Development and Evaluation of Photocatalytic Linear Engineered Titanium Dioxide Nanomaterials for the Removal of Disinfection Byproduct Precursors from Drinking Water

Photocatalysis has long been touted as a potential drinking water treatment technology but has proven difficult to implement at full scale. This project aimed to address two of the perennial challenges preventing the use of photocatalysis for drinking water treatment: the need to safely remove the photocatalyst from the water after treatment and the danger that incomplete mineralization of contaminants will lead to the formation of intermediate compounds that are more reactive or toxic than their parent compounds. A suite of titanium dioxide-based linear engineered nanomaterials (LENs) was synthesized and compared to standard commercial titanium dioxide nanoparticles in terms of filterability, settleability, surface characteristics, crystal phase structure, available surface area, photonic efficiency, and propensity to form hydroxyl radicals. The LENs were also evaluated in terms of their ability to remove disinfection byproduct (DBP) precursors from two natural surface water matrices via adsorption and photocatalysis. DBPs, which form when naturally occurring organic precursor compounds interact with chemical disinfectants used in drinking water treatment, are suspected carcinogens and are widely regulated throughout the world. In this study, photocatalysis increased the DBP formation potential of both water matrices at short irradiation times. Longer treatment times resulted in decreased in DBP formation potential. Adsorption removed DBP precursors from the water without transforming them. The surface area and crystal phase structure of the nanomaterials were identified as important drivers of photocatalytic treatment effectiveness and regenerability. Adsorption efficacy was mainly impacted by surface area, agglomeration, and charge interactions. The effects of both adsorption and photocatalysis on DBP formation potential were strongly influenced by the composition of the water matrix being treated. The results of this project have informed the conceptual design of two titanium dioxide-based water treatment processes for DBP precursor removal: a single step photocatalytic system and a two-step adsorption and regeneration system.