Dr. Wang Zhenxing Nanchang University, Professor Li Yuexiang made progress in mussels series Bionic table / Interface Modification and research in the field of water treatment

water pollution and shortage of freshwater resources has become a global issue. According to United Nations statistics, in 2025, two-thirds of the world\’s population could face water shortages, so the development and application of water treatment materials and technology is particularly important. Water separation filter material comprises a material, adsorbent material, catalytic material, and solar thermal water purification material appeared in recent years. Above its material properties of water table / interfacial properties (micro-nano structures, invasive aperture, the charge, the specific surface area, etc.) is directly related, therefore, a need to develop an active table / interfacial modification and regulation method. In recent years, dopamine poly (PDA) represented mussels biomimetic coating process due to the simple preparation mild, with excellent adhesion and good secondary reactivity, received extensive attention in various fields including water treatment, including. However, dopamine monomer prices prepared PDA more expensive, is not conducive to the use of mass production, and therefore need to find an inexpensive alternative. To this end, researchers have developed coating polyphenol inexpensive, readily available, but limited to tannic acid represented polyphenol coating table and chemically inert hydrophobic material / interface modifying effect. To solve this problem, Professor Li Yuexiang team Dr. Wang Zhenxing by a hydrophobic membrane easily adsorbed inspire protein and tanned leather, developed based on protein adsorption – tannic acid-curable water-repellent film superhydrophilic surface modification method, to achieve the efficient modification of the polyphenols more hydrophobic materials ( Journal of materials Chemistry a , 2018, 6 , 13959; Figure 1).

FIG adsorbing a protein-based – tannic acid-hardening hydrophobic material modified policy table interface

In addition to higher cost outside, PDA coating there is another problem: usually obtained PDA mostly thinner coating a smooth coating, it is difficult to significantly change the material sheet / interfacial profile, limiting its application must set up a large number of rough surface in the micro- and nanostructures. Although this problem can be obtained by adding a large amount of nanoparticles in the polymerization process of dopamine or dopamine concentrations greatly improved to solve, but this will increase the cost and cumbersome manufacturing process. In fact, polyphenols coatings have also reported similar problems. Recently, Dr. Wang Zhenxing, and Professor Li Yuexiang openMade tannic acid (TA) -3-aminopropyl triethoxysilane (the APTES) coating (i.e. coating TA-APTES), effectively solves the above problem ( Journal of Materials Chemistry A , 2018, 6, 3391; Figure 2). TA-APTES coating preparation process is simple mild, PDA-like having excellent adhesion and universality, can be realized on a variety of materials (polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, stainless steel mesh, copper mesh, etc.) table / interface modifier, and a coating having a PDA and polyphenols do not have previously reported extensive micro- and nanostructures, it favors the production of high performance functional material. In addition, low price APTES and TA, TA-APTES conducive to the application of the coating.

Preparation and unique structure of Figure II TA-APTES coated schematic

Secondary reactive coating is important to extend the application of the coating. Further studies showed that TA-APTES coated surface containing a large amount of a small amount of phenolic hydroxyl group and an amino group, a secondary reactive PDA-like coating provides a good platform for the preparation of a variety of functional coating further functional material ( Journal of Membrane Science , 2018, 564, 317). To demonstrate the advantages of TA-APTES coating, the coating selected for comparison PDA, secondary modification by the same methods and procedures, based on the functional material coating and TA-APTES coated PDA (adsorbent, catalytic materials were prepared , oil-water separation material). Thanks to the unique TA-APTES coated micro- and nanostructures, performance based TA-APTES resultant coating the functional material is far superior PDA-based coating material ( Chemical Engineering Journal , 2019, 360, 299 ; Figure 3). The above-mentioned Studies have shown that TA-APTES PDA is expected to replace coating in certain areas.

