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Thermal Blanket
A thermal blanket is a device used in thermal desorption to clean soil contamination. The primary function of a thermal blanket is to heat the soil to the boiling point of the contaminants (usually 100 to 325 °C and as high as 900 °C) so that they break down. A vacuum pulls the resulting gas (along with volatilized contaminants) into a separate air cleaner that may use various methods, such as activated carbon, carbon filters and high-heat ovens, to completely destroy the contaminants. Aside from evaporation and volatilization, the contaminants may also be removed from the soil through other mechanisms such as steam distillation, pyrolysis, Redox, oxidation, and other chemical reactions. Due to their placement, the thermal blanket can only be used in shallow areas, which is around 1 meter. The process can take more than 24 hours to treat 6 inches of soil and up to 4 days for contaminated areas with depths of 12 to 18 inches. Deep contamination (contamination at depth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Contamination
Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste. The most common chemicals involved are petroleum hydrocarbons, polynuclear aromatic hydrocarbons (such as naphthalene and benzo(a)pyrene), solvents, pesticides, lead, and other heavy metals. Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapour from the contaminants, or from secondary contamination of water supplies within and underlying the soil. Mapping of contaminated soil sites and the resulting clean ups are time-consuming and expensive tasks, and require expertise in geology, hydrology, chemistry, computer m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Activated Carbon
Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that greatly increase the surface area available for ''adsorption '' or chemical reactions. (Adsorption, not to be confused with Absorption (chemistry), absorption, is a process where atoms or molecules adhere to a surface). The pores can be thought of as a microscopic "sponge" structure. Activation is analogous to making popcorn from dried corn kernels: popcorn is light, fluffy, and its kernels have a high surface-area-to-volume ratio. ''Activated'' is sometimes replaced by ''active''. Because it is so porous on a microscopic scale, one gram of activated carbon has a surface area of over , as determined by gas absorption and its porosity can run 10ML/day in terms of treated water per gram. Researchers at Cornell University synthesized an ultrahigh surface area activated ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Distillation
Steam distillation is a separation process that consists of distilling water together with other volatile and non-volatile components. The steam from the boiling water carries the vapor of the volatiles to a condenser; both are cooled and return to the liquid or solid state, while the non-volatile residues remain behind in the boiling container. If, as is usually the case, the volatiles are not miscible with water, they will spontaneously form a distinct phase after condensation, allowing them to be separated by decantation or with a separatory funnel. Steam distillation can be used when the boiling point of the substance to be extracted is higher than that of water, and the starting material cannot be heated to that temperature because of decomposition or other unwanted reactions. It may also be useful when the amount of the desired substance is small compared to that of the non-volatile residues. It is often used to separate volatile essential oils from plant material. f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrolysis
Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Greek language, Greek-derived morpheme, elements ''pyro-'' (from Ancient Greek : - "fire, heat, fever") and ''lysis'' ( : - "separation, loosening"). Applications Pyrolysis is most commonly used in the treatment of organic compound, organic materials. It is one of the processes involved in the charring of wood or pyrolysis of biomass. In general, pyrolysis of organic substances produces volatile products and leaves Char (chemistry), char, a carbon-rich solid residue. Extreme pyrolysis, which leaves mostly carbon as the residue, is called carbonization. Pyrolysis is considered one of the steps in the processes of gasification or combustion. Laypeople often confuse pyrolysis gas with syngas. Pyrolysis gas has a high percentage of heavy tar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redox
Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. The oxidation and reduction processes occur simultaneously in the chemical reaction. There are two classes of redox reactions: * Electron transfer, Electron-transfer – Only one (usually) electron flows from the atom, ion, or molecule being oxidized to the atom, ion, or molecule that is reduced. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * Atom transfer – An atom transfers from one Substrate (chemistry), substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously, the oxidation state of oxygen decreases as it accepts electrons r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, energy change as new products are generated. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the Atomic nucleus, nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive Chemical element, elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reagent, reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more Product (c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In Situ Thermal Desorption
