本論文研究合成鈣礬石去除磷之反應, 其中鈣礬石之合成是由富含鈣的氧化鈣與硫酸鋁溶液在 酸鹼值12的條件下下混合 24 小時生成。吸附之前，鈣礬石在 60℃ 下乾燥一天然後碾碎，並以 100 目篩子過篩。含磷酸鹽之合成廢水用於吸附實驗，初始濃度在約200 – 1,000 毫克 PO 4 /公升之範圍內。吸附反應可以用擬二階動力學模型（R2 = 0.98）來描述。平衡吸附實驗之數據在pH範圍 11.05 - 12.04 下，符合 Langmuir和 Freundlich 等溫吸附模型。酸鹼值對磷酸鹽吸附量影響較小，但吸附量受到磷酸鹽初始濃度和溫度影響較大。熱力學分析表明，由合成鈣礬石之移除反應是自發的、吸熱的、並具有隨機性的行為。此外，由固體定性分析（FE-SEM 和XRD）結果，我們推斷羥基磷灰石在高酸鹼值和高溫下形成。這項研究結果表明，鈣礬石是一種有效的除磷吸附劑，反應機制包括與鈣礬石所含硫酸根離子置換，以及沉澱反應。

Phosphate removal by using synthesized ettringite was investigated in this study. Ettringite was synthesized by mixing CaO suspension and aluminum sulfate solution at pH 12 for 24 h. It was dried at 60oC for one day, crushed, and sieved through 100 mesh sieve before used for experiments. Synthetic wastewater containing phosphate was used for adsorption. Initial concentration was in a range of ca. 200 – 1000 mg PO4/L. The adsorption reaction could be described by a pseudo-second-order kinetic model (R2 = 0.98). The results of equilibrium experiments could be modeled by both Langmuir and Freundlich adsorption isotherms in pH range of 11.05 – 12.04. The phosphate uptake capacity was less dependent on pH, yet was affected by initial phosphate concentration and temperature. Thermodynamic analysis revealed that the reaction was spontaneous, endothermic, and exhibited randomness behavior. Besides, solid characterization by FE-SEM and XRD inferred the evidence of hydroxyapatite formation at high pH and high temperature. The results of this study show that ettringite is an effective sorbent for phosphate removal. The reaction mechanisms included adsorption via the replacement of sulfate with phosphate and precipitation.

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