Phosphate adsorption by a Cu(II)-loaded polyethersulfone-type metal affinity membrane with the presence of coexistent ions

• DETA-PES-Cu(II) membrane shows an excellent property of phosphate uptake.
• The interference of four ions follows the order of SO42− > Mg(II) > Cl− > Ca(II).
• Phosphate uptake still dominates the adsorption with the existence of four ions.
• Phosphate uptake of the membrane is a spontaneous and endothermic process.
• DETA-PES-Cu(II) membrane is valuable for recovering phosphate from seawater.

A polyethersulfone (PES)-type metal affinity membrane loading Cu(II) was employed to remove phosphate from the solution. Techniques of scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and solid-state nuclear magnetic resonance spectroscopy (NMR) were used to characterize the membrane. Effects of pH, initial phosphate concentration, temperature, contact time, as well as the coexistent Cl−, SO42−, Mg(II), and Ca(II) on the phosphate adsorption by this membrane were evaluated. The adsorption kinetics and the adsorption isotherms of the membrane toward phosphate were investigated. In addition, the breakthrough curves of the membrane were measured. The coexistent Cl−, SO42−, Mg(II), and Ca(II) ions decreases the phosphate uptake of the membrane. Their negative effects on the uptake of phosphate follow the order: SO42− > Mg(II) > Cl− > Ca(II), considering the existent concentrations of them in seawater. Adsorption isotherms and adsorption kinetics of this metal affinity membrane toward phosphate are fitted to the Langmuir and the Lagergren second-order models. The phosphate uptake of the membrane is a spontaneous and endothermic process. In spite of the presence of these four ions, the PES-type metal affinity membrane shows an excellent uptake of phosphate. Therefore, the PES-type metal affinity membrane loading Cu(II) will be valuable for removing phosphate from seawater.