[Adsorption of Phosphate and Heavy Metals by Lanthanum Modified Zeolite and Its Performance in Sediment Inactivation]

Due to the large scale of mining and smelting activities, considerable amounts of heavy metals are discharged into the environment and accumulate in the sediment of rivers and lakes. The combined pollution of heavy metals and the intrinsic phosphorus in sediment calls for novel remediation technologies. In this study, lanthanum-modified zeolite (LMZ) was employed as an inactivation agent for the immobilization of phosphorus, zinc, and lead in sediments. The adsorption capacities as well as the inactivation performance of LMZ for P, Zn, and Pb were investigated, and the adsorption mechanisms were explored via desorption experiments, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results indicated that the adsorption maximums of LMZ for P, Zn, and Pb were 53.76, 27.70, and 123.45 mg·g^-1, respectively. Pre-adsorption of Zn and Pb had a negligible effect on the P adsorption by LMZ, whereas the adsorption of Zn and Pb were inhibited significantly by the pre-adsorption. P, Zn, and Pb in the sediment were transformed to more stable or less bioavailable forms by dosing 0.83% and 1.66% weight percentages of LMZ. It was found that P, Zn, and Pb were adsorbed through the formation of inner-sphere complexes. Further, desorption experiments and XRD patterns suggested that electrostatic attraction and surface precipitation also contributed to the adsorption of Zn and Pb, respectively.