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), UV254 photolysis, UV254/H2O2, single ozonation, O3/H2O2, catalytic ozonation (AC, MWCNT and TiO2 as catalysts) and some solar driven processes such as TiO2 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 UV254/H2O2 treatment resulted in excellent removal of TBA primarily due to the oxidation capability of hydroxyl radicals (kHO = 3.310(9) M(-1) s(-1)) generated from H2O2 photolysis. As the H2O2 initial concentration was increased from 5 to 50 mg L(-1) the HO exposure per UV fluence (RHO,UV) increased, making the process more efficient. Single ozonation also allowed complete removal of the herbicide though the process was slow (kO3=15.4 M(-1) s(-1) at pH > 4). The ozonation process could be greatly accelerated by the enhanced generation of HO through O3/H2O2 and O3/AC processes, which also led to more efficient processes in terms of ozone utilization. Commercial TiO2 (TiO2-P25) and lab prepared anatase TiO2 (TiO2-cat) nanoparticles catalyzed the removal of TBA by solar photocatalysis. In contrast, a lab prepared MWCNT-TiO2 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 O3 and HO has been suggested after TBA degradation intermediates identification.
Departamento de Ingeniería Química y Química Física, Instituto Universitario de Investigación del Agua, Cambio Climático y Sostenibilidad (IACYS), Universidad de Extremadura, Av. de Elvas s/n, 06071 Badajoz, Spain. Electronic address: pmalvare@unex.es.
Pedro M
PM
Álvarez
Departamento de Ingeniería Química y Química Física, Instituto Universitario de Investigación del Agua, Cambio Climático y Sostenibilidad (IACYS), Universidad de Extremadura, Av. de Elvas s/n, 06071 Badajoz, Spain.
Diego H
DH
Quiñones
Departamento de Ingeniería Química y Química Física, Instituto Universitario de Investigación del Agua, Cambio Climático y Sostenibilidad (IACYS), Universidad de Extremadura, Av. de Elvas s/n, 06071 Badajoz, Spain.
Isidro
I
Terrones
Departamento de Ingeniería Química y Química Física, Instituto Universitario de Investigación del Agua, Cambio Climático y Sostenibilidad (IACYS), Universidad de Extremadura, Av. de Elvas s/n, 06071 Badajoz, Spain.
Ana
A
Rey
Departamento de Ingeniería Química y Química Física, Instituto Universitario de Investigación del Agua, Cambio Climático y Sostenibilidad (IACYS), Universidad de Extremadura, Av. de Elvas s/n, 06071 Badajoz, Spain.
Fernando J
FJ
Beltrán
D000327:Adsorption; D006861:Hydrogen Peroxide; D037742:Nanotubes, Carbon; D010084:Oxidation-Reduction; D010126:Ozone; D014874:Water Pollutants, Chemical
D037742:Nanotubes, Carbon; D014874:Water Pollutants, Chemical; D010126:Ozone; D006861:Hydrogen Peroxide
Activated carbon; Adsorption; Carbon nanotubes; Solar photo-ozonation; Terbuthylazine; Titania