CN111807630A - A high-efficiency molybdenum removal vertical underflow constructed wetland purification device - Google Patents

Abstract

The invention provides a high-efficiency molybdenum removal vertical underflow constructed wetland purification device, which includes a water inlet mechanism, a purification area and a water outlet mechanism. The purification area sequentially includes a soil layer, a composite matrix layer, a fine sand layer, a supporting The composite matrix layer is a composite matrix of modified cinder and pyrite, and the soil layer is planted with plants; a water inlet mechanism is arranged above the purification zone, and a water outlet mechanism is arranged at the bottom of the purification zone. As one of the components of the filler layer, the composite matrix involved in the present invention has the advantages of high molybdenum removal efficiency, wide source, cheap and easy to obtain, simple preparation and the like. The invention combines the adsorption material with the artificial wetland, and has high removal efficiency for heavy metal molybdenum sewage, and the molybdenum concentration in the effluent of the artificial wetland meets the quality standard of groundwater in my country.

Description

A high-efficiency molybdenum removal vertical underflow constructed wetland purification device

technical field

The invention relates to the technical field of artificial wetland sewage ecological treatment, in particular to a high-efficiency molybdenum removal vertical underflow artificial wetland purification device.

Background technique

Molybdenum (Mo) is one of the transition elements with biological activity, and it is also an essential trace element for animals and plants. A proper intake is beneficial to the normal physiological activities of the living body. However, once the molybdenum intake is excessive, it will damage the health of the organism, and even lead to molybdenum poisoning of the organism. In China's "Drinking Water Sanitation Standard" and "Surface Water Environmental Quality Standard", the mass concentration limit of molybdenum in the specific project of the surface water source of centralized drinking water is 0.07mg L ^-1 . The hexavalent molybdate ion (Mo(VI)) is relatively stable in the environment and is easily taken up by organisms in most systems, so when the concentration of Mo(VI) in the aqueous solution exceeds 5ppm, it will cause harm to the environment. In industrial applications, molybdenum has important economic value as a component of fertilizers, catalysts, metal alloys and rust inhibitors. However, due to the relatively backward molybdenum mining technology and insufficient management of alkaline molybdenum tailings, the water pollution of molybdenum in some areas at home and abroad is relatively serious.

At present, the domestic methods of treating molybdenum wastewater mainly include four types: ion exchange method, chemical precipitation method, adsorption method and constructed wetland method. The ion exchange method has the disadvantages of high cost and difficult operation and maintenance, while the chemical precipitation method is prone to secondary pollution. Although the adsorption method is widely used, it is not suitable for the treatment requirements of molybdenum non-point source pollution. Constructed wetland is a water treatment ecosystem constructed by imitating natural wetlands. This process has received extensive attention due to its advantages of low construction and operation cost, simple management, and relatively stable purification effect.

Constructed wetland is an ecological engineering technology for sewage treatment. It is developed on the basis of the degradation of sewage in natural wetlands. It uses the triple synergy of physics, chemistry and biology in the natural ecosystem to purify sewage. Among them, the subsurface wetland system, that is, the seepage of water under the surface of the filler, can make full use of the biofilm on the surface of the filler and the root system of plants and other various functions to treat wastewater, and has good sanitary conditions, so it is widely used. The removal of heavy metals from constructed wetlands mainly relies on the matrix layer in the system. However, the removal efficiency of molybdenum by ordinary constructed wetland substrates is low. Therefore, the development of new efficient molybdenum-removing constructed wetland substrates is one of the research hotspots. The research on molybdenum removal substrates at home and abroad mainly focuses on the following: iron ore, soil, chelating resin, chitosan and activated carbon. Relevant studies have shown that substrates with larger surface areas and rich in iron and aluminum oxides are better for molybdenum removal. Due to the extremely low removal efficiency of soil molybdenum and the high cost of materials such as chelating resin, chitosan and activated carbon, slag containing both iron and aluminum oxides and a large surface area may be a suitable material for the matrix of constructed wetlands for molybdenum removal. . As an industrial waste, coal slag has a large specific surface area, but most of the coal slag is alkaline, which is not conducive to the removal of molybdenum in water, so we modified it with sulfuric acid. At the same time, pyrite, which is relatively abundant in the crust, was also selected in the constructed wetland matrix in this study. Because pyrite itself has an acid-generating effect, and the rich sulfur and iron elements are beneficial to the removal of molybdenum in water. However, pyrite itself has a small specific surface area, so combining it with modified coal slag with a large surface area as a constructed wetland substrate may receive a good molybdenum removal effect.

