method of heavy metal wastewater. BACKGROUND

[0002] Heavy metal pollution refers to environmental pollution caused by heavy metals or their compounds. Current heavy metal wastewater in China mainly comes from smelting, mining, pesticide, electrolysis, pigment and pharmaceutical industries. Due to the characteristics of heavy metals such as non-degradability, enrichment and toxicity, heavy metal wastewater is the most serious environmental pollution and the most harmful industrial wastewater to human beings. The Japanese "Minamata disease" and "Itai-Itai disease" are caused by mercury-containing wastewater and cadmium-containing wastewater pollution, respectively. Studies have shown that heavy metal pollution has multiple and multi-level effects on human health, and its toxicological effects include causing reproductive disorders, affecting normal fetal development, and threatening the health of children and adults. Therefore, it is necessary to study the correct and efficient way to treat heavy metal wastewater, and to achieve the resource utilization of heavy metals to avoid resource waste.

[0003] At present, the treatment methods of heavy metal wastewater at home and abroad can be roughly divided into two categories: one is to adsorb, concentrate and separate under the condition of not changing the chemical state of heavy metal ions, and the representative methods include adsorption method, ion exchange method, membrane separation method, evaporation concentration method and reverse osmosis method. Among them, the adsorption method uses cheap biomass and mineral materials as raw materials, such as livestock and poultry manure, tobacco stems, walnut shells, zeolite, attapulgite and pyrrhotite, etc. These raw materials or modified products have strong adsorption effect on heavy metal ions in wastewater, but the treatment period is long; the adsorption capacity is limited, and the heavy metal content in the treated solid is only 1-5%, which cannot meet the requirements of resource utilization; at the same time, the treated heavy metals in waste are not stable and can easily dissolve to cause secondary pollution, which becomes a dangerous waste.

[0004] The other method is to convert the heavy metal ions in dissolved state in wastewater into insoluble heavy metal compounds, and then remove them from wastewater by precipitation or flotation separation. The representative methods include ferrite coprecipitation, hydroxide precipitation, oxidation-reduction precipitation, electrolysis and biological method. Among them, the most commonly used methods are oxidation-reduction precipitation and hydroxide precipitation, but these methods have the common problem that the precipitated particles are small, which need a sedimentation tank, and it is difficult to completely separate the newly formed small particles from water, so the water treatment effect is not obvious; at the same time, the sediment sludge is a dangerous waste, and the sludge quantity is large and the water content is high, so the sludge treatment is difficult.

[0005] In summary, there is an urgent need for a heavy metal wastewater treatment method with short treatment period, large treatment capacity, not easy to cause secondary pollution and realizing resource utilization of heavy metals. SUMMARY

[0006] Therefore, the present application aims to provide a resource treatment method of heavy metal wastewater.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions.

[0008] The present application provides a resource treatment method of heavy metal wastewater, comprising the following steps.

[0009] The biomass raw material is carbonized to obtain biochar powder;

[0010] The heavy metal wastewater is mixed with concentrated nitric acid to obtain acidified heavy metal wastewater;

[0011] The biochar powder is mixed with the acidified heavy metal wastewater to perform a hydrothermal reaction, so as to obtain an alkali carbonate-biochar composite and treated wastewater.

[0012] Preferably, the biomass raw material is one or more of municipal sludge, livestock and poultry manure, crop straw, fruit shell and straw.

[0013] Preferably, the carbonization temperature is 700-900℃, and the holding time is 2-5h.

[0014] Preferably, the heavy metal ions in the heavy metal wastewater include one or more of Cu 2+ , Pb 2+ , Cd 2+ , Ni 2+ , Co 2+ , Zn 2+ , Mg 2+ and Fe 2+ , and the concentration of the heavy metal ions in the heavy metal wastewater is 0.5-500mg / L.

[0015] Preferably, the pH value of the acidified heavy metal wastewater is 4-5.

[0016] Preferably, the solid-liquid ratio of the biochar powder to the acidified heavy metal wastewater is 1-3g:20-30mL.

[0017] Preferably, the temperature of the hydrothermal reaction is 150-200℃, the pressure is 0.2-2MPa, and the holding time is 8-10h.

[0018] Preferably, when the heavy metal wastewater includes Cu 2+ , the obtained alkali carbonate-biochar composite is used as a sewage treatment bactericide;

[0019] When the heavy metal wastewater includes Ni 2+The obtained basic carbonate-biochar composite is used as an electroplating material;

[0020] When the heavy metal wastewater contains Co 2+ The obtained basic carbonate-biochar composite is used as an industrial catalyst.

[0021] Preferably, the obtained basic carbonate-biochar composite is calcined, and the obtained calcined product is used as an industrial waste gas adsorption degradation agent.

[0022] Preferably, the obtained basic carbonate-biochar composite is calcined, and the obtained heavy metal oxide is obtained.

[0023] The heavy metal oxide is mixed with an acid solution, and the obtained mixture is electrolyzed to recover the heavy metal.

[0024] The present application provides a resourceful treatment method of heavy metal wastewater, comprising the following steps: carbonizing a biomass raw material to obtain biochar powder; mixing the heavy metal wastewater with concentrated nitric acid to obtain acidified heavy metal wastewater; mixing the biochar powder with the acidified heavy metal wastewater to perform a hydrothermal reaction, and obtaining a basic carbonate-biochar composite and treated wastewater.

