磷酸化鈦鋯氧化物表面特性分析與對NH4+離子吸附行為探討

Abstract

本研究以離子液體輔助水熱法合成之磷酸化鈦鋯氧化物固體酸作為NH4+離子吸附劑，並對其表面特性進行分析以探討其對NH4+離子吸附行為的影響；透過一系列批次實驗進行探討等溫和動力吸附模式，其操作參數包括:不同吸附劑量、pH值和溫度對NH4+離子吸附能力的影響。研究結果發現，磷酸化鈦鋯氧化物團聚形成粒徑大小為400~500nm，比表面積為247±20m2/g，陽離子交換容量(cation exchange capacity , CEC )約為250±20meq/g，零電位點（pH of zero point charge , pHzpc）介於3.3±0.2，而分散於水溶液中可使溶液pH值降至4.4±0.5，表示磷酸化鈦鋯氧化物具有酸性及陽離子交換能力；動力吸附平衡時間為30min，符合擬二階動力模式；磷酸化鈦鋯氧化物對於NH4+吸附行為較符合Freundlich吸附模式且為自發性放熱反應，H0= -5.76kJ/mole，最佳吸附劑量為70g/L，不同pH環境下吸附量隨著pH值增加而增加至pH值為6.25；在固態酸鹼吸附劑上，對於銨離子去除條件為靜電引力吸附及離子交換。

This study investigated the surface properties and NH4+ adsorption characteristics of the phosphated titanium-zirconium oxide solid acid prepared by an ionic-liquid assisted hydrothermal method. In addition, the correlation between the adsorption capability and the surface properties of the adsorbent was elucidated. Adsorption isotherm and kinetic study were carried out from a series of batch tests. Moreover, the influences including adsorbent dosage, pH values, and temperatures on the adsorption capability were examined. The results showed that the aggregated particles had a size ranged between 400-500 nm with the specific surface area of 247±20m2/g. The cation exchange capacity (CEC) was 250±20meq/100g, and the pH at zero-point-of-charge (pHzpc) was 3.3±0.2. Dispersion of the adsorbent in water decreased the pH to 4.4±0.5, indicating acidity and cationic exchanging ability of the phosphated titanium-zirconium oxide. The adsorption equilibrium time was 30 minutes and the adsorption kinetic data can be well fitted by a pseudo-second-order model. The Freundlich model fits the adsorption isotherm and the adsorption was an exothermic process with H0= -5.76 kJ/mol. The optimal adsorbent dosage was 70g/L, and the adsorption amount increased with the pH values till pH= 6.25. These results reveal that the ammonia ions are removed in terms of electrostatic attraction and cation ion exchange on the solid-acid-based adsorbent.