Abstract: The invention relates to a method for recycling metal pickling baths, including rinsing baths and air washers. Said method is characterized in that a) before the recycling process, free acids in the liquid waste flows to be treated are converted into a metallic salt form, b) water is separated from the largely acid-free metallic salt solution produced in order to obtain a concentrated metal salt solution, and c) the concentrated metal salt solution is subjected to a thermal method in order to obtain metal oxides and free acids. The invention also relates to a corresponding device. The inventive method and device enable the degree of acid recovery and also the production of metal oxides to be significantly increased, with lower operating costs.

Abstract: In a method for recovering acid from an aqueous etching mixture containing HF, HNO3, H2SiF6 and HNO2 which has been used for purifying polycrystalline silicon, the used etching mixture is distilled progressively so that approximately from 20 to 50 wt. % of the mixture is distilled off as dilute acid containing more than 90 wt. % of the silicon dissolved as hexafluorosilicic acid in a first fraction, and the water contained in the used etching mixture having been reduced by approximately 10-30 wt. %, this water-depleted mixture is then concentrated by evaporation to a residue of about 1 to 5 wt. % of the initial amount of used etching mixture during which a second fraction is distilled off, and the residue is disposed of.

Abstract: Process for producing a nitric acid of a concentration from 75 to 99.9% from a more diluted nitric acid, wherein a nitric acid of a concentration of about 45 to 70% is rectified in contact with a liquid extraction medium to prevent the formation of a nitric acid-water-azeotropic mixture, and the vapors of the concentrated nitric acid are condensed and a concentrated nitric acid is obtained and wherein additionally the extraction medium is reconstituted through reconcentration and returned into the extractive rectification, wherein the nitric acid to be concentrated is fed as a boiling liquid or partially vaporized to the extractive rectification preferably carried out in two columns (K 1.0, K 1.

Abstract: A method process to convert inhibited red fuming nitric acid (IRFNA) and/or nitrogen tetraoxide to either dilute or concentrated (98%+) nitric acid. The method describes a process to remove all of the normal inhibitors (if required), that have been reported to been used in IRFNA. The process described will provide nitric acid free of contaminates which are undesirable when using the nitric acid in reactions to produce other products.

Abstract: A method that employs a dilute solution, such as a dilute hydrogen peroxide solution, and concentrates the dilute solution to a yield a concentrated solution. A concentrated solution prepared by the method of the invention is useful as a rocket fuel, a laser fuel and industrial and laboratory chemical reagents.

Abstract: Highly purified ammonia for use in processes for the production of high-precision electronic components is prepared on-site by drawing ammonia vapor from a liquid ammonia reservoir, passing the vapor through a filter capable of filtering out particles of less than 0.005 micron in size, and scrubbing the filtered vapor in a high-pH aqueous scrubber.

Abstract: Highly purified ammonia for use in semiconductor manufacturing is prepared on-site by drawing ammonia vapor from a liquid ammonia reservoir, passing the vapor through a filter capable of filtering out particles of less than 0.005 micron in size, and scrubbing the filtered vapor in a high-pH aqueous scrubber.

Abstract: Highly purified ammonia for use in processes for the production of high-precision electronic components is prepared on-site by drawing ammonia vapor from a liquid ammonia reservoir, passing the vapor through a filter capable of filtering out particles of less than 0.005 micron in size, and scrubbing the filtered vapor in a high-pH aqueous scrubber.

Abstract: This invention relates to an improved process for storing and transporting toluenediamine, particularly for long term storage or storage in large containers, e.g., shipboard containers. The improvement in the process resides in substantially reducing the melting or freezing point of anhydrous toluenediamine obtained by the fractional distillation of a reaction product generated by the hydrogenation of dinitrotoluene. Such melting point reduction is accomplished by maintaining a water concentration in the toluenediamine in an amount of from 5 to 15% by weight under molten conditions for storage and transport. Preferably the level of water maintained in the toluenediamine is from about 7 to 10% by weight.

Abstract: A method of recycling and purifying cleaning chemicals used in the production of semiconductor circuits and containing hydrofluoric acid and or hydrochloric acid. Recycling of such chemicals is accomplished using separation and reconstitution steps Hydrofluoric acid and hydrochloric acid cannot be distilled directly from a chemical solution as they form azeotropes with water. A low vapor pressure substance such as sulfuric acid or phosphoric acid is used to break the azeotrope while increasing the purity of the recovered chemicals and decreasing disposal problems. The method is useable at the point of use of the chemicals.

Abstract: A process for treating an aqueous solution mainly containing nitric acid and hydrofluoric acid. The process involves distilling to provide an aqueous solution concentrated in nitric acid and hydrofluoric acid for the separation thereof, then separating by distillation.

Abstract: Aqueous solutions of N-methylmorpholine N-oxide having color numbers below 200 APHA, based on an N-methylmorpholine N-oxide content of 50% by weight, are produced by reacting aqueous hydrogen peroxide solutions with aqueous solutions of N-methylmorpholine having a water content of at least 35% by weight.

Abstract: Volatile acids containing metal salt impurities, such as metal pickling solutions-are regenerated by a process in which the acid is subjected to sulfuric acid distillation. Resulting volatile acid vapor is condensed and recycled to the pickle tank, while the residual acid mixture is treated in an acid sorption unit, preferably of the acid retardation type. Acid sorbed in the acid sorption unit is periodically eluted with water and recycled, while metal impurities are rejected in a deacidified by-product solution.

Abstract: An integrated continuous processes for concentrating "weak" nitric acid and concurrently reconcentrating the spent dehydrating agent used to break the nitric acid azeotrope to obtain "strong" nitric acid, the processes involving direct coupling of the nitric acid concentration with the reconcentration of the spent dehydrating agent so that less energy input is required. The major proportion of the feed "weak" nitric acid is vaporized before being fed countercurrently into a column to contact a large volume of the dehydrating agent, this vaporization being one of the two major sources of energy input, the second being through the reboiler at the bottom of the column. Energy input is balanced by energy rejection through condensation of strong nitric acid vapor and water vapor.

Abstract: A method for improving ruthenium decontamination efficiency in a nitric acid recovery system in which a nitric acid solution containing ruthenium is subjected to an evaporation treatment in a nitric acid evaporator. The method is characterized by carrying out the evaporation treatment of the nitric acid solution in the presence of hydrazine in a concentration of 20 to 5000 mg per liter of the solution in the evaporator. By the action of hydrazine, the evaporation of ruthenium contained in the solution is suppressed during the evaporation treatment, and hence the ruthenium decontamination efficiency is remarkably improved.

Abstract: A method of separating acids or bases from vapors which are conveyed along with distillation vapors during concentration of a solution, comprising, passing said distillation vapors containing an acid or base, while being maintained at their existing pressure and temperature, through a salt solution which boils at said temperature and pressure, wherein, if an acid is to be removed from the distillation vapors, the salt solution contains a salt having an anion corresponding to that of the acid while being supplied with a base in an amount required to neutralize the acid, the cation of the base proportion corresponding to that of the salt, while, if a base is to be removed from the distillation vapors, the salt solution contains a salt having a cation corresponding to that of the base while being supplied with an acid in an amount required to neutralize the base in the distillation vapors, the anion of the acid corresponding to that of the salt so that salts are formed during neutralization which correspond to t

Abstract: Process for working up aqueous nitric acid which is of a concentration above the azeotropic concentration and contains organic compounds in solution for suspension wherein said nitric acid of a concentration about the azeotropic concentration is distilled off in one or more rectification steps until the azeotropic nitric acid is obtained. In the process, certain specified ratios of nitric acid and water to organic constituents must be maintained.