layered double

aqueous solutions

adsorption capacity

calcium carbonate

phosphate adsorption

pb ii

phosphate sorption

initial concentration

Chemical Engineering Journal

A novel La-incorporated nanostructured ternary (hydr)oxides adsorbent (MALZ) was prepared and employed for enhanced phosphate removal in this study. The results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that MALZ presented an amorphous surface with Mg, Al and La homogeneously dispersed on the outer region of zeolite. Effective phosphate removal was obtained over a wide pH range of 4–10 and the equilibrium pH after phosphate adsorption was in near neutrality. A relatively fast adsorption of phosphate was observed in the kinetics experiment, and the maximum adsorption capacity of MALZ (12.5 wt% La) was determined at 80.8 mg P/g at pH 6.6 in the equilibrium adsorption isotherm study. The coexisting anions (e.g., Cl−, SO42− and NO3−) had insignificant effects on phosphate adsorption. The adsorption–desorption experiment suggested that MALZ could be regenerated by 0.5 M NaOH solution and maintained 75.8% of its initial phosphate adsorption capacity at the fourth adsorption–desorption cycle. The combined results of zeta potential analysis, SEM, XRD and X-ray photoelectron spectroscopy demonstrated that electrostatic attraction, ligand exchange of surface hydroxyl groups by phosphate and the complexation of forming inner-sphere complex (LaPO4·xH2O) were the main adsorption mechanisms. Furthermore, La played a key role in the complexation of phosphate, while the introduction of Mg and Al further facilitated the dispersion of La and enhanced the surface charge of the adsorbent.

Enhanced phosphate removal by zeolite loaded with Mg–Al–La ternary (hydr)oxides from aqueous solutions: Performance and mechanism