Study of controlled pulsed illumination (CPI) efficiency in the homogeneous UV-LED/S2O82− process for the removal of organic dye from contaminated water

Abstract

The present investigation aims to shed light on the efficiency of the irradiation-based advanced oxidation processes using controlled pulsed illumination (CPI) in a homogeneous process. A more in-depth emphasis has been applied considering the ultraviolet-light emitting diodes/persulfate (LED/S2O82−) system. Irradiation-driven processes can present unexpected behaviour under a pulsed irradiation compered to continuous irradiation. This behaviour can be explained by Parrando's paradox concept. The removal efficiency of organic dyes under a continuous illumination source was compared to the CPI system employing a pulsed UV-LED/S2O82− photoreactor to explore CPI performance. The efficiency of the pulsed UV-LED/PS method was investigated using three organic dyes as model pollutants and duty cycle and pulse period as parameters of the pulsed irradiation source. The duty cycle and pulse period have a crucial impact on the pulsed system efficiencies, which were studied in the values of 10 %, 25 %, 50 %, 75 %, 90 %, and 99 % for pulse periods from 1 ms (ms) to a few hundred ms in the current study. For all experiments, the electrical energy consumption (EEO) values were calculated, and the CPI values were compared to the continuous illumination values. According to the results, duty cycles and pulse periods of (10 %, 800 ms), (10 %, 1 ms), and (10 %, 800 ms), with the EEO amounts of 58.29, 120.65, and 29.62 kWh per order showed the best performance for the removal of organic dyes, respect to continuous irradiation and other CPI experiments in terms of saving energy. Besides, the game theory and the collision hypothesis were scrutinized to justify the achieved results.

Keywords

• Duty cycle
• Pulse period
• Energy consumption
• Saving energy
• Controlled pulse illumination
• Parrondo's paradox concept