Critical layer in liquid-solid system influencing the remediation of chromium using zeolite-supported sulfide nano zero-valent iron

Sulfidated nano zero-valent iron particles were immobilized on ZSM-5 zeolite(Z/S-nZⅥ)and used for hexavalent chromium(Cr(Ⅵ))remediation.The performance of Z/S-nZⅥimproved with the increase in Cr(Ⅵ)concentration(<60 mg/L),while the performance significantly decreased for a Cr(Ⅵ)concentration of more than 60 mg/L.The adsorption behavior for Cr(Ⅵ)was different from that reported in previous studies.The improved performance can be tailored for increasing efficiency of nano zero-valent iron(nZⅥ)corrosion,while the degree of corrosion of nZⅥwas affected by the concentration of the pollutant as discussed by kinetics,X-ray diffraction(XRD)and X-ray photoelectron spectrometer(XPS)analyses.The experiments for the dissolution of ferrous ions and the dosage of adsorbent demonstrated that the critical layer in the liquid-solid system changed with the increase in the concentration of Cr(Ⅵ)(Cr(Ⅵ):Z/S-nZⅥ>0.6).Moreover,the removal mechanisms of Cr(Ⅵ)were elucidated through XRD,transmission electron microscopy(TEM)and XPS techniques.This results demonstrate that the species of chromium in the critical layer changed from Cr(Ⅲ)to Cr(Ⅵ)as the concentration of chromium increased from low to high.Furthermore,the critical layer was composed of Cr(Ⅵ),Fe(Ⅱ),O and H elements.Additionally,the experiments of coexisting ions and aging time confirmed that Z/S-nZⅥpossessed high selectivity and stability to ensure efficiency and cost-effectiveness in practical applications.

环境水体中腐殖酸与共存物的相互作用

腐殖酸(humic acid,HA)凭借着其赋存特性和独特的化学活性在环境治理领域备受关注。值得注意的是,在共存反应体系中,HA不可避免的与共存物相互作用,进而使反应体系变得复杂,结果导向与预期不同。因此,研究HA与共存物之间的相互作用对于正确理解环境水污染复杂性问题,开发具有协同处理共存物的新型环境功能材料具有重要意义。本文综述了HA参与的共存污染物体系下目标污染物协同/拮抗去除效果,包括无机污染物共存体系、有机污染物共存体系和微生物共存体系。针对HA自身的结构特点和理化性质,系统分析了HA与共存污染物之间的相互作用机理,主要涉及配位作用、静电作用、吸附作用、疏水作用、π-π相互作用和氧化还原作用等。最后,对HA在共存污染体系下目标污染物的去除所面对的挑战和未来的研究方向进行了展望。