[0025] Meanwhile, the resource treatment method provided by the application has the advantages of short treatment period (only 2-5 hours of hydrothermal reaction), large treatment capacity, and no influence of complex components and heavy metal ion concentration of wastewater, and the heavy metal ions can be stably adsorbed on the surface of the basic carbonate of the biochar and are not easy to cause secondary pollution, and the method has the advantages of stability and high efficiency. In addition, the heavy metals can be recovered by electrolysis, or the basic carbonate can be treated by calcination to realize high value-added utilization, and the method has better economic benefits and social value. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A resource treatment flowchart of heavy metal wastewater;

[0027] Figure 2 A physical picture of biochar before and after hydrothermal treatment of heavy metals in Example 1;

[0028] Figure 3 An XRD diagram of biochar before and after hydrothermal treatment of heavy metals in Example 1;

[0029] Figure 4 A micro-morphology of biochar before and after hydrothermal treatment of heavy metals in Example 1;

[0030] Figure 5 A physical picture of solid product obtained by hydrothermal reaction in Comparative Example 3. DETAILED DESCRIPTION

[0031] The application provides a resource treatment method of heavy metal wastewater, comprising the following steps:

[0032] Carbonizing the biomass raw material to obtain biochar powder;

[0033] Mixing the heavy metal wastewater with concentrated nitric acid to obtain acidified heavy metal wastewater;

[0034] Mixing the biochar powder with the acidified heavy metal wastewater, and performing hydrothermal reaction to obtain a basic carbonate-biochar composite and treated wastewater.

[0035] The biomass raw material is carbonized to obtain biochar powder in the application. In the application, the biomass raw material is preferably one or more of municipal sludge, livestock and poultry manure, crop straw, fruit shell and straw.

[0036] The biomass raw material is preferably dried in the application, and the drying is preferably sun drying or oven drying.

[0037] In the present application, the carbonization is preferably carried out in a tube furnace, and the carbonization is preferably carried out under a nitrogen atmosphere. In the present application, the temperature of the carbonization is preferably 700-900℃, more preferably 700-800℃; the holding time is 2-5h, more preferably 3-4h. In the present application, the heating rate to the carbonization temperature is preferably 5℃ / min. In the present application, the biomass raw material absorbs heat in the carbonization reactor, and the water is first evaporated and escaped, and the internal chemical composition of the biomass hardly changes. Secondly, the volatile pyrolysis stage. The biomass continues to absorb heat to about 200℃, and the internal macromolecular chemical bonds are broken and rearranged, and the organic matter gradually volatilizes, and the internal thermal decomposition reaction of the material begins, and the gaseous combustible of the volatile matter combusts under the condition of oxygen deficiency, and the combustion is static penetration diffusion combustion, which can provide heat support for the decomposition of the material layer by layer. Finally, the overall carbonization stage. In this stage, the temperature is 300-800℃, and the raw material is rapidly thermally decomposed, and liquid products such as wood tar and acetic acid and combustible gases such as methane and ethylene are produced, and with the separation and precipitation of most of the volatile matter, the final remaining solid product is coke composed of carbon and ash.

[0038] In the present application, after the carbonization, the present application preferably crushes and sieves the obtained carbonization product to obtain a biochar powder. In the present application, the particle size of the biochar powder is preferably 40-60 mesh. In the present application, the specific surface area of the biochar powder is preferably 351.98-386.55m 2 / g, the pore volume is preferably 0.16-0.18cm3 / g, and the pore size is preferably 0.05-0.07mm.

[0039] In the present application, the heavy metal wastewater is mixed with concentrated nitric acid to obtain acidified heavy metal wastewater. In the present application, the heavy metal ions in the heavy metal wastewater preferably include one or more of Cu 2+ , Pb 2+ , Cd 2+ , Ni 2+ , Co 2+ , Zn 2+ , Mg 2+ , and Fe 2+ . The concentration of heavy metal ions in the heavy metal wastewater is preferably 0.5-500mg / L, more preferably 1-400mg / L, and further preferably 10-300mg / L.

[0040] In the present application, the mass concentration of the concentrated nitric acid is preferably 55-58%, more preferably 56-57%. In the present application, after the heavy metal wastewater is mixed with the concentrated nitric acid, the pH value of the obtained acidified heavy metal wastewater is preferably 4-5, more preferably 4.3-4.8, and further preferably 4.5. In the present application, the mixing mode is preferably that the concentrated nitric acid is added dropwise into the heavy metal wastewater. In the present application, the role of the nitric acid is to provide hydrogen ions, and in the reaction system, the generation of ion clusters is promoted.

[0041] In the present application, the biochar powder is mixed with the acidified heavy metal wastewater to perform a hydrothermal reaction, so as to obtain a basic carbonate-biochar composite and treated wastewater. In the present application, the solid-liquid ratio of the biochar powder to the acidified heavy metal wastewater is preferably 1-3:20-30, and more preferably 1:20. The present application does not have special requirements for the mixing mode, and any mixing mode known to those skilled in the art can be used, for example, stirring mixing.

[0042] In the present application, the hydrothermal reaction is preferably performed in a hydrothermal reaction kettle. In the present application, the temperature of the hydrothermal reaction is preferably 150-200℃, more preferably 160-180℃; the pressure is preferably 0.2-2 MPa, more preferably 0.5-1.5 MPa; and the holding time under pressure is preferably 2-5 h, more preferably 3-4 h. In the present application, in the process of the hydrothermal reaction, the high temperature and high pressure in the reaction kettle cause the metal ions in the aqueous solution to aggregate or generate ion clusters; after the completion of the hydrothermal reaction, the temperature and pressure are reduced (temperature difference), so as to generate convection, and the sol / ion clusters at the interface between the solution and the biochar form a supersaturated state to generate crystallization nucleation, which is loaded on the surface of the biochar to obtain a basic carbonate-biochar composite.

[0043] After the hydrothermal reaction, the present application preferably performs solid-liquid separation on the obtained hydrothermal reaction liquid to obtain a basic carbonate-biochar composite and treated wastewater. The present application does not have special requirements for the solid-liquid separation mode, and any solid-liquid separation mode known to those skilled in the art can be used, for example, filtration.

