Kirkendall Effect Boosts Phosphorylated nZVI for Efficient Heavy Metal Wastewater Treatment

Kirkendall Effect Boosts Phosphorylated nZVI for Efficient Heavy Metal Wastewater Treatment

Removal of non-biodegradable heavy metals has been the top priority in wastewater treatment and the development of green technologies remains a significant challenge. We demonstrate that phosphorylated nanoscale zero-valent iron (nZVI) is promising for removal of heavy metals (Ni-II, Cu-II, Cr-VI, Hg-II) via a boosted Kirkendall effect. Phosphorylation confines tensile hoop stress on the nZVI particles and "breaks" the structurally dense spherical nZVI to produce numerous radial nanocracks. Exemplified by Ni-II removal, the radial nanocracks favor the facile inward diffusion of Ni-II and the rapid outward transport of electrons and ferrous ions through the oxide shell for surface (Ni-II/electron) and boundary (Ni-II/Fe-0) galvanic exchange. Accompanied by a pronounced hollowing phenomenon, phosphorylated nZVI can instantly reduce and immobilize Ni-II throughout the oxide shell with a high capacity (258 mgNig(-1) Fe). For real electroplating factory wastewater treatment, this novel nZVI performs simultaneous Ni-II and Cu-II removal, producing effluent of stable quality that meets local discharge regulations.

去除不可生物降解的重金属一直是废水处理的首要任务，而绿色技术的开发仍然是一项重大挑战。我们证明，磷酸化纳米零价铁（nZVI）通过增强的柯肯德尔效应在去除重金属（镍（II）、铜（II）、铬（VI）、汞（II））方面很有前景。磷酸化对nZVI颗粒施加了周向拉应力，并使结构致密的球形nZVI“破裂”，产生大量径向纳米裂纹。以去除镍（II）为例，径向纳米裂纹有利于镍（II）容易地向内扩散，以及电子和亚铁离子通过氧化层快速向外传输，以进行表面（镍（II）/电子）和边界（镍（II）/铁（0））的电偶交换。伴随着明显的中空现象，磷酸化的nZVI能够在整个氧化层中立即还原并固定镍（II），且容量较高（258毫克镍/克铁）。对于实际的电镀厂废水处理，这种新型的nZVI能够同时去除镍（II）和铜（II），产生质量稳定且符合当地排放规定的出水。