부산대학교 도서관

Phosphogypsum (PG) waste causes several environmental problems. The present work proposes an attractive process to recycle this industrial waste via the wet conversion and contributes to solve this problem. In our previous work, we tried to convert the PG by KOH at ambient temperature, but its total conversion was limited at the concentration of 0.6 M which requires a high cost to recrystallize K2SO4 from the filtrate. Therefore, to avoid the formation of syngenite (parasitic phase) and to increase the PG reactivity, we have varied the temperature parameter in this work. The experiments are performed with stoichiometric proportions. According to experimental results, optimal reaction conditions are obtained at 80 °C during one hour and permitted having two valuable products: Ca(OH)2 as precipitate and high concentrated K2SO4 solution. These products find their applications in several industrial fields. In order to prove their quality, the complete PG decomposition is evidenced by X-ray diffraction and Fourier transform infrared spectroscopy. Thermogravimetric analysis combined to mass spectrometry measurements shows the partial carbonation of the portlandite into calcite and allows there quantification. Scanning electron microscopy images reveals two different types of grain shape in the precipitate. Economical and numerical approach permits to calculate the benefit of about 500 $ per ton of PG converted in addition the resolution of a serious environmental problem.