A method for selectively recovering salt components from waste salts containing nitrates, nitrites, and hydroxides generated when heat treating steel parts in a salt bath

摘要

The salts component of nitrate/nitrite/hydroxide containing materials used in the tempering of steel is recovered by reducing the used salts to a grain size of 1 to 50 mm, dissolving the used salts in a solution of nitric acid containing H2O2 at 40 - 90 degrees C., filtering off the insoluble residue and precipitating KNO3 by cooling the concentrated neutralised salt solution to -10 to 20 degrees C. NaCl is crystallised out by further concentration of the solution at 60-120 degrees C. and NaNO3 is crystallised out from the remaining solution by the addition of concentrated HNO3.