Selective removal of bromide and iodide from natural waters using a novel AgCl-SPAC composite at environmentally relevant conditions

The removal of bromide (Br-) and iodide (I-) from source waters mitigates the formation of brominated and iodinated disinfection by-products (DBPs), which are more toxic than their chlorinated analogues. In this study, we report on our recently developed environmental-friendly method for the preparation of novel silver chloride/superfine activated carbon composite (AgCI-SPAC) to rapidly and selectively remove Br- and I- from surface waters. The material characteristics were tracked, before and after treatment, using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS) spectroscopies. The results showed very fast removal kinetics of Br- and I- by AgCI-SPAC with equilibrium times at 150 s and <105, respectively (i.e., 2-3 orders of magnitudes faster than previously tested Ag-based composites). In addition, AgCl-SPAC was evaluated under eight different Cl- concentrations up to 400 mg/L and exhibited high removal efficiencies for I- (i.e., >90% at all tested conditions) and Br- (i.e, >80% at Cl- = 0.5-200 mg/L, and 60-75% at extreme Cl- conditions = 300-400 mg/L). Unlike previous Ag-based composites, AgCl-SPAC performance was not affected by elevated concentrations of two types of natural organic matter (2-16 mg-NOM/L). The superior performance was further confirmed in four different surface waters and one groundwater. After the removal of Br- and I- from all waters by AgCl-SPAC, the subsequent DBPs formation (tri-halomethanes, haloacetic acids, and haloacetonitriles), total organic halogens (TOX), bromine substitution factor (BSF), and calculated cytotoxicity under the uniform formation conditions (UFC) decreased significantly. Overall, this novel composite represents a promising alternative approach, to be integrated continuously or seasonally, for controlling the formation of brominated and/or iodinated DBPs at water treatment plants. (C) 2019 Elsevier Ltd. All rights reserved.