鸟粪石-沸石复合材料对水中镉的吸附性能研究

研究以氧化镁负载沸石回收污水中氮磷得到的鸟粪石-沸石复合材料(STR-NZ)为吸附剂,用于对水体中重金属镉的吸附去除.实验采用SEM-EDS、XRD和FTIR等手段对STR-NZ材料进行表征,并考察了投加量、初始pH和反应时间等对STR-NZ材料去除水中Cd~(2+)的影响.结果表明:氧化镁负载沸石材料主要以鸟粪石沉淀的方式实现对水中磷酸盐和氨氮的回收;STR-NZ对水溶液中Cd~(2+)的吸附量随pH的增大呈先增加后趋于平衡的趋势,当Cd~(2+)的初始浓度为50 mg·L~(-1)时,STR-NZ的最佳投加量为0.2 g·L~(-1),Cd~(2+)最大吸附量为249.35 mg·g~(-1), STR-NZ对Cd~(2+)的吸附动力学符合准二级动力学模型,对Cd~(2+)的等温吸附符合Langmuir等温吸附模型,STR-NZ主要通过Cd_5(PO_4)_3(OH)沉淀的方式实现对水中Cd~(2+)的去除.

Adsorption of cadmium onto struvite-zeolite composite in aqueous solution

Struvite-zeolite composite (STR-NZ), which obtained through the recovery of phosphate and ammonia nitrogen from wastewater by using magnesium oxide-supported zeolite material, was used for the adsorption of heavy metal cadmium in aqueous solution. The obtained STR-NZ materials were characterized by using SEM-EDS, XRD and FTIR, and the influence of dosage, initial pH and reaction time on the adsorption removal of Cd²⁺ by STR-NZ was investigated. The results showed that the recovery of phosphate and ammonia nitrogen from wastewater by magnesium oxide-supported zeolite was mainly assigned to struvite precipitation. The adsorption of Cd²⁺ on STR-NZ firstly increased with the increase of pH and then reached balance. When the initial concentration of Cd²⁺ was 50 mg·L^-1, the maximum adsorption capacity of Cd²⁺ was 249.35 mg·g^-1 with the addition dosage of STR-NZ 0.2 g·L^-1. The kinetic adsorption results of Cd²⁺ on STR-NZ fit the pseudo- second-order kinetic model, and the adsorption isotherms fitted by Langmuir model. The removal of Cd²⁺ from solution by STR-NZ is mainly attributed to the formation of Cd₅(PO₄)₃(OH) precipitate.