聚甲基丙烯酸改性多孔二氧化硅的制备及其对亚甲基蓝的吸附性能研究

Adsorption behavior of grafted microparticles PMAA/SiO_(2) for methylene blue

采用两步法将功能性单体甲基丙烯酸(MAA)成功接枝于多孔二氧化硅(SiO_(2))微粒表面,制得了PMAA/SiO_(2)复合型固体吸附剂,通过静态吸附实验研究了该功能微粒对亚甲基蓝的吸附性能,考察了介质pH值和温度等因素对吸附性能的影响规律,并探讨了其吸附机理。结果表明,两步法制备的PMAA/SiO_(2)接枝微粒具有均一的尺寸分布和规整的外观,且对亚甲基蓝具有较强的吸附能力,吸附的主要驱动力是氢键和静电相互作用,吸附容量可达256.3 mg/g,吸附等温线符合Langmuir方程模型。接枝微粒的吸附容量随介质pH值的升高先增大后减小,当pH约为8时吸附效果最佳;温度的升高会减弱微粒的吸附能力。热力学参数△G、△H和△S均为负值,表明PMAA/SiO_(2)对亚甲基蓝的吸附是一个自发的放热反应。

The composite PMAA/SiO_(2) solid adsorbents were successfully fabricated via a two-step method in which the functional monomer methacrylic acid(MAA)were grafted ontOthe surface of porous silica particles(SiO_(2)).The static adsorption behavior of composite PMAA/SiO_(2) particles for methylene blue was investigated,and effects of various factors,such as the pH value and temperature on the adsorption performance were examined.Results show that the as-prepared PMAA/SiO_(2) particles are homogeneous and uniform,and have very strong adsorption ability and high affinity for methylene blue with adsorption capability reaching 256.3 mg/g.The isotherm adsorption behavior is satisfactorily fitted tOthe Langmuir equation.The adsorption capability increases with the increasing pH value when pH<8 and decreases with the increase of pH value when pH>8.Besides,the adsorption capability monotonically decreases with the enhancement of temperature.Thermodynamic parameters such as △G,△H and △S are negative,indicating that the adsorption of methylene blue is a spontaneous and exothermic process.