The melting point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium; the melting point of a substance depends on pressure and is specified at a standard pressure such as 1 atmosphere or 100 kPa. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point; because of the ability of some substances to supercool, the freezing point is not considered as a characteristic property of a substance. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is always "the principle of observing the disappearance rather than the formation of ice", that is, the melting point. For most substances and freezing points are equal. For example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures.
For example, agar melts at 85 °C and solidifies from 31 °C. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances, the freezing point of water is not always the same as the melting point. In the absence of nucleators water can exist as a supercooled liquid down to −48.3 °C before freezing. The chemical element with the highest melting point is tungsten, at 3,414 °C; the often-cited carbon does not melt at ambient pressure but sublimes at about 3,726.85 °C. Tantalum hafnium carbide is a refractory compound with a high melting point of 4215 K. At the other end of the scale, helium does not freeze at all at normal pressure at temperatures arbitrarily close to absolute zero. Many laboratory techniques exist for the determination of melting points. A Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip, revealing its thermal behaviour at the temperature at that point. Differential scanning calorimetry gives information on melting point together with its enthalpy of fusion.
A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window and a simple magnifier. The several grains of a solid are placed in a thin glass tube and immersed in the oil bath; the oil bath is heated and with the aid of the magnifier melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, optical detection is automated; the measurement can be made continuously with an operating process. For instance, oil refineries measure the freeze point of diesel fuel online, meaning that the sample is taken from the process and measured automatically; this allows for more frequent measurements as the sample does not have to be manually collected and taken to a remote laboratory. For refractory materials the high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees.
The spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source, calibrated as a function of temperature. In this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer. For temperatures above the calibration range of the source, an extrapolation technique must be employed; this extrapolation is accomplished by using Planck's law of radiation. The constants in this equation are not known with sufficient accuracy, causing errors in the extrapolation to become larger at higher temperatures. However, standard techniques have been developed to perform this extrapolation. Consider the case of using gold as the source. In this technique, the current through the filament of the pyrometer is adjusted until the light intensity of the filament matches that of a black-body at the melting point of gold.
This establishes the primary calibration temperature and can be expressed in terms of current through the pyrometer lamp. With the same current setting, the pyrometer is sighted on another black-body at a higher temperature. An absorbing medium of known transmission is inserted between this black-body; the temperature of the black-body is adjusted until a match exists between its intensity and that of the pyrometer filament. The true higher temperature of the black-body is determined from Planck's Law; the absorbing medium is removed and the current through the filament is adjusted to match the filament intensity to that of the black-body. This establishes a second calibration point for the pyrometer; this step is repeated to carry the calibration to hi
The codling moth is a member of the Lepidopteran family Tortricidae. They are major pests to agricultural crops fruits such as apples and pears; because the larvae are not able to feed on leaves, they are dependent on fruits as a food source and thus have a significant impact on crops. The caterpillars stop it from growing, which leads to premature ripening. Various means of control, including chemical and preventative, have been implemented; this moth has a widespread distribution, being found on six continents. Adaptive behavior such as diapause and multiple generations per breeding season have allowed this moth to persist during years of bad climatic conditions. Although the geographic origin of codling moths is unclear, there are theories of these moths originating from either Europe or the Mediterranean. Scholars believe. There is still debate on. Today, the codling moths are spread all over the world, ranging from Europe, Africa and South America and islands in the Pacific. Viability and fitness of the codling moths are dependent on humidity levels and climate.
Under observation, the optimal conditions for moth growth and survival were 75 % humidity. If the temperature is favorable and high levels of relative humidity led to hindrance in pupation. At a temperature below 0 °C, the larvae become inactive and turn lifeless. However, researchers observed that if the temperature is returned to optimal levels, the larvae regained normal activity. Codling moths have been located at altitudes as high as 1000-1500m; because the codling moth is polyphagous, or able to utilize a variety of food sources, the availability of specific food resources does not determine their optimal habitat. Various stages of the moth's life history, from eggs to pupae, can be found on host plants which the larvae feed on; these plants include apple, walnut and apricot trees. Codling moths are not large, as the full grown adult codling moth has an average length of 10mm and wingspan of 20mm; the wings fold into a tent-like shape. They are distinguished from other similar moths in the family Tortricidae by the distinctive patterns on their fore-wings.