[0044] In the present application, the content of heavy metal ions in the treated wastewater is preferably 0.1-0.4 mg / L, and more preferably 0.2-0.3 mg / L. In the present application, the precipitation rate of the heavy metals in the heavy metal wastewater is above 99%, and the pH and heavy metal content of the treated wastewater meet the discharge standard.

[0045] In the present application, when the heavy metal wastewater contains Cu 2+ , the obtained basic carbonate-biochar composite is preferably used as a sewage treatment bactericide.

[0046] In the present application, when the heavy metal wastewater contains Ni 2+When the heavy metal wastewater includes Co

[0047] In the present application, when the heavy metal wastewater includes Co 2+ When the heavy metal wastewater includes Co

[0048] After obtaining the basic carbonate-biochar composite, the present application further preferably includes calcining the obtained basic carbonate-biochar composite to obtain heavy metal oxides; mixing the heavy metal oxides with an acid solution, electrolyzing the obtained mixed solution, and recovering heavy metals.

[0049] In the present application, the temperature of the calcination is preferably 350℃, and the time is preferably 3-5h. In the present application, the calcination is preferably performed under anoxic or hypoxic conditions. The present application preferably regulates the metal loading of the obtained calcination product, so that the metal loading of the obtained calcination product is between 5-20wt%, more preferably 10-15wt%.

[0050] immersing the basic carbonate-biochar composite in a soluble metal salt solution, and taking out the immersed composite for calcination.

[0051] In the present application, the metal species of the soluble metal salt solution is the same as that of the basic carbonate.

[0052] In the present application, the concentration of the soluble metal salt solution is preferably 0.5-5mol / L, and is specifically preferably 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5mol / L.

[0053] In the present application, the industrial waste gas treated by the industrial waste gas adsorption degradation agent is preferably one or several of PH3, H2S, and HF.

[0054] After obtaining the basic carbonate-biochar composite, the present application further preferably includes calcining the obtained basic carbonate-biochar composite to obtain heavy metal oxides; mixing the heavy metal oxides with an acid solution, electrolyzing the obtained mixed solution, and recovering heavy metals.

[0055] In the present application, the temperature of the calcination is preferably 700-900℃, and the time is preferably 2-5h.

[0056] In the present application, the acid solution is preferably a sulfuric acid solution or a hydrochloric acid solution, and the mass concentration of the acid solution is preferably 5-10%, more preferably 6-8%. The present application does not have special requirements for the electrolysis method, and the electrolysis method well known to those skilled in the art can be used.

[0057] The resource processing flow chart of the heavy metal wastewater in the present application is shown in Figure 1

[0058] The resource processing method of the heavy metal wastewater provided by the present application will be described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0059] Example 1

[0060] The biomass raw material of this example is walnut shell; a solution containing 500 mg / L of Cu 2+ The heavy metal wastewater, as a simulated high-concentration copper-containing heavy metal wastewater, is treated according to the following steps:

[0061] (1) The walnut shell is carbonized in a tubular furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700℃ for 4h;

[0062] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the high-concentration heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.3, for acidification treatment;

[0063] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180℃, the pressure at 0.3 MPa, and the time at 9h;

[0064] (4) The mixed solution after reaction is subjected to solid-liquid separation to obtain basic copper carbonate attached to the biochar and a filtrate; the filtrate is directly discharged or used as process water for recycling; the basic copper carbonate is directly used as a water treatment bactericide; or the basic copper carbonate is incinerated at 350℃ for 3.5h to obtain copper oxide, which is then dissolved in a mass concentration of 8% sulfuric acid solution to form a dissolved solution, and the dissolved solution obtained by electrolysis is used to recover copper; or the basic copper carbonate is calcined at 500℃, and after adjusting the metal loading, a high-performance Cu-based catalyst for purifying PH3, H2S and HF is obtained.

[0065] The purification effect of the high-concentration copper-containing heavy metal wastewater in Example 1 is analyzed by atomic absorption spectrophotometry to measure the initial concentration of the high-concentration copper-containing heavy metal wastewater and the copper ion concentration of the wastewater after one treatment, as shown in Table 1:

[0066] Table 1 Concentration of wastewater before and after treatment ​

[0067]

[0068] Images of biochar before and after hydrothermal treatment of heavy metals are shown below. Figure 2 As shown in the image, the physical picture of walnut shell-based biochar is a typical example of black carbon material. Figure 2 (a) of the sample changes color from black to copper green after a hydrothermal reaction. Figure 2 (b)). After roasting, it turns into black granules. Figure 2 (c) in the middle.

[0069] The crystal phase composition of the three materials was confirmed by XRD, such as Figure 3 As shown, for walnut shell-based biochar, a broad peak with a 2θ range of 15–35° and a weak peak at 26.5° can be observed, corresponding to typical amorphous carbon. Compared with walnut shell-based biochar, a series of characteristic peaks attributed to basic copper carbonate (Cu2(OH)2CO3) (2θ = 11.9, 14.8, 17.5, 18.9, 24.1, 29.9, 31.3, 32.2, 35.6°, PDF#76-0660) can be observed on the XRD pattern of biochar after hydrothermal reaction, indicating that highly crystalline Cu2(OH)2CO3 is formed on the surface of biochar during the hydrothermal reaction. A series of characteristic diffraction peaks corresponding to CuO (2θ = 32.5, 35.4, 38.9, 48.8, 58.2, 61.3°, PDF#80-0076) can be observed on the XRD pattern of the calcined biochar, indicating that Cu2(OH)2CO3 in the biochar after hydrothermal reaction is converted into high-purity active component CuO after calcination. By controlling the Cu loading, it can efficiently adsorb and degrade industrial waste gas pollutants such as H2S, PH3, and HF.

