PHOTOCATALYSIS AS A VIABLE MEANS OF DEGRADING AZO DYES

The presence of synthetic chemicals and man-made activities has constituted a major source of water and land pollution, the contamination of biosphere have become a great concern to environmentalist, scientists, and the whole humanity. These pollutants are destroying the aesthetic value of the environment and causing the earth to be unfit or inhabitable to man. 

As an effort to remediates the environment from the adverse effects of the pollutants several techniques has been employed in order to get reed of the pollutant in the environment such techniques include filtrations, adsorption and advance oxidation process. One of the appealing facts is that the effort to remediates the environment and promotes sustainable development has yielded positive results.

It is a known fact that most of this pollutant cannot be easily broken down into smaller nontoxic molecules by ordinary measures, in another word they are non-biodegradables. The quest for a robust and a viable method to convert the pollutant into a benign form has been ongoing for several decades. In this article, our major focus is channeled towards the adoption of photocatalysis as a method of degradation of organic waste (effluent). Azo dyes are the probe molecules that our recent research work aims to convert into an innocuous molecule.

Dye pollutant produced from textile industries are becoming a major source of environmental contamination. Among the various dyes used in the textile industries, 60-70% are azo compounds, these dyes are made up of N=N unit in their molecular structure and are dissolved in water during the dyeing process. These soluble dyes are carcinogenic (cancer agents) in humans. Various methods of degradation convert these dyes from one phase to another. One of the methods employed by modern scientists for the degradation of these dyes is known as advanced oxidation methods.

The term photocatalysis can be generally used to describe a process in which light is used to activate a substance which is further broken down into simpler constituent. A catalyst is a chemical substance that speeds up the rate of a chemical reaction without taking part in the reaction. The word photo simply means “light”, therefore photocatalysis is a catalyst that is active under the effect of light. Photocatalysis works under the principle of photochemistry which is a branch of chemistry that is concerned with the chemical effect of light. it is generally used to describe a chemical reaction caused by the action of ultraviolet, visible or infra-red radiation. Photoexcitation is the first step in a photochemical process where the reactant is elevated to a state of the higher energy i.e. excited state. Light must be absorbed by a chemical substance in other for a chemical reaction to take place

One of the most effective photocatalysts that have gained a wider usage in recent times is titanium dioxide (TiO2). The principle of a photocatalytic reaction is straightforward, the photocatalyst (TiO2) uses a photon (light) to excite an electron from the valence band (ground state) to the conduction band resulting in an excited state and creation an electron-hole pair. These electrons and positive holes drive reduction (electron gain) and oxidation (electron loss) of the compounds absorbed on the surface of the photocatalyst. 

The research conducted in our laboratory in late 2016 using titanium dioxide doped silver nanoparticles prepared using micro emulation methods indicated that 1%Ag-TiO2 converts about 60% of the azo dye into water, ammonia and carbon dioxide. Our observation shows that photocatalysis is very effective in converting organic pollutant into environmental friendly molecules. 

In a nutshell, the process of photocatalysis is employed for the degradation of azo dyes because the dyes are oxidized and reduced into simpler and harmless substance. Other application of photocatalysis includes water purification, surface cleansing, anti-microbial activity and other environmental remediation which involves gas phase reactions.

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The ability to harnessed the potential power of nature like sunlight and atmospheric oxygen for the remediation of the environment and the generation of renewable energy has given birth to the technology of photocatalysis and photo reforming crude glycerol from lignocellulosic agricultural waste.
Photocatalysis is a complex word containing two roots word “Photo” is something relating to or produced by light, and “catalysis” means the process of making a chemical reaction happen more quickly by using a catalyst. The process involves the use of electromagnetic wave (light) in the presence of semiconductor materials to mineralize organic pollutant in the environment into harmless simple molecules like ammonia and water. Meanwhile, photo reforming uses a similar technique but it involves the conversion of glycerol to hydrogen.

Normally, in any scientific process entails challenges and shortcoming which need to be overcome to make it a viable process. This is what science without border is all about.