| abstract |
Humic acid salts are produced, with a high output of useful products, by a liquid-phase oxidation of the mixture of an alkaline agent with a lignin-containing plant raw material having the total content of dry substances of 12-20 %, said oxidation being carried out in two stages. In a first stage, pre-oxidation is carried out at a temperature of 50-190 DEGREE C and a pressure of 0.5-3 MPa associated with simultaneous treatment with an oxygen-containing gas until a pH of 10,5-12 is reached. The second stage, i.e. oxidation is carried out in the similar conditions at a temperature of 170-200 DEGREE C until a pH of 8,5-10 is reached. |