Column Experiments
All the experiments were conducted in a glass column with an inner diameter of 1.4 cm, a height of 25 cm, and a medium—porosity sintered—pyrex disc at its bottom in order to prevent any loss of material. This column was packed with an absorbent composite (14.1 g) which con- tained either sand or brick as the support material. The adsorption capacity of these different absorbents was in- vestigated for a bed height of about 10 cm. The iron(II)- containing influent ([Fe2+] = 9.6 mg/L) passed at room
temperature through the column downward using a peri- staltic pump at a flow rate of 10 mL per minute. Before being used in every experiment, about 5 bed volumes of Milli-Q water were passed through the column: 1) first in order to remove any unbound and thin particles/iron ox-ide(s)/hydroxide(s); 2) second to check the absence of soluble iron in the effluent by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy); and 3) third to confirm the stability of the FeOOH coating on brick grains. Effluent samples were collected at various time intervals, and the concentration of soluble iron in the effluent was analyzed with time using an ICP-AES spectrometer model: Varian Pro axial view