Nitrogen-rich hierarchical porous polyphosphazene for rapid and efficient adsorption of anionic contaminants: Kinetics, isotherm, thermodynamics and mechanism.

A new nitrogen-rich hierarchical porous polymer (PCPM) was synthesized via a self-catalyzed polycondensation from hexachlorocyclotriphosphazene and melamine under the solvothermal condition, which presented a high adsorption capacity and a fast adsorption kinetics towards three typical water-soluble micropollutants. [Display omitted] • Novel nitrogen-rich hierarchical porous polyphosphazenes were facilely synthesized. • The adsorbent has rich mesopores and a high specific surface area of 321.1 m2/g. • The adsorbent exhibited a high adsorption capacity and a fast adsorption kinetics. • Q max was 187.5, 336.2, and 320.4 mg g−1 for Cr (VI), CR and DCF, respectively. • The adsorption is the result of synergistic action of multiple adsorption mechanisms. The rapid and highly-efficient uptake of waterbody contaminants by polymer-based adsorbent is still a challenge. Herein, a new nitrogen-rich hierarchical porous polymer (PCPM) was synthesized via a self-catalyzed polycondensation between hexachlorocyclotriphosphazene and melamine. The PCPM possessed hierarchical pore architecture with specific surface area of 321.1 m2/g and pore size distribution from 1.3 to 63.0 nm. Owing to the remarkable porous texture and nitrogen-rich active sites with high electron density, PCPM exhibited a high adsorption capacity of 187.5, 336.2, and 320.4 mg g−1 for Cr (VI), Congo red (CR), and diclofenac sodium (DCF), respectively. Moreover, the adsorption rate of these contaminants onto PCPM was very fast, reaching 90 % of adsorption equilibrium capacity for Cr (VI), CR and DCF within the first 7 min, 45 min and 30 min, respectively. Adsorption data revealed that the adsorption process conformed to pseudo-second-order kinetics and Langmuir isotherm model. The removal process was spontaneous, exothermic for Cr (VI) and endothermic for CR and DCF. FT-IR and XPS analysis demonstrated that electrostatic interaction and hydrogen bonding contributed to the adsorption of CR and DCF onto PCPM, while the removal mechanism of Cr (VI) by PCPM included redox reaction and chelation besides the above two interactions. [ABSTRACT FROM AUTHOR]