The process to recover both melamine and oxyaminotriazines (OAT) from the mother
liquors of melamine crystallisation comprising the following steps: a) addition
to a melamine and OAT containing aqueous solution at high temperature of an alkaline
agent until the solution pH reach a value equal or higher than 11; b) most of melamine
crystallisation by solution cooling; c) separation and recovery of precipitated
melamine; d) acidification of the obtained solution, after precipitated melamine
separation, in order to reach a pH of about 7; e) the suspension obtained in d)
above after precipitated melamine recovery, is subject to filtration according
to tangential filtration technique obtaining a clear permeate which contains as
a solution all melamine which did not precipitate in step b) and a retentate comprising
of OAT dispersion; f) OAT deprived mother liquors from e) are recycled to row melamine
solution preparation step; in such a way almost the total amount of melamine, which
did not precipitate in step b), is recovered; g) OAT are recovered from step e)
retentate by using any conventional separation technics.