[0070] The microstructure of walnut shell biochar before and after hydrothermal reaction is as follows: Figure 4 As shown, (a) represents the microstructure before the hydrothermal reaction, and (b) represents the microstructure after the hydrothermal reaction. Before the hydrothermal reaction, the biochar surface is rough and irregular, with no other substances attached, and numerous "wormhole"-like channels are distributed on the surface, indicating a rich porous structure. After the hydrothermal reaction, a large number of directionally growing flake-like Cu2(OH)2CO3 particles can be observed on the surface. High-magnification SEM images show that these flake-like nanosheets have a very smooth surface.

[0071] Example 2

[0072] The biomass raw material in this embodiment is walnut shells; this embodiment is formulated with Cu... 2+ Pb 2+ Cd 2+Each 500 mg / L of heavy metal wastewater, as a simulated high concentration of heavy metal wastewater, was treated according to the following steps:

[0073] (1) Walnut shell was carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters were: carbonization at 700℃ for 4h;

[0074] (2) 0.5 mL of concentrated nitric acid solution was added dropwise to the high concentration of heavy metal wastewater, and the pH of the wastewater after adding the acid solution was 4.5, and the wastewater was acidified;

[0075] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater were mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180℃, the pressure at 0.3 MPa, and the time at 9h;

[0076] The purification effect of the high concentration of heavy metal wastewater in Example 2 was analyzed: the initial concentration and the ion concentration after the first treatment of the high concentration of heavy metal wastewater were measured by atomic absorption spectrophotometry, and the details are shown in Table 2.

[0077] Table 2 Concentration of wastewater before and after treatment

[0078]

[0079] Example 3

[0080] The biomass raw material of this example is walnut shell; this example prepares a low concentration of copper-containing heavy metal wastewater containing 50 mg / L of Cu 2+ The heavy metal wastewater, as a simulated low concentration of copper-containing heavy metal wastewater, was treated according to the following steps:

[0081] (1) Walnut shell was carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters were: carbonization at 700℃ for 4h;

[0082] (2) 0.5 mL of concentrated nitric acid solution was added dropwise to the low concentration of copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution was 4.3, and the wastewater was acidified;

[0083] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater were mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180℃, the pressure at 0.3 MPa, and the time at 9h;

[0084] The purification effect of the low concentration of copper-containing heavy metal wastewater in Example 3 was analyzed: the initial concentration and the ion concentration after the first treatment of the low concentration of copper-containing heavy metal wastewater were measured by atomic absorption spectrophotometry, and the details are shown in Table 3.

[0085] Concentration of wastewater before and after treatment

[0086]

[0087] Example 4

[0088] The biomass raw material of this example is walnut shell; the heavy metal wastewater containing Cu 2+ , Pb 2+ , Cd 2+ 50 mg / L respectively is prepared as simulated low-concentration heavy metal wastewater, and is treated according to the following steps:

[0089] (1) The walnut shell is carbonized in a tube furnace, and then is crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 meshes; the carbonization reaction parameters are: carbonization at 700 ℃ for 4 h;

[0090] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the low-concentration heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.5, and the acidification treatment is carried out;

[0091] (3) The walnut shell-based biochar powder and the heavy metal wastewater after acidification treatment are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and are reacted at a certain temperature and pressure, and the temperature is controlled at 180 ℃, the pressure is 0.3 MPa, and the time is 9 h;

[0092] The purification effect of the low-concentration heavy metal wastewater in Example 4 is analyzed: the atomic absorption spectrophotometer is used to measure the initial concentration and the ion concentration after the first treatment of the low-concentration heavy metal wastewater, and the details are shown in Table 4.

[0093] Concentration of wastewater before and after treatment

[0094]

[0095] Example 5

[0096] The biomass raw material of this example is municipal sludge; the heavy metal wastewater containing 500 mg / L of Cu 2+ is prepared as simulated high-concentration copper-containing heavy metal wastewater, and is treated according to the following steps:

[0097] (1) The municipal sludge is carbonized in a tube furnace, and then is crushed and sieved to obtain municipal sludge-based biochar powder with a particle size of 40-60 meshes; the carbonization reaction parameters are: carbonization at 700 ℃ for 4 h;

[0098] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the high-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.8, and the acidification treatment is carried out;

[0099] (3) The municipal sludge-based biochar powder and the acidified heavy metal wastewater were mixed in a hydrothermal reactor at a solid-liquid ratio of 1:20 and reacted under certain temperature and pressure conditions, with the temperature controlled at 180℃, the pressure at 0.3MPa, and the time at 9h.

[0100] Analysis of the purification effect of high-concentration copper-containing heavy metal wastewater in Example 5: The initial concentration and the ion concentration of the high-concentration copper-containing heavy metal wastewater after one treatment were measured by atomic absorption spectrophotometer, as detailed in Table 5.

[0101] Table 5. Concentration of wastewater before and after treatment

[0102]

[0103] Example 6

[0104] The biomass raw material in this embodiment is municipal sewage sludge; this embodiment is formulated with Cu... 2+ Pb 2+ Cd 2+ Wastewater containing 500 mg / L of heavy metals, with a pH of 4-5 after adding acid, was used as a simulated high-concentration heavy metal wastewater and treated according to the following steps:

[0105] (1) The municipal sludge was carbonized in a tubular furnace, then crushed and screened to obtain municipal sludge-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters were: carbonization at 700℃ for 4 hours.

[0106] (2) Add 0.5 mL of concentrated nitric acid solution to the high-concentration heavy metal wastewater. After adding the acid, the pH of the wastewater is 4.4, and acidification treatment is carried out.

