Chemical warfare agents and treatment strategies

Chemical warfare agents is the substances that have toxic effects on the environment and human. Which cause a large number of deaths and disabilities in a short time.The short term effects of these agents  may be leads to 

long term reflections which can  affect the next generation. During the world war it plays a vital role to destroying anything. Five million deaths were happened  only due to nerve agents. The World War II has used large scale  of the use of chemical agents. Due to these detrimental effects, their usage is restricted or prohibited by various international organizations. Chemical

agents have been used by some countries and terrorist groups. Effects of these agents can take part vary from basic symptoms such as nose irritation to serious problems such as respiratory arrest. Healthcare professionals working in  these agents should have sufficient knowledge and know about precaution methods  and be aware of their effects on the body.

In 1915 Clorine was used by Germany when nearly 10,000

people died and over a million people got injured by chemical agents. Syria also used chemical agents against civilions in  2012. After this the utilization of chemical

weapons  against civilians in Douma city, East Ghouta and Syria was increased. Chemical warfare agents are cheap and toxic compounds which are produced and can be stored easily. They may be utilized as a weapon. Their use is controlled by Organisation for the Prohibition of Chemical Weapons (OPCW) (Geneva) and Chemical Weapons Convention (CWC), some countries and terrorist groups disobey the prohibition. 

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Reference: DOI: 10.5455/annalsmedres.2018.08.166

Photocatalytic water splitting

Photocatalytic water splitting is an artificial photosynthesis process with photocatalysis in a photoelectrochemical cell used for the dissociation of water into hydrogen and oxygen , using artificial, natural light.Hydrogen fuel production has most attention when  the  global warming has grown. Methods such as photocatalytic water splitting are being investigated to produce hydrogen, a clean-burning fuel. Water splitting holds particular promise since it utilizes water, an inexpensive renewable resource.

 Photocatalytic water splitting has the simplicity of using a catalyst and sunlight to produce hydrogen out of water.

When H2O is split into O2 and H2, the ratio of its products is 2:1.

 The process of water-splitting is a highly endothermic process . Water splitting occurs naturally in photosynthesis when the energy of a photon is absorbed and converted into the chemical energy through a complex biological pathway .Theoretically, infrared light has enough energy to split water into hydrogen and oxygen; however, this reaction is very slow because the wavelength is greater than 750 nm. The potential must be less than 3.0 V to make efficient use of the energy present across the full spectrum of sunlight. Water splitting can transfer charges, but not be able to avoid corrosion for long term stability.Due to the transparency of water to visible light, photolysis can only occur with a radiation wavelength of 180 nm or shorter.Materials used in photocatalytic water splitting fulfill the band requirements outlined previously and typically have dopants and/or co-catalysts added to optimize their performance.Most semiconductors with suitable band structures to split water absorb mostly UV light; in order to absorb visible light, it is necessary to narrow the band gap.

Reference: https://en.wikipedia.org/wiki/Photocatalytic_water_splitting#Method_of_evaluation

The sol-gel synthesis and photocatalytic activity of Gd-SiO2-TiO2 photocatalyst

Abstract:

The sol-gel method was used to synthesize Gd-SiO2-TiO2 composite

photocatalysts. The sample showes the optimal photocatalytic activity during the methylene blue (MB) degradation. When the calcination temperature was lower than 550 ºC, Gd-SiO2-TiO2 photocatalyst has an anatase crystal structure. After doping of Si and Gd, the absorption wavelength thresholds of the sample approached 407 nm. Gd-SiO2-TiO2 photocatalyst showed the degradation efficiency about 90% to methylene blue (MB) under irradiation of simulated sunlight.

. Introduction:

Now a days Environmental pollution becomes more and more serious problems . And organic pollution has become a serious problem in water environments. These pollutants could not be removed thoroughly by general physical and
chemical methods. Because of the mild reaction conditions, low cost and avoidance of secondary pollution. The photocatalytic oxidation technology s an important and potential applications in fields of pollutant degradation and decomposition of water to hydrogen.
 The synthesis and photocatalytic activity of TiO2 have been investigated widely. Various techniques were carried out to develop TiO2 with high photocatalytic activity . And some research results indicate that the TiO2/SiO2 mixed oxide has higher activity than pure TiO2 while used as the photocatalyst . The added SiO2
strengthens the thermostability of anatase TiO2, increases its specific area and enhances its photocatalytic activity. 



