凹凸棒土负载硫化纳米零价铁对水中Cu(Ⅱ)的去除机理研究

针对纳米零价铁易团聚及表面形成钝化层的缺点,本文以凹凸棒土为载体、以硫代硫酸钠为硫化试剂,制备了凹凸棒土负载硫化纳米零价铁(S-nZVI@ATP)复合材料,并考察了复合材料对水中Cu(Ⅱ)的去除效果。由SEM可观察到,经过凹凸棒土负载及硫化改性后的纳米零价铁串珠状结构变短,且被分散为单个的球形颗粒;比表面积测定结果表明,S-nZVI@ATP复合材料的BET比表面积为46.04m~2/g,与纳米零价铁相比提高了约1.35倍;由TEM观察到,经硫化的纳米零价铁颗粒界面处包裹了一层FeS,粒径由57.6nm增至118.5nm。S-nZVI@ATP复合材料去除水中Cu(Ⅱ)的机理主要是硫化纳米铁界面处的Fe~0将Cu~(2+)还原为Cu~0以及FeS转化为溶度积更小的CuS,该过程符合Langmuir-Hinshelwood吸附/还原模型和Langmuir等温吸附模型。本实验条件下,复合材料对Cu(Ⅱ)的最大吸附-还原量可达9.25mmol/g(587.8mg/g)。

Mechanism of Cu(II) removal from aqueous solution by attapulgite-loaded sulfide-modified nanoscale zero-valent iron

Aiming at overcoming the disadvantages of aggregation and passivation of nanoscale zero-valent iron, the attapulgite-loaded sulfide-modified nanoscale zero-valent iron was prepared by using attapulgite as carrier and sodium thiosulfate as sulfidation reagent, and its removal of Cu(II) from the aqueous solution was investigated. It can be obversed by SEM that the bead-like structure of nZVI after attapulgite loading and sulfidation modification becomes shorter and was even dispersed into individual spherical particles. The measured results of specific surface areas indicate that the BET specific surface area of the S-nZVI@ATP composite is 46.04 m²/g, which is around 1.35 times higher than that of nZVI. In addition, according to the obvervation by TEM, a layer of FeS is wrapped around the surface of a sulfide-modified nZVI particle, and the corresponding particle size increases from 57.6 nm to 118.5 nm after sulfidation. The mechanism of Cu(II) removal by S-nZVI@ATP composite can be attributed to the reduction of Cu²⁺ to Cu⁰ by Fe⁰ at the inferface of sulfide-modified nZVI in aqueous solution and the conversion of FeS to CuS with a smaller solubility product. The removal process fits well with Langmuir-Hinshelwood adsorption/reduction model and Langmuir adsorption isotherm model. Under the experiment conditions, the maximum adsorption-reduction capability of Cu(II) by composite reaches 9.25 mmol/g (587.8 mg/g).