[0107] (3) The municipal sludge-based biochar powder and the acidified heavy metal wastewater were mixed in a hydrothermal reactor at a solid-liquid ratio of 1:20 and reacted under certain temperature and pressure conditions, with the temperature controlled at 180℃, the pressure at 0.3MPa, and the time at 9h.

[0108] Analysis of the purification effect of high-concentration heavy metal wastewater in Example 6: The initial concentration and ion concentration of high-concentration heavy metal wastewater after one treatment were measured by atomic absorption spectrophotometer, as detailed in Table 6.

[0109] Table 6. Concentration of wastewater before and after treatment

[0110]

[0111] Example 7

[0112] The biomass raw material in this embodiment is municipal sewage sludge; this embodiment prepares a solution containing 50 mg / L Cu. 2+Heavy metal wastewater, as a simulated low-concentration copper-containing heavy metal wastewater, is treated according to the following steps:

[0113] (1) Municipal sludge is carbonized in a tube furnace, and then broken and sieved to obtain municipal sludge-based biochar powder with a particle size of 40-60 meshes; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0114] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the low-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.5, for acidification treatment;

[0115] (3) The municipal sludge-based biochar powder and the acid-treated heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.3 MPa, and the time at 9h;

[0116] The purification effect of the low-concentration copper-containing heavy metal wastewater in Example 7 is analyzed: the initial concentration and the ion concentration after the first treatment of the low-concentration copper-containing heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 7.

[0117] Table 7 Concentration of wastewater before and after treatment

[0118]

[0119] Example 8

[0120] The biomass raw material of this example is municipal sludge; in this example, low heavy metal wastewater containing Cu 2+ , Pb 2+ , and Cd 2+ each at 50 mg / L is prepared as a simulated low-concentration heavy metal wastewater, and is treated according to the following steps:

[0121] (1) Municipal sludge is carbonized in a tube furnace, and then broken and sieved to obtain municipal sludge-based biochar powder with a particle size of 40-60 meshes; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0122] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the low-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.5, for acidification treatment;

[0123] (3) The municipal sludge-based biochar powder and the acid-treated heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.3 MPa, and the time at 9h;

[0124] The purification effect of the low-concentration heavy metal wastewater in Example 8 was analyzed: the initial concentration and the ion concentration after the first treatment of the low-concentration heavy metal wastewater were measured by atomic absorption spectrophotometry, and the details are shown in Table 8.

[0125] Table 8 Concentration of wastewater before and after treatment

[0126]

[0127] Example 9

[0128] The biomass raw material of this example was municipal sludge and walnut shell; in this example, a Cu 2+ heavy metal wastewater was prepared, which was used as a simulated high-concentration copper-containing heavy metal wastewater, and was treated according to the following steps:

[0129] (1) The mixed biomass of municipal sludge and walnut shell was carbonized in a tubular furnace, and the mass ratio of municipal sludge to walnut shell was 1:2. After crushing and sieving, a biochar powder with a particle size of 40-60 mesh was obtained. The carbonization reaction parameters were: carbonization at 700℃ for 4h;

[0130] (2) 0.5mL of concentrated nitric acid solution was added dropwise to the high-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution was 4.5, for acidification treatment;

[0131] (3) The biochar powder and the acidified heavy metal wastewater were mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure. The temperature was controlled at 180℃, the pressure was 0.3MPa, and the time was 9h;

[0132] The purification effect of the high-concentration copper-containing heavy metal wastewater in Example 9 was analyzed: the initial concentration and the ion concentration after the first treatment of the high-concentration copper-containing heavy metal wastewater were measured by atomic absorption spectrophotometry, and the details are shown in Table 9.

[0133] Table 9 Concentration of wastewater before and after treatment

[0134]

[0135] Example 10

[0136] The biomass raw material of this example was municipal sludge and walnut shell; in this example, a Cu 2+ heavy metal wastewater was prepared, which was used as a simulated low-concentration copper-containing heavy metal wastewater, and was treated according to the following steps:

[0137] (1) The mixed biomass of municipal sludge and walnut shell was carbonized in a tubular furnace, and the mass ratio of municipal sludge to walnut shell was 1:2. After crushing and sieving, a biochar powder with a particle size of 40-60 mesh was obtained. The carbonization reaction parameters were: carbonization at 700℃ for 4h;

[0138] (2) Adding 0.5 mL of concentrated nitric acid solution to the low-concentration copper-containing heavy metal wastewater, the pH of the wastewater after adding the acid solution is 4.5, and the acidification treatment is performed;

[0139] (3) Mixing the biochar powder and the acidified heavy metal wastewater according to a solid-liquid ratio of 1:20 in a hydrothermal reaction kettle and reacting under a certain temperature and pressure, the temperature is controlled to be 180°C, the pressure is controlled to be 0.3 MPa, and the time is controlled to be 9 h;

[0140] The purification effect of the low-concentration copper-containing heavy metal wastewater in Example 10 is analyzed: the initial concentration and the ion concentration after the first treatment of the low-concentration copper-containing heavy metal wastewater are measured by an atomic absorption spectrophotometer, and the details are shown in Table 10.

[0141] Table 10 Concentration of wastewater before and after treatment

[0142]

[0143] Example 11

[0144] The biomass raw material of this example is walnut shell; in this example, the heavy metal wastewater containing Cu 2+ 500 mg / L is prepared as simulated high-concentration copper-containing wastewater, and is treated according to the following steps:

[0145] (1) Carbonizing the walnut shell in a tube furnace, and then crushing and sieving to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700°C for 4 h;

[0146] (2) Adding 0.5 mL of concentrated nitric acid solution to the high-concentration copper-containing wastewater, the pH of the wastewater after adding the acid solution is 4.3, and the acidification treatment is performed;

[0147] (3) Mixing the walnut shell-based biochar powder and the acidified heavy metal wastewater according to a solid-liquid ratio of 1:20 in a hydrothermal reaction kettle and reacting under a certain temperature and pressure, the temperature is controlled to be 160°C, the pressure is controlled to be 0.4 MPa, and the time is controlled to be 10 h;

[0148] The purification effect of the high-concentration heavy metal wastewater in Example 11 is analyzed: the initial concentration and the ion concentration after the first treatment of the high-concentration heavy metal wastewater are measured by an atomic absorption spectrophotometer, and the details are shown in Table 11.

