CN103464101A - Resource utilization method of plant bamboo reed after restoring heavy metal contaminated soil - Google Patents

Abstract

The invention discloses a method for resource utilization of plant reed bamboo for repairing heavy metal polluted soil. Air-dry and crush the remediation plant Arundos arundis polluted by heavy metals, add a catalytic modifier under a controlled oxygen atmosphere, calcinate at 200-800°C for 0.5-4 hours, and cool to obtain biochar, which is produced by Arundis biochar The rate is 25%-75%. Using Arundis biochar to adsorb heavy metals and their compounds in polluted soil, waste water or waste gas, with an adsorption capacity of 0.4-6.0 mg/g; at the same time, it can be returned to metallurgical enterprises as energy raw materials or reducing agents for comprehensive utilization. The invention provides an engineering approach for remediating plant biomass resource utilization in polluted soil and solving its potential secondary pollution problem.

Description

A method for resource utilization of plant reed bamboo for remediation of heavy metal-contaminated soil

technical field

The invention relates to the field of comprehensive utilization of solid waste resources. Specifically, the present invention relates to a method of preparing biochar by utilizing the biomass of the remediation plant Arundos multiflora harvested on heavy metal-contaminated soil, and at the same time using biochar to absorb heavy metals in polluted soil, waste water or waste gas, as an energy material for heavy-duty enterprises or to reduce agent method.

Background technique

Luzhu is a perennial gramineous plant widely distributed in southern my country, with fast growth and large biomass. Arundis biomass contains a large amount of cellulose and lignin, and has a high calorific value of combustion. Most of the components of Arundis biomass are charcoal after being calcined. Yang Haiping's research shows that the precipitation of volatile substances in the process of biochar preparation is mainly concentrated at 300-600 °C; at high temperatures (>800 °C), biochar mainly contains carbon and a small amount of oxygen, and there is almost no residual hydrogen. Biochar has a well-developed pore structure and abundant surface groups, so it has a good removal effect on heavy metals and organic matter (especially heavy metals), and is stable and corrosion-resistant and not easy to decompose. It is an ideal adsorbent. At the same time, biochar is also a good reducing agent. Wang Yongbin et al. reported that the effect of reducing and magnetizing limonite by biomass is better than that of lignite, and the reduction and magnetization effect of biomass can be reduced by 100%. Above ℃ (down to about 650℃).

Reed bamboo is resistant to barrenness, drought and flood, and has the advantages of strong stress resistance. There have been related research reports at home and abroad on the tolerance and enrichment performance of Arundos arundis to heavy metals. Papazoglou's research showed that Arundis radiata showed good tolerance when grown in soil with 973.8mg kg ^–1 Cd and 2543.3mg kg ^–1 Ni. Mirza's study showed that Arundis can grow normally in the nutrient solution with As concentration of 600μg L ^-1 , showing good tolerance and accumulation. Studies by Han Zhiping et al. have shown that Arundorrhizae has Cu ²⁺ , Ni ²⁺ , Cd ²⁺ , Pb ²⁺ , Zn ²⁺ , Hg ²⁺ , and Cr ⁶⁺ 7 concentrations below 100 mgkg ^-1 and Cr ⁶⁺ 7 It can survive normally in all kinds of polluted environments, showing a strong tolerance to a single high-content heavy metal polluted environment; it can also survive under the influence of 105mg kg ^–1 Cu, 103mg kg ^–1 Ni, and 55mg kg ^–1 Cr alone normal growth. Studies by Guo Zhaohui and others have shown that the annual biomass of the aboveground parts of Arundis reed growing on As53.2, Cd31.9, Pb728.4, Zn968mg kg ^-1 polymetallic contaminated soil can reach 3000kg/mu, and can absorb As, Cd, Pb and Zn have a certain remedial effect on polluted soil. The above studies show that Arundis can be used as a remediation plant for heavy metal-contaminated soil for remediation of contaminated soil. However, the rehabilitated Arundos reticulum harvests contain a certain amount of heavy metals, which may cause secondary pollution of heavy metals if not properly disposed of. However, the current prior art does not consider the issue of how to safely and comprehensively utilize biomass such as reed bamboo containing heavy metals. The present invention aims to use heavy metals to pollute reed bamboo to prepare biochar, and continue to use biochar to reduce the effective content in polluted soil, treat waste water or waste gas containing heavy metals, and finally send it to heavy-duty enterprises as biomass energy or reducing agent. To achieve the purpose of treating waste with waste and comprehensive utilization.

