PPs can be designed to be with multiple functionalities by introducing various functional monomers, which endows them with novel properties and extensive applications in adsorption 26, 27, separation 28, 29, catalysis 30, hydrogen storage 31 and so on. Porous polymers (PPs) have been regarded as a kind of promising and unique materials, which have received considerable interests 24, 25. Thus, further work are strongly desired to solve these problems. Although the adsorbents prepared by cross-linking method showed good adsorption performance for Cs +, however, the cross-linked persimmon tannin, tea leaves and persimmon waste adsorbents were difficult to recycle and reused, which were not economically attractive. synthesized a kind of cross-linked persimmon waste to uptake Cs + from wastewater and obtained an adsorption capacity of 71.8 mg/g 23. For example, Gurung and co-workers developed cross-linked persimmon tannin and tea leaves for Cs + removal, and it showed favorable selectivity and removal efficiency 22. After that, easily available biomass materials with abundant polyphenolic groups have been used for Cs + adsorption. demonstrated the phenolic hydroxyl exchange mechanism for Cs + 21. More recently, it has been reported that resorcinol formaldehyde (RF) resin had a favorable affinity for Cs + due to the presence of phenolic hydroxyl groups 20, and Yang et al. Therefore, the development of cost-effective, durable and effective Cs + adsorption materials are still particularly urgent. Unfortunately, they still suffered from several problems, such as considerable preparation cost, unsatisfactory adsorption performance and insufficient stability, thus majority of the adsorbents aforementioned were not environmental friendly, economically and industrially attractive. To date, Prussian blue (PB) analogues 12, 13, titanate nanomaterials 14, metal oxides and sulfides 15, natural zeolites 16, ammonium molybdophosphate 17, 18 and other adsorbents 19 were developed and used for the removal of Cs + from radioactive effluents. Taking disposal cost and removal efficiency into consideration, adsorption is considered as one of the most effective and clean techniques, and has been widely used in Cs + removal. So far, considerable efforts have been made to explore available methodologies for hazardous Cs + removal from radioactive wastewater, such as liquid-liquid solvent extraction, chemical precipitation, electrochemical techniques and adsorption process 10, 11, 12. Therefore, effective techniques for the decontamination of radioactive Cs + from wastewater are indispensable and highly desirable. For example, the accidents occurred at Chernobyl in 1986 and Fukushima in 2011 severely impacted the local environments, and the surrounding areas are still classified as dangerous regions due to the leakage and serious emission of 137Cs and other radio-isotopes 8, 9. In addition, long-term exposure to 137Cs-contanining wastewater would lead to horrible diseases such as cancer, leukemia and genetic disorder 7. The generation of hazardous 137Cs by nuclear waste and unforeseen nuclear plant accidents has seriously threatened the global environment and human health. Among them, radio-isotope 137Cs is considered as the most hazardous nuclide due to the serious gamma radiation, long half-life as well as high solubility being an alkaline element 5, 6. Growing concern about the remediation of radioactive waste generated from nuclear power plants and unforeseen accidents have been given worldwide for the sake of human health and environmental issues 1, 2, 3, 4. As a result, we hope this work could provide ideas about the potential utilization of biomass polyphenol in environmental remediation. Moreover, the Cs-laden GAPP could be facilely eluted and reused in consecutive adsorption-desorption processes. GAPP exhibited significantly high adsorption performance toward Cs + compared to Na + and K +, making it possible in selective removal of Cs + from ground water in presence of co-existing competitive ions. Among them, porous polymers prepared with gallic acid as starting material (GAPP) could adsorb Cs + at wide pH value range effectively, and the optimal adsorption capacity was up to 163.6 mg/g, placing it at top material for Cs + adsorption. Batch experiments demonstrated their potentialities for adsorptive separation of Cs + from aqueous solution. The structure and morphologies of the polymer were characterized by BET, TEM, SEM, XRD, TGA and FT-IR techniques. In this work, a series of polyphenol porous polymers were derived from biomass polyphenols via a facile azo-coupling method.
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