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

A novel adsorbent of ZrO 2 /PEI/Fe 3 O 4 functionalized MWCNTs composite (MWCNTs@Fe 3 O 4 @PEI-Zr) possessing a high affinity to phosphate and easily separated from aqueous solution was proposed in this work. The ZrO 2 and PEI modified on the surface act as active sites for the removal of phosphate, while the Fe 3 O 4 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 m 2 g -1 with a larger number of mesopores. As-prepared MWCNTs@Fe 3 O 4 @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@Fe 3 O 4 @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@Fe 3 O 4 @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@Fe 3 O 4 @PEI-Zr. This work demonstrated that the highly efficient, easy separable, high stability and reusability MWCNTs@Fe 3 O 4 @PEI-Zr composite has the potential for phosphate removal.