Contents of the invention

The present invention aims to effectively utilize the biomass of Arundos rex that has repaired heavy metal-contaminated soil, and use it as a raw material to produce biochar, which is used to reduce the effective content of heavy metals in polluted soil, treat waste water or waste gas containing heavy metals, and finally send it to heavy-duty enterprises as biochar. Material energy or reducing agent, to achieve the purpose of waste treatment and comprehensive utilization.

A method for resource utilization of a plant remedial heavy metal polluted soil, comprising the following steps:

1) Cutting, air-drying and crushing the remedial remedial heavy metal-contaminated soil;

2) Add 0.5wt%-5wt% of ferric salt, aluminum salt, calcium salt, sodium salt to the crushed Arundis powder, or a combination of two kinds of catalytic modification materials, and calcinate in a calciner with controlled oxygen atmosphere , the calcination temperature is 200-800°C, and the calcination time is 0.5-4h; during the calcination process, a negative pressure system is used to condense and recover volatile matter to achieve deoiling of the carbon powder, or after calcination and cooling, the carbon powder and the carbon powder are mixed according to the mass ratio of 1:5-10. Alcohol is mixed, stirred, washed and deoiled; the charcoal powder is pressed into lumps or sticks to obtain biochar;

3) Biochar is used to adsorb heavy metals and their compounds in polluted soil, waste water or waste gas, so that the effective content of heavy metals in polluted soil can be significantly reduced, and waste water or waste gas can be purified;

4) The biochar obtained in step 2) or the biochar in step 3) that has adsorbed heavy metals and their compounds in polluted soil, waste water or waste gas are sent to non-ferrous metal smelting enterprises for comprehensive utilization as energy materials or reducing agents.

The heavy metals include one or more of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn.

The crushing in step 1) is to use a crushing machine to crush the air-dried reed bamboo harvest into short rod-shaped pieces or powders below 1-2 cm.

The catalytic modification material described in step 2) is formulated into a solution or emulsion, and sprayed evenly on the powder of Arundis basilica before or during calcination.

The controlled oxygen atmosphere in step 2) is to control the calciner to be an oxygen-deficient or near-oxygen-free atmosphere. (Use muffle furnaces, tube furnaces, lift furnaces and other calciners with nitrogen and argon gas, or specially designed reaction furnaces that can control the entry of oxygen, and control the calciner to be in an oxygen-deficient or near-oxygen-free atmosphere.)

Using the above method, the yield of biochar is generally 25%-75%.

By adopting the above-mentioned method, the adsorption capacity of heavy metals and their compounds in the biochar adsorption polluted soil, waste water or waste gas can reach 0.4-6.0 mg/g.

The forming measure adopted in the above method is to compress the biomass charcoal powder into small lumps or short sticks by ordinary pressing machine.

technical effect

The invention proposes a feasible engineering approach for resource utilization of bulk reed bamboo harvests after engineering restoration of heavy metal polluted soil. For the first time, the biomass containing a small amount of heavy metals such as As, Cd, Pb, Zn was controlled by oxygen atmosphere and added catalytic modification materials to obtain biochar containing a small amount of heavy metals at a lower calcination temperature and used to adsorb heavy metals in polluted soil to prevent heavy metals Diffusion of pollutants; adsorption of low-concentration heavy metals and compounds in waste water or waste gas to achieve deep purification of waste water or waste gas; sent as energy raw materials to metallurgical processes to provide heat sources, or used as reducing agents to create a reducing atmosphere or directly reduce metal oxides, effectively The comprehensive utilization of heavy metal-containing biomass has been realized effectively.

