Synthesis of zeolite and aluminum-modified zeolite from lake sediment for simultaneous immobilization of cationic and anionic pollutants in lakes

Abstract

Aiming at the development of ecologically safe and environmentally friendly materials to immobilize both anionic and cationic pollutants in eutrophic lakes, we have attempted to synthesize zeolites and aluminum-modified zeolites (AMZs) from four lake sediments by a fusion-assisted hydrothermal method. Characterization by X-ray fluorescence spectrometry, X-ray diffraction analysis, Fourier-transform infrared spectrometry, scanning electron microscopy, and specific surface area measurements confirmed that zeolites including Na–X, Na–P1, and hydroxysodalite were successfully synthesized, and the AMZs composed of zeolite and amorphous hydrous aluminum oxide were formed. The cation-exchange capacity (representing the ability to adsorb cationic pollutants) and the phosphate adsorptive capacity (representing the ability to adsorb anionic pollutants) of zeolites (204.3–305.7 cmol/kg and 9.3–16.3 mgP/g, respectively) and AMZs (105.7–309.2 cmol/kg and 26.8–38.9 mgP/g, respectively) were much higher than those of the original lake sediments (3.7–6.4 cmol/kg and 0.5–1.7 mgP/g, respectively). Incubation of sediment in lake water under anoxic conditions, which are commonly encountered at the beds of eutrophic lakes, triggered substantial release of phosphorus, iron, manganese, and ammonium, but amendment with AMZ significantly reduced the concentrations of these pollutants in the overlying water. Our findings demonstrated that zeolite and AMZ synthesized from lake sediments may be applied as suitable materials for the remediation of eutrophic lakes.