These brown spots enclosed in gold rings are called “little mirrors” because they resemble small mirrors with a golden rim. The slender antennae are mildly curved near the distal end; the dorsal side of the abdomen is bare, while the ventral side is covered in scales. Though most of the moths are brown or gray in color, it has been observed that the maturity of the fruits the larvae feed on can lead to variation in color in the adult moth; the codling moth caterpillars bore into a fruit within 24 hours of hatching from their eggs traveling between 1.5m to 3m in search of a fruit. Because they are susceptible to predation, drying up, or being washed away between the period of hatching and boring into a fruit, the caterpillars are prompt in finding a fruit to feed on. Although apples are their dominant food source, they are polyphagous, feeding on a wide variety of fruits from pear, apricot, plums and chestnuts, they are unable to survive by feeding on leaves of the fruit trees. It was believed that the searching behavior of the caterpillar for fruit to feed on or for a pupation site was random.
However, the caterpillar is exposed and susceptible to predation, drying up, energy depletion during this searching period. Thus, it was hypothesized that the searching behavior uses thigmotatic sense, which means the caterpillars use contact reflex to search. Caterpillars use phototaxis to locate fruits to feed on, they are photopositive. This is adaptive because fruits tend to be located at the ends of the branches where there is most sunlight. Therefore, by following light, the larvae are able to move closer to fruits. Once the caterpillar has located a fruit to feed on, it starts penetrating the epidermis of the fruit; as the caterpillar makes way into the fruit, scraps of the skin and frass build up near the entrance of the hole. These pieces are glued together by silk threads released from the caterpillar to create a cap; this cap protects the caterpillar by blocking the entrance. It takes the caterpillar 45 minutes to bore into the fruit and about 15 minutes to cap; the caterpillar bores through the fruit.
There, the caterpillar bites into the halts the growth of the fruit. The fruit ripens prematurely as a result. By doing so, the caterpillar gains beneficial resources, such as fat; such feeding behavior lasts for 23 to 27 days and the caterpillar feeds on an average of one to two fruits during this time. Fruits attacked by the codling moth caterpillars have developed methods of resisting the caterpillars. Methods of resistance include thickening of the epidermis of the fruit and using stony cells to protect the seed. Fuzziness of the fruit has been observed to deter codling moth caterpillars. Stony cells, which are present in some pears, have shown to help in resisting codling moth caterpillars. Stony cells are found in the endocarp of fruits such as walnuts; the endocarp is the innermost layer of a fruit's pericarp. In pears, stone cells are found in groups of cells found in the fruit pulp; these cells are found reaching up to 10 µm. At maturity, these cells are composed out of 30% cellulose, 30% glucuronoxylans, 40% lignins, which are biopolymers that are commonly
Simplified molecular-input line-entry system
The simplified molecular-input line-entry system is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules; the original SMILES specification was initiated in the 1980s. It has since been extended. In 2007, an open standard called. Other linear notations include the Wiswesser line notation, ROSDAL, SYBYL Line Notation; the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo and Albert Leo and Corwin Hansch for supporting the work, Arthur Weininger and Jeremy Scofield for assistance in programming the system." The Environmental Protection Agency funded the initial project to develop SMILES. It has since been modified and extended by others, most notably by Daylight Chemical Information Systems.
In 2007, an open standard called "OpenSMILES" was developed by the Blue Obelisk open-source chemistry community. Other'linear' notations include the Wiswesser Line Notation, ROSDAL and SLN. In July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is considered to have the advantage of being more human-readable than InChI; the term SMILES refers to a line notation for encoding molecular structures and specific instances should be called SMILES strings. However, the term SMILES is commonly used to refer to both a single SMILES string and a number of SMILES strings; the terms "canonical" and "isomeric" can lead to some confusion when applied to SMILES. The terms are not mutually exclusive. A number of valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol. Algorithms have been developed to generate the same SMILES string for a given molecule; this SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, is termed the canonical SMILES.
