Insights into the removal of terbuthylazine from aqueous solution by several treatment methods.

This paper reports the removal of the s-triazine herbicide terbuthylazine (TBA) from aqueous solution by various treatment methods including adsorption onto activated carbon (AC) and multiwalled carbon nanotubes (MWCNT), UV 254 photolysis, UV 254 /H 2 O 2 , single ozonation, O 3 /H 2 O 2 , catalytic ozonation (AC, MWCNT and TiO 2 as catalysts) and some solar driven processes such as TiO 2 photocatalytic oxidation and photo-ozonation. TBA was adsorbed onto AC and MWCNT following a pseudo-second order kinetics and Freundlich isotherm. Rapid small scale column tests showed that TBA could be removed from solution by adsorption onto AC better than atrazine. The UV 254 /H 2 O 2 treatment resulted in excellent removal of TBA primarily due to the oxidation capability of hydroxyl radicals (k HO = 3.3 10 9 M −1 s −1 ) generated from H 2 O 2 photolysis. As the H 2 O 2 initial concentration was increased from 5 to 50 mg L −1 the HO exposure per UV fluence ( R HO ,UV ) increased, making the process more efficient. Single ozonation also allowed complete removal of the herbicide though the process was slow (k O3 = 15.4 M −1 s −1 at pH > 4). The ozonation process could be greatly accelerated by the enhanced generation of HO through O 3 /H 2 O 2 and O 3 /AC processes, which also led to more efficient processes in terms of ozone utilization. Commercial TiO 2 (TiO 2 -P25) and lab prepared anatase TiO 2 (TiO 2 -cat) nanoparticles catalyzed the removal of TBA by solar photocatalysis. In contrast, a lab prepared MWCNT-TiO 2 composite was not useful as catalyst in solar photo-oxidation processes because of the HO scavenging nature of the MWCNT used as support. A mechanism for TBA degradation by O 3 and HO has been suggested after TBA degradation intermediates identification. [ABSTRACT FROM AUTHOR]