Reference:

https://www.sciencedirect.com/science/article/abs/pii/S0009261419306578

IR spectroscopy

Infrared Spectroscopy is the analysis of infrared light interacting with a molecule. This can be analyzed in three ways by measuring absorption, emission and reflection. The main use of this technique is in organic and inorganic chemistry. It is used by chemists to determine functional groups in molecules. IR Spectroscopy measures the vibrations of atoms, and based on this it is possible to determine the functional groups.5 Generally, stronger bonds and light atoms will vibrate at a high stretching frequency (wavenumber).
Topic hierarchy

How an FTIR Spectrometer Operates
FTIR spectrometers (Fourier Transform Infrared Spectrometer) are widely used in organic synthesis, polymer science, petrochemical engineering, pharmaceutical industry and food analysis. In addition, since FTIR spectrometers can be hyphenated to chromatography, the mechanism of chemical reactions and the detection of unstable substances can be investigated with such instruments.
Identifying the Presence of Particular Groups
This page explains how to use an infra-red spectrum to identify the presence of a few simple bonds in organic compounds.

Infrared: Application
Infrared spectroscopy, an analytical technique that takes advantage of the vibrational transitions of a molecule, has been of great significance to scientific researchers in many fields such as protein characterization, nanoscale semiconductor analysis and space exploration.

Infrared: Interpretation
Infrared spectroscopy is the study of the interaction of infrared light with matter. The fundamental measurement obtained in infrared spectroscopy is an infrared spectrum, which is a plot of measured infrared intensity versus wavelength (or frequency) of light.

Infrared: Theory
Infrared (IR) spectroscopy is one of the most common and widely used spectroscopic techniques employed mainly by inorganic and organic chemists due to its usefulness in determining structures of compounds and identifying them. Chemical compounds have different chemical properties due to the presence of different functional groups.

Interpreting Infrared Spectra
 The wavelengths found in infrared radiation are a little longer than those found in visible light. IR spectroscopy is useful for finding out what kinds of bonds are present in a molecule, and knowing what kinds of bonds are present is a good start towards knowing what the structure could be.

Gibb's Phase Rule

The Phase Rule describes the possible number of degrees of freedom in a (closed) system at equilibrium, in terms of the number of separate phases and the number of chemical constituents in the system. It was deduced from thermodynamic principles by J. W. Gibbs in the 1870s.
The Degrees of Freedom [F] is the number of independent intensive variables (i.e. those that are independent of the quantity of material present) that need to be specified in value to fully determine the state of the system. Typical such variables might be temperature, pressure, or concentration.
A Phase is a component part of the system that is immiscible with the other parts (e.g. solid, liquid, or gas); a phase may of course contain several chemical constituents, which may or may not be shared with other phases. The number of phases is represented in the relation by P.
The Chemical Constituents are simply the distinct compounds (or elements) involved in the equations of the system. (If some of the system constituents remain in equilibrium with each other whatever the state of the system, they should be counted as a single constituent.) The number of these is represented as C.
The rule is:
F = C - P + 2.


Reference 
http://kj-gibbs.uio.no/phase_rule.html

Corrosion and Its Prevention

The loss of material(metals or alloys) or its useful properties by chemical interaction with its environment is known as corrosion. Corrosion is an electrochemical process. Corrosion leads to a tremendous loss. Corrosion is the reverse of metal extraction.

Examples:

 Rusting of iron. 
Blackening of silver articles in atmosphere.
 Fogging of nickel.

