Ranitidine abatement in chemically activated persulfate systems : assessment of industrial iron waste for sustainable applications -

Abstract

This work assessed the use of industrial iron-based scrap in the activation of persulfate (PS) into sulfate radicals (SRs) for the removal of ranitidine (RAN) (28.5 μM) from aqueous systems. Knowing that Fe2+ released from iFe is the main activator toward PS, the optimal molar ratio of Fe2+:PS was investigated and appeared to be 1:1. A comparative study between industrial iron (iFe) and commercial iron (cFe) at 2 successive experimental runs, each for 1 h, revealed that iFe present some advantages over cFe in terms of reaction stoichiometric efficiency (RSE) and sludge formation. A low load of iFe (1 mg - 20 mL) was utilized to provide adequate amounts of Fe for PS activation without leaving excessive Fe residuals in water. It was feasible to get almost a complete RAN removal over 1 h reaction with a ratio of dissolved iron species (equivalent to Fe2+):PS of only 0.166:1. The employment of iFe in PS-based AOPs was evaluated at different ionic strength conditions controlled by sodium perchlorate background electrolyte. It was also assessed in chloride-containing solutions and bromide-containing solutions at [I] = 100 mM. Results showed that the increase in ionic strength lowered down the rate of RAN degradation. However, halides appeared enhancing PS activation for RAN removal rather than quenching. The reactivity of bromide was slightly more advantageous than the reactivity of chloride. In both ionic matrices, iFe has sustained its activity with optimum concentration of bromide and chloride at 1 mM. Total organic carbon (TOC) was analyzed at different PS:iFe molar ratios. It was revealed that the amount of iron corrosion products (ICPs) formed is directly related to the concentration of PS and to the amount of iFe used. Although degradation was successful at low iFe load, mineralization was negligible. However, co-precipitation could be more significant at higher iFe levels. The HPLC-MS chromatograms showed the presence of a RAN intermediate detected at 331 m-z that dissipates gradually throughout the trea