Manganese dioxide modified biochar composite material as well as a preparation method and an application thereof

[0054] Example 1:

[0055] A biochar composite material modified by manganese dioxide of the present invention includes manganese dioxide and biochar; the biochar composite material modified by manganese dioxide is achieved through the neutralization of manganese in potassium permanganate and manganese acetate tetrahydrate It is prepared by loading the generated manganese dioxide on the biochar.

[0056] A method for preparing the manganese dioxide-modified biochar composite material of the foregoing embodiment includes the following steps:

[0057] S1. Mix pig manure and camphor sawdust at a mass ratio of 4:1 and perform aerobic composting for 60 days to obtain a mixture. The mixture is washed several times with deionized water, dried at 80°C, ground, and passed through a 100 mesh sieve , Put it in a sealed bag and save it for later use.

[0058] S2. Place the mixture after passing the 100-mesh sieve in step S1 in a quartz boat, and then put the quartz boat in a tube furnace and calcinate in a nitrogen atmosphere. The specific calcining process is: at a rate of 10°C/min The temperature is raised to 400°C (400-700°C can be implemented) for calcination, and the residence time is 2h to obtain biochar.

[0059] S3. Take 15g of biochar in step S2 and mix with 3.16g potassium permanganate, dissolve it with 150mL of deionized water, and ultrasonically shake for 30min at room temperature (30min~1h can be implemented) to obtain biochar and permanganate Potassium mixture; under the condition of continuous stirring with a magnetic stirrer, slowly add 100 mL of a 0.3mol/L manganese acetate tetrahydrate solution to the mixture containing biochar and potassium permanganate for a neutralization reaction to produce Dark-brown precipitates to obtain a manganese dioxide-modified biochar composite material suspension; finally, the manganese dioxide-modified biochar composite material suspension is heated to 80°C and kept at this temperature for 30min (30min~1h can be implemented) , To stabilize the manganese dioxide produced on the surface of the biochar, rinse with deionized water until the rinse solution is neutral, and dry at 80°C to obtain the manganese dioxide modified biochar composite material, which is stored for later use.

[0060] figure 1 This is the scanning electron microscope image (SEM image) of the biochar composite material modified by manganese dioxide in this example. The outer image is an SEM image magnified 2000 times, and the inner image is the black square in the outer image after 10 times magnification. SEM image (ie, magnified 20000 times). figure 2 This is the energy spectrum (EDAX diagram) of the biochar composite material modified by manganese dioxide in this example. image 3 The transmission electron microscope image (TEM image) of the biochar composite material modified by manganese dioxide in this example.

[0069] Example 2:

[0070] An application of the manganese dioxide modified biochar composite material of the present invention in the treatment of heavy metal wastewater, wherein the manganese dioxide modified biochar composite material comes from Example 1, and the heavy metal wastewater is lead-containing heavy metal wastewater or cadmium-containing heavy metal wastewater .

[0071] The treatment of lead-containing heavy metal wastewater includes the following steps: weighing 13 parts of the manganese dioxide-modified biochar composite material in Example 1 in an Erlenmeyer flask with an added amount of 0.40g/L, and adding an ionic strength of 0.01mol/L , Lead-containing heavy metal wastewater with a pH value of 5.0±0.2, in which the initial concentration of lead in the lead-containing heavy metal wastewater is 0.5mg/L, 1.0mg/L, 5.0mg/L, 10.0mg/L, 20.0mg/L, 40.0 mg/L, 60.0mg/L, 80.0mg/L, 100.0mg/L, 120.0mg/L, 150.0mg/L, 180.0mg/L and 210.0mg/L. After mixing, the oscillating adsorption reaction was carried out under the conditions of 170 rpm and 25° C. for 12 hours to complete the treatment of heavy metal wastewater.

[0072] The treatment of cadmium-containing heavy metal wastewater includes the following steps: weigh 13 parts of the manganese dioxide-modified biochar composite material in Example 1 in an Erlenmeyer flask with an added amount of 0.40g/L, and add an ionic strength of 0.01mol/L , The cadmium-containing heavy metal wastewater with a pH of 5.0±0.2, in which the initial concentration of cadmium in the cadmium-containing heavy metal wastewater is 0.5mg/L, 1.0mg/L, 2.0mg/L, 5.0mg/L, 10.0mg/L, 15.0, respectively mg/L, 20.0mg/L, 30.0mg/L, 40.0mg/L, 50.0mg/L, 60.0mg/L, 80.0mg/L and 100.0mg/L. After mixing, the oscillating adsorption reaction was carried out under the conditions of 170 rpm and 25° C. for 12 hours to complete the treatment of heavy metal wastewater.

[0073] After the oscillating adsorption reaction is completed, pour the suspension into the syringe, and separate the manganese dioxide modified biochar composite material from the mixed solution through a 0.22μm filter membrane. Take an appropriate amount of the filtered solution, dilute the volume with dilute nitric acid, and use flame atomic spectrophotometry The instrument measures the concentration of lead or cadmium in the solution after adsorption equilibrium, and uses the following formula (1) to calculate the removal rate of lead or cadmium of the biochar composite material modified by manganese dioxide to judge the treatment effect of the adsorbent synthesized by the present invention .

