Y型分子筛嵌载纳米铁去除水中As(Ⅲ)的性能及机理

Performance and mechanism of As(Ⅲ) removal from aqueous solution by Y molecular sieve embedded with nano-iron

针对纳米铁易团聚和钝化的缺点,采用Y型分子筛作为载体使其嵌载、分散于具有较大比表面积的分子筛表面,制备了Y型分子筛嵌载纳米铁复合材料,对比了负载前后纳米铁去除水中As(Ⅲ)的性能,探讨了复合材料去除As(Ⅲ)的动力学和机理。结果表明,纳米铁的比表面积为19.60 m^(2)·g^(-1),而Y型分子筛嵌载纳米铁复合材料的比表面积达到了583.51 m^(2)·g^(-1),因此,复合材料中纳米铁对水中As(Ⅲ)的去除量由嵌载前的23.2 mg·g^(-1)(Fe)提高到了140.0 mg·g^(-1)(Fe),增大了约6倍。复合材料对As(Ⅲ)的去除反应符合拟二级动力学模型和Langmuir等温吸附模型,最大吸附量为11.896 mg·g^(-1)。复合材料对As(Ⅲ)的去除机理主要包括Fe0与水腐蚀产生的H2O2将As(Ⅲ)氧化成As(V),多孔材料中Fe0腐蚀产生的新生态铁氢氧化物对As(Ⅲ)和As(V)的吸附作用,以及Fe0腐蚀产生的Fe(Ⅲ)与As(Ⅲ)及其氧化产物As(V)的共沉淀作用。

Aiming at the disadvantages of nano-iron,such as easy agglomeration and passivation,Y molecular sieve was used as the carrier,and nano-iron was embedded and dispersed on the surface of molecular sieve with large specific surface area.Y molecular sieve embedded with nano-iron composite material was prepared.The removal performances of As(Ⅲ)in water by nano-iron before and after loading were compared,and the kinetics and mechanism of the As(Ⅲ)removal by composite material were discussed.The results showed that the specific surface area of Y molecular sieve embedded with nano-iron composite material increased from 19.60 m^(2)·g^(-1)to 583.51 m^(2)·g^(-1)compared with nano-iron,so its ability to remove As(Ⅲ)increased from 23.2 mg·g^(-1)(Fe)to 140.0 mg·g^(-1)(Fe),increased about 6 times.The removal of As(Ⅲ)by the composite material accorded with pseudo-second-order kinetic model and Langmuir isothermal adsorption model,and the maximum adsorption capacity was 11.896 mg·g^(-1).The removal mechanism of As(Ⅲ)by composite materials mainly included oxidation of As(Ⅲ)and As(V)by H2O2generated by Fe~0 and water corrosion,As(Ⅲ)and As(V)adsorption by newly formed iron hydroxides produced by Fe~0 corrosion in porous materials,and the co-precipitation of Fe(Ⅲ)by Fe~0 corrosion with As(Ⅲ)and their oxidation products As(V).