ZSM-5分子筛表面酸碱性质及对Co~(2+)的吸附

采用XRD、FTIR和酸碱滴定等手段对ZSM-5分子筛性质进行研究。采用静态批实验方法研究pH值、离子强度、固液比、平衡时间和Co2+浓度等因素对Co2+在ZSM-5分子筛表面上吸附的影响。结果表明,ZSM-5分子筛对Co2+具有较好的吸附能力和吸附容量;在低pH值下ZSM-5分子筛表面吸附位是以XH、YOH、YO-、YOH2+和XNa形态为主;而在高pH值条件下以YO-和XNa两种形态为主。Co2+在ZSM-5分子筛上的吸附符合准二级动力学;吸附作用受离子强度和pH值影响比较明显。在低pH值下,Co2+主要与ZSM-5分子筛表面发生离子交换作用(X2Co);在高pH值下以表面络合吸附为主(主要形成YOHCo2+和YOCo+两种形态)。

Characterization of ZSM-5 Zeolite and Its Application in the Removal of Co2+ From Aqueous Solutions

ZSM 5 zeolite is characterized by XRD, FTIR and acid base titration in detail. The results show that the main sorption sites are =XNa, =YOH and =YO^- in all pH ranges. The sorption of Co²⁺ on ZSM-5 zeolite is strongly dependent on pH value and ionic strength under ambient conditions. The sorption edges of Co²⁺ on ZSM-5 zeolite in 0.01mol/L NaClO₄ is modeled using a quasi-mechanistic sorption model (1-site protolysis non electrostatic surface complexation and cation exchange (1-SPNE SC/CE) model). The Co²⁺ sorption edges could be modeled in the pH range about 3 to 7 using cation exchange reactions for Co²⁺/Na⁺ and three surface complexation reactions on the sorption sites forming =X₂Co, =YOCo⁺ and =YOHCo²⁺ complexes appear successively with increasing of pH values.