[0149] Table 11 Concentration of wastewater before and after treatment

[0150]

[0151] Example 12

[0152] The biomass raw material of this example is walnut shell; this example is prepared with Cu 2+ 50 mg / L of heavy metal wastewater, as a simulated high-concentration copper-containing wastewater, is treated according to the following steps:

[0153] (1) Walnut shell is carbonized in a tube furnace, and after crushing and sieving, walnut shell-based biochar powder with a particle size of 40-60 mesh is obtained; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0154] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the high-concentration copper-containing wastewater, and the pH of the wastewater after adding the acid solution is 4.5, for acidification treatment;

[0155] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 160°C, the pressure at 0.4 MPa, and the time at 10h;

[0156] The purification effect of the high-concentration heavy metal wastewater in Example 12 is analyzed: the initial concentration and the ion concentration after the first treatment of the high-concentration heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 12.

[0157] Table 12 Concentration of wastewater before and after treatment

[0158]

[0159] Comparative Example 1

[0160] Preparation of Cu-containing wastewater 2+ 500 mg / L of heavy metal wastewater, as a simulated high-concentration copper-containing wastewater, is treated according to the following steps:

[0161] (1) 0.5 mL of concentrated nitric acid solution is added dropwise to the high-concentration copper-containing wastewater, and the pH of the wastewater after adding the acid solution is 4.3, for acidification treatment;

[0162] (2) 20 mL of the acidified heavy metal wastewater is taken and added to a hydrothermal reaction kettle and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.3 MPa, and the time at 9h;

[0163] The purification effect of the high-concentration heavy metal wastewater in Comparative Example 1 is analyzed:

[0164] There is no obvious difference in the color of the solution before and after the reaction, and no solid product (basic copper carbonate) is generated.

[0165] The initial concentration and the ion concentration after the first treatment of the high-concentration heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 13.

[0166] Table 13 Concentration of wastewater before and after treatment

[0167]

[0168] Comparative Example 2

[0169] Preparation of Cu 2+ Wastewater containing 50 mg / L of heavy metals, used as a simulation of high-concentration copper-containing wastewater, was treated according to the following steps:

[0170] (1) Add 0.5 mL of concentrated nitric acid solution to the high-concentration copper-containing wastewater. After adding the acid, the pH of the wastewater is 4.5, and acidification treatment is carried out.

[0171] (2) Take 20 mL of acidified heavy metal wastewater, add it to a hydrothermal reactor and react it under certain temperature and pressure, controlling the temperature at 180℃, the pressure at 0.3 MPa and the time at 9 h.

[0172] Analysis of the purification effect of Comparative Example 2 on high-concentration heavy metal wastewater:

[0173] There was no significant difference in the color of the solution before and after the reaction, and no solid product (basic copper carbonate) was generated.

[0174] The initial concentration of high-concentration heavy metal wastewater and the ion concentration after one treatment were measured using an atomic absorption spectrophotometer, as detailed in Table 14.

[0175] Table 14 Concentration of wastewater before and after treatment

[0176]

[0177] Comparative Example 3

[0178] The biomass raw material for this comparative ratio is walnut shells; the formulation contains Cu 2+ Wastewater containing 500 mg / L of heavy metals, used as a simulation of high-concentration copper-containing wastewater, was treated according to the following steps:

[0179] (1) The walnut shells were carbonized in a tube furnace, then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters were: carbonization at 700℃ for 4 hours.

[0180] (2) Walnut shell-based biochar powder and untreated heavy metal wastewater were mixed in a hydrothermal reactor at a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180℃, the pressure at 0.3MPa, and the time at 9h.

[0181] Analysis of the purification effect of Comparative Example 3 on high-concentration heavy metal wastewater:

[0182] The color of the solution after the reaction becomes lighter and the basic copper carbonate generated is not completely adsorbed on the carbon, as shown in Figure 5

[0183] The initial concentration of the high-concentration heavy metal wastewater and the ion concentration after the first treatment were measured by atomic absorption spectrophotometry, and the details are shown in Table 15.

[0184] Table 15 Concentration of wastewater before and after treatment

[0185]

[0186] Comparative Example 4

[0187] The biomass raw material of this comparative example is walnut shell; a heavy metal wastewater containing Cu 2+ 50 mg / L is prepared as simulated high-concentration copper-containing wastewater, and is treated according to the following steps:

[0188] (1) The walnut shell is carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0189] (2) The walnut shell-based biochar powder and the heavy metal wastewater without acid treatment are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature being controlled at 180°C, the pressure being 0.3 MPa, and the time being 9h;

[0190] The purification effect of the high-concentration heavy metal wastewater in Comparative Example 4 is analyzed:

[0191] The color of the solution after the reaction becomes lighter and the basic copper carbonate generated is not completely adsorbed on the carbon.

[0192] The initial concentration of the high-concentration heavy metal wastewater and the ion concentration after the first treatment were measured by atomic absorption spectrophotometry, and the details are shown in Table 16.