There have been many technical achievements on the ecological treatment of constructed wetland sewage, such as the Chinese patent number CN105594642A, the authorization announcement date is May 25, 2016. The patent discloses a patent document titled "A Multi-stage Surface Flow Constructed Wetland Ecological Symbiosis System Based on Pond Ridge and Its Using Method"; Chinese Patent No. CN105600932A, the authorization announcement date is May 25, 2016. This patent discloses a patent document titled "A Modular Constructed Wetland Sewage Treatment Device"; Chinese Patent No. CN102642978A, date of authorization announcement on August 22, 2012. The patent discloses a patent document titled "A High Efficiency Circulating Vertical Flow Constructed Wetland and Equipment Suitable for Dispersive Treatment of Sewage"; Chinese Patent No. CN105600934A, dated May 25, 2016. The patent discloses a patent document titled "A New Type of Constructed Wetland". These wetland systems have received good removal effects for specific pollutants, but the wetland structure is relatively complex, and the operation and maintenance costs are relatively high.

There are also related invention patents in the aspect of constructed wetland composite matrix. For example, Chinese patent number CN210163197U, the date of authorization announcement is March 20, 2020. This patent discloses a patent document titled "A Constructed Wetland Treatment Device Using Composite Fillers"; Chinese Patent No. CN101293711B, dated July 20, 2011. The patent discloses a patent document titled "A Rapidly Assembled Constructed Wetland Sewage Treatment System and Its Filling Unit"; Chinese Patent No. CN102765804B, dated April 16, 2014, published a document entitled " A patent document of a constructed wetland sewage treatment method based on modular built-in void fillers"; Chinese Patent No. CN110790388A, the date of authorization announcement on February 14, 2020, a published document entitled "Composite vertical underflow based on functional packing structure" Constructed Wetland Sewage Purification System" patent document. Most of these constructed wetlands are used to remove organic pollutants or inorganic non-metal ions, but the ability to treat heavy metal anions is unknown.

In terms of adsorption materials for removing heavy metal anions, for example, Chinese Patent No. CN106268720B, the date of authorization announcement on September 11, 2018, published a document entitled "Preparation of Biochar composite adsorption materials for removing molybdate in surface water Method" patent document; Chinese Patent No. CN106423087A, date of authorization announcement on February 22, 2017. The patent discloses a patent document entitled "Preparation of Magnetic Chitosan Carbon Balls and Application in Adsorption and Removal of Cr(VI) in Water"; Chinese Patent No. CN106582500A, Authorization Announcement Date: April 6, 2017 . This patent discloses a patent document entitled "A kind of adsorbable and degradable Cr(VI) diatomite composite material and its preparation method"; Chinese patent number: CN106622099A, the authorization announcement date is May 10, 2017, published The title is "Preparation of an arsenic adsorption material and its renaturation and reuse method". Although the raw materials of these composite materials are cheap and easy to obtain, they have the disadvantage of complicated preparation process, and the adsorption efficiency still needs to be improved.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to develop a high-efficiency molybdenum removal vertical underflow artificial wetland purification device. As one of the components of the filler layer, the composite matrix involved in the present invention has the advantages of high molybdenum removal efficiency, wide source, cheap and easy to obtain, simple preparation and the like. The invention combines the adsorption material with the artificial wetland, and has high removal efficiency for heavy metal molybdenum sewage.

To achieve the above purpose, the present invention is achieved through the following technical solutions:

A high-efficiency molybdenum removal vertical underflow constructed wetland purification device includes a water inlet mechanism, a purification area and a water outlet mechanism, and the purification area sequentially includes a soil layer, a composite matrix layer, a fine sand layer, and a supporting layer from top to bottom. The composite matrix layer is a combined matrix of modified cinder and pyrite, and the soil layer is planted with plants; a water inlet mechanism is arranged above the purification zone, and a water outlet mechanism is arranged at the bottom of the purification zone.

Preferably, the water inflow mechanism adopts intermittent water inflow to simulate the molybdenum tailings leachate caused by precipitation flushing. One week is a cycle, the total time for water inflow and treatment is 3-4 days, and the total time for emptying and idle is 3 days. ~4d.

