Rational design of magnetic infinite coordination polymer core-shell nanoparticles as recyclable adsorbents for selective removal of anionic dyes from colored wastewater

In this study, novel magnetic infinite coordination polymer Fe3O4@Tb/AMP core-shell nanoparticles were rationally designed and fabricated as recyclable adsorbents for selective removal of anionic dyes from colored wastewater. The core-shell nanoparticles used in this study are composed of two components: the shell is the supramolecular infinite coordination polymers (ICPs) network formed by terbium ions (Tb3+) and adenosine 5'-monophosphate monohydrate (AMP) ligands and the core is the Fe3O4 nanoparticles which are encapsulated into the ICP network by the self-adaptive inclusion process. The prepared core-shell nanoparticles showed superiority in strong magnetism and selective adsorption towards anionic dyes, such as Alizarin Red (AR) and Congo Red (CR). Parameters that influenced the adsorption process, such as solution pH, salt concentration and adsorbent dosage were investigated. Under the optimal conditions, adsorption kinetics, isotherms and thermodynamics were also determined. Notably, this nano-adsorbent exhibited rapid adsorption feature (almost 96% dye removal in 5 min) and the adsorption isotherm data fitted quite well with the Langmuir model with an estimated maximum adsorption capacity of 357.14 mg g(-1) for AR and 909.09 mg g(-1) for CR at 298 K. This capacity could be further enhanced at the higher temperatures. In addition, the Fe3O4@Tb/AMP core-shell nanoparticles could be regenerated by a simple salt/ethanol-washing method and used with high recyclability over five cycles. With the magnetically separable Fe3O4@Tb/AMP core-shell nanoparticles as adsorbents, selective removal of toxic anionic dyes from colored wastewater could be realized directly, which is of great importance for the sustainable development of dye contaminated wastewater treatment technology.