These algorithms first convert the SMILES to an internal representation of the molecular structure. Various algorithms for generating canonical SMILES have been developed and include those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, the Chemistry Development Kit. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database; the original paper that described the CANGEN algorithm claimed to generate unique SMILES strings for graphs representing molecules, but the algorithm fails for a number of simple cases and cannot be considered a correct method for representing a graph canonically. There is no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, double bond geometry; these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES.
A notable feature of these rules is. The term isomeric SMILES is applied to SMILES in which isotopes are specified. In terms of a graph-based computational procedure, SMILES is a string obtained by printing the symbol nodes encountered in a depth-first tree traversal of a chemical graph; the chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree. Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes. Parentheses are used to indicate points of branching on the tree; the resultant SMILES form depends on the choices: of the bonds chosen to break cycles, of the starting atom used for the depth-first traversal, of the order in which branches are listed when encountered. Atoms are represented by the standard abbreviation of the chemical elements, in square brackets, such as for gold. Brackets may be omitted in the common case of atoms which: are in the "organic subset" of B, C, N, O, P, S, F, Cl, Br, or I, have no formal charge, have the number of hydrogens attached implied by the SMILES valence model, are the normal isotopes, are not chiral centers.
All other elements must be enclosed in brackets, have charges and hydrogens shown explicitly. For instance, the SMILES for water may be written as either O or. Hydrogen may be written as a separate atom; when brackets are used, the symbol H is added if the atom in brackets is bonded to one or more hydrogen, followed by the number of hydrogen atoms if greater than 1 by the sign + for a positive charge or by - for a negative charge. For example, for ammonium. If there is more than one charge, it is written as digit.
Mangosteen known as the purple mangosteen, is a tropical evergreen tree believed to have originated in the Sunda Islands of the Malay archipelago and the Moluccas of Indonesia. It grows in Southeast Asia, southwest India and other tropical areas such as Colombia, Puerto Rico and Florida, where the tree has been introduced; the tree grows from 6 to 25 m tall. The fruit of the mangosteen is sweet and tangy, somewhat fibrous, with fluid-filled vesicles, with an inedible, deep reddish-purple colored rind when ripe. In each fruit, the fragrant edible flesh that surrounds each seed is botanically endocarp, i.e. the inner layer of the ovary. Seeds are almond-shaped and -sized. Mangosteen belongs to the same genus as the other, less known, such as the button mangosteen or the charichuelo. Mangosteen is a native plant to Southeast Asia. Valued for its juicy, delicate texture and sweet and sour flavour, the mangosteen has been cultivated in Malaysia, Sumatra, Mainland Southeast Asia, the Philippines since ancient times.
The 15th-century Chinese record Yingya Shenglan described mangosteen as mang-chi-shih, a native plant of Southeast Asia of white flesh with delectable sweet and sour taste. A description of mangosteen was included in the Species Plantarum by Linnaeus in 1753; the mangosteen was introduced into English greenhouses in 1855. Subsequently its culture was introduced into the Western Hemisphere, where it became established in West Indies islands Jamaica, it was established on the Americas mainland in Guatemala, Honduras and Ecuador. The mangosteen tree does not grow well outside the tropics. There is a legend about Queen Victoria offering a reward of 100 pounds sterling to anyone who could deliver to her the fresh fruit. Although this legend can be traced to a 1930 publication by the fruit explorer, David Fairchild, it is not substantiated by any known historical document, yet is responsible for the uncommon designation of mangosteen as the "Queen of Fruit"; the journalist and gourmet R. W. Apple, Jr. once said of the fruit, "No other fruit, for me, is so thrillingly, intoxicatingly luscious...