Preferably, the modified coal slag is prepared by the following method: put the coal slag into clean water for 1 d, then grind, rinse, and naturally dry, and screen to obtain coal slag with a particle size of 1 to 2 mm or less; 2.0 to 4.0 mol/ L of H ₂ SO ₄ solution is added to the above-mentioned cinder, shaken for 8 to 10 hours, and the vibration speed is 200 r/min, then washed with water until it does not contain SO ₄ ^2- , and air-dried to obtain it.

Preferably, the pyrite is prepared by the following method: the crude pyrite is washed with water for 1 d, then ground, rinsed, naturally dried, and screened to obtain pyrite with a particle size of 1 to 2 mm or less.

Preferably, the volume ratio of the modified coal slag and pyrite is 5:1 to 1:1.

Preferably, the plant grown in the soil layer is cattail.

Preferably, the planting density of the cattail is 20-30 plants/m ² .

Preferably, the supporting layer includes a fine gravel layer and a coarse gravel layer in sequence from top to bottom.

Preferably, the water outlet mechanism includes a plurality of water outlet pipes located at the bottom of the supporting layer, the water outlet pipes located in the supporting layer are provided with a plurality of water inlet holes along the length direction thereof, and the water outlet pipes located outside the supporting layer are provided with a plurality of water inlet holes. An outlet valve is installed on the outlet pipe.

Compared with the prior art, the beneficial effects of the present invention are:

(1) A high-efficiency molybdenum-removing vertical underflow constructed wetland purification device of the present invention combines adsorbent materials with constructed wetlands to produce a comprehensive effect, and the adsorbent matrix materials have a wide range of sources, low prices, and can achieve waste resource utilization.

(2) The high-efficiency vertical underflow composite matrix filler constructed wetland purification device of the present invention has high removal efficiency for heavy metal molybdenum sewage, the average removal rate can reach more than 85.3%, and the molybdenum concentration in the constructed wetland effluent meets my country's groundwater quality standards (GB/T 14848). -93) Class IV (≤0.5 mg/L).

Description of drawings

Fig. 1 is the structural representation of high-efficiency molybdenum removal vertical underflow constructed wetland purification device;

In the figure: 1-water inlet mechanism; 2-water inlet mechanism; 21-water outlet mechanism; 22-composite matrix layer; 23-fine sand layer; 24-fine gravel layer; 25-coarse gravel layer; 26-plant; 3- and water outlet mechanism; 31-plant; 32-water inlet hole; 33-water outlet valve.

Figure 2 is a graph showing the removal rate of Mo(VI) in water by the constructed wetland system.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention. examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

This embodiment provides a high-efficiency molybdenum removal vertical underflow constructed wetland purification device suitable for molybdenum tailings non-point source sewage treatment. As shown in FIG. 1, the purification device includes a water inlet mechanism 1, a purification zone 2 and a water outlet mechanism 3. Zone 2 includes a soil layer 21 , a composite matrix layer 22 , a fine sand layer 23 and a supporting layer in sequence from top to bottom.

The soil layer 21 was planted with cattail, and the planting density of the cattail was 26 plants/m ² . The composite matrix layer 22 is a combined matrix of modified coal slag and pyrite, and the supporting layer sequentially includes a fine gravel layer 24 and a coarse gravel layer 25 from top to bottom.

A water inlet mechanism 1 is arranged above the purification zone 2 , and a water outlet mechanism 3 is arranged at the bottom of the purification zone 2 . The water inlet mechanism 1 adopts intermittent water inlet to simulate the leachate of molybdenum tailings caused by precipitation flushing, one week is a cycle, water inlet + treatment time = 4d, emptying + idle time = 3d. The water outlet mechanism 3 includes a plurality of water outlet pipes 31 located at the bottom of the supporting layer, the water outlet pipes 31 located in the supporting layer are provided with a plurality of water inlet holes 32 along the length direction thereof, and the water outlet pipes 31 located outside the supporting layer are provided. A water outlet valve 33 is installed on it.

Wherein, the volume ratio of modified coal slag:pyrite in the composite matrix layer=3:1.

The modified coal slag is prepared by the following method: put the coal slag into clean water for 1 d, then grind, rinse, and naturally dry, and screen to obtain the coal slag with a particle size of less than 2 mm; add 4.0 mol/L H ₂ SO ₄ solution to the The above-mentioned cinder is shaken for 10h, and the vibration speed is 200r/min, then washed with water until it does not contain SO ₄ ^2- , and air-dried to obtain it.