[0193] Table 16 Concentration of wastewater before and after treatment

[0194]

[0195] Comparative Example 5

[0196] The biomass raw material of this comparative example is walnut shell; a heavy metal wastewater containing Cu 2+ 500 mg / L is prepared as simulated high-concentration copper-containing wastewater, and is treated according to the following steps:

[0197] (1) The walnut shell is carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700°C for 4h; ​

[0198] (2) Adding 0.5 mL of concentrated nitric acid solution to the high-concentration copper-containing wastewater, the pH of the wastewater after adding the acid solution is 4.5, and the acidification treatment is performed;

[0199] (3) Mixing the walnut shell-based biochar powder and the heavy metal wastewater after acidification treatment according to a solid-liquid ratio of 1:20 in a hydrothermal reaction kettle and reacting under a certain temperature and pressure, the temperature is controlled at 130°C, the pressure is 0.1 MPa, and the time is 9h;

[0200] The purification effect of the high-concentration heavy metal wastewater in Comparative Example 5 is analyzed: the initial concentration and the ion concentration after the first treatment of the high-concentration heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 17.

[0201] Table 17 Concentration of wastewater before and after treatment

[0202]

[0203] Comparative Example 6

[0204] The biomass raw material of this comparative example is walnut shell; a heavy metal wastewater containing Cu 2+ 50mg / L is prepared as simulated high-concentration copper-containing wastewater, and is treated according to the following steps:

[0205] (1) Carbonizing the walnut shell in a tube furnace, then crushing and sieving to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0206] (2) Adding 0.5 mL of concentrated nitric acid solution to the high-concentration copper-containing wastewater, the pH of the wastewater after adding the acid solution is 4.5, and the acidification treatment is performed;

[0207] (3) Mixing the walnut shell-based biochar powder and the heavy metal wastewater after acidification treatment according to a solid-liquid ratio of 1:20 in a hydrothermal reaction kettle and reacting under a certain temperature and pressure, the temperature is controlled at 130°C, the pressure is 0.1 MPa, and the time is 9h;

[0208] The purification effect of the high-concentration heavy metal wastewater in Comparative Example 6 is analyzed: the initial concentration and the ion concentration after the first treatment of the high-concentration heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 18.

[0209] Table 18 Concentration of wastewater before and after treatment

[0210]

[0211] Comparative Example 7

[0212] The biomass raw material of this comparative example is walnut shell; a heavy metal wastewater containing Cu 2+500 mg / L of heavy metal wastewater, as a simulated high-concentration copper-containing wastewater, is treated according to the following steps:

[0213] (1) The walnut shell is carbonized in a tube furnace, and after crushing and sieving, walnut shell-based biochar powder with a particle size of 40-60 mesh is obtained. The carbonization reaction parameters are: carbonization at 500°C for 4h;

[0214] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the high-concentration copper-containing wastewater, and the pH of the wastewater after adding the acid solution is 4.5, for acidification treatment;

[0215] (3) The walnut shell-based biochar powder and the acid-treated heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.3 MPa, and the time at 9h;

[0216] The purification effect of the high-concentration heavy metal wastewater in Comparative Example 7 is analyzed: the initial concentration and the ion concentration after the first treatment of the high-concentration heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 19.

[0217] Table 19 Concentration of wastewater before and after treatment

[0218]

[0219] Comparative Example 8

[0220] The biomass raw material of this comparative example is walnut shell; a Cu 2+ 50 mg / L of heavy metal wastewater, as a simulated high-concentration copper-containing wastewater, is treated according to the following steps:

[0221] (1) The walnut shell is carbonized in a tube furnace, and after crushing and sieving, walnut shell-based biochar powder with a particle size of 40-60 mesh is obtained. The carbonization reaction parameters are: carbonization at 500°C for 4h;

[0222] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the high-concentration copper-containing wastewater, and the pH of the wastewater after adding the acid solution is 4.5, for acidification treatment;

[0223] (3) The walnut shell-based biochar powder and the acid-treated heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.3 MPa, and the time at 9h;

[0224] The purification effect of the high-concentration heavy metal wastewater in Comparative Example 8 is analyzed: the initial concentration and the ion concentration after the first treatment of the high-concentration heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 20.

[0225] Concentration of wastewater before and after treatment

[0226]

[0227] Comparative Example 9

[0228] The biomass raw material of this comparative example is walnut shell; a Cu-containing solution with a concentration of 500 mg / L is prepared 2+ The heavy metal wastewater, as simulated low-concentration copper-containing heavy metal wastewater, is treated according to the following steps:

[0229] (1) Walnut shell is carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0230] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the low-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.2, for acidification treatment;

[0231] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.3 MPa, and the time at 4h;

[0232] Analysis of the purification effect of the low-concentration copper-containing heavy metal wastewater in Comparative Example 9: the initial concentration and the ion concentration after the first treatment of the low-concentration copper-containing heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 21.

[0233] Concentration of wastewater before and after treatment

[0234]

[0235] Comparative Example 10

[0236] The biomass raw material of this comparative example is walnut shell; a Cu-containing solution with a concentration of 50 mg / L is prepared 2+ The heavy metal wastewater, as simulated low-concentration copper-containing heavy metal wastewater, is treated according to the following steps:

[0237] (1) Walnut shell is carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0238] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the low-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.5, for acidification treatment;

[0239] (3) Walnut shell-based biochar powder and acidified heavy metal wastewater were mixed in a hydrothermal reactor at a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure. The temperature was controlled at 180°C, the pressure was 0.3 MPa, and the time was 4 h;

[0240] The purification effect of low-concentration copper-containing heavy metal wastewater in Comparative Example 10 was analyzed. The initial concentration and ion concentration after the first treatment of low-concentration copper-containing heavy metal wastewater were measured by atomic absorption spectrophotometry, as shown in Table 22.

