Jinag Bo-Hui, Lin Jian-Wei, Zhan Yan-Hui, Xing Yun-Qing, Huang Hong, Chu Ming, Wang Xing-Xing
College of Marine Science, Shanghai Ocean University, Shanghai 201306, China.
Huan Jing Ke Xue. 2017 Jun 8;38(6):2400-2411. doi: 10.13227/j.hjkx.201611081.
In this study, zirconium-modified bentonites (ZrMBs) with different zirconium loading levels were prepared, and the adsorption behaviors of phosphate on these ZrMBs were comparatively investigated using batch experiments. The results showed that the kinetic process of phosphate on ZrMBs well followed the pseudo-second-second kinetic model. The kinetic process was divided into three stages, including a rapid external surface adsorption stage, a gradual adsorption stage where both the intra-particle diffusion and film diffusion were rate-controlled, and a final equilibrium adsorption stage. The equilibrium adsorption data of phosphate on ZrMBs could be well described by the Langmuir, Freundlich, Sips and Dubinin-Radushkevich isotherm models. Phosphate adsorption onto ZrMBs was more favorable under strongly acidic condition than under weakly acidic or neutral condition, while phosphate adsorption onto ZrMBs under weakly acidic or neutral condition was more favorable than that under alkaline condition. Coexistence of Na and K slightly enhanced phosphate adsorption onto ZrMBs, while coexisting Ca greatly enhanced the phosphate adsorption. The presence of HCO or SO inhibited the adsorption of phosphate on ZrMBs. The mechanism for phosphate adsorption onto ZrMBs followed the ligand exchange and inner-sphere complexing mechanism. The phosphate adsorption capacity for ZrMB increased with increasing loading level of zirconium, while the amount of phosphate adsorbed on unit mass of ZrO in ZrMB decreased with increasing loading amount of zirconium in ZrMB. When the loading amount of ZrO in ZrMB increased from 3.61% to 13.15%, the maximum phosphate adsorption capacity (MPAC) for ZrMB increased from 3.83 to 9.03 mg·g, while a further increase in the ZrO loading amount to 19.63% resulted in a slight increase of MPAC to 9.66 mg·g. However, an increase in the loading amount of ZrO in ZrMB from 3.61% to 19.63% caused a decrease of the MPAC for the ZrO located in ZrMB from 106 to 49.2 mg·g. Considering both cost and adsorption capacity of adsorbent, the ZrMB with 13.15% of zirconium loading amount could be more suitably used as an adsorbent to remove phosphate from aqueous solution than the other ZrMBs.
在本研究中，制备了具有不同锆负载量的锆改性膨润土（ZrMBs），并采用批量实验比较研究了这些ZrMBs对磷酸盐的吸附行为。结果表明，磷酸盐在ZrMBs上的动力学过程很好地遵循准二级动力学模型。该动力学过程分为三个阶段，包括快速的外表面吸附阶段、颗粒内扩散和膜扩散均为速率控制的逐渐吸附阶段以及最终的平衡吸附阶段。磷酸盐在ZrMBs上的平衡吸附数据可以用Langmuir、Freundlich、Sips和Dubinin-Radushkevich等温线模型很好地描述。在强酸性条件下，磷酸盐在ZrMBs上的吸附比在弱酸性或中性条件下更有利，而在弱酸性或中性条件下，磷酸盐在ZrMBs上的吸附比在碱性条件下更有利。Na和K的共存略微增强了磷酸盐在ZrMBs上的吸附，而Ca的共存极大地增强了磷酸盐的吸附。HCO或SO的存在抑制了磷酸盐在ZrMBs上的吸附。磷酸盐在ZrMBs上的吸附机制遵循配体交换和内球络合机制。ZrMB对磷酸盐的吸附容量随锆负载量的增加而增加，而ZrMB中单位质量ZrO上吸附的磷酸盐量随ZrMB中锆负载量的增加而减少。当ZrMB中ZrO的负载量从3.61%增加到13.15%时，ZrMB的最大磷酸盐吸附容量（MPAC）从3.83增加到9.03 mg·g，而ZrO负载量进一步增加到19.63%导致MPAC略有增加至9.66 mg·g。然而，ZrMB中ZrO的负载量从3.61%增加到19.63%导致ZrMB中ZrO的MPAC从106降至49.2 mg·g。综合考虑吸附剂的成本和吸附容量，负载量为13.15%锆的ZrMB比其他ZrMB更适合用作从水溶液中去除磷酸盐的吸附剂。