FIG three groups based on PDA exhibit a plurality of functions than the water activity of the material prepared TA-APTES secondary reactionsBetter performance functional material

Further studies showed that, after the coating process ferric ion, i.e., (TA-APTES) -Fe (III) coating, with good optical absorption characteristics, may be light can be efficiently converted into thermal energy, is expected as a new material for the photothermal solar desalination. Studies have shown that the (TA-APTES) – Fe (III) photothermal coating has good universality , it can be polyvinylidene fluoride microfiltration membranes, nylon fabric, urethane sponge , cotton, wood, paper and other ordinary materials into a wide variety of solar thermal desalination composite material used. In (TA-APTES) – Fe (III) a modified polyester sponge after coating an example: the composite material having a light-heat in the wavelength range 250-2500nm high light absorption characteristics, which is highly light absorbing large phenolic hydroxyl and trivalent iron complex of transition dd, the coating itself as well as micro- and nanostructures resulting porous sponge. In which a sunlight intensity (1kW -2 m) up to an amount of water evaporated 1.43 kg m -2 h -1 , the photothermal conversion efficiency of 90%. Further investigated the ability of seawater desalting, was found to significantly reduce the concentration of each ion of the photothermal material obtained in the condensed water, the condensed water collected purity exceeds international drinking water standards. Furthermore, this coating may impart excellent light resistance to oil pollution hot material properties, it can still maintain a stable water evaporation efficiency oily wastewater treatment. Further, the novel light-heat coating of a strong acid and alkali (pH: 2-12), rinse-resistance, resistance to freezing and thawing cycles. More importantly, the coating has excellent flexibility and universality, can be modified to achieve different materials having any morphology, and thus is very easy to design, to further improve the rate of water evaporation (it is expected to 3D printing and combined preparation photothermal material having a complicated structure). Compared with various types of solar thermal material previously reported, the class coating has a unique advantage: gentle preparation process is simple, without complex and expensive equipment, low-cost, universal good, compatible with a variety of structural design, with versatility Wait. It is expected to become the unique advantages of the above-described powerful tool for preparing high performance desalination photothermal material (Versatile coating with multifunctional performance for solar steam generation, Nano Energy , 2020, Accepted; Figure IV).

Figure IV (TA-APTES) -Fe (III) as a coating material for the general versatility photothermal solar desalination

In the course of the study, further found: for purposes of wood, simply placing an aqueous solution of tannic acid soak for a period of time, and then placed in an aqueous solution after immersing containing ferric ions, can be converted into a variety of wood desalination photothermal material ( Nano Energy , 2020, 71, 104650; Figure V) used. Currently photothermal method for preparing wood-base material reported in the literature there are mainly two: one is carbonized; the other is a surface coating. The flat surface of the carbonization temperature of the timber was placed on a hot plate, the contact surface by high temperature carbonization. This technique requires high temperatures, and more difficult to achieve an uneven or irregular surface uniformly carbonized wood; In addition, after the high-temperature carbonization of the wood surface will lose a large amount of hydrophilic groups, which results in the adhesion of underwater oil resistant reduced water droplets easily adhere clogged pores, resulting in greatly reduced water production performance. Coating technology is prepared photothermal material is applied to the wood surface. Commonly used coating material is a photothermal material such as carbon black, no adequate bonding force between the timber and because these materials are easy to drop in external force. Compared with the above-described method has been reported, the new method does not require special equipment or high pressure and temperature, the green, and the light-heat the formed coating has excellent mechanical stability (long period of time does not come off sonication) and excellent in anti-submarine oil adhesion, is also applicable to a variety of wood of any shape, design and development of high performance wood-based desalination photothermal material and provides a new way of thinking.

Figure V (a) preparing a schematic view of a wood-based material, photothermal, stability (b) heat the resulting light wood-base material, (c) a timber having a specific structure designed photothermal conversion material

based on long-term research work in mussel bionic table / interface modification Dr. Wang Zhenxing Nanchang University , LeeProfessor Gordon the and Shore Road Harbin Institute of Technology , Zhongshan University Professor Cheng Fu Hao Yang and Argonne National Laboratory researcher Seth B. Darling , etc. people cooperation, summarized and analyzed in detail the progress of recent years mussels bionic table / interfacial modification technology in the field of water treatment and challenges, and prospects the development of this area, related work published in Cell in the form of a review of its Journal of materials flagship Matter (Mussel-inspired surface engineering for water-remediation materials, Matter, 2019, 1, 115-155; Figure 6).

Figure VI-based table interface modification technology mussels bionic applications in water treatment

The work was supported by the National Natural Science Foundation of China, national key R & D program, Jiangxi natural funded Science Foundation. Thanks Ji Sheng strong (has master degree) and Han Ming was (graduate student) two students hard work.