Causes of corrosion

Most metals exist in nature in combined forms that is in the form of ore. So extraction of metal from its ores is an unnatural process in which component of a stable system is being separated. Ore extraction Metal corrosion corrosion product Stable gain es mteta stable loss of es stable During the process of extraction a number of steps like concentration, Roasting ,and Smelting are involved and finally the ore is reduced into metal. therefore metals in their finally refined state are highly unstable and have a tendency to revert back in their original state that is to stable state by the process of corrosion(oxidation).

Rusting of iron is the most popular example of corrosion.

Usually the Surface of metal is covered with a thin layer of oxide. When this layer is broken, bare surface is exposed to the environment and this area act as an anode while the remaining area act as cathode. since the medium is exposed to the atmosphere, it contain dissolved oxygen.

Types of corrosion

 Uniform corrosion:

This is also called general corrosion. The surface effect produced by most direct chemical attacks (e.g., as by an acid) is a uniform etching of the metal.

Galvanic Corrosion :
Galvanic corrosion is an electrochemical action of two dissimilar metals in the presence of an electrolyte and an electron conductive path. It occurs when dissimilar metals are in contact.

 Crevice or contact corrosion:

Crevice or contact corrosion is the corrosion produced at the region of contact of metals with metals or metals with nonmetals. It may occur at washers, under barnacles, under applied protective films.

Corrosion in Concrete Concrete is a widely-used structural material that is frequently reinforced with carbon steel reinforcing rods, post-tensioning cable or pre-stressing wires. The steel is necessary to maintain the strength of the structure, but it is subject to corrosion.

 Erosion corrosion :
Erosion corrosion is the result of a combination of an aggressive chemical environment and high fluid-surface velocities.

 Dealloying Dealloying is a rare form of corrosion found in copper alloys, gray cast iron, and some other alloys. Dealloying occurs when the alloy loses the active component of the metal and retains the more corrosion resistant component in a porous "sponge" on the metal surface.

Factors affecting corrosion

1. Presence of impurities in metals Speed of corrosion increases with the presence of impurities in the metals because these impurities help in setting up the voltaic cells.

 2. Presence of electrolyte Electrolytes present in water also increases the rate of corrosion e.g. corrosion of iron in sea water takes place in large extent than in distilled water because sea water contains salts i.e.electrolytes.

Position of metals in electrochemical series

Highly reactive metals undergo corrosion faster than least reactive metals. Reactivity of metals can be found from the electrochemical series. e.g.Au Cu Pb Fe Zn Al Mg Na K Reactivity increases 4. Presence of carbon dioxide in water Presence of carbon dioxide in natural water also increases the rusting of iron because it acts as an electrolyte and increases the flow of electron from one place to another.

 Presence of protective coating

When the iron surface is coated with the metal, which is more reactive than the iron, then the rate of corrosion is retarded e.g. when iron is coated with zinc, iron is protected from rusting.

PREVENTION OF CORROSION

Corrosion is slow but continuously eating away the metal and consequence of rusting. Rusting can be avoided by not letting moist air come in contact with the metal surface .Following methods could gain fully be adopted to minimize rusting and corrosion

 Methods of preventing corrosion and rusting

Tarring

 Painting

Enameling

 Galvanizing

 Sheradising

 Tin plating

 electroplating

 Tarring: metal is dipped in hot coal tar so that a film of it is sticks to the surface which protect the surface from rusting and corrosion. Pipes or ends of poles to be embedded in the earth are usually given this protective treatment.

 Painting: Paints usually the lead paints are applied on the surface to be protected. Exposed metal surfaces as in case of roof and bridge structure are given this treatment which has to be repeated after regular interval of time.

Enameling: Enamels consist of high grade bases like zinc oxide or lead oxide ground in oil or varnish. they dry slowly leaving a hard tough and elastic film which is smooth and durable.Enamle painted surfaces are washable and are not affected by acids,alkali,gases or steam. Even tough they are more costly than ordinary paints yet because of their durability. They are equally good for use both on external and internal work.

