Abstract
Phosphate pollution from point and discrete sources is a serious threat to the aquatic ecosystem in both industrialized and developing countries. The release of excessive amounts of phosphates into the river streams and lakes from agricultural runoffs, septic tanks and sewage system causes serious and widespread environmental problems. The present study investigated the preparation of cerium oxide partially reduced graphene oxide (CeO2-PRGO) nanocomposite and its applications as an efficient adsorbent to remediate water containing phosphate. The (CeO2-PRGO) nanocomposite was prepared via the modification of GO sheets with sodium dodecyl sulfate (SDS) followed by the nucleation of CeO2 nanoparticles onto the surface of SDS-GO nanosheets. The chemical structure and morphology of the CeO2-PRGO adsorbent were characterized using several analytical techniques including UV-Vis, FTIR, Raman, XRD, XPS, SEM, and TEM. The batch adsorption experiments for the removal of phosphate ions onto the surface of CeO2-PRGO revealed that the maximum adsorption capacity was 45.8 mg/g at pH = 4, initial concentration 100 ppm, dosage 1 g/L, contact time 150 min, and room temperature. CeO2-PRGO composite exhibited remarkable selectivity for phosphate in presence of interfering anions including Cl-, I-, and NO3- that exist widely in real water samples. The experimental data was explicated by the theoretical Langmuir adsorption isotherm module and the pseudo-second-order kinetic module. The experimental data fitted well with the modules (R2>99%) suggesting the adsorption of phosphate ions onto the surface of CeO2-PRGO nanocomposite take place through the generation of a monolayer of phosphate ions onto the surface of CeO2PRGO. The adsorption mechanism was suggested to be an interaction between phosphate ions and Ce3+ sites on the surface of ceria nanoparticles on the adsorbent surface. The results showed that 100% of adsorbed phosphate ions can be regenerated by using 0.5 M NaOH and about 100% removal efficiency even after five adsorptiondesorption cycles. Additionally, CeO2-PRGO composite can determine trace levels of phosphate in real water samples which acquire well for its promising in environmental applications.