Xie Xianchuan research group of Nanjing University: simple synthesis of water soluble porous cyclodextrin polymer for rapid removal of organic micro pollutants in water

Water pollution has become an important environmental problem restricting human survival and economic development, among which organic micro pollutant pollution is a widespread and urgent problem Among many treatment methods, adsorption method is the most commonly used one because of its low cost, high efficiency and simple operation Traditional adsorbents, such as activated carbon and resin, have the disadvantages of slow adsorption rate, difficult regeneration, and difficult biodegradation Cyclodextrin is a product of starch hydrolysis Its unique external hydrophilic and internal hydrophobic cavity structure makes it have a good affinity for a variety of pollutants Therefore, more and more attention has been paid to cyclodextrin based adsorbents Up to now, most of the cyclodextrin polymers are nonporous with low specific surface area In recent years, although porous cyclodextrin polymers have been reported, all of them are synthesized in organic phase, which not only increases the production cost and industrial production difficulty, but also is not conducive to environmental protection Therefore, it is of great significance to prepare porous cyclodextrin polymer in aqueous phase Recently, Professor Xie Xianchuan's research group of Nanjing University School of environment has made important progress in this field, and relevant research results are published online in the Green Chemistry Journal (DOI: 10.1039 / c9gc02422k) with the title of "simple synthesis of a swollable porus β - cyclodextrin based polymer in the acute phase for the rapid removal of organic micro polymers from water" (DOI: 10.1039 / c9gc02422k ）Assistant researcher Xu Guizhou is the first author of the paper, and associate professor Xie Xianchuan is the corresponding author of the paper Brief introduction of Xie Xianchuan research group the main research direction of Xie Xianchuan research group of Nanjing University is comprehensive control and treatment of water pollution in river basin / region At present, SCI papers have been published on the development and application of new water treatment materials, resource treatment and risk control of waste water, in-situ monitoring of environmental pollutants, migration and transformation, etc Several papers, some of which were published in the top international journals such as green chemistry, environment science and technology, water research, Journal of agricultural and food chemistry At present, the research group has 7 master students, 2 doctoral students and 2 research assistants The research team welcomes excellent doctors, masters and undergraduates who are interested in the field of water treatment or new material development to join the team Leading scientific research achievements: simple synthesis of water soluble porous cyclodextrin polymer for the rapid removal of organic micro pollutants in water Because of the wide sources of cyclodextrin materials, low cost, and special affinity for a variety of pollutants, scientists have been keeping a strong interest in this kind of materials As adsorbents, materials need to have porous structure and high specific surface area However, most of the cyclodextrin materials reported in the literature are pore free polymers made by crosslinking cyclodextrin and flexible molecules In recent years, it has been reported that porous cyclodextrin polymer can be prepared by introducing rigid structure However, all the porous cyclodextrin polymers were prepared in organic phase How to prepare porous cyclodextrin polymer in water is still a challenge In order to prepare porous cyclodextrin polymer with swelling, the rigid and flexible crosslinking agents were used to crosslink cyclodextrin in water phase The author selected the most commonly used flexible cross-linking agent epichlorohydrin and rigid cross-linking agent tetrafluorobenzonitrile to react with β - cyclodextrin in NaOH aqueous solution (Figure 1) Reaction temperature 90 ℃, reaction time 3 h At the end of the reaction, the light yellow cyclodextrin polymer powder can be obtained by simple washing, purification and drying By scanning electron microscopy and carbon dioxide adsorption analysis, the polymer has more macroporous structure (hundreds of nanometers) and microporous structure (< 1 nm) (Fig 2) Fig 1 synthesis route and a typical network structure of cyclodextrin polymer (t-e-cdp) (source: greenchemistry) Fig 2 synthesis and morphology of t-e-cdp (a) the actual synthesis process of t-e-cdp; and (b) the photos and electron micrographs of t-e-cdp and EPI (source: greenchemistry) firstly, the author selected the common organic micro pollutant bisphenol A (BPA) in water and studied its adsorption performance The results show that the adsorption rate of bisphenol A is super fast, and the adsorption equilibrium can be achieved within 10 minutes, and the removal rate of bisphenol A reaches 97% (Fig 3) The results show that the adsorption process is in accordance with the quasi second-order kinetic model and the elovich model, and the elovich model has a better fitting effect, which shows that the adsorption of bisphenol A by the material is a multiple adsorption mechanism In addition, the adsorption rate constant of BPA was 45-581 times of that of commercial activated carbon and resin In order to verify the feasibility of the application of the material in the actual water, the influence of different pH, salt concentration and humic acid on the adsorption performance of the material was investigated with bisphenol A as the model pollutant The results show that the material still has good adsorption performance under various hydrochemical conditions After being used, the material can be regenerated only by simple washing with methanol at room temperature, and the adsorption performance of the regenerated material has not decreased significantly after being recycled for many times In addition to bisphenol A, the adsorption properties of the material for other organic micro pollutants in water were further investigated, including 2-naphthol, 3-phenylphenol, bisphenol s, ethinylestradiol, estriol and estradiol Similar to bisphenol A, almost all pollutants can reach adsorption equilibrium within 10 minutes, and the removal rate of all pollutants reaches more than 90% in equilibrium (Figure 4) In the end, the author also studied the adsorption performance of the materials to the pollutants under the environmental concentration by using the self-made low concentration pollutant mixture in the laboratory and the pollutant mixture added outside the actual water body as the research object After eluting and recovering the adsorbed pollutants, it was found that the organic micro pollutants have high recovery rate Furthermore, it shows that the material has a rapid removal rate and excellent adsorption performance for pollutants under environmental concentration Fig 3 Relationship between removal rate of BPA on different adsorbents and time (source: greenchemistry) Fig 4 the relationship between t-e-cdp removal rate of different pollutants and time (source: greenchemistry) generally speaking, the author prepared a kind of porous cyclodextrin polymer in water phase for the first time by using both flexible crosslinker and rigid crosslinker Because of the porous nature of the material and the easy access to the adsorption sites, it shows super fast adsorption performance for a variety of organic micro pollutants in water In addition, the synthesis process of the material is simple, green, low cost, and it is easy to scale up production, and the method can be used for reference to the synthesis of other porous materials in the water phase As a new environmental friendly adsorbent, the material is expected to be used for rapid removal and advanced treatment of pollutants in water This work has been supported by national major science and technology projects for water pollution prevention and control (2015zx07204 and 2017zx07602), National Natural Science Fund (41203062 and 51438008), Jiangsu Natural Science Fund (BK 20151378 and be2015708) and basic research fund of Central University (0905143800001) Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information website, chembeangoapp, chembeango official micro blog, CBG information wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the representative research groups in China, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit