Removal of natural organic matter and disinfection byproduct precursors from drinking water using photocatalytically regenerable nanoscale adsorbents.

Disinfection byproduct precursors (DBPs) were removed from raw surface water obtained from two Canadian drinking water treatment plants via adsorption to two regenerable linear engineered TiO ₂ nanomaterials (LENs). The temperature employed in the final heating step of the LEN synthesis procedure was varied to produce two distinct nanomaterials, NB 550 and NB 700. The LENs had similar dimensions but differed in terms of surface characteristics, surface area, and crystal structure. Unlike the commercial TiO ₂ nanoparticles, both LENs were easily removed from the treated water via settling or filtration. Although neither of the LENs were as effective for NOM adsorption as commercial nanoparticles, both were able to remove substantial amounts of DBP precursors. NB 550 reduced the trihalomethane (THM) formation potential of both water sources by up to 40% and their haloacetic acid (HAA) formation potential by approximately 50%. NB 700 reduced the THM formation potential of one water source by 25% and that of the other by 40%. HAA precursor removal by NB 700 ranged from 25% to 30%. The adsorption of DOC, UV254, THM precursors, and HAA precursors by commercial nanoparticles and the LENs fit a modified Freundlich adsorption isotherm model. When the LENs were regenerated via exposure to UVA light they experienced a gradual loss in adsorption capacity of up to 50% over five regeneration cycles. This loss occurred more quickly for the less photoactive of the two nanomaterials, and was affected by water source, suggesting that components of the water matrices may have interfered with regeneration.
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