Capture and storage of hydrogen gas by zero-valent iron

Granular Fe-o, used to reductively degrade a variety of contaminants in groundwater, corrodes in water to produce H-2(g). A portion enters the Fe-o lattice where it is stored in trapping sites such as lattice defects and microcracks. The balance is dissolved by the groundwater where it may exsolve as a gas if its solubility is exceeded. Gas exsolution can reduce the effectiveness of the Fe-o treatment zone by reducing contact of the contaminant with iron surfaces or by diverting groundwater flow. It also represents a lost electuson resource that otherwise could be involved in reductive degradation of contaminants. It is advantageous to select an iron for remediation purposes that captures a large proportion of the H-2(g) it generates. This study examines various aspects of the H-2(g) uptake process and has found 1) H-2(g) does not have to be generated at the water/iron interface to enter the lattice. It can enter directly from the gas/water phases, 2) exposure of granular sponge iron to H-2(g) reduces the dormant period for the onset of iron corrosion, 3) the large quantities of H-2(g) generated by nano-Fe-o injected into a reactive barrier of an appropriate granular iron can be captured in the lattice of that iron, and 4) lattice-bound hydrogen represents an additional electron resource to Fe-o for remediation purposes and may be accessible using physical or chemical means. (C) 2013 Elsevier B.V. All rights reserved.