Fe-Ce oxide; Arsenic; Porous soil; Micromodel; Laser-induced breakdown spectroscopy;CONTAMINATED SOILS; POROUS-MEDIA; PORE-SCALE; TRANSPORT; NANOPARTICLES; VISUALIZATION; REMEDIATION; GROUNDWATER; AMENDMENTS

Iron materials have shown great potential to remediate arsenic (As) contaminated sites. It's very important to reveal the reaction process between iron materials and As from the perspective of pore scale, but relevant research was inadequate. In order to directly investigate the migration and As adsorption mechanism of starch-modified Fe-Ce oxide in pore scale, a silicon-based micromodel observation platform was established in this study. The results of Charge coupled Device images showed that the sedimentation surface area of SFC occupied about 57.02% of the large porosity zone, but only 23.27% of the small porosity zone. To further reveal the 3D distribution of Fe and As elements inside the pore network, Laser Induced Breakdown Spectroscopy was introduced. The results revealed that less As was adsorbed as less SFC intruded in the small porosity zone. When the large porosity zone was blocked by SFC, a permeability barrier was created to adsorb As from upstream. This study also explored the effect of particle size reduction on SFC migration, and found it might be a better candidate for more SFC penetrated into small porosity zone. Combined with various high-resolution and sensitivity-detection methodologies, more colloidal migration mechanisms can be investigated using this technology in the future. (C) 2017 Elsevier B.V. All rights reserved.