The simulation of in situ arsenic removal from groundwater with

2.4. The simulation of in situ arsenic removal from groundwater with the iron coating
After the completion of the experiment, the iron-coated quartz sand was collected from the column and processed as described in Section 2.3. The concentrations of iron and arsenic and the amount of adsorbed arsenic concentrations were then determined.
2.5. Chemical analysis
The concentration of fluorescein sodium and iron in the collected samples was measured using FG2216 portable spectrophotometer (HACH, DR2800). The arsenic concentration in the solutions was determined using 'FG2216' an atomic fluorescence spectrometer (AFS, Beijing Haitian Instruments). The phenanthroline method was used to determine the iron concentration after the iron was reduced to Fe(II) by the reducing agent (hydroxylamine hydrochloride, 10 wt.%). The detection limit of spectrophotometer for both fluorescein sodium and ferrous ion concentration analysis was 0.01 mg/L and the atomic fluorescence spectrometer for arsenic concentration determination was 0.1 μg/L. The standards and replicates were measured in every ten samples as an analysis routine for arsenic, fluorescein sodium and ferrous ion concentration determination. Unless otherwise stated, the reproducibility was better than 5% relative for all compounds analyzed.