Leaching of heavy metals by citric acid from fly ash generated in municipal waste incineration plants |
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Authors: | Kai Huang Katsutoshi Inoue Hiroyuki Harada Hidetaka Kawakita Keisuke Ohto |
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Institution: | (1) Department of Applied Chemistry, Saga University, Honjo 1, Saga 840-8502, Japan; |
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Abstract: | The leaching behavior of heavy metals from municipal waste incineration (MWI) fly ash was investigated in this study. The
leaching process includes two steps, i.e., fly ash was firstly washed with water, and then subjected to citric acid leaching.
The main parameters of the washing process such as liquid/solid ratio, washing time, and number of washing were tested. The
optimum conditions for water washing were found as follows: washing time 5–10 min, liquid/solid ratio 10:1 (ml:g), and number
of washing was twice; under these conditions, 86% Na, 70% K, 12% Ca, 1.2% Al, and 0.5% Pb were removed from the fly ash in
the prewashing. From the results of screening tests of leaching lixiviants, citric acid was found to be the most effective
leaching agent, taking account of its environmentally benign characteristics. Optimum metal extraction can be achieved with
citric acid under the following conditions: pH 3.0, liquid/solid ratio 40 (ml:g), citric acid concentration 0.10 mol/dm3, contact time 20 min at room temperature. |
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