Acid-based chemical treatments

An alternative to acid-based chemical purifications is thermal annealing. This strategy has been reported to lead to the removal of most amorphous carbon impurities, as well as of residual catalyst particles. It has even been reported to increase the graphitic perfection of the CNTs. Formation of graphitic shells and other undesirable nanoparticles, however, may be promoted. Note that thermal annealing can also be used in combination with acid-based chemical treatments. ... 

A volatile, amine-based chemical treatment usually added to the boiler FW, designed to neutralize the corrosive effects of carbonic acid in steam/condensate and raise condensate pH. 

Ion exchange Reverse osmosis Nano-filtration Electro dialysis Crystallization Evaporation Acid Base Heat treatment UV light Chemical oxidation... 

For chemical waste, fly ash, and soil/sediment samples, the extract must be concentrated to approximately 10 mL prior to acid-base washing treatment. Concentrate the extract by either of the two procedures listed above. 

Chemical treatment (type, solution concentration, dose, etc.) coagulants and flocculants (organic or inorganic) acid/base for treatment and pH correction... 

Fig. 11. Chemical treatment of Kevlar to increase hydrophilictty and bondability to epoxy resin matrices. Treatment with either strong base or strong acid causes chain scission at the surface. From ref. [57].

Usually metal-free phthalocyanine (PcH2) can be prepared from phthalonitrile with or without a solvent. Hydrogen-donor solvents such as pentan-l-ol and 2-(dimethylamino)ethanol are most often used for the preparation.113,127 128 To increase the yield of the product, some basic catalyst can be added (e.g., DBU, anhyd NH3). When lithium or sodium alkoxides are used as a base the reaction leads to the respective alkali-metal phthalocyanine, which can easily be converted into the free base by treatment with acid and water.129 The solvent-free preparation is carried out in a melt of the phthalonitrile and the reductive agent hydroquinone at ca. 200 C.130 Besides these and various other conventional chemical synthetic methods, PcH2 can also be prepared electrochemically.79... 

Evaporators require the continuous low level (1-3 ppm) application of a suitable antisealant chemical treatment. Traditionally, polyphosphate has been used (sometimes in conjunction with an antifoam and/or a dispersant agent), but it generally performs poorly because of a lack of thermal stability. Treatments based on polymaleic acid (PMA) and other modem organic polymers tend to perform much better. 

A premium antiscalent product in this group is Belros 435 from Great Lakes Chemical Corporation (originally the brand was owned by Ciba-Geigy, then FMC). Belros 435 is a 35% w/w, phos-phinoacrylic acid-based product, similar in chemistry to the Belclene 161 (also from Great Lakes) used as a high-stability dispersant in BW internal treatment formulations. 

Industrial applications inclnde the production of petrochemicals, fine chemicals and pharmacenticals (particnlarly throngh asymmetric catalysis), hydrometallurgy, and waste-treatment processes. Many life processes are based on metallo-enzyme systems that catalyse redox and acid-base reactions. 

The successful assembly of organic compounds on a solid support represents only part of the challenge in SPOS. After completion of synthetic sequence, the compounds must be cleaved from linkers attached to polymer by a chemical or photochemical reaction, for example, treatment of a polymer-bound compound with acids, bases, nucleophiles, redox reagents, and even photons. Acid-labile linker and amine-cleavable Marshall linker are two major classes of hnkers used in combinatorial synthesis. 

Chemical treatments Keller et al. (1981) hydrolyzed Kevlar 49 fibers with acid (HCl, H2SO,)) or base (NaOH) to produce reactive amino groups, to which a small... 

The general treatment of acid-base systems begins with charge and mass balances and equilibrium expressions. There should be as many independent equations as chemical species. Substitute a frac-... 

All cooling water treatment programs, whether designed in-house or via a water treatment service company, continue to focus on the minimization of hard water crystalline scales and sludges in the system as a major criteria for success. Program techniques employed are either pretreatment processes, such as lime-soda softening or ion exchange, the use of sulfuric acid or polymer-based chemicals that operate in an alkaline environment, or combinations of some or all of these processes. 

Many cooling system operators using sulfuric acid today probably started out in the past employing chemical treatment programs based on acid dosing... 

NOTE Acid dosing with chromate-based cooling water programs continues to be used in many countries around the world, even in some fully industrialized and developed nations, and most often quite safely, despite the general environmental concerns from this form of chemical treatment. Such concerns need to continue to be voiced, however, as there are some irresponsible operators who use chromates and discharge directly into water courses, contravening local prohibitory regulations (that also may not be adequately enforced). 

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