Corn straw transforms!See how the "garbage" used to purify the water body?

The original clear lake became strange colors, and it exudes a bad smell? The small fish and shrimp all turned their stomach and died, and even the duck didn't want to go swimming? In fact, this may be the outbreak of the cyanobacteria in the lake. In addition, the red tide, moss, and the flood of water plants belong to the rich and nutritious water body. This phenomenon is not difficult to see in my country.

The richness of water bodies can cause the rapid reproduction of algae and other plankton, the amount of oxygen dissolving oxygen in the water body, and the harm of water quality, thereby threatening a large number of fish and other organisms, and even the water body loss to regulate regional climate and maintain the balance of regional ecosystem balance. The phosphate is one of the culprits that cause these problems, and removing phosphate in the water body is of great significance.

Recently, scientists have found that the special structure of corn straw can help filter the phosphorus in adsorbing water, thereby achieving the effect of purifying the water body. How does the humble corn straw make this mission efficiently complete this mission? Can it be done by straw alone? Does the phosphorus removal effect make us satisfied?

How can the corn straw as a garbage counterattack into a "phosphorus master"?

Corn straw is a typical agricultural waste. The annual output in my country is close to 300 million tons, and the global annual output is as high as 1 billion tons. At present, the main treatment methods of abandoned straws include incineration, used as animal feed, fermentation, etc., which have low economic benefits and even cause environmental pollution. And this study cleverly provides solutions for the two major environmental problems through "waste pollution", which not only provides green and environmentally friendly adsorbents for the removal of water phosphate, but also provides a new type of value -added use of waste straw stalks. way.

Figure 1. Internal structure of corn straw

In order to meet their own growth needs, corn straw has naturally evolved and developed a developed quality transmission system composed of vitamin bundles, catheters, interclass wires, and tattoos. High pore rate, external solution can enter the inside of the tissue cells through vascular bundles and ducts, and the cells can also be passed through the micropores on the cytoplasm, pores, and even micropores on the cell membrane. In addition, corn straw has the advantages of cheap and easy gain, green environmental protection, and good mechanical properties. These characteristics are pursued by designing and forming adsorbents, and it is also difficult to achieve at the same time as chemical synthesis methods.

What is MOFS? What role does it play in the phosphorus removal project? How to remove phosphorus with corn straw?

Metal organic framework (MOFS) material is a type of crystalline porous material formed by an inorganic metal center (metal ion or metal cluster) and organic ligands that forms a periodic network structure through self -assembly. MOFS has the advantages of high surface area, low density, easy to regulate and modifying, and has huge application potential in the field of water body repair. However, synthetic MOFS is usually a nano/micron -level powder. In practical applications, it is necessary to shape the adhesive or chip, just like using cement to make sand into a brick. The mass transmission is blocked, which greatly reduces the efficiency of MOFS. How to shape MOFS into applications on the premise of maintaining the inherent characteristics of MOFS is still challenging.

In order to solve the above problems, the porous catalytic material research group led by Researcher Wang Guanghui of Qingdao Energy Institute used the abandoned corn straw (MS) as a carrier to introduce MOFS materials to develop a new type of MOFS device for continuous flowing phosphorus removal. Therefore, the research team uses the solvent thermal method (in a closed high-pressure kettle, with n, n-di metamimamide as the solvents, and under the self-reinforcement pressure of a certain temperature and solution Assembled), composite materials (UIO-66/MS) of MOFS and corn straw were prepared, and "Taoist Nature" was achieved through "Taoist Nature".

First of all, immerse the precursor solution of the synthetic MOFS in the straw, so that the forefront solution is filled with the tissue cells of the straw like the tissue liquid, which is convenient for MOFS to grow inside the straw. The metal ions and organic ligands are attracted to the surface of the straw by attracting or hydrogen bonding, providing an core point for the growth of MOFS. Therefore, after a nuclear reaction, Mr. MOFS Granules grew on the surface of the cell wall of the straw to form a uniform single -layer MOFS film. This distribution form avoids the accumulation of MOFS particles, so that the adsorbent sites can be fully exposed, so that MOFS The adsorption performance of phosphate phosphate is fully exerted. In addition, due to the natural cylindrical shape and compression elasticity of straw, UIO-66/MS materials can be installed in the glass tube. The gap between the straw and the wall of the tube can be filled with a single filter device. Series and parallel).

What is the effect of phosphorus removal?

The adsorption capacity of the MOFS on Ps in the obtained material is as high as 269.7 mg · G-1, and the adsorption rate is significantly higher than the molding MOFS catalyst prepared by the chip legal system; The adsorption performance of the material on phosphate is almost not affected by common anion (chloride, nitrate root, root, carbonate root, etc.) in common water bodies. In the continuous flow experiment (300 L · m-2 · H-1), the UIO-66/MS device can repair the phosphorus pollution water with an initial PPM of 3 PPM to the requirements of the first-class sewage discharge standard in China (<0.5 PPM). The work "one stone and two birds" provides solutions for the removal of water phosphate and the value -added use of abandoned straw. Figure 2. The synthesis schematic diagram and structural signs of UIO-66/MS

Figure 3. UIO-66/MS's adsorption performance diagram of phosphate

Figure 4. Pores and catalytic materials team photos

Produced: Popular Science China

Author: Li Dechang (Institute of Qingdao Biological Energy and Process of Chinese Academy of Sciences)

Producer: China Science Popularization Expo

references:

1. Original link: https://doi.org/10.1016/j.cej.2022.136461

De-Chang Li1, Qian Zhang1, Wen-Quan Wang and Guang-Hui Wang*. Filter fabrication by constructing metal-organic frameworks membrane on waste maize straw for efficient phosphate removal from wastewater. Chem. Eng. J., 2022, 136461.

2. Patent: a method and application of MOF/corn straw composite materials and devices, application numbers: 2022103903279.

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