Effect of Pumice and Sand on the Sustainability of Granular Iron Beds for the Aqueous Removal of CuII, NiII, and ZnII

Current knowledge of the basic principles underlying the design of Fe-0 beds is weak. The volumetric expansive nature of iron corrosion was identified as the major factor determining the sustainability of Fe-0 beds. This work attempts to systematically verify developed concepts. Pumice and sand were admixed to 200g of Fe-0 in column studies (50:50 volumetric proportion). Reference systems containing 100% of each material have been also investigated. The mean grain size of the used materials (in mm) were 0.28 (sand), 0.30 (pumice), and 0.50 (Fe-0). The five studied systems were characterized (i) by the time dependent evolution of their hydraulic conductivity (permeability) and (ii) for their efficiency for aqueous removal of Cu-II, Ni-II, and Zn-II (about 0.3mM of each). Results showed unequivocally that (i) quantitative contaminant removal was coupled to the presence of Fe-0, (ii) additive admixture lengthened the service life of Fe-0 beds, and (iii) pumice was the best admixing agent for sustaining permeability while the Fe-0/sand column was the most efficient for contaminant removal. The evolution of the permeability was well-fitted by the approach that the inflowing solution contained dissolved O-2. The achieved results are regarded as starting point for a systematic research to optimize/support Fe-0 filter design.