Magnetic ZrO2/PEI/Fe3O4 functionalized MWCNTs composite with enhanced phosphate removal performance and easy separability

A novel adsorbent of ZrO2/PEI/Fe3O4 functionalized MWCNTs composite (MWCNTs@Fe3O4@PEI-Zr) possessing a high affinity to phosphate and easily separated from aqueous solution was proposed in this work. The ZrO2 and PEI modified on the surface act as active sites for the removal of phosphate, while the Fe3O4 allows for the easy separation by applying an external magnetic field. Compared to traditional separation like centrifugation, magnetic separation markedly reduces energy consumption and provides more possibilities for application. The composite exhibits a relatively high surface area of 162.9 m2 g-1 with a larger number of mesopores. As-prepared MWCNTs@Fe3O4@PEI-Zr is found to have a relatively high phosphate adsorption capacity of 21.14 mg P g-1 and it can be recovered rapidly from water under an external magnetic field. Moreover, MWCNTs@Fe3O4@PEI-Zr exhibits an outstanding anti-interference capability in terms of the coexisting ion and ionic strength of solutions. Importantly, the dissolution of Zr and Fe are negligible (less than 0.015 mg L-1) over a wide pH range of 4.04-9.98, indicating that the MWCNTs@Fe3O4@PEI-Zr is a structurally stable hybrid composite particle with strong interaction. Furthermore, it shows a good reusability and 86.2% removal efficiency of phosphate remains after three consecutive cycles. Both the ligand exchange and the electrostatic attraction are mainly responsible for phosphate removal by MWCNTs@Fe3O4@PEI-Zr. This work demonstrated that the highly efficient, easy separable, high stability and reusability MWCNTs@Fe3O4@PEI-Zr composite has the potential for phosphate removal.

Automated summary

A novel adsorbent composite material was proposed, which has a high affinity to phosphate and can be easily separated from aqueous solution. The composite has a high surface area with a large number of mesopores, and exhibits excellent anti-interference capability and reusability. This study demonstrated the potential of the composite material for phosphate removal.