Dual-active-sites oriented mesoporous zirconia nanofibers for enhanced removal of phosphate in the presence of humic acid

Abstract

Excessive phosphate in water will inevitably cause eutrophication and further trigger major environmental issues. Efficient removal of phosphate is of great significance to inhibit water eutrophication, however, humic acid (HA) in water aggravates the uncertainty of phosphate removal. In this work, mesoporous zirconia nanofiber (MZN) was synthesized and applied as an adsorbent for phosphate removal in the presence of HA. The performance and mechanism of the enhanced removal of phosphate by MZN in the presence of HA was systematically studied. The results show that MZN has higher adsorption capacity, stronger affinity, and faster adsorption rate for phosphate in solution with HA than that without HA. In the presence of HA, HA is adsorbed on MZN through complexation, which introduces carboxyl and hydroxyl groups to MZN surface, increasing phosphate adsorption through hydrogen bonding. The boosted removal mechanism of phosphate can be ascribed to the dual-active-sites effect between the complexation of MZN to phosphate and the hydrogen bonding of the adsorbed HA to phosphate. The adsorption of phosphate by MZN in the presence of HA follows the outer-sphere complexation. Column adsorption experiment showed that MZN is feasible and effective for the treatment of phosphate in water containing HA based on the discharge standard of phosphate, and can be reused repeatedly through regeneration. The results indicate that MZN holds a great promise in efficient removal of phosphate in the presence of HA.