Professor Purdue University Fort Wayne, Indiana, United States
Abstract Submission: Disinfection by ultrasound and carbon nanotubes (CNTs) provide attractive alternatives to conventional methods for water and wastewater treatment. This study explored inactivation of Escherichia coli (E. coli) by 5 mg/L pristine short or long multi-walled CNTs (MWCNTs) or 20 kHz ultrasound individually or through a combination of the treatments in DI water, Suwannee River natural organic matter (SRNOM), or sodium dodecyl sulphate (SDS) solutions. The results indicated that dispersity of MWCNTs was the single most important factor determining the inactivation rate of E. coli. The dispersity of short MWCNTs in solutions increased in the order of DI < 10 mgC/L SRNOM < 2 mM SDS. Correspondingly, the greatest log inactivation of E. coli was achieved in SDS when short MWCNTs were used alone (0.67±0.12) and combined with ultrasound (1.80±0.02) in 10 minutes. Short MWCNTs alone had a slightly greater inactivation (0.29±0.07) in SRNOM solution than in DI water (0.18±0.05). However, long MWCNTs had a little higher inactivation in DI (0.24±0.03) than short ones (0.18±0.05), because of better dispersity in DI. The observed synergistic inactivation when ultrasound and short MWCNTs were used together in 2 mM SDS suggests that the ultrasound better energized the MWCNTs when they were well dispersed, although SDS and MWCNTs can occupy the reaction sites at the cavitational bubble-water interfacial regions and scavenge •OH radicals. The results suggest that sonophysical effects are more important to inactivate E. coli than sonochemical effects. Ultrasound inactivates E. coli and/or energizes MWCNTs through the mechanisms of acoustic streaming, microstreaming, microstreamers, and transient cavitation collapse generated shock waves and micro jets (transitional forms), and localized hot temperature. The results of study indicate the cytotoxicity of CNTs is impinging the bacterial cells.
.jpg "Dong Chen, Ph.D., P.E. photo")
