Ammonium molybdophosphate/metal-organic framework composite as an effective adsorbent for capture of Rb+ and Cs+ from aqueous solution

A new composite adsorbent (AMP@MOF-76(Sm)) grafted ammonium molybdophosphate onto MOF-76(Sm) was synthesized via a solvothermal method and well-characterized by SEM-EDS, particle size analysis , N 2 adsorption-desorption isotherms, TG, FT-IR, XRD and XPS analysis . The adsorption behaviors of Rb + and Cs + on synthesized AMP@MOF-76(Sm) were investigated depending on the parameters of solution pH, ionic strength, contact time, ion concentration and temperature. The adsorbent can adsorb Rb + and Cs + from the solution when the solution pH ranged from 4.0 to 10.0 and the coexisted ion (Na + ) has little effect on the adsorption amounts of both Rb + and Cs + . The adsorption kinetic data fitted well with pseudo-second order kinetic models . The adsorption equilibrium of Rb + and Cs + on AMP@MOF-76(Sm) is better explained by the Langmuir isotherm model and the maximum adsorption amounts for Rb + and Cs + are 0.490 ​mmol ​g −1 and 0.434 ​mmol ​g −1 , respectively. Furthermore, the AMP@MOF-76(Sm) could be easily reused at least four times using 3.0 ​mmol ​L −1 ammonia nitrate as the eluent . The mechanism of the adsorption of Rb + and Cs + is proposed to be a combination of electrostatic attraction and ion exchange mechanism.