The present invention adds the catalytic modification material in the calcination process of the heavy metal-containing Arundos arundoides biomass, which can significantly increase the yield of Arundos arundis biochar and the quantity of surface active functional groups, increase the surface adsorption capacity of the biochar, and reduce the heavy metals in Arundos arundis during the calcination process. The overflow and loss of Arundis biochar and the leaching rate of heavy metals after calcination have effectively solved the potential secondary pollution problem in the comprehensive utilization of Arundis biochar containing heavy metals.

The present invention deoils the prepared biochar, which can further increase its adsorption capacity, and is used to efficiently adsorb heavy metals and compounds in polluted soil, waste water or waste gas, so that the effective content of heavy metals in polluted soil is significantly reduced, and waste water Or the heavy metals in the exhaust gas meet the emission standard requirements after adsorption and purification.

Description of drawings

Fig. 1 is a process flow diagram of the present invention;

Fig. 2 is the SEM photograph of biochar of the present invention;

(a) Unwashed biochar; (b) Alcohol-washed biochar;

Fig. 3 Adsorption effect of Arundis biochar on As, Cd, Pb in wastewater.

Detailed ways

The present invention will be further described below in conjunction with specific examples, rather than limiting the present invention.

Example 1: Preparation of biochar by using the plant Arundos multiflora remediation of heavy metal-contaminated soil

Harvest the aerial parts of Arundos rex containing heavy metals from the soil of the heavy metal-contaminated site, wash the harvest with tap water and deionized water in turn, cut into small pieces of 1-2 cm, fix them at 105°C for 30 minutes, and dry them at 60°C. Put the dried reed bamboo pieces into the tube-type lifting furnace, spray 1mol/L sodium hydroxide solution at the same time, so that sodium hydroxide accounts for 0.5wt% of the reed bamboo powder, heat under nitrogen protection, and control the calcination Calcined at 300°C for 2 hours, cooled and crushed to below 20 meshes to obtain heavy metal-containing Arundos biochar. Under the calcination conditions, the biochar yield of Arundis is about 55%, and the calorific value of biochar reaches 29.53kJ/g. The surface of the biochar prepared above has a large number of pores and oil droplets (Figure 2a); after washing with alcohol for 30 minutes, the oil droplets on the surface of the biochar disappeared and a large number of pores appeared (Figure 2b); The contents of As, Cd, Pb and Zn in the charcoal were 16-33, 0.9-15, 21-80, 106-263 mg/kg in turn, indicating that the biochar contained a certain amount of heavy metals. At the same time, Arundox rex harvested from unpolluted soil was selected to be calcined in a tubular lift furnace under nitrogen protection at a calcination temperature of 300°C and a calcination time of 2 hours to prepare unpolluted Arundox biochar. Under the calcination conditions, the yield of unpolluted Arundos reed biochar is about 35%, and the contents of As, Cd, Pb, Zn in the biochar are 0.21-7.26, 0.03-0.50, 0.22-3.62, 15-96.66 mg /kg. It indicated that the content of heavy metals in the biochar prepared from the remediation of heavy metal-contaminated soil was significantly increased.

