Photo Catalytic Degradation Review

1828 words - 8 pages

In Post-industrial era majority of the water bodies (surface water, ground water and river bodies) and industrial water .Most of them are toxic endocrine disrupting, causing genetic defects or causes cancer to humans, animals and aquatic life in general.

There are various ways for the treatment of wastewater, which are categorized as Physical which includes treatment by screening, sedimentation, floatation and filtration of the contaminants present in the water; The chemical method which comprises of precipitation, coagulation, carbon filtering and disinfection. The most widely used technique is a combination of physical and chemical processes which include activated carbon ...view middle of the document...

This review paper gives an summary of the understanding of the mechanism of heterogeneous, homogeneous photocatalysis & various equipment’s used in the process of photocatalysis ie (through photochemical AOP). The paper also analyses the demerits of the aforementioned process and the alternatives used to overcome them.

Chapter 2
Heterogeneous photo catalysis Mechanism
The semiconductor TiO2 has been widely employed as a photocatalyst for inducing a series of reductive and oxidative reactions on its surface. The catalyst acts as if it has got a distinct lone electron characteristic in its outer orbital. The mechanism of this type of photocatalysis can be summarized as below:-

When photon energy (hν) of greater than or equal to the band gap energy of TiO2 is illuminated onto its surface, usually 3.2 eV (λ < 400 nm) the lone electron will be photo excited to the empty conduction band in femtoseconds. The excitation leaves behind an empty unfilled valence band, and thus creating the electron-hole pair.
In the absence of electron scavengers, the photoexcited electron recombines with the valence band hole in nanoseconds with simultaneous dissipation of heat energy.

Thus, the presence of electron scavengers (like dissolved oxygen) is vital for prolonging the recombination and successful functioning of photocatalysis. The electron scavenger like dissolved oxygen gets reduced to superoxide in the conduction band and the pollutant (P) gets consecutively gets oxidized to (P+).
Without the presence of water molecules, the highly reactive hydroxyl radicals (OH.) could not be formed and impede the photodegradation of liquid phase organics. This was evidenced from a few reports that the photocatalysis reaction did not proceed in the absence of water molecules.

The reduced superoxide ion (O2-) and the hydroxyl radical formed after the hydrolyzing of water help in the degradation of the effluent (P+) to convert it into carbon dioxide and water. In case of aromatic pollutant compounds first hydroxylation by electrophilic aromatic substitution mechanism takes place. Further oxidation leads to ring opening which in turn converts itself into carboxylic acids and aldehydes. In certain cases these carboxylic acids undergo decarboxylation reaction to form harmless carbon dioxide and water. It is also worthwhile to note that the amount of successive oxidation of pollutant depends on the time for which reaction takes place as more reaction time leads to more surface activation of semiconductors which in turn forms more radical species which facilitate the degradation of the pollutant.

The physical mechanism of any heterogeneous photocatalytic process follows that of adsorption.
Firstly the mass transfer of the effluent from the bulk phase (liquid) to that of the semiconductors surface takes the second step the pollutant gets adsorbed to the photon activated surface of the semiconductor. Then photocatalytic...

Find Another Essay On photo catalytic degradation review

Chemistry and Tissue Engineering: Synthetic Polymers

1371 words - 6 pages mechanical and degradation properties (Jeanie and David, 2003; Armentano et al., 2010). Among the most extensively used biopolymers for tissue engineering are poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(ε-caprolactone) (PCL), poly(methyl methacrylate) (PMMA) and their copolymers (Shalumon et al., al., 2012; Kreja et al., 2012; Hajiali et al., 2011; Pereira et al., 2012). Polymer Applications References PLA biodegradable surgical suture

The Evolution and Gentic Basis of Human Pigmentation

2445 words - 10 pages mediates melanin synthesis by tyrosinase trafficking and proton transport to melanosomes (Fracasso et. al, 2013). Several studies indicate that the MATP gene plays important roles in the normal pigmentation variations and shows a strong signature of selection in the European populations (Parra, 2007) The rate limiting reactions of melanogenesis depend on the catalytic activity of tyrosinase. The gene which encodes this enzyme is located on chromosome


5925 words - 24 pages Enzymes Enzymes are catalysts. Most are proteins. (A few ribonucleoprotein enzymes have been discovered and, for some of these, the catalytic activity is in the RNA part rather than the protein part. Link to discussion of these ribozymes.) Enzymes bind temporarily to one or more of the reactants of the reaction they

3 tests to identify Escherichia coli

1443 words - 6 pages and molecular biology reviews. 16: 1-29. 2) Krajewska, B. 2009. Ureases I. Functional, catalytic and kinetic properties: A review. Journal of Molecular Catalysis B: Enzymatic. 59: 9-21. 3) Roberts, G.D., C.D. Horstmeier, G.A. Land and J.H. Foxworth. 1978. Rapid urea broth test for yeasts. Journal of Clinical Microbiology. 7: 584-588. 4) Vaughn, R.H., J.T. Osborne, G.T. Wedding and J. Tabachnick. 1950. The utilization of citrate by Escherichia coli. Journal of Bacteriology. 60: 119-127.