I'd rather eat one than a hot fudge sundae, which for a big Ohio boy is saying a lot." Since 2006, private small-volume orders for fruits grown in Puerto Rico were sold to American specialty food stores and gourmet restaurants who serve the flesh segments as a delicacy dessert. Mangosteen is propagated by seedlings. Vegetative propagation is difficult and seedlings are more robust and reach fruiting earlier than vegetative propagated plants. Mangosteen produces a recalcitrant seed, not a true seed defined, but rather described as a nucellar asexual embryo; as seed formation involves no sexual fertilization, the seedling is genetically identical to the mother plant. If allowed to dry, a seed dies but if soaked, seed germination takes between 14 and 21 days when the plant can be kept in a nursery for about 2 years growing in a small pot; when the trees are 25–30 cm, they are transplanted to the field at a spacing of 20–40 m. After planting, the field is mulched in order to control weeds. Transplanting takes place in the rainy season because young trees are to be damaged by drought.
Because young trees need shade, intercropping with banana, rambutan, durian or coconut leaves is effective. Coconut palms are used in areas with a long dry season, as palms provide shade for mature mangosteen trees. Another advantage of intercropping in mangosteen cultivation is the suppression of weeds; the growth of the trees is retarded if the temperature is below 20 °C. The ideal temperature range for growing and producing fruits is 25–35 °C with a relative humidity over 80%; the maximal temperature is 38–40 °C, with both leaves and fruit being susceptible to scorching and sunburn, while the minimum temperature is 3–5 °C. Young seedlings prefer a high level of shade and mature trees are shade-tolerant. Mangosteen trees have a weak root system and prefer deep, well drained soils with high moisture content growing on riverbanks; the mangosteen is not adapted to limestone soils, alluvial soils or sandy soils with low organic matter content. Mangosteen trees need a 3 -- 5 week dry season. Mangosteen trees are sensitive to water availability and application of fertilizer input, increased with the age of trees, regardless of region.
Maturation of mangosteen fruits takes 5–6 months, with harvest occurring when the pericarps are purple. In breeding of perennial mangosteen, selection of rootstock and grafting are significant issues to overcome constraints to production, harvesting or seasonality. Most of the genetic resources for breeding are in germplasm collections, whereas some wild species are cultivated in Malaysia and the Philippines. Conservation methods are chosen because storage of seeds under dried and low temperature conditions has not been successful; because of the long duration until the trees yield fruits and the long resulting breeding cycles, mangosteen breeding has not proven attractive for transplanting or research. Breeding objectives that may enhance mangosteen production include: Drought tolerance sensitivity to drought in the first 5 years after germination Tree architecture to produce a tree with a crown, regular and pyramid-shaped Fruit quality including i) overcoming bitter taste components caused by changes in pulp, pericarp or aril and ii) pericarp cracking resulting from excessive water uptake Rootstock for improved ad
A larvicide is an insecticide, targeted against the larval life stage of an insect. Their most common use is against mosquitoes. Larvicides may be stomach poisons, growth regulators, or biological control agents; the biological control agent Bacillus thuringiensis known as Bt, is a bacterial disease specific to Lepidopteran caterpillars. Bacillus thuringiensis israelensis known as Bti, Bacillus sphaericus, which affect larval mosquitoes and some midges, have come into increasing use in recent times. Bti and B. sphaericus are both occurring soil bacterium registered as larvicides under the names Bacticide, Teknar, LarvX, VectoLex CG. In granular form, pellets are distributed on the surface of stagnant water locations; when the mosquito larvae ingest the bacteria, crystallized toxins are produced that destroy the digestive tract, resulting in death. These larvicides will last only a few weeks in water and pose no danger to humans, non-targeted animal species, or the environment when used according to directions.
Methoprene is an insect growth regulator agent that interrupts the growth cycle of insect larvae, preventing them from development beyond the pupa stage. MetaLarv and Altosid are products containing S-methoprene as the active ingredient, they are applied to larger bodies of water in the form of time-release formulations that can last from one to five months. Use of this larvicide does not pose an unreasonable health risks to humans or other wildlife and it will not leach into the ground water supply. Methoprene is moderately toxic to some fish, shrimp and crayfish, toxic to some fish and freshwater invertebrates. Temephos, marketed as Abate and ProVect, is an organophosphate which prevents mosquito larvae from developing resistance to bacterial larvicides. Due to the small amount needed and the fast rate that temephos breaks down in water, this type of larvicide does not pose an unreasonable health risk to humans, but at large doses it can cause nausea or dizziness. There is not a large risk to terrestrial species, but there is a toxic concern for non-targeted aquatic species.
