(374f) Solar Photocatalytic Treatment of Atrazine-Contaminated Agricultural Water in the Rio Grande Basin | AIChE

(374f) Solar Photocatalytic Treatment of Atrazine-Contaminated Agricultural Water in the Rio Grande Basin


Ye, X. - Presenter, Lamar University
Chen, D. H. - Presenter, Lamar University
Tadmor, R. - Presenter, Lamar University
Flaherty, D. K. - Presenter, Lamar University
Wang, B. - Presenter, Lamar University
Sternes, K. - Presenter, Sul Ross State University

To develop a cost-effective and nearly maintenance-free solar treatment process for herbicides in agricultural water, we studied the photocatalytic decomposition of dissolved atrazine, an herbicide contaminant common in the Rio Grande Basin rivers and agricultural run-off water. Atrazine (C8H14ClN5), widely used in corn, sorghum and wheat fields, is toxic to water-life (leopard frogs, etc) and can cause prostate cancer, cardiovascular damage etc. to human beings [1-3]. Without treatment, the atrazine-contaminated water is hazardous and detrimental to the water sustainability in the Rio Grande Basin.

The available atrazine treatment methods include active carbon adsorption, UVC decomposition and photocatalytic decomposition [4-10]. As photocatalytic decomposition has the potential to use visible light, it could be a nearly maintenance-free process for environmental remediation. In our lab, we demonstrated that atrazine decomposed under a 4W fluorescent light (Fig. 1) with Degussa P-25 and BA-PW25 (Ecodevice, Japan) TiO2 photocatalysts suspended in a 2 L atrazine solution. The kinetic data of the photochemical decomposition of atrazine can be fitted with a first-order rate equation:

 dC/dt = - kC                                                 (1)

The photocatalysis results in a main product, hydroxyatrazine, that can further decompose to CO2 and water.  Hydroxyatrazine is relatively harmless compared to atrazine. The optimum catalyst loading was found to be around 0.3% by weight (Fig. 2).


Fig. 1 Atrazine photocatalytic decomposition under 4 W fluorescent light in a 2 L batch reactor with BA-PW 25 as the photocatalyst.


Fig. 2. Optimum loading of BA-PW 25 photocatalyst in a suspension

Using a 395 nm optical filter, we also observed the activities of the photocatalysts, Fig. 3.


Fig. 3. Atrazine photodecomposition under 4 W fluorescent light with 395 nm filter in 2 L batch reactor.

In a sunny day, atrazine rapidly decomposes from 56 ppb to below 3 ppb in 30 minutes in a 2 L reactor with Degussa P-25 as the photocatalyst under sunlight, while another photocatalyst BA-PW 25 needs 6 hours (Fig. 4). The latter has the following kinetic equation with a R2= 0.997.

dC/dt = -0.448C                                              (2)


 Fig. 4. Atrazine photodecomposition in a 2 L batch reactor under solar light in a sunny day

Atrazine photodecomposition with immobilized photocatalyst will be reported in a separate paper.                                        


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