The pyrite is prepared by the following method: the crude pyrite is washed with water for 1 d, then ground, rinsed, and naturally dried, and the pyrite with a particle size of less than 2 mm is obtained by screening.

Example 2

Same as Example 1, the difference is that the composite matrix layer is soil.

Example 3

Same as Example 1, the difference is that the composite matrix layer is modified cinder.

Example 4

Same as Example 1, the difference is that the volume ratio of modified coal slag:pyrite in the composite matrix layer=5:1.

Example 5

Same as Example 3, the difference is that water intake + treatment time = 2d, emptying + idle time = 5d

Molybdenum removal tests were carried out on the constructed wetlands in the above examples 1-5 respectively.

For the corresponding wetland model, the constructed wetlands in Examples 1-5 were placed in a cylindrical plastic bucket with a height of 60 cm, a bottom diameter of 25 cm, and a top diameter of 38 cm.

In the models of Examples 1-5, the composition and arrangement sequence of the high-efficiency molybdenum removal vertical underflow constructed wetland purification device is shown in Table 1.

Table 1 Sequence of composition and arrangement of vertical subsurface constructed wetland purification devices

The target pollutant molybdenum of the experiment was prepared with sodium molybdate (Na ₂ MoO ₄ ·2H ₂ O), and the average influent molybdenum concentration was 3.2 mg/L. The effluent water samples were collected 1 min after each effluent. The molybdenum content in the water samples was measured by thiocyanate spectrophotometry, and the minimum detection concentration was 5ug/L.

The test data after the operation of each device for 3 months shows that the constructed wetland systems in Examples 1-5 of the present invention all have a certain removal effect on molybdate in sewage. The removal rates of molybdenum in Examples 1 and 4 are significantly higher than those in Examples 2, 3, and 5. The details are shown in Table 2.

Table 2 The experimental results of removing molybdenum in different examples

Among them, FIG. 2 is a diagram showing the removal rate of molybdate in sewage by the constructed wetland system in Example 1 at different times.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. a high-efficiency molybdenum removal vertical underflow constructed wetland purification device, is characterized in that, comprises water inlet mechanism (1), purification zone (2) and water outlet mechanism (3), and described purification zone (2) is successively from top to bottom It comprises a soil layer (21), a composite matrix layer (22), a fine sand layer (23), and a supporting layer, wherein the composite matrix layer (22) is a combined matrix of modified cinder and pyrite, and the soil layer ( 21) Plants (26) are planted; a water inlet mechanism (1) is arranged above the purification zone (2), and a water outlet mechanism (3) is arranged at the bottom of the purification zone (2). 2. high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 1, is characterized in that, described water inlet mechanism (1) adopts intermittent water inlet to simulate the molybdenum tailings leachate caused by precipitation flushing, and one week is a cycle, the total time for water inflow and treatment is 3-4d, and the total time for emptying and idle is 3-4d. 3. high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 1, is characterized in that, described modified cinder is prepared by the following method: cinder is put into clear water to wash 1d, then carry out grinding, rinsing, Natural drying, screening to obtain cinder with a particle size of 1-2 mm or less; adding 2.0-4.0 mol/L H ₂ SO ₄ solution to the above-mentioned cinder, shaking for 8-10 hours at a speed of 200 r/min, and then washing with water until it does not contain SO ₄ ^2- , air-dried and ready to use. 4. high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 1, is characterized in that, described pyrite is prepared by the following method: pyrite crude product is washed 1d through clear water, then grind, rinse , natural drying, and screening to obtain pyrite with a particle size of 1 to 2 mm or less. 5 . The high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 1 , wherein the volume ratio of the modified coal slag and pyrite is 5:1 to 1:1. 6 . 6 . The high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 1 , wherein the plants ( 26 ) planted in the soil layer ( 21 ) are cattails. 7 . 7 . The high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 6 , wherein the planting density of the cattail is 20-30 plants/m ² . 8 . The high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 1 , wherein the supporting layer comprises a fine gravel layer (24) and a coarse gravel layer (25) sequentially from top to bottom. 9 . 9. The high-efficiency molybdenum removal vertical underflow constructed wetland purification device according to claim 1, wherein the water outlet mechanism (3) comprises a plurality of water outlet pipes (31) located at the bottom of the supporting layer, located in the supporting layer The water outlet pipe (31) is provided with a plurality of water inlet holes (32) along its length direction, and a water outlet valve (33) is installed on the water outlet pipe (31) located outside the supporting layer.

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