[0074]

[0075] In formula (1): a is the removal rate (%);

[0076] C 0 Is the initial concentration of lead or cadmium in the solution before adsorption (unit: mg/L);

[0077] C is the concentration of lead or cadmium in the solution after the adsorption reaches equilibrium (unit: mg/L);

[0078] Table 1 shows the removal effect of the manganese dioxide modified biochar composite material of the present invention on lead or cadmium wastewater with different concentrations.

[0079] Table 1 The removal effect of the biochar composite material modified by manganese dioxide of the present invention on different concentrations of lead or cadmium wastewater

[0080] Lead concentration (mg/L)

[0081] It can be seen from Table 1 that when the addition amount of the manganese dioxide-modified biochar composite material of the present invention is 0.40 g/L, as the concentration of heavy metals (lead or cadmium) increases, the manganese dioxide-modified biochar composite material affects The overall removal rate of lead or cadmium is in a downward trend. The maximum removal rate of lead reaches 100%, and the maximum removal rate of cadmium is 94.80%.

[0082] Example 3:

[0083] An application of the manganese dioxide modified biochar composite material of the present invention in the treatment of heavy metal wastewater. The manganese dioxide modified biochar composite material comes from Example 1. The heavy metal wastewater is lead-containing heavy metal wastewater or cadmium-containing heavy metal wastewater .

[0084] The treatment of lead-containing heavy metal wastewater includes the following steps: weighing 39 parts of the manganese dioxide-modified biochar composite material in Example 1 in 39 conical flasks at an added amount of 0.40 g/L, and dividing them into three groups. Add lead-containing heavy metal wastewater with an ionic strength of 0.01 mol/L and a pH of 5.0±0.2 to each group of conical flasks. The initial concentration of lead in the lead-containing heavy metal wastewater is 0.5 mg/L, 1.0 mg/L, and 5.0 mg, respectively. /L, 10.0mg/L, 20.0mg/L, 40.0mg/L, 60.0mg/L, 80.0mg/L, 100.0mg/L, 120.0mg/L, 150.0mg/L, 180.0mg/L and 210.0mg /L. After mixing, the above three groups of Erlenmeyer flasks are placed on a constant temperature shaker, and the temperature is 25°C, 35°C, 45°C, and the rotation speed is 170rpm for 12h vibration adsorption reaction to complete the treatment of heavy metal wastewater.

[0085] The treatment of cadmium-containing heavy metal wastewater includes the following steps: weighing 39 parts of the manganese dioxide modified biochar composite material in Example 1 in 39 conical flasks according to an added amount of 0.40 g/L, and dividing them into three groups. Add cadmium-containing heavy metal wastewater with an ionic strength of 0.01mol/L and a pH of 5.0±0.2 to each group of conical flasks. The initial concentration of cadmium in the cadmium-containing heavy metal wastewater is 0.5mg/L, 1.0mg/L, 2.0mg, respectively. /L, 5.0mg/L, 10.0mg/L, 15.0mg/L, 20.0mg/L, 30.0mg/L, 40.0mg/L, 50.0mg/L, 60.0mg/L, 80.0mg/L and 100.0mg /L. After mixing, the above three groups of Erlenmeyer flasks are placed on a constant temperature shaker, and the temperature is 25°C, 35°C, 45°C, and the rotation speed is 170rpm for 12h vibration adsorption reaction to complete the treatment of heavy metal wastewater.

[0086] After the oscillating adsorption reaction is completed, pour the suspension into the syringe, and separate the manganese dioxide modified biochar composite material from the mixed solution through a 0.22μm filter membrane. Take an appropriate amount of the filtered solution, dilute the volume with dilute nitric acid, and use flame atomic spectrophotometry The instrument measures the concentration of lead or cadmium in the solution after adsorption equilibrium, and uses the following formula (2) to calculate the change in adsorption capacity and adsorption effect of the manganese dioxide modified biochar composite material of the present invention at different temperatures.

[0087]

[0088] In formula (2): Q is the adsorption capacity (unit: mg/g);

[0089] C 0 Is the initial concentration of lead or cadmium in the solution before adsorption (unit: mg/L);

[0090] C is the concentration of lead or cadmium in the solution after the adsorption reaches equilibrium (unit: mg/L);

[0091] m is the amount of adsorbent (unit: mg);

[0092] V is the volume of the aqueous solution (unit: mL).

[0093] The adsorption capacity (mg/g) of the biochar composite material modified by manganese dioxide modified by the present invention on lead or cadmium at different temperatures is shown in Table 2.

[0094] Table 2 The adsorption amount of lead or cadmium on the biochar composite material modified by manganese dioxide of the present invention at different temperatures

[0095]

[0096] It can be seen from Table 2 that when the temperature is 45°C, the manganese dioxide modified biochar composite material of the present invention has the highest adsorption capacity for heavy metal wastewater with an initial lead concentration of 210.0 mg/L, which can reach 305.75 mg/g, and the adsorption capacity for cadmium The adsorption capacity of heavy metal wastewater with an initial concentration of 100.0mg/L can reach up to 55.80mg/g. Under the same initial concentration of lead or cadmium, the adsorption amount of heavy metal lead or cadmium by the manganese dioxide modified biochar composite material of the present invention increases with the increase of temperature, which indicates that the adsorption process is an endothermic process. Increased, the activity of the active sites of the adsorbent is enhanced, thereby promoting the adsorption of heavy metals. Therefore, when the temperature is higher than 45°C, the adsorption capacity of lead or cadmium on the biochar composite material modified by manganese dioxide will increase, but too high temperature is not conducive to reducing production costs.