Removal of phosphate at low concentration from water by porous PVA/Al2O3 composites.

The porous polyvinyl alcohol (PVA)/Al2O3 composite by supporting activated alumina on the cross-linked network of PVA has been successfully prepared and its property for the removal of phosphate in aqueous solution was also evaluated. The structure of the PVA/Al2O3 was examined by scanning electron microscopy. It showed that the activated alumina particles with an average size of 1 µm were evenly dispersed and fixed in the cross-linked network structure of PVA. The effects of adsorption time, solution temperature, pH, initial concentration of phosphate, Al2O3 loading rate, dosage and coexisting ions on the phosphate removal were further studied. The results showed that the highest removal phosphate efficiency of 95% can be obtained with the Al2O3 loading rate of PVA/Al2O3 being 60 wt.% at pH of 4 at 30 °C. The maximum adsorption capacities of PO43- by PVA/Al2O3 suggested by the Langmuir isothermal model was 10.12 mg/g. The adsorption process of phosphate can be fit well with a pseudo-second-order model (R2 = 0.9900). The PVA/Al2O3 composite exhibited a high selective adsorption of phosphate in the presence of commonly coexisting anions except the obvious effect of CO32- in water. Meanwhile, the PVA/Al2O3 composite can be easily separated and recovered due to the granulation of adsorbent. PVA/Al2O3 composite also shows the excellent properties of regeneration and recycling use with the removal efficiency of phosphate was 88.93%, 88.38% and 94.34% after three cycles, respectively. It can be proposed that the PVA/Al2O3 composite is a promising recyclable adsorbent for removing phosphate at low concentration from aqueous solution.