Method for extracting fulvic acid from straw pulp black liquor by ammonium sulfite method

Abstract

The invention provides a method for extracting fulvic acid from straw pulp black liquor by an ammonium sulfite method, comprising: acid with the conditioning of below pH5 is added into the ammonium sulfite straw pulp black liquor so as to separate lignin, later flocculant is added for removing the lignin by filtration, finally the filtrate is the fulvic acid solution; and the fulvic acid solution can also be dried for preparing crude fulvic acid or further purified for obtaining fulvic acid of high purity. The extracted fulvic acid has expensive price; the lignin, which is a by-product of the invention, also has wide usage; and the invention can also be used as soil conditioner or water-reducing agent, and can get good economic benefit.

Description

technical field [0001] The invention provides a method for extracting fulvic acid from straw pulp black liquor by an ammonium method, and belongs to the field of straw pulp black liquor treatment. Background technique [0002] Fulvic acid is a type of humic acid, which can be isolated from humic acid derived from coal, or directly extracted from peat and weathered coal. Fulvic acid from this source is collectively referred to as mineral-sourced fulvic acid. For example, the Chinese patent with the application number CN01141835.4 provides a method for producing high-purity fulvic acid with supercritical CO2, using peat, lignite and weathered coal as raw materials. After chemical reaction and extraction, solid Liquid separation; the separated liquid is then extracted with supercritical CO2; the extract is dried to obtain high-purity fulvic acid after removing the entraining agent. [0003] Another major source of fulvic acid comes from agricultural and forestry waste, which i...

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Problems solved by technology

[0005] There is no report of extracting fulvic acid from black liquor at present, but the Chinese patent application number 91106561 proposes a comprehensive treatment method for extracting humic acid from papermaking black liquor. The method is to add formic acid and acetic acid to papermaking black liquor , hydrochloric acid or sulfuric acid, adjust the pH of the wastewater to 3 to 6.5, add coagulants such as polyferric sulfate, basic aluminum chloride or polyacrylic acid amine, and separate the condensed humic acid solids, and the wastewater is used in paper production Or treat to meet discharge standards

[0006] However, the above-mentioned patent did not realize that fulvic acid can be directly extracted from black liquor, and most of the obtained humic acids are black humic acid and brown humic acid, because black humic acid and brown humic acid are insoluble in water , becomes a gel-like precipitate under acidic conditions. Compared with fulvic acid, the biological activity of black humic acid and brown humic acid is very low, and the utilization value is far apart.

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