Photocatalytic Degradation Of Atrazine Research Articles

Photocatalytic degradation of atrazine using suspended and supported TiO2

The degradation of 6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine (atrazine) by heterogeneous photocatalysis using suspended and supported TiO2 is reported. The influence of reaction parameters such as catalyst and atrazine concentrations, pH, light intensity and temperature has been investigated and the optimal conditions for the abatement of atrazine have been identified. The primary degradation and the total mineralization of atrazine have been monitored by high performance liquid chromatography (HPLC) and total organic carbon (TOC), respectively. Atrazine got destroyed in both suspended and supported systems, but its complete mineralization is not observed, probably due to the formation of cyanuric acid as a stable product. The activation energy for the degradation reaction of atrazine is determined as 2.6kcalmol−1. The efficiencies of photodegradation in both suspended and supported systems (the latter in a 150ml flow reactor) are compared and the results indicate that the catalytic activity of TiO2 is not affected when it is immobilized using a functionalized polymer. It is observed that the durability of the supported catalyst activity is reduced after six or seven runs, but it could be fully re-activated by a simple heat treatment at 480°C for 1h. The findings clearly suggest that immobilized photocatalysts could indeed be developed for photocatalysis, without compromising on the activity of the primary catalyst particles.

Photochemical processes for atrazine degradation: methodological approach

Numerous studies have been carried out on s-triazines, and more specifically on atrazine, with the long-term objective of resolving the problems caused by these herbicides: removing them from drinking water. However, applications have remained too limited. So far, processes based on photochemical degradation have been little implemented. We, therefore, investigated the development of photochemical processes, emphasizing their capacity to degrade triazine by photolytic and photocatalytic mode. The study sought to assess the performance of these systems. Experiments showed that according to a medium pressure mercury source (UV–Vis irradiation), the photolytic degradation of atrazine was very efficient, with a best atrazine degradation half-life shorter than 5 min. The main degradation pathway was deshalogenation. The photocatalytic degradation of atrazine under irradiation over 290 nm in the presence of titanium dioxide was shown to be efficient too, with a half-life of about 20 min. In this case an experimental design was conducted so as to assess the influence of various parameters: pH, water medium, and amount of catalyst. There has been observational evidence for the efficiency of the processes investigated here and for potential technological developments as regards drinking water treatment.

Photocatalytic degradation of atrazine by porphyrin and phthalocyanine complexes

This study principally focused on a new kind of photochemical reaction catalyst: porphyrin and phthalocyanine complexes. In a first step, the preparation of the catalysts was optimized. A resin has been chosen to be the support of the complexes. Efficiency of catalytic activity is performed on the degradation of a pesticide: atrazine. The best atrazine degradation occurs with 4.6% of complexes versus substrate. The role of the surface has also been shown to be important. Then, their performances were demonstrated in terms of kinetics and degradation routes, compared to a classical catalyst: titanium dioxide. This study seeks to assess the efficiency of these systems both in a mercury lamp reactor and under solar irradiation which reduces energy costs. The best atrazine degradation half-life found for the complexes is about 200 min with the iron phthalocyanine. These catalysts exhibit particular oxidation activities. Indeed, the degradation routes have been found different between the semi-conductor and the metallic complexes. These complexes are able to cleave the triazinic ring more efficiently than the titanium dioxide.

Large solar plant photocatalytic water decontamination: Degradation of atrazine

Photocatalytic degradation of atrazine was successfully and efficiently carried out in a large modular flow trough system under solar light. The degradation leads to complete mineralization of the alkyl substituents of s-triazine, giving trihydroxy-s-triazine as a final product. An efficient detoxification can be attained. The presence of 1 × 10 −3 m of peroxydisulphate, kept constant during the treatment, is sufficient to remove 98% of atrazine with very short residence times (less than 6 min), and to convert the parent triazine to more than 90% of trihydroxy-s-triazine in less than 2 h. The peroxydisulphate is particularly advantageous when large amounts of polluted ground water have to be treated. The factors affecting the total efficiency are discussed in view of a simple model for the primary events in the photocatalytic system.

Photocatalytic degradation of atrazine and other s-triazine herbicides

The photocatalytic degradation of s-triazine herbicides (atrazine, simazine, trietazine, prometon, and prometryn) has been investigated by using particulate TiO 2 as photocatalyst under simulated solar light. The herbicides are rapidly degraded. Several intermediates have been identified, and cyanuric acid has been recognized as the final product of the degradation process for all the investigated herbicides. A proposal mechanism of the process is presented

DEGRADATION OF ATRAZINE IN SOIL THROUGH INDUCED PHOTOCATALYTIC PROCESSES

The authors observed photocatalytic degradation of atrazine in the presence of semiconductor metal oxide particulates (TiO{sub 2}, ZnO) suspended in aqueous solution under simulated sunlight irradiation. The half-life for the process is ca. 5 and 80 min for TiO{sub 2} and ZnO, respectively (at an initial atrazine concentration of 25 mg/liter with 0.5 g of semiconductor per liter and with a photon flux of 3 {times} 10{sup {minus}5} einstein/min, and over a cell cross section of 4 cm{sup 2}). The authors investigated the catalytic activity of different soils. The weak photocatalytic activity of the soils (2 g/liter) is dramatically increased by the addition of 0.5 g of the semiconductor per liter. Half-lives are 10 to 40 minutes, depending on the nature of the soil.