Air Pollution

1988 words - 8 pages sulfur dioxide, most oxides of nitrogen, carbon monoxide and un-burnt hydrocarbons are those directly emitted into the atmosphere (Welburn 3). Secondary air pollutants like ozone and photo-activated irritants such as preoxyacetyl nitrate are formed as a consequence of subsequent reactions in the atmosphere involving primary pollutants and other agents such as strong light (Welburn 3). Perhaps the least difficult of these problems are those caused by

The Discovery of CRISPR/Cas System

2895 words - 12 pages systems. In this review, I intend to shed light on historical context, CRISPR as a genome editing tool, highlight the current models for the adaptation, processing and interference stages, discuss the regulation of the CRISPR/Cas systems and finally, give an outlook. Discovery of CRISPR/Cas system Ishino et al in 1987 was the first to report interspaced palindromic repeat sequences, this he did by showing five 29 bp repeats with 32 spacers close

Protein Recognition by Synthetic Receptors

3846 words - 15 pages occurring functionalities and may be susceptible to degradation by cellular activities13. Introduction of α,α-disubstituted aminoacids into the peptide sequence forms a hydrocarbon stapled backbone. Hydrocarbon stapled peptides were found to mimic (BID) BH3 peptide and bind much higher affinity to Mcl-1 than the corresponding unmodified peptide. This pre-organised peptide is

Ethylene Genetics

7685 words - 31 pages known as EILS regulate the expression of another group of genes (EREBPs) that are in turn intimately involved with the regulation of the ethylene-target genes.This review will cast a look back at the major advances that have occurred over the last five years in the elucidation of the ethylene response pathway featuring the three main steps - perception, signalling and response. Arabidopsis thaliana will be especially focused on as most of the

Toward Sustainable organizations for the 21st Century

7912 words - 32 pages . It showed that the unparalleled economic growth of the previous 50 years had'resulted in a substantial and largely irreversible loss in the diversity of life on Earth' and that 'gains in human well-being and economic development … have been achieved at growing costs in the form of the degradation of many ecosystem services … and the exacerbation of poverty for some groups of people. These problems, unless addressed, will


4816 words - 19 pages some corporations to globalize.Globalization - the growing integration of economies and societies around the world Rapid growth and poverty reduction in China, India, and other countries that were poor 20 years ago, has been a positive aspect of globalization. But globalization has also generated significant international opposition over concerns that it has increased inequality and environmental degradation .BusinessCollapse of commodities


6173 words - 25 pages Photovoltaic Power Generation * by Tom Penick and Bill Louk *Photo is from "Industry-Photovoltaic Power Stations1," e/4/4.6/01.html, December 1, 1998. PHOTOVOLTAIC POWER GENERATION Submitted to Gale Greenleaf, Instructor EE 333T Prepared by Thomas Penick and Bill Louk December 4, 1998 ii ABSTRACT This report is an overview of photovoltaic power generation. The purpose of the report is to

Similar Essays

Thermal Characteristics Of Different Plastics Essay

2929 words - 12 pages 700̊C, is it possible to produce gasoline directly from the derived oil without any further processes. Based on the studies of thermal characteristics of various plastic types, the requirement of high temperature for the degradation of plastic into oil and the effect of both temperature and residence time on the yield and more importantly on the composition, catalytic pyrolysis is preferred to enable the production of valuable oil products in

Study Of New Biotinylated Analogue Of Dequalinium For Protein Kinase C??Inhibition And Identification Of The Binding Sites

2027 words - 8 pages PKC in vitro and in cells. C10-DECA consists of two quinolinium moieties linked by a ten-carbon methylene bridge. Previous studies have shown that, PKC activity in vitro can be irreversibly inhibited when treated with 250nM of DECA and irradiated with 366nm of light. DECA directly interacts with catalytic domain of PKCα such that ring moieties bind at two distinct sites in a trans-oid fashion. The identity of these two sites remains unknown

Bio Outline

5257 words - 21 pages Complexes (Not shown in Alberts diagrams) (1) One associated with each PS (2) Designated LHC I and LHC II (3) Collections of pigment molecules imbedded in thylakoid membrane (4) In close physical proximity if not physically attached to PS's (5) Funnel excitation energy to reaction centers via inductive resonance.USE PHOTO REVIEW HANDOUT W/ EXPLANATION BELOW 6. Non-Cyclic electron Photophosphorylation (Figure13-34 = Z Scheme with electron volt

Edc Removal Essay

1532 words - 7 pages ]. BPA enters the human body mainly through food. The next principal mode of its transmission is through water. Wastewater treatment effluents, polycarbonate plastics natural degradation, landfill leachate, Industrial wastewaters are some the ways BPA enter the aquatic system. It was published that BPA concentrations in municipal landfill leachates are as high as 26-8400 µg/dm3 [13]. They are present in the influents as well as in the effluents of the