Phosphate Adsorption from Solution by Zirconium-Loaded Carbon Nanotubes in Batch Mode

A highly effective zirconium-modified carbon nanotube (Zr-CNTs) adsorbent was prepared to remove phosphate (PO43-) from solution in batch mode. Characterizations of Zr-CNTs were analyzed using FTIR, TEM, XRD, XPS, and Raman techniques. The effects of solution pH, ionic strength, phosphate concentration, and contact time on adsorption quantity were presented. The acidic solution was beneficial to the adsorption of PO43- on Zr-CNTs. There was no significant effect with coexisting anions such as Cl- and SO42-. The adsorption quantity was 10.9 mg.g(-1) (according to P element) at 303 K. The adsorption isotherms were better fitted by the Freundlich model, whereas the kinetic data were better correlated with the Elovich model, which suggested that the adsorption process may be chemical adsorption. The adsorption of PO43- was a spontaneous, entropy-increasing, and endothermic process. XPS analysis showed that the complexation between Zr-CNTs and PO43- was the main adsorptive mechanism. In addition, the adsorbed PO43- was effectively desorbed by 0.010 mol.L-1 NaOH solution. This adsorbent has important potential for removal of PO43- from solution.