Example 2: Toxicity leaching test of Arundos rex biochar containing heavy metals

Toxicity leaching experiments were carried out using the Arundis biochar prepared in Example 1. The leaching experiment refers to the method of "Toxic Leaching Method for Solid Waste Leaching and Horizontal Oscillating Method (HJ557-2010)", using water leaching and acid leaching to carry out the toxicity leaching test: take 20mL deionized water, adjust the pH to 2.5 and 5.5, and then add 0.2g containing The heavy metal Arundophyllum biochar was shaken in a constant temperature water bath shaking box at room temperature for 24 hours, then centrifuged and filtered, and the contents of As, Cd, Pb, and Zn in the supernatant were measured. At the same time, do a blank test (without adding biochar) to eliminate experimental errors. It can be seen from Table 1 that the content of heavy metals in the leaching solution of unpolluted Arundos biochar is extremely low; the concentrations of As, Cd, Pb, and Zn in the leaching solution of Arundos biochar containing heavy metals under neutral and acidic conditions are also much lower than The standard identification value of leaching toxicity (GB5085.3-2007) can be safely applied to the adsorption treatment of heavy metals in polluted soil, wastewater and waste gas.

Table 1 Concentrations of As, Cd, Pb, and Zn in the leaching solution of Arundos rex biochar

^* The identification value of heavy metals in the standard identification value of leaching toxicity (GB5085.3-2007) is calculated by its total amount. "ND" means not detected.

Example 3: Adsorption capacity test of Arundos rex biochar containing heavy metals

The heavy metal adsorption test in the simulated wastewater was carried out using the Arundis biochar prepared in Example 1 (the raw material was harvested from the heavy metal-contaminated soil of the heavy metal-contaminated site). The test operation process is as follows: Prepare a series of simulated wastewater containing As, Cd, and Pb with concentration gradients of 5mg/L, 10mg/L, 25mg/L, and 50mg/L. Add 0.2g of biochar to 20ml of simulated wastewater, shake it at room temperature for 24h, measure the concentration of heavy metal ions in the solution after adsorption, and calculate the adsorption of biochar to As, Cd, and Pb in wastewater by using the concentration difference of the solution. The experimental results showed (Fig. 3) that Arundis biochar had a certain adsorption effect on As, Cd, and Pb in wastewater, and the adsorption effect increased with the concentration of As, Cd, and Pb in wastewater. Within the test range, the adsorption capacity reached 4.08, 1.30, 0.86mg/g respectively.

Claims (5)

1. a method of repairing the plant giantreed recycling of heavy-metal contaminated soil, is characterized in that, comprises the following steps:

1) to the giantreed of repairing heavy-metal contaminated soil cradled, air-dry, broken;

2) the catalytic modification material of one or both combinations in the molysite of the interpolation of the giantreed powder after fragmentation 0.5wt%-5wt%, aluminium salt, calcium salt, sodium salt is calcined calcining heat 200-800 ℃, calcination time 0.5-4h in the calcining furnace of controlling the oxygen atmosphere; In calcination process, adopt negative pressure system condensation recovery volatile matter to realize charcoal end de-oiling, or the mass ratio according to 1:5-10 wash de-oiling by charcoal end and alcohol mix and blend after calcining is cooling; Charcoal end briquet group or excellent bar, obtain charcoal;

3) adopt heavy metal and compound thereof in charcoal adsorption fouling soil, waste water or waste gas, Heavy Metals in Contaminated Soils available state content is significantly reduced, purify liquid waste or waste gas;

4) by step 2) charcoal that obtains or by having adsorbed the charcoal of heavy metal in contaminated soil, waste water or waste gas and compound thereof in step 3), send the utilization of non-ferrous metal metallurgy Enterprise Integrated as energy and material or reducing agent.

2. method according to claim 1, is characterized in that, described heavy metal comprises one or more in As, Cd, Cr, Cu, Hg, Ni, Pb, Zn.

3. method according to claim 1, is characterized in that, the described fragmentation of step 1) is to adopt broken facility that air-dry giantreed cutting is broken into to 1-2cm following rod-short fritter or Powdered thing.

4. method according to claim 1, is characterized in that step 2) described catalytic modification material, first be mixed with solution or emulsion, before calcining or calcining the time be sprayed at equably on the giantreed powder.

5. method according to claim 1, is characterized in that step 2) described control oxygen atmosphere is to control calcining furnace to be anoxic or to approach anaerobic atmosphere.