There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The surface science of titanium dioxide

TiO2 photocatalysis and related surface phenomena

http://publicationslist.org/data/meng.chong/ref-18/sdarticle.pdf

Recent Developments in Photocatalytic Water Treatment Technology: A Review

Photoinduced reactivity of titanium dioxide

Reference GGEC-ARTICLE-2008-057doi:10.1002/jctb.1873View record in Web of Science Record created on 2008-01-23, modified on 2016-08-08

Advanced oxidation processes for water treatment: advances and trends for R & D

New perspectives for Advanced Oxidation Processes.

Photocatalytic decolorization and degradation of dye solutions and wastewaters in the presence of titanium dioxide.

In the present study, the photocatalytic degradation of an organophosphorous insecticide, dichlorvos, using two different photocatalysts (TiO 2 and ZnO) has been investigated. The blank experiments for either illuminated dichlorvos solution or the suspension containing TiO 2 or ZnO and dichlorvos in the dark showed that both illumination and the catalyst were necessary for the destruction of the pesticide. Dichlorvos disappearance is achieved in ∼20 min when treated with illuminated TiO 2 and in ∼120 min with illuminated ZnO. The degradation of the organic molecule follows first-order kinetics according to the Langmuir–Hinshelwood model. It was observed that the initial rate increases linearly with an increase in the amount of catalyst up to a level where it reaches a plateau. Temperature and pH also affect the rate of the reaction. The addition of an oxidant (H 2 O 2 or K 2 S 2 O 8 ) to the TiO 2 suspensions leads to an increase in the rate of photooxidation. On the contrary, the addition of hydrogen peroxide in ZnO suspensions caused a decrease in the reaction rate. Moreover, illuminated TiO 2 suspensions were proved to be quite effective in mineralizing dichlorvos. Measurements of chlorine and phosphate ions gave valuable information about how this process is achieved. On the other hand, ZnO suspensions could not lead in complete mineralization of the insecticide. Addition of the oxidants enhances mineralization for both photocatalytic systems. Finally, toxicity measurements showed that toxicity increases during treatment independently from the type of catalyst or the oxidant that has been used, indicating the inefficient detoxification capacity of the processes.

Semiconductor-sensitized photodegradation of dichlorvos in water using TiO2 and ZnO as catalysts

The photocatalytic degradation of Reactive Black 5, a textile azo dye, has been investigated in aqueous heterogeneous solutions containing semiconductor oxides as photocatalysts. The disappearance of the organic molecule follows approximately a pseudo-first kinetic order according to the Langmuir-Hinshelwood model. CO 2 , NO 3 - , and SO 4 2- ions have been identified as mineralization products. Various commercial photocatalysts were compared with respect to their decolorization efficiency, as well as the production of CO 2 . The effect of pH and H 2 O 2 on the reaction rate was ascertained.

Ioannis Poulios

Papers

Advanced oxidation processes for water treatment: advances and trends for R & D

New perspectives for Advanced Oxidation Processes.

Photocatalytic decolorization and degradation of dye solutions and wastewaters in the presence of titanium dioxide.

Semiconductor-sensitized photodegradation of dichlorvos in water using TiO2 and ZnO as catalysts

Photodegradation of the textile dye Reactive Black 5 in the presence of semiconducting oxides