Treatment and resource recovery from inorganic fluoride-containing waste produced by the pesticide industry |
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Authors: | Yang Li Hua Zhang Zhiqi Zhang Liming Shao and Pinjing He |
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Institution: | 1. State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China 2. Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China;Research and Training Center on Rural Waste Management, Ministry of Housing and Urban-Rural Development of P.R.China,Shanghai 200092, China |
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Abstract: | The rapid development of the fluorinated pesticide industry has produced a large amount of fluorine-containing hazardous waste, especially inorganic fluoride-containing waste (IFCW). A two-step process, including extraction and recovery, was developed to recover fluorine as synthetic cryolite from IFCW produced by the pesticide industry. The optimum conditions for extraction were found to be a temperature of 75°C, an initial pH (pHi) of 12, a 4-hr incubation time and a liquid-to-solid ratio of 40 mL/g; these conditions resulted in a fluorine extraction ratio of 99.0%. The effects of pH and the F/Al molar ratio on fluorine recovery and the compositional, mineralogical and morphological characteristics of the cryolite products were investigated. Field-emission scanning electron microscopy of recovered precipitates showed changes in morphology with the F/Al molar ratio. Coupling Fourier transform and infrared spectroscopy, X-ray diffraction indicated that the formation of AlF63 − was restricted as increasing pH. Both the amount of fluorine recovered and the quality of the cryolite were optimized at initial pH = 3 and a F/Al molar ratio 5.75. This study proposed a reliable and environmentally friendly method for the treatment of fluoride-containing wastes, which could be suitable for industrial applications. |
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Keywords: | Fluoride-containing waste Fluorine extraction Fluorine recovery Cryolite |
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