Utilizing UV-LED pulse width modulation on TiO2 advanced oxidation processes to enhance the decomposition efficiency of pharmaceutical micropollutants

The presence of pharmaceutical and personal care products (PPCPs) in aquatic systems has been a growing cause for concern. Advanced oxidation processes such as UV/TiO2 (ultraviolet light/titanium dioxide) can break down PPCPs into smaller constituents, reducing the pharmaceutical activity. However, this process is limited by low photonic efficiency under UV systems. Controlled periodic illumination (CPI) is a promising solution to overcome the issues concerning low photonic efficiencies. Using a CPI controlled UV-LED/TiO2 process, a mixture of eighteen PPCP compounds were analyzed for their degradation removal on porous titanium - titanium dioxide (PTT) substrates. The kinetic rate constants of PPCPs may be analyzed using multiple regression analysis with parameters such as net charge at experimental pH, solubility, and molecular weight. Negatively charged PPCP compounds were found to have the highest removal compared to neutral and positively charged compounds due to electrostatic attraction forces. Decreasing the duty cycle under CPI or the UV-LED illumination period did not significantly change the individual and cumulative PPCP compound removal, suggesting that the CPI controlled UV-LED/TiO2 processes using PTT substrates were effective in reducing energy requirements without sacrificing removal performance.