Abstract
There are increasing demands and great potential of coal gasification in China, but there is a lack of studies focused on the disposal and utilization of coal fly ash produced by the gasification process. In this study, a coal fly ash sample derived from a gasifier in Jincheng, China, was utilized as raw material for the synthesis of zeolite by alkali fusion followed by hydrothermal treatments. The effects of operation conditions on the cation exchange capacity (CEC) of synthesized zeolite were investigated. The synthesized zeolite with the highest CEC (270.4 meq/100 g), with abundant zeolite X and small amount of zeolite A, was produced by 1.5 h alkali fusion under 550 °C with NaOH/coal fly ash ratio 1.2 g/g followed by 15 h hydrothermal treatment under 90 °C with liquid/solid ratio 5 mL/g and applied in Ni2+ removal from water. The removal rate and the adsorption capacity of Ni2+ from water by the synthesized zeolite were determined at the different pH, contact time, adsorbent dose and initial Ni2+ concentration. The experimental data of adsorption were interpreted in terms of Freundlich and Langmuir equations. The adsorption of Ni2+ by the synthesized zeolite was found to fit sufficient using the Langmuir isotherm. More than 90% of Ni2+ in water could be removed by synthesized zeolite under the proper conditions. We show that the coal fly ash produced by the gasification process has great potential to be used as an alternative and cheap source in the production of adsorbents.
Highlights
Nickel is widely used in electroplating and metal finishing for improving the corrosion resistance as well as decorative characteristics [1]
The characteristics of zeolite synthesized from coal fly ash produced by the gasification process by alkali fusion followed by hydrothermal treatments under varied conditions were analyzed
The zeolite was synthesized from the coal fly ash by alkali fusion followed by hydrothermal treatments [26]
Summary
Nickel is widely used in electroplating and metal finishing for improving the corrosion resistance as well as decorative characteristics [1]. A large number of Ni2+ -containing wastewater is produced. The treatment of wastewater containing heavy metals in a safe, effective and economic way is always challenging. Several methods have been developed to remove heavy metals from wastewater, such as precipitation, ion exchange, adsorption, membrane filtration and electrodialysis, but many of these methods need high capital costs when they are applied to large scale wastewater treatment. Adsorption is recognized to be a feasible method for the removal of heavy metals from wastewater because the adsorbent can be chosen from a wide variety of budget materials, such as synthetic zeolite from coal fly ash [6,7]
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