Preparation method of mineral modified biochar for adsorbing heavy metal cadmium ions

Abstract

The invention relates to the technical field of heavy metal ion adsorption, in particular to a preparation method of mineral modified biochar for adsorbing heavy metal cadmium ions, which comprises the following specific steps: mixing and stirring crushed minerals and crushed biomass to obtain a mixture; placing the mixture in a porcelain crucible, and placing the porcelain crucible in an atmosphere furnace for carbonization to obtain mineral modified biochar; wherein the crushed mineral is crushed and sieved meerschaum or Wulan tea spar with uniform particle size; the crushed biomass is water hyacinth, bagasse, rice husks, corn stalks, peanut stalks, peanut shells, rice stalks or luffa stems which are crushed and sieved and have uniform particle sizes. The preparation method of the mineral modified biochar is simple in step and low in cost, and the prepared mineral modified biochar has a good adsorption effect on cadmium and has a good application prospect in the technical field of heavy metal ion adsorption.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal ion adsorption, and in particular to a method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions. Background Art

[0002] According to the research on the cumulative distribution characteristics and probabilistic risk assessment of cadmium in China's farmland soil, data from 2000 to 2022 showed that the cadmium content in China's farmland soil ranged from 0.012 to 23.33 mg kg -1 , the geometric mean is 0.473 mg kg -1 , which is 1.58 times the risk screening value of cadmium in agricultural soil in China. Among them, the soil cadmium content in Central China is the highest, followed by Southwest China, South China, Northwest China, Northeast China, East China and North China. The ecological risk and health risk assessment study of heavy metal cadmium in soil in ten provinces and cities in China showed that the average cadmium concentration in 1,730 soil samples from 2013 to 2020 was 0.29 mg kg -1 , of which the point-to-point rate of exceeding the standard was 29.6%. At present, the problem of excessive cadmium content in agricultural products caused by soil cadmium accumulation is becoming increasingly prominent, and has become an important factor affecting ecological environmental safety and human health.

[0003] The agricultural product pollution caused by soil cadmium accumulation has attracted widespread attention from countries around the world, and countries around the world have been actively studying measures to prevent and control soil cadmium pollution. From the research results of controlling soil cadmium pollution, first, through legislation and policy means to strengthen pollution source prevention and control, cut off the way heavy metal pollutants such as cadmium enter farmland, such as the EU's "Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment Directive" (RoHS) and "Waste Electrical and Electronic Equipment Directive" (WEEE), and China's "Soil Pollution Prevention and Control Action Plan"; second, through physical, chemical or biological remediation technology to separate cadmium from contaminated soil, remove soil cadmium stocks, such as the use of thermal desorption, soil leaching, electroremediation, phytoremediation and other remediation technologies; third, by improving agricultural production technology or developing environmentally friendly products, reduce soil cadmium activity or inhibit crop cadmium accumulation, such as the use of passivators, organic fertilizers and other methods. However, most soil cadmium pollution control and remediation technologies have problems such as high cost or easy to cause secondary pollution.

[0004] In recent years, there has been an increasing number of studies on using agricultural waste with low or no economic value to prepare biochar and use it as an adsorbent to reduce soil cadmium pollution. From the perspective of resource utilization, the development of soil cadmium pollution control and remediation technology related to biochar is a strategy that is worth trying. However, the adsorption capacity of traditional biochar for cadmium is insufficient, and it is not stable or efficient under certain conditions, and its ability to control and remediate soil cadmium pollution is limited. As a new type of adsorbent, modified biochar has good adsorption properties due to its advantages such as wide sources, low cost, environmental friendliness, high specific surface area and abundant surface active sites. In recent years, it has become a hot topic in the fields of environment and energy. Developing a method for modifying biochar with simple steps, low cost and good effect to enhance the adsorption capacity of biochar for cadmium is a problem that technicians in this field need to solve urgently. Therefore, the present invention crushes minerals and agricultural wastes separately, mixes them in a certain proportion and carbonizes them to obtain mineral-modified biochar. Its preparation method is simple in steps and low in cost, and it should have potential research prospects and application value in the field of heavy metal ion adsorption technology. Summary of the invention

[0005] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0006] A method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions comprises the following specific steps:

[0007] Step 1: mixing and stirring the crushed mineral and the crushed biomass to obtain a mixture;

[0008] Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral-modified biochar.