Galvanizing: Depositing a fine film of zinc on the iron/steel surfaces is termed as galvanizing. The surfaces to be galvanizing is first cleared of all foreign matter by giving it an acid wash to be followed by a wash of clean water. the surface is then dried and dipped in molten zinc.The fine film of zinc that get deposited protect the surface from contact with atmosphere and consequence oxidation. Removal of the zinc film caused by scratches.

Sheradising: Surface to be treated is cleaned of all foreign deposits by washing it with acid solution and then with clean water. It is then dried and covered with zinc dust and enclosed in steel boxes to be heated in a furnace under controlled temperatures. Molten zinc spreads over the whole surface and on cooling forms a thin protective layer. Sherading gives better protection than galvanizing.

Tin plating: After cleaning the surface with acid wash followed by wash with clean water and drying, it is dipped in a bath of molten tin. A protective covering of tin layer if left on the surface.

Electroplating: By the process of electrolysis a thin film of nickel,cromium,copper or zinc is deposited on the surface to be protected. The surface to be protected is made the cathode and the metal to be deposited is made the anode.

 https://slideplayer.com/slide/5705698/

TiO2 photocatalysis: Design and applications

 Abstract:

 

TiO2 photocatalysis is widely used in a variety of applications in the environmental and energy fields, self-cleaning surfaces, air and water purification systems, sterilization, hydrogen evolution etc.,.

 The dimensionality associated with the structure of a TiO2 material can affect its properties and functions, including its photocatalytic performance, and also more specifically its surface area, adsorption, reflectance, adhesion, and carrier transportation properties. TiO2 photocatalysts can be classified into zero-, one-, two-, and three-dimensional structures.

Introduction:

                  Photocatalysis is focusing area in recent years. Photocatalysis currently used in a various products across a wide range of research areas, such as  environmental and energy fields. The photocatalytic properties of certain materials have been used to convert solar energy into chemical energy to oxidize or reduce materials to obtain useful materials including hydrogen and hydrocarbons, and to remove pollutants and bacteria.

TiO2 has been the most widely studied and used in many applications because of its strong oxidizing abilities for the decomposition of organic pollutants, superhydrophilicity (A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water), chemical stability, long durability, non toxicity, low cost, and transparency to visible light. The photocatalytic properties of TiO2 are derived from the formation of photogenerated charge carriers (hole and electron) which occurs upon the absorption of UV light corresponding to the band gap. The photogenerated holes in the valence band diffuse to the TiO2 surface andreact with adsorbed water molecules, forming hydroxyl radicals (•OH). The photogenerated holes and the hydroxyl radicals oxidize nearby organic molecules on the TiO2 surface. Meanwhile, electrons in the conduction band typically participate in reduction processes, which are typically react with molecular oxygen in the air to produce superoxide radical anions((a radical is an atom, molecule, or ion that has an unpaired valence electron.With some exceptions, these unpaired electrons make radicals highly chemically reactive).


 TiO2 surfaces become superhydrophilic with a contact angle of less than 5◦ under UV-light irradiation.The majority of the holes are subsequently consumed by reacting directly with adsorbed organic species or adsorbed water, producing •OH radicals .a small proportion of the holes is trapped at lattice oxygen sites and may react with TiO2 itself, which weakens the bonds between the lattice titanium and oxygen ions.The construction of TiO2 nano- or micro-structures with interesting morphologies and properties has recently attracted considerable attention. Many TiO2 nanostructural materials, such as spheres, nanorods, fibers, tubes, sheets, and interconnected architectures, have been fabricated. Nanostructured TiO2 materials are widely used not only in photocatalysis, but also in dye-sensitized solar cells, lithium-ion batteries.It is well known that there are many factors which can exert significant influence on photocatalytic performance, including the size, specific surface area etc..,. the development of performance improvements by adjusting these factors remains the focus of photocatalysis research. Structural dimensionality is also a factor which can affect the photocatalytic performance and also has a significant impact on the properties of TiO2 materials. For example, a sphere with zero dimensionality has a high specific surface area, resulting in a higher rate of photocatalytic decomposition of organic pollutants.



 Reference :
https://www.sciencedirect.com/science/article/pii/S1389556712000421