Simple Aminated Modified Zeolite 4A Synthesized Using Fly Ash and Its Remediation of Mercury Contamination: Characteristics and Mechanism

Abstract

In this study, through simple ammonia impregnation, more amine functional groups could be introduced into the zeolite 4A synthesized using fly ash, which efficiently improved the mercury ion removal capacity of modified zeolites. The impregnation-modification mechanism of NH3·H2O, ammonium chloride, and silane coupling agent (KH792) for zeolite 4A, and the Hg2+ ion removal-efficiency by aminated zeolites, were studied and compared. Through ion exchange and hydroxyl reactions, NH3·H2O impregnation introduced the same kinds of nitrogen-containing groups into zeolite as KH792 grafting, which was more than the NH4Cl modification. The Hg2+ ion adsorption capacity of NH3·H2O-zeolite was higher than those of KH792-zeolite and NH4Cl-zeolite through ion exchange and the complexation of nitrogen-containing groups. When coexisting with Pb2+, Cu2+, and Zn2+ ions, the Hg2+ ion removal rate of NH3·H2O-zeolite was still higher than 99%. After five adsorption and desorption cycles, the Hg2+ ion removal rate of NH3·H2O-zeolite was 72.03%. When NH3·H2O-zeolite was added to the leaching of mercury-contaminated soil, the content of soluble mercury significantly decreased. Therefore, we synthesized a potential cheap and safe adsorbent using fly ash as the main raw material through the simple NH3·H2O impregnation modification for the treatment of mercury-contaminated water and soil.