Therefore, temephos should be limited only to sites where less hazardous larvicides are ineffective and with intervals between applications. Sound energy transmitted into water at specific frequencies cause larvae air bladders to rupture damaging internal tissues causing death or latent effects prohibiting further maturity. Larviciding techniques can include the addition of surface films to standing water to suffocate mosquito larvae, or the genetic modification of plants so that they produce a larvicide in plant tissues. Research on botanical oils has found neem oil to be larvicidal. Larvicidal activity of neem oil formulation against mosquitoes. Median lethal concentration of the formulation against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti was found to be 1.6, 1.8 and 1.7 ppm respectively. The formulation showed 95.1% and,99.7% reduction of Aedes larvae on day 1 and day 2 respectively. Index of pesticide articles EPA explanations of various larvicides
Garcinia is a genus of flowering plants in the family Clusiaceae native to Asia, Australia and southern Africa, Polynesia. The number of species is disputed, with various sources recognizing between 50 and about 400; the plants in this genus are called saptrees, garcinias, or monkey fruit. Many species are threatened by habitat destruction, at least one species, G. cadelliana, from South Andaman Island, is or completely extinct already. The fruits are a food source for several animals, such as the archduke butterflies of tropical eastern Asia which relish the sap of overripe mangosteens. Garcinia species are evergreen dioecious and in several cases apomictic; the fruit is a berry with fleshy endocarp. The fruit of most species of Garcinia are eaten locally; the best-known species is Garcinia mangostana, now cultivated throughout Southeast Asia and other tropical countries, having become established in the late 20th century. Less well-known, but still of international importance, are kandis with small round red fruits with subacid taste and melting flesh, the lemon drop mangosteen with yellow fruit that look like a wrinkled lemon, the thin-skinned orange button mangosteen.
In addition, mangosteen rind extract is used as a spice. It figures prominently in Kodava culture, G. multiflora is used to flavour and colour the famous bún riêu soup of Vietnam, where this plant is known as hạt điều màu. Garcinia gummi-gutta yields a spice used in South Asia, in particular in Kerala, where it is called kodumpulli. Most species in Garcinia are known for their gum resin, brownish-yellow from xanthonoids such as mangostin, used as purgative or cathartic, but most – at least in former times – as a pigment; the colour term gamboge refers to this pigment. Extracts of the exocarp of certain species – G. gummi-gutta, but G. mangostana – are contained in appetite suppressants, but their effectiveness at normal consumption levels is unproven, while at least one case of severe acidosis caused by long-term consumption of such products has been documented. Furthermore, they may contain significant amounts of hydroxycitric acid, somewhat toxic and might destroy the testicles after prolonged use.
Bitter kola seeds are used in folk medicine. G. mannii is popular as a chew stick in western Africa, freshening the breath and cleaning the teeth. G. subelliptica, called fukugi in Japanese, is the floral emblem of Tarama on Okinawa. The Malaysian town of Beruas – spelled "Bruas" – derives its name from the seashore mangosteen, known locally as pokok bruas; as of December 2018, Kew's Plants of the World Online lists nearly 400 accepted species. Selected species include
In chemistry, photocatalysis is the acceleration of a photoreaction in the presence of a catalyst. In catalysed photolysis, light is absorbed by an adsorbed substrate. In photogenerated catalysis, the photocatalytic activity depends on the ability of the catalyst to create electron–hole pairs, which generate free radicals able to undergo secondary reactions, its practical application was made possible by the discovery of water electrolysis by means of titanium dioxide. The earliest mention of photocatalysis dates back to 1911, when German chemist Dr. Alexander Eibner integrated the concept in his research of the illumination of zinc oxide on the bleaching of the dark blue pigment, Prussian blue. Around this time and Kozak published an article discussing the deterioration of oxalic acid in the presence of uranyl salts under illumination, while in 1913, Landau published an article explaining the phenomenon of photocatalysis, their contributions led to the development of actinometric measurements, measurements that provide the basis of determining photon flux in photochemical reactions.
