Self-Powered Water Flow-Triggered Piezocatalytic Generation of Reactive Oxygen Species for Water Purification in Simulated Water Drainage

Ambient water motions presented in urban drainage systems is a rich source of renewable mechanical energy. Harvesting this energy to trigger the generation of reactive oxygen species (ROS) for water purification is a desirable yet underexplored solution. Herein, the water flow from a spiral reactor to simulate pipeline drainage was utilized to provide mechanical energy to power itself to initiate the piezo-response of molybdenum disulfide (MoS2) that was added into water flowing in the reactor. The piezocatalytic degradation efficiency of benzothiazole by MoS2 reached 94.8% after 24 cycles (ca. 144 s), which was 8.8 and 4.9 times higher than that of quiescent solution of MoS2 and non-piezoelectric commercial MoS2, respectively. Furthermore, the water flow-driven system can be extended to degrade different kinds of organic contaminants, including benzotriazole and various antibiotics (enrofloxacin, ciprofloxacin, metronidazole, etc.). All target pollutants were degraded with electric energy per order EEO in the range of 0.0161 to 0.0616 kW h/m3. In this process, the running water from the spiral reactor drove MoS2 to generate piezoelectric charges, which in turn reacted with dissolved oxygen and water to generate ROS including the hydroxyl radical, superoxide anion, and singlet oxygen to decompose the target pollutants. The system retained piezo-degradation efficiencies (>80%) in different aqueous matrices including rainwater, saline water, and pharmaceutical sewage and could be reused four times maintaining a good performance (>90%). This investigation provides a facile self-powered piezocatalytic process by harnessing ambient energy from the water flow of simulated water drainage to purify wastewater.