We explore the feasibility of using thermosensitive hydrogels based on copolymers of acrylic acid (AAC) and N-[3-(dimethylamino)propyl] acrylamide (DMAPAA) [P(AAC-co-DMAPAA)] for adsorption and desorption of phosphate in aqueous solutions by a temperature swing. The hydrogels were protonated when they swelled in acidic solution at room temperature, exhibiting good adsorption capacity of phosphate. The phosphate ions were desorbed at high temperature due to the ionic repulsion of carboxyl groups caused by the dissociation of hydrogen bonding. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effects of solution pH and temperature on phosphate removal were investigated. Kinetic data revealed that the adsorption of phosphate fitted the pseudo-first-order model. Isotherm data showed that the Freundlich model was more suitable than the Langmuir model. Effective desorption of phosphate was observed by raising the solution temperature to 55°C, and repeated adsorption and desorption behaviors were achieved within three consecutive cycles by a temperature swing between 25°C and 55°C. These findings suggest the possible phosphate removal and recovery from aqueous solutions by changing the environmental temperature.

中文翻译：

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温度诱导的磷酸盐在水溶液中的聚（丙烯酸-co-N- [3-（二甲基氨基）丙基]丙烯酰胺）水凝胶上的吸附和解吸

我们探索使用基于丙烯酸（AAC）和N- [3-（二甲基氨基）丙基]丙烯酰胺（DMAPAA）[P（AAC-co-DMAPAA）]共聚物的热敏水凝胶在水中吸附和解吸磷酸盐的可行性温摆的解决方案。水凝胶在室温下在酸性溶液中溶胀时会质子化，显示出良好的磷酸盐吸附能力。由于氢键解离引起的羧基离子排斥，使得磷酸根离子在高温下解吸。通过傅立叶变换红外光谱（FTIR），扫描电子显微镜（SEM）和热重分析（TGA）对水凝胶进行表征。研究了溶液的pH值和温度对磷酸盐去除的影响。动力学数据表明，磷酸盐的吸附符合拟一阶模型。等温线数据表明，Freundlich模型比Langmuir模型更合适。通过将溶液温度提高到55°C，可以观察到磷酸盐的有效解吸，并且在25°C至55°C的温度范围内连续三个循环内实现了重复的吸附和解吸行为。这些发现表明，通过改变环境温度可以从水溶液中去除磷酸盐并从水中回收。并且在25°C至55°C的温度范围内连续三个循环获得了重复的吸附和解吸行为。这些发现表明通过改变环境温度可能从水溶液中去除和回收磷酸盐。并且在25°C至55°C的温度范围内连续三个循环获得了重复的吸附和解吸行为。这些发现表明，通过改变环境温度可以从水溶液中去除磷酸盐并从水中回收。