锆负载颗粒沸石改良底泥对水中磷酸盐的吸附行为

通过批量吸附实验考察了锆负载颗粒沸石改良底泥对水中磷酸盐的吸附特征,并采用分级提取法分析了被改良底泥中锆负载颗粒沸石所吸附磷酸盐的形态分布特征.结果发现,与Freundlich和Dubinin-Radushkevich模型相比,Langmuir模型可以更好地用于描述改良底泥对水中磷酸盐的吸附等温行为.改良底泥对水中磷酸盐的吸附动力学过程可以较好地采用准二级动力学模型和Elovich模型加以描述,膜扩散和颗粒内扩散共同构成了缓慢吸附阶段速率的限制步骤.溶液共存的SO_4~(2-)和HCO_3~-降低了改良底泥对水中磷酸盐的吸附,而共存的Na~+、K~+、Mg~(2+)和Ca~(2+)却增强了对磷酸盐的吸附,且Ca~(2+)的增强效果大于Mg~(2+),后者的增强效果又大于Na~+和K~+.改良底泥对水中磷酸盐的吸附能力明显强于未改良底泥,前者的最大单位吸附量为336 mg·kg~(-1),明显高于后者的最大单位吸附量(215 mg·kg~(-1)).被改良底泥中锆负载颗粒沸石所吸附的磷酸盐主要以较为稳定的NaOH-P和最为稳定的Res-P形态存在,不容易被重新释放出来.上述的研究结果显示,向底泥中添加锆负载颗粒沸石可以显著增加底泥对水中磷酸盐的吸附能力,锆负载颗粒沸石是一种有希望的可以用于底泥内源磷释放控制的底泥改良剂.

Adsorption Behavior of Phosphate from Water on Zirconium-loaded Granular Zeolite-amended Sediment

In this study, a zirconium-loaded granular zeolite (ZrGZ) was prepared, characterized and used as a sediment amendment to control internal phosphorus (P) loading in water samples from a heavily polluted river. The adsorption characteristics of phosphate on ZrGZ-amended sediment were investigated using batch experiments, and the stability of P in phosphate-adsorbed ZrGZ was evaluated using a sequential chemical extraction method. Results showed that the Langmuir isotherm model was more suitable for describing the equilibrium adsorption data of phosphate on ZrGZ-amended sediment than the Freundlich and Dubinin-Radushkevich isotherm models. The adsorption process of phosphate on ZrGZ-amended sediment could be well described by the pseudo-second-order and Elovich kinetic models, and both film and intra-particle diffusion controlled the adsorption rate during the gradual adsorption stage. The coexistence of SO₄^2- and HCO₃^- inhibited the adsorption of phosphate on ZrGZ-amended sediment, while coexisting Na⁺, K⁺, Mg²⁺ and Ca²⁺ enhanced the phosphate adsorption, and this promoting effect decreased in the order of Ca²⁺ > Mg²⁺ > Na⁺/K⁺. The ZrGZ-amended sediment exhibited a higher phosphate adsorption capacity than the unamended sediment, and the maximum phosphate adsorption capacity derived from the Langmuir isotherm model was found to be 336 mg·kg^-1, which was higher than that for the unamended sediment (215 mg·kg^-1). Sequential tests showed that P in phosphate-adsorbed ZrGZ mainly existed in the form of NaOH-rP and Res-P, which was relatively unreactive. These results indicated that ZrGZ addition enhanced the phosphate adsorption capacity of river sediment, and that ZrGZ was a promising amendment for controlling the release of P from river sediment.