Anion exchange resin-supported nZVI permeable reactive barriers for removal of nitrates from groundwater

The use of zero-valent iron nanoparticles (nZVI) as a reactive medium in permeable reactive barriers (PRBs) has often been used to remediate contaminated groundwater especially with oxo-anions such as nitrates and chromates, as well as chlorinated organics. Nitrates have received special attention because they can easily reach groundwater, the main source being agricultural activities. However, ZVI nanoparticles have some limitations in practical applications. The main drawback is that they are extremely small and can easily agglomerate due to their colloidal and magnetic characteristics. To solve the issue regarding the nZVI tendency to be agglomerated when used alone, a wide range of supporting materials were used to immobilize nZVI without decreasing its reactivity. In this respect, both organic materials (i.e. ion exchange resins, chelating resins, polymeric substrates, etc.), as well as inorganic materials (i.e. clay minerals, metal oxides, zeolites, etc.) were used. The physical-chemical characteristics of the materials used as support have a major influence on the size and distribution of nZVI particles immobilized on them. In addition, the support material has the role of concentrating the reactive phases by adsorption, which favors the redox reactions that take place in the system.
Therefore, this paper tests the performance of a new reactive barrier, based on nZVI deposited on a strongly basic anion exchange resin for removing nitrates from a simulated groundwater.