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Outline
Iron phosphate dihydrate (FePO4·2H2O) is usually synthesized via three technical routes, including ammonium process, sodium process and iron process. A systematical evaluation of its thermodynamic properties is presented, which can reveal the phase transition behavior of iron phosphate dihydrate during the dehydration process, and provide a theoretical basis for selection of technical route for industrial synthesis. The enthalpy change (ΔH), entropy change (ΔS), Gibbs free energy change (ΔG), and logarithm of the reaction equilibrium constant (lgK）of the core reaction of those three processes are calculated by using HSC Chemistry 6.0 software, and the thermodynamic data of dehydration process are verified by performing a thermogravimetry-differential scanning calorimetry (TG-DSC) experiment. The results show that the synthesis by sodium process has the lowest ΔG and the highest lgK, indicating its thermodynamic spontaneity and reaction rate are optimum, followed by the ammonium process, while the iron process presents the worst performance. The TG-DSC experiment results show that the dehydration process of iron phosphate dihydrate is exothermic at 709.9 ℃, corresponding to the transformation of FePO4 from α-quartz phase to β-quartz phase. Featuring high spontaneity and rapid reaction, the sodium process is considered as a industrial synthesis with thermodynamic advantage.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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