Abstract
Chlorofluorocarbons (CFCs), which possess the characteristics of high volatility and destroy ozone layer, are hardly disposed of through traditional methods. With a tightly closed reaction environment and high-temperature water medium, CFCs can react and generate inorganic Cl- and F- under subcritical water conditions, which is very useful to enhance leaching and enrich rare metals. Therefore, in the current study, CFCs and photovoltaic wastes containing gallium arsenide (GaAs) were co-processed for mineralization and enhanced leaching simultaneously. Based on frontier orbital theory and bond energy theory, possible decomposition pathways of CFCs were speculated. Enhanced leaching process was studied in detail. When experimental conditions were 300 °C and 8.8 MPa, the mineralization rates of organofluorine and organochlorine in CFCs were 83.68% and 93.37%, respectively. Leaching agent generated by the hydrothermal treatment of CFCs leached GaAs effectively, and the leaching rates of gallium and arsenic were 95.74% and 99.89%, respectively. Converting CFCs into leaching agent will not only avoid ozone layer depletion but also save the cost of hazardous waste treatment and realize economic benefits. Environmental impact assessment indicated that the proposed Ga recycling route allows remarkable reduction of total environmental impacts compared with published processes.
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