Quaternized straw supported by La(OH)3 nanoparticles for highly-selective removal of phosphate in presence of coexisting anions: Synergistic effect and mechanism

Abstract

The excessive presence of phosphorus in surface water is the primary cause of eutrophication and it is necessary to remove phosphorus from water prior to discharge. Lanthanum (La) has been demonstrated a high affinity for phosphate and an attractive ligand for removing phosphorus from water. To this end, we used straw as a raw material for quaternization and loaded it with La(OH)3 nanoparticles to create a composite material (AM-La) with exceptional phosphate affinity. In the presence of a high nitrate concentration, AM-La effectively promoted the adsorption capacity of 116–125% for phosphate. AM-La also exhibited remarkable selectivity towards phosphate in the presence of other competing anions, such as Cl−, HCO3−, and SO42−. The synergistic effects of ion exchange, electrostatic attraction, and lanthanum phosphate formation by ligand exchange were identified as the major mechanisms of phosphate removal by AM-La, which was also confirmed by the characterization of AM-La before and after adsorption, as well as the influence of solution pH. The results of phosphate adsorption/desorption in coexisting ions and actual water samples demonstrated that AM-La possessed excellent regeneration ability and practical application potential.