[0241] Table 22 Concentration of wastewater before and after treatment

[0242]

[0243] Comparative Example 11

[0244] The biomass raw material of this comparative example was walnut shell; a Cu 2+ heavy metal wastewater containing 500 mg / L was prepared as a simulated low-concentration copper-containing heavy metal wastewater and treated according to the following steps:

[0245] (1) Walnut shell was carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh. The carbonization reaction parameters were: carbonization at 700°C for 4 h;

[0246] (2) 0.5 mL of concentrated sulfuric acid solution was added to the low-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution was 4.1. Acidification treatment was performed;

[0247] (3) Walnut shell-based biochar powder and acidified heavy metal wastewater were mixed in a hydrothermal reactor at a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure. The temperature was controlled at 180°C, the pressure was 0.3 MPa, and the time was 9 h;

[0248] The purification effect of low-concentration copper-containing heavy metal wastewater in Comparative Example 11 was analyzed. The initial concentration and ion concentration after the first treatment of low-concentration copper-containing heavy metal wastewater were measured by atomic absorption spectrophotometry, as shown in Table 23.

[0249] Table 23 Concentration of wastewater before and after treatment

[0250]

[0251] Comparative Example 12

[0252] The biomass raw material of this comparative example was walnut shell; a Cu 2+ heavy metal wastewater containing 50 mg / L was prepared as a simulated low-concentration copper-containing heavy metal wastewater and treated according to the following steps:

[0253] (1) Walnut shell was carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters were: carbonization at 700°C for 4h;

[0254] (2) 0.5 mL of concentrated sulfuric acid solution was added dropwise to the low-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution was 4.7, and the wastewater was acidified;

[0255] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater were mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.3 MPa, and the time at 9h;

[0256] The purification effect of the low-concentration copper-containing heavy metal wastewater in Comparative Example 12 was analyzed: the initial concentration and the ion concentration after the first treatment of the low-concentration copper-containing heavy metal wastewater were measured by atomic absorption spectrophotometry, and the details are shown in Table 24.

[0257] Table 24 Concentration of wastewater before and after treatment

[0258]

[0259] Example 13

[0260] The biomass raw material of this comparative example was walnut shell; a copper-containing heavy metal wastewater containing 500 mg / L of Cu 2+ was prepared as simulated low-concentration copper-containing heavy metal wastewater and treated according to the following steps:

[0261] (1) Walnut shell was carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters were: carbonization at 700°C for 4h;

[0262] (2) 0.5 mL of concentrated nitric acid solution was added dropwise to the low-concentration copper-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution was 4.2, and the wastewater was acidified;

[0263] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater were mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature controlled at 180°C, the pressure at 0.1 MPa, and the time at 9h;

[0264] The purification effect of the low-concentration copper-containing heavy metal wastewater in Comparative Example 13 was analyzed: the initial concentration and the ion concentration after the first treatment of the low-concentration copper-containing heavy metal wastewater were measured by atomic absorption spectrophotometry, and the details are shown in Table 25.

[0265] Table 25 Concentration of wastewater before and after treatment

[0266]

[0267] Comparative Example 14

[0268] The biomass raw material of this comparative example is walnut shell; the Cu-containing wastewater of this example is prepared by adding CuSO4 to the wastewater, and the Cu concentration is 50 mg / L 2+ The heavy metal wastewater, as simulated low-concentration Cu-containing heavy metal wastewater, is treated according to the following steps:

[0269] (1) The walnut shell is carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700°C for 4h;

[0270] (2) 0.5 mL of concentrated nitric acid solution is added dropwise to the low-concentration Cu-containing heavy metal wastewater, and the pH of the wastewater after adding the acid solution is 4.3, and the wastewater is acidified;

[0271] (3) The walnut shell-based biochar powder and the acidified heavy metal wastewater are mixed in a hydrothermal reactor at a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure, with the temperature being controlled at 180°C, the pressure being 0.1 MPa, and the time being 9h;

[0272] The purification effect of the low-concentration Cu-containing heavy metal wastewater in Comparative Example 14 is analyzed: the initial concentration and the ion concentration after the first treatment of the low-concentration Cu-containing heavy metal wastewater are measured by atomic absorption spectrophotometry, and the details are shown in Table 26.

[0273] Table 26 Concentration of wastewater before and after treatment

[0274]

[0275] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for resourceful treatment of heavy metal wastewater, characterized in that, The following steps are adopted: (1) Walnut shell is carbonized in a tube furnace, and then crushed and sieved to obtain walnut shell-based biochar powder with a particle size of 40-60 mesh; the carbonization reaction parameters are: carbonization at 700℃ for 4h; (2) adding 0.5 mL of concentrated nitric acid solution to the high-concentration heavy metal wastewater, the pH of the wastewater being 4.3 after adding the acid solution, and performing acidification treatment; the high-concentration heavy metal wastewater containing 500 mg / L of Cu 2+ heavy metal; (3) The walnut shell-based biochar powder and the acid-treated heavy metal wastewater are mixed in a hydrothermal reaction kettle according to a solid-liquid ratio of 1:20 and reacted at a certain temperature and pressure; the temperature is controlled at 180℃, the pressure is 0.3MPa, and the time is 9h; (4) The mixed solution after reaction is subjected to solid-liquid separation to obtain basic copper carbonate attached to the biochar and a filtrate; the filtrate is directly discharged or used as process water for recycling; the basic copper carbonate is directly used as a water treatment bactericide; or the basic copper carbonate is incinerated at 350℃ for 3.5h to obtain copper oxide, which is then dissolved in an 8% sulfuric acid solution to form a dissolved solution, and the dissolved solution obtained by electrolysis is used to recover copper; or the basic copper carbonate is calcined at 500℃, and after adjusting the metal loading, a high-performance Cu-based catalyst capable of purifying PH3, H2S and HF is obtained.

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