Some problems on standardization of mineral source (coal - based) fulvic acid (3)

2019-12-23 16:20

Separation and extraction problem

1. Separation of fulvic acid

In 2009, the national humic acid Standard working group was set up to conduct systematic research on humic acid related standards, and a series of humic acid method standards and product standards have been revised successively. In this process, due to the different professional and research depth of the revised standards, the revised standards also produced many differences in the industry, but basically reached a consensus on the separation conditions, that is, pH=1 as the separation conditions of humic acid. With further research, it is doubtful whether the isolated parts dissolved in dilute acid contain the mineral source fulvic acid.

2, mineral source humic acid extraction containing fulvic acid problem

In the laboratory, lignite of Inner Mongolia was used for alkali extraction and acid precipitation. After partial explosion, the dilute acid solution was neutralized with trisodium phosphate to pH=8, resulting in a large amount of grayish white precipitation, which was detected to contain iron, zinc, manganese, calcium, magnesium and other elements. Compared with the lignite sample, the organic carbon in dilute acid solution is only about 0.1%, and the peak ultraviolet spectrum is only about 200 nm. This indicates that most of the separated substances are inorganic salts, and a very small amount of organic matter also has the characteristