2.2. Experimentation for Cr(VI) removal
The ability of Cu-foams to remove Cr(VI) from natural water was evaluated by laboratory-scale column tests. A piece of Cu-foam was fixed into a PVC tube to achieve a total height of 45 mm. The top side of the tube was connected to a peristaltic pump which supplied the Cr(VI)-containing water through the foam. The test water, which simulates typical natural water characteristics, was prepared according to the National Sanitation Foundation (NSF) standard [23]: 252 mg NaHCO3, 12.14 mg NaNO3, 0.178 mg NaH2PO4•H2O, 2.21 mg NaF, 70.6 mg NaSiO3•5H2O, 147 mg CaCl2•2H2O and 128.3mgMgSO4•7H2O were diluted in 1 L of distilled water. NSF water spiked with 100 μg/L Cr(VI) flowed through the column at a rate of 100 mL/h resulting in empty bed contact time 5.4 min. The pH was adjusted to remain stable throughout the test period and variations in the range of 6–8were regulated by adding drops of an HCl solution. Residual Cr(VI) concentration in the effluentwas determined by the diphenylcarbazide method using aHitachi U-5100UV/VIS spectrophotometer equippedwith 10 cmpathlength measurement cells. Total Cr and Cu concentrations were measured by graphite furnace atomic absorption spectrophotometry
using a Perkin Elmer Analyst 800 instrument.