In situ thermal desorption (ISTD) is an intensive thermally enhanced environmental remediation technology that uses thermal conductive heating (TCH) elements to directly transfer heat to environmental media. The ISTD/TCH process can be applied at low (100 °C) temperature levels to accomplish the remediation of a wide variety of contaminants, both above and below the water table. ISTD/TCH is the only major in situ thermal remediation (ISTR) technology capable of achieving subsurface target treatment temperatures above the boiling point of water and is effective at virtually any depth in almost any media. TCH works in tight soils, clay layers, and soils with wide heterogeneity in permeability or moisture content that are impacted by a broad range of volatile and semi-volatile organic contaminants. History ISTD using TCH was developed by Shell Oil Co. in the late 1980s and grew out of research and development for enhanced oil recovery. During the mid-1990s Shell Oil Company ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nichrome
Nichrome (also known as NiCr, nickel-chromium or chromium-nickel) is a family of alloys of nickel and chromium (and occasionally iron) commonly used as resistance wire, heating elements in devices like toasters, electrical kettles and space heaters, in some dental restorations (fillings) and in a few other applications. Patented in 1906 by Albert Marsh (US patent 811,859), nichrome is the oldest documented form of resistance heating alloy. The A Grade nichrome alloy is 80% nickel and 20% chromium by mass, but there are many other combinations of metals for various applications. Properties C Grade Nichrome is consistently silvery in color, is corrosion-resistant, has a high melting point of approximately , and has an electrical resistivity of around 1.12 μΩ·m, which is around 66 times higher resistivity than copper of 16.78 nΩ·m. Some nichrome formulations have a resistivity as low as 1.0 μΩ·m or as high as 1.5 μΩ·m. Almost any conductive w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dioxins And Dioxin-like Compounds
Dioxins and dioxin-like compounds (DLCs) are a group of chemical compounds that are persistent organic pollutants (POPs) in the environmental pollutant, environment. They are mostly by-products of burning or various industrial processes or, in the case of dioxin-like polychlorinated biphenyl, PCBs and polybrominated biphenyl, PBBs, unwanted minor components of intentionally produced mixtures. Some of them are highly toxic, but the toxicity among them varies 30,000-fold. They are grouped together because their mechanism of action is the same. They activate the aryl hydrocarbon receptor (AH receptor), albeit with very different binding affinities, leading to high differences in toxicity and other effects. They include: * Polychlorinated dibenzodioxins, Polychlorinated dibenzo''-p-''dioxins (PCDDs), or simply dioxins. PCDDs are derivatives of dibenzodioxin, dibenzo''-p-''dioxin. There are 75 PCDD congener (chemistry), congeners, differing in the number and location of chlorine atoms, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychlorinated Dibenzofurans
Polychlorinated dibenzofurans (PCDFs) are a family of organic compounds with one or several of the hydrogens in the dibenzofuran structure replaced by chlorines. For example, 2,3,7,8-tetrachlorodibenzofuran (TCDF) has chlorine atoms substituted for each of the hydrogens on the number 2, 3, 7, and 8 carbons (see structure in the upper left corner of the second image). Polychlorinated dibenzofurans with chlorines at least in positions 2,3,7 and 8 are much more toxic than the parent compound dibenzofuran, with properties and chemical structures similar to polychlorinated dibenzodioxins. These groups together are often inaccurately called dioxins. They are known developmental toxicants, and suspected human carcinogens. PCDFs tend to co-occur with polychlorinated dibenzodioxins (PCDDs). PCDFs can be formed by pyrolysis or incineration at temperatures below 1200 °C of chlorine containing products, such as PVC, PCBs, and other organochlorides, or of non-chlorine containing pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Dutch Shell
Shell plc is a British multinational oil and gas company, headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New York Stock Exchange. A core component of Big Oil, Shell is the second largest investor-owned oil and gas company in the world by revenue (after ExxonMobil), and among the world's largest companies out of any industry. Measured by both its own emissions, and the emissions of all the fossil fuels it sells, Shell was the ninth-largest corporate producer of greenhouse gas emissions in the period 1988–2015. Shell was formed in April 1907 through the merger of Royal Dutch Petroleum Company of the Netherlands and The "Shell" Transport and Trading Company of the United Kingdom. The combined company rapidly became the leading competitor of the American Standard Oil and by 1920 Shell was the largest producer of oil in the world. Shell first ente ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soil Contamination
Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste. The most common chemicals involved are petroleum hydrocarbons, polynuclear aromatic hydrocarbons (such as naphthalene and benzo(a)pyrene), solvents, pesticides, lead, and other heavy metals. Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapour from the contaminants, or from secondary contamination of water supplies within and underlying the soil. Mapping of contaminated soil sites and the resulting clean ups are time-consuming and expensive tasks, and require expertise in geology, hydrology, chemistry, computer m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
