Important progress made by Chinese researchers in recovering organic dyes from wastewater

Important progress made by Chinese researchers in recovering organic dyes from wastewater

Recently, researchers from the Key Laboratory of Biomimetic Materials and Interface Science, Institute of Physical and Chemical Technology, Chinese Academy of Sciences proposed a new fully dispersed strategy for surface heterogeneous nanostructured particles, and prepared fully dispersed hydrophilic hydrophobic heterogeneous microspheres. These microspheres show excellent fully dispersed performance in a series of solvents (water, ethanol, octane, etc.), and realize the recovery of organic dyes from wastewater.

Fully dispersed hydrophilic hydrophobic heterogeneous microspheres

    Organic dyes are a commonly used color additive, widely used in industry, scientific research, and various aspects of daily life. Dyes make our clothing, food, and daily necessities colorful; Dyes emit light under a microscope to achieve imaging, helping us reveal the mysteries of the microscopic world. Data shows that the global production of organic dyes has reached 700000 tons per year, of which nearly 10% to 15% are discharged into industrial and household wastewater, becoming an important source of water pollution and posing a threat to the ecological environment and public health.

    The existing treatment methods for dye wastewater, such as coagulation flocculation and biodegradation, can remove most of the organic dyes in the wastewater. However, these methods still face problems such as incomplete dye removal, limited types of suitable dyes, and the possibility of secondary pollution caused by the generated sludge. In recent years, with the rapid development of nanotechnology and material technology, some emerging materials and dye wastewater treatment technologies have emerged, including catalytic oxidation, nanofiltration, and porous particle adsorption. Catalysts, membranes, and adsorption materials can be reused after completing dye wastewater treatment, but the recovery of dyes is rarely valued. The reason for this is that in the process of organic dye desorption, eluents containing inorganic acids, bases, or salts are usually added to the aqueous solution, making the recovery process of organic dyes more complex.

    In recent years, Wang Shutao, a research team of the Institute of Physical and Chemical Technology of the Chinese Academy of Sciences, has proposed a new method of lotion interfacial polymerization to synthesize heterostructure microspheres, and has made a series of innovative achievements in its efficient separation and application. A variety of lotion interfacial polymerization synthesis methods have been developed, and a series of heterogeneous microspheres with different sizes, chemical compositions, pores, and surface nanostructures have been prepared. The separation of trace glycopeptides in complex biological fluids, the separation of proteins with similar sizes, the separation of viral nucleic acids, and the separation of trace circulating tumor cells in the peripheral blood of cancer patients have been realized, and chromatographic columns, differential separation columns, microfluidic, paper chromatography and other separation devices have been constructed.

        Figure 1. Characterization of hydrophilic hydrophobic heterogeneous microspheres. The team used the lotion interfacial polymerization synthesis method developed earlier to synthesize hydrophilic hydrophobic heterospheres, and confirmed their surface heterostructure through transmission electron microscopy, photoinduced force microscopy, atomic force microscopy and other characterization.

Figure 2. Comparison of dispersion performance of hydrophilic hydrophobic heteromicrospheres, hydrophilic microspheres, and hydrophobic microspheres.

    Figure 3. Hydrophilic hydrophobic heterogeneous microspheres achieve dye recovery from wastewater. Dyes are adsorbed by microspheres in water; Filtration separation; The microspheres are dispersed in organic solvents to achieve dye desorption; Low temperature distillation to achieve dye recovery; Microspheres are used for recycling dyes.

    The surface of hydrophilic hydrophobic heterogeneous microspheres has alternating hydrophilic and hydrophobic components (Figure 1), which is conducive to the spreading of high polar solvents (water), medium polar solvents (organic solvents such as ethanol), and low polar solvents (oily organic solvents such as octane). In addition, in the hydrophilic region, it is easy to introduce charged groups, which can provide electrostatic repulsion between particles and achieve good dispersion in different solvents (Figure 2). By utilizing this unique total dispersion, the team developed a strategy for separating and recovering dyes from wastewater containing organic dyes. Dyes are adsorbed onto microspheres in water, purified water is obtained through filtration, and microspheres with adsorbed dyes are dispersed into organic solvents to achieve dye desorption. Organic solvents with dissolved dyes are obtained through filtration, and the dyes are recovered through distillation, while the microspheres are recycled (Figure 3).

    Hydrophilic hydrophobic heterogeneous microspheres provide a promising material for the recovery of organic dyes. In the process of recycling organic dyes, only organic solvents need to be added, without the need to add eluents containing inorganic acids, bases, or salts. Organic solvents are easily removed from dyes through simple distillation, avoiding the complex steps of removing inorganic acids, bases, and salts. This type of material has broad application prospects in the separation and analysis of complex samples such as environmental pollutant treatment, resource recycling, marine resource enrichment and extraction, and biomolecular detection.