After a brief stint of lack of research on photocatalysis, in 1921, Baly et. al used ferric hydroxides and colloidal uranium salts as catalysts for the creation of formaldehyde under light in the visible spectrum. However, it wasn’t until 1938, when Doodeve and Kitchener discovered that TiO2, a highly-stable and non-toxic oxide, in the presence of oxygen, could act as a photosensitizer for bleaching dyes, as ultraviolet light absorbed by TiO2 led to the production of active oxygen species on its surface, resulting in the blotching of organic chemicals via photooxidation; this would mark the first observation of the fundamental characteristics of heterogeneous photocatalysis. Research in photocatalysis subsided for over 25 years due to lack of interest and absence of practical applications. However, in 1964, V. N. Filimonov investigated isopropanol photooxidation from ZnO and TiO2. A few years in 1970, Formenti et. al and Tanaka and Blyholde observed the oxidation of various alkenes and the photocatalytic decay of nitrous oxide, respectively.
However, a breakthrough in photocatalysis research occurred in 1972, when Akira Fujishima and Kenichi Honda discovered electrochemical photolysis of water occurring between connected TiO2 and platinum electrodes, in which ultraviolet light was absorbed by the former electrode, electrons would flow from the platinum electrode to the TiO2 electrode. This was one of the first instances in which hydrogen production could come from a clean and cost-effective source, as the majority of hydrogen production back – and still today – came/comes from natural gas reforming and gasification. Fujishima’s and Honda’s findings have lead to other advancements in photocatalysis. Future research conducted by Wagner and Somorjai and Sakata and Kawai delineated the production of hydrogen on the surface of strontium titanate via photogeneration, the generation of hydrogen and methane from the illumination of TiO2 and PtO2 in ethanol, respectively. Research and development in photocatalysis in electrochemical photolysis of water, continues today, but so far, nothing has been developed for commercial purposes.
In 2017, Chu et al. assessed the future of electrochemical photolysis of water, discussing its major challenge of developing a cost-effective, energy-efficient photoelectrochemical tandem cell, which would, “mimic natural photosynthesis.” In homogeneous photocatalysis, the reactants and the photocatalysts exist in the same phase. The most used homogeneous photocatalysts include ozone and photo-Fenton systems; the reactive species is the •OH, used for different purposes. The mechanism of hydroxyl radical production by ozone can follow two paths. O3 + hν → O2 + O O + H2O → •OH + •OH O + H2O → H2O2 H2O2 + hν → •OH + •OHSimilarly, the Fenton system produces hydroxyl radicals by the following mechanism Fe2+ + H2O2→ HO• + Fe3+ + OH− Fe3+ + H2O2→ Fe2+ + HO•2 + H+ Fe2+ + HO• → Fe3+ + OH−In photo-Fenton type processes, additional sources of OH radicals should be considered: through photolysis of H2O2, through reduction of Fe3+ ions under UV light: H2O2 + hν → HO• + HO• Fe3+ + H2O + hν → Fe2+ + HO• + H+The efficiency of Fenton type processes is influenced by several operating parameters like concentration of hydrogen peroxide, pH and intensity of UV.
The main advantage of this process is the ability of using sunlight with light sensitivity up to 450 nm, thus avoiding the high costs of UV lamps and electrical energy. These reactions have been proven more efficient than the other photocatalysis but the disadvantages of the process are the low pH values which are required, since iron precipitates at higher pH values and the fact that iron has to be removed after treatment. Heterogeneous catalysis has the catalyst in a different phase from the reactants. Heterogeneous photocatalysis is a discipline which includes a large variety of reactions: mild or total oxidations, hydrogen transfer, 18O2–16O2 and deuterium-alkane isotopic exchange, metal deposition, water detoxification, gaseous pollutant removal, etc. Most common heterogeneous photocatalysts are transition metal oxides and sem