Chemical activation of persulfate (PS) into sulfate radicals was carried out using iron waste material collected from a workshop of the car industry. The material was characterized by SEM/EDX to contain mostly Fe0 however traces of metallic (Mn), semi-metallic (Si) and non-metallic (C) impurities. This provided excellent properties to the solid waste material in terms of PS activator agents (e.g. Fe2+, iron corrosion products). Ranitidine (RAN), a stomach acid inhibitor usually found at trace level in water supplies was chosen as pharmaceutical probe. Experiments were carried out (over 1 h) in RAN-spiked solutions (28.5 mM) and operational parameters were optimized so as to degrade RAN with the highest reaction stoichiometric efficiency (RSE). The effects of pH, iron load, PS content, Cl-, Br- and ionic strength [I] were studied. Results showed that varying the ionic strength from 0 to 500 mM using NaClO4 as neutral background electrolyte decreased the degradation pseudo-first order rate constant (kobs) from 0.050 to 0.021 min-1. However, the calculated RSE were more improved at 100 < [I] <250mM (64 and 99%, respectively). Chloride (0.1-100 mM) as well as bromide (0.001-10 mM) effect at [I] = 100 mM showed an improvement of kobs by a factor of 1.8 and 2.2 folds, respectively compared to that of chloride/bromide free solutions. Results showed also that increasing the concentration of the oxidant while keeping the same molar ratio with iron activator (PS:Fe) did not improve the mineralization process at circumneutral pH. HPLC/MS analyses showed the presence of several peaks having the same molecular ion 331 m/z. This corresponds to hydroxylated RAN isomers identified after their fragmentation in the ion source confirming thereby the responsibility of hydroxyl radicals in the oxidation process. PS oxidation using iron waste is an advantage for the treatment of industrial and/or hospital effluents basically having high ionic strength.

On the removal of ranitidine by iron-waste activated persulfate in aqueous systems

248th National Meeting (2014)

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