Synthesis of N/P/S Co-doped porous carbons by carbonizing polyphosphazene microspheres for highly selective adsorption of Pb (II)

Heteroatom-doping has emerged as a promising approach for enhancing the properties of carbon materials, particularly in the treatment of heavy-metal wastewater. However, the simultaneous synthesis of multi-heteroatom co-doped carbon materials poses significant complexity and challenges. Consequently, there is an increasing demand for the development of non-toxic and straightforward methods to prepare such materials. In this study, we present a novel approach for the synthesis of N/P/S co-doped porous carbonaceous adsorbents using polyphosphazene as precursors. Our focus is specifically on their effectiveness in adsorbing Pb (II). The results reveal that the synthesized adsorbents, denoted as carbonized polyphosphazene or CZ-600 exhibited a high carbon content co-doped with N, P and S atoms, as well as an abundance of oxygen-containing functional groups and a porous structure. These characteristics collectively contribute to the exceptional adsorption capacity of CZ-600 for Pb (II), with a maximum adsorption capacity of 121.7 mg/g and an equilibrium time as short as 20 min. Further investigations of the adsorption process involve fitting adsorption isotherm, kinetic, and thermodynamic models, revealing chemical adsorption as the predominant mechanism, supported by contributions from micropore adsorption and electrostatic interactions. This work proposes a sustainable and efficient solution for the treatment heavy-metal wastewater, which not only advances the understanding of heteroatom-doped carbon materials but also provides valuable insights into their practical applications in environmental remediation.