Effect of Zeolitization of CFBC Fly Ash on Immobilization of Cu2+, Pb2+, and Cr3+

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• 作者：Feihu Li ; Qin Li ; Jianping Zhai ; Guanghong Sheng
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2007
• 出版时间：October 24, 2007
• 年：2007
• 卷：46
• 期：22
• 页码：7087 - 7095
• 全文大小：603K
• 年卷期：v.46,no.22(October 24, 2007)
• ISSN：1520-5045

文摘

Two zeolitization processes, hydrothermal and molten-salt, were used to examine the effect of zeolitizationof circulating fluidized-bed combustion (CFBC) fly ash on the immobilization of Cu²⁺, Pb²⁺, and Cr³⁺ inthis study. As a consequence of zeolitization, most of the dissolved Cu²⁺, Pb²⁺, and Cr³⁺ had been immobilizedin the synthetic aluminosilicate-aggregates-enriched matrixes under hydrothermal conditions, reaching maximumimmobilization efficiencies of ~89.1%, ~82.4%, and ~99.1%, respectively; whereas under molten-saltconditions, the synthetic cancrinite-enriched matrixes were most effective to immobilize Cu²⁺, Pb²⁺, andCr³⁺ with maximum immobilization efficiencies of ~94.5%, ~50.7%, and ~38.3%, respectively. Examinationsof the synthetic matrixes by X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-rayspectrometry (SEM/EDS), and sequential EDTA extractions suggest that physicochemical reactions responsiblefor the immobilization of heavy metal ions were ascribed to the speciation of insoluble species such ascarbonates/silicates, hydroxides, and oxides and especially to the encapsulation of such species inaluminosilicates aggregates or cancrinite-enriched agglomerates. Furthermore, it is also proved that thespeciation of soluble chromate in molten-salt processes contributed to the unexpected low immobilizationefficiency of Cr³⁺ and that the Ca-enriched CFBC fly ash is an appropriate candidate for immobilization ofCu²⁺ and Pb²⁺. Both zeolitization processes could be employed in solidification/stabilization of soils andsediments contaminated by heavy metals.