[0009] As a preferred embodiment of the method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions described in the present invention, the mass ratio of the crushed mineral to the crushed biomass in step 1 is 0.4 to 1:1.

[0010] As a preferred embodiment of the method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions described in the present invention, the mineral crushed in the step one is sepiolite or ulan citrine with uniform particle size after crushing and sieving, and the particle size of the crushed mineral is 0.25-1 mm; the biomass crushed is water hyacinth, bagasse, rice husk, corn stalk, peanut stalk, peanut shell, rice stalk or loofah vine with uniform particle size after crushing and sieving, and the particle size of the crushed biomass is 0.25-1 mm.

[0011] As a preferred embodiment of the method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions described in the present invention, the stirring time in step 1 is 1 to 3 hours.

[0012] As a preferred embodiment of the method for preparing a mineral-modified biochar for adsorbing heavy metal cadmium ions described in the present invention, the carbonization in step 2 is an oxygen-limited temperature carbonization method, and the oxygen limitation in the oxygen-limited temperature carbonization method is the introduction of nitrogen as a protective gas.

[0013] As a preferred embodiment of the method for preparing a mineral-modified biochar for adsorbing heavy metal cadmium ions according to the present invention, the carbonization temperature in step 2 is 250-650°C, and the heating rate is 5-25°C·min -1 , the carbonization time is 1 to 5 hours.

[0014] Compared with existing technologies:

[0015] The preparation method of the mineral-modified biochar in the present invention has simple steps and low cost. The prepared mineral-modified biochar has a good adsorption effect on cadmium and has great application prospects in the field of heavy metal ion adsorption technology. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0017] Embodiment 1:

[0018] The present invention provides a method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions, comprising the following specific steps:

[0019] Step 1: Mixing and stirring the crushed mineral and the crushed biomass for 1 hour to obtain a mixture, wherein the mass ratio of the crushed mineral to the crushed biomass is 0.4:1; in addition, the crushed mineral is sepiolite having a uniform particle size after crushing and sieving, and the crushed mineral particle size is 0.25 mm; the crushed biomass is water hyacinth having a uniform particle size after crushing and sieving, and the crushed biomass particle size is 0.25 mm;

[0020] Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral modified biochar, wherein the carbonization is an oxygen-limited temperature carbonization method, wherein the oxygen-limited temperature carbonization method is to introduce nitrogen as a protective gas, and the carbonization temperature is 250°C and the heating rate is 5°C·min -1 , the carbonization time is 1h.

[0021] Embodiment 2:

[0022] The present invention provides a method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions, comprising the following specific steps:

[0023] Step 1: Mixing and stirring the crushed mineral and the crushed biomass for 2 hours to obtain a mixture, wherein the mass ratio of the crushed mineral to the crushed biomass is 0.7:1; in addition, the crushed mineral is sepiolite having a uniform particle size after crushing and sieving, and the crushed mineral particle size is 0.5 mm; the crushed biomass is water hyacinth having a uniform particle size after crushing and sieving, and the crushed biomass particle size is 0.5 mm;

[0024] Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral modified biochar, wherein the carbonization is an oxygen-limited temperature carbonization method, wherein the oxygen-limited temperature carbonization method is to introduce nitrogen as a protective gas, and the carbonization temperature is 450°C and the heating rate is 15°C·min -1 , the carbonization time is 2.5h.

[0025] Embodiment 3:

[0026] The present invention provides a method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions, comprising the following specific steps:

[0027] Step 1: Mixing and stirring the crushed mineral and the crushed biomass for 3 hours to obtain a mixture, wherein the mass ratio of the crushed mineral to the crushed biomass is 1:1; in addition, the crushed mineral is sepiolite having a uniform particle size after crushing and sieving, and the crushed mineral particle size is 1 mm; the crushed biomass is water hyacinth having a uniform particle size after crushing and sieving, and the crushed biomass particle size is 1 mm;

[0028] Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral modified biochar, wherein the carbonization is an oxygen-limited temperature carbonization method, wherein the oxygen-limited temperature carbonization method is to introduce nitrogen as a protective gas, and the carbonization temperature is 650°C and the heating rate is 25°C·min -1 , the carbonization time is 5h.

[0029] Embodiment 4:

[0030] The present invention provides a method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions, comprising the following specific steps:

[0031] Step 1: Mixing and stirring the crushed mineral and the crushed biomass for 1 hour to obtain a mixture, wherein the mass ratio of the crushed mineral to the crushed biomass is 0.4:1; in addition, the crushed mineral is Ulan tea crystal stone with uniform particle size after crushing and sieving, and the crushed mineral particle size is 0.25 mm; the crushed biomass is water hyacinth with uniform particle size after crushing and sieving, and the crushed biomass particle size is 0.25 mm;

[0032] Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral modified biochar, wherein the carbonization is an oxygen-limited temperature carbonization method, wherein the oxygen-limited temperature carbonization method is to introduce nitrogen as a protective gas, and the carbonization temperature is 250°C and the heating rate is 5°C·min -1 , the carbonization time is 1h.

[0033] Embodiment 5:

[0034] The present invention provides a method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions, comprising the following specific steps:

[0035] Step 1: Mix and stir the crushed mineral and the crushed biomass for 2 hours to obtain a mixture, wherein the mass ratio of the crushed mineral to the crushed biomass is 0.7:1; in addition, the crushed mineral is Ulan tea crystal stone with uniform particle size after crushing and sieving, and the crushed mineral particle size is 0.5 mm; the crushed biomass is water hyacinth with uniform particle size after crushing and sieving, and the crushed biomass particle size is 0.5 mm;

[0036] Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral modified biochar, wherein the carbonization is an oxygen-limited temperature carbonization method, wherein the oxygen-limited temperature carbonization method is to introduce nitrogen as a protective gas, and the carbonization temperature is 450°C and the heating rate is 15°C·min -1 , the carbonization time is 2.5h.

[0037] Embodiment 6:

[0038] The present invention provides a method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions, comprising the following specific steps:

[0039] Step 1: Mixing and stirring the crushed mineral and the crushed biomass for 3 hours to obtain a mixture, wherein the mass ratio of the crushed mineral to the crushed biomass is 1:1; in addition, the crushed mineral is Ulan tea crystal stone with uniform particle size after crushing and sieving, and the crushed mineral particle size is 1 mm; the crushed biomass is water hyacinth with uniform particle size after crushing and sieving, and the crushed biomass particle size is 1 mm;

[0040] Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral modified biochar, wherein the carbonization is an oxygen-limited temperature carbonization method, wherein the oxygen-limited temperature carbonization method is to introduce nitrogen as a protective gas, and the carbonization temperature is 650°C and the heating rate is 25°C·min -1 , the carbonization time is 5h.

[0041] The mineral-modified water hyacinth charcoal prepared according to the above method contains sepiolite or ulan citrine with strong adsorption capacity for cadmium ions, which can improve the adsorption capacity of biochar for cadmium ions in wastewater.

[0042] The adsorption rates of cadmium ions in wastewater by the mineral modified water hyacinth charcoal prepared in the above Examples 1 to 6 were compared to obtain the following data:

[0043] As can be seen from the table below, the cadmium ion concentration in the wastewater is 400 mg·L -1 When the hyacinth charcoal modified by meerschaum prepared in Examples 1 to 3 has a good performance in the adsorption rate of cadmium ions, and after being used in 10mL of cadmium-containing wastewater, Example 2 has the best effect; the hyacinth charcoal modified by Ulan tea crystal stone prepared in Examples 4 to 6 has a good performance in the adsorption rate of cadmium ions, and after being used in 10mL of cadmium-containing wastewater, Example 5 has the best effect. In comparison, under the premise that the biomass particle size, stirring time, mass ratio, carbonization temperature, heating rate, and carbonization time are completely consistent, the adsorption rate of cadmium ions by the hyacinth charcoal modified by Ulan tea crystal stone is higher than that by the hyacinth charcoal modified by meerschaum.

[0044]

[0045] Wherein: the adsorption rate of cadmium ions = (the adsorption amount of cadmium ions / the total amount of cadmium in the wastewater) × 100%.

[0046] In addition, rice straw and water hyacinth were used as raw materials for preparing biochar or mineral-modified biochar, and the cadmium adsorption and cadmium desorption performance of Ulancha crystal stone modified biochar were studied as follows:

[0047] Using rice straw as raw material, the adsorption performance of Ulan tea crystal stone modified rice straw charcoal and ordinary rice straw charcoal on cadmium ions in wastewater is compared as follows:

[0048]

[0049] Among them: "ND" means not detected.

[0050] Based on the above, it can be seen that when the cadmium ion concentration in the wastewater is greater than 0, the adsorption amount of cadmium ions by the rice straw charcoal modified with Ulan citrine will be greater than that by ordinary rice straw charcoal. Therefore, the adsorption effect of the rice straw charcoal modified with Ulan citrine on cadmium ions is greater than that of ordinary rice straw charcoal.

[0051] Using water hyacinth as raw material, the performance comparison of the adsorption of cadmium ions in wastewater by water hyacinth charcoal modified with Ulan tea crystal stone and ordinary water hyacinth charcoal is as follows:

[0052]

[0053]

[0054] Among them: "ND" means not detected.

[0055] Based on the above, it can be seen that when the cadmium ion concentration in the wastewater is greater than 0, the adsorption amount of cadmium ions by water hyacinth charcoal modified with Ulan tea crystal stone will be greater than that of ordinary water hyacinth charcoal. Therefore, the adsorption effect of water hyacinth charcoal modified with Ulan tea crystal stone on cadmium ions is greater than that of ordinary water hyacinth charcoal.

[0056] Rice straw and water hyacinth were used as raw materials for preparing mineral-modified biochar, respectively. The cadmium desorption performance of Ulan citrine-modified rice straw charcoal and Ulan citrine-modified water hyacinth charcoal was compared as follows:

[0057]

[0058] Among them: "ND" means not detected.

[0059] Based on the above, it can be seen that the cadmium ion concentration in wastewater is between 0 and 400 mg·L -1 Within the range, the cadmium desorption amounts of rice straw charcoal modified by Ulan citrine and water hyacinth charcoal modified by Ulan citrine were both undetectable, indicating that the cadmium adsorbed by rice straw charcoal and water hyacinth charcoal modified by Ulan citrine cannot be completely desorbed in a short period of time.

[0060] Combining the data on cadmium adsorption and desorption of water hyacinth charcoal modified by Ulan citrine, it can be comprehensively judged that water hyacinth charcoal modified by Ulan citrine can almost completely adsorb cadmium in wastewater, and it cannot be desorbed at all in a short time. Therefore, water hyacinth charcoal modified by Ulan citrine can be used as an excellent adsorbent for cadmium-containing wastewater.

[0061] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions, characterized in that: The specific steps are as follows: Step 1: mixing and stirring the crushed mineral and the crushed biomass to obtain a mixture; Step 2: Place the mixture in a porcelain crucible and carbonize it in an atmosphere furnace to obtain mineral-modified biochar.

2. The method for preparing a mineral-modified biochar for adsorbing heavy metal cadmium ions according to claim 1, characterized in that: The mass ratio of the crushed mineral to the crushed biomass in the step 1 is 0.4 to 1:

1.

3. The method for preparing a mineral-modified biochar for adsorbing heavy metal cadmium ions according to claim 1, characterized in that: The mineral crushed in the step 1 is sepiolite or ulan citrine with uniform particle size after crushing and sieving, and the particle size of the crushed mineral is 0.25-1 mm; the biomass crushed is water hyacinth, bagasse, rice husk, corn stalk, peanut stalk, peanut shell, rice stalk or loofah vine with uniform particle size after crushing and sieving, and the particle size of the crushed biomass is 0.25-1 mm.

4. The method for preparing a mineral-modified biochar for adsorbing heavy metal cadmium ions according to claim 1, characterized in that: The stirring time in step 1 is 1 to 3 hours.

5. The method for preparing a mineral-modified biochar for adsorbing heavy metal cadmium ions according to claim 1, characterized in that: The carbonization in step 2 is an oxygen-limited temperature carbonization method, and the oxygen-limited temperature carbonization method is to introduce nitrogen as a protective gas.

6. The method for preparing mineral-modified biochar for adsorbing heavy metal cadmium ions according to claim 5, characterized in that: In the step 2, the carbonization temperature is 250-650°C, and the heating rate is 5-25°C·min -1 , the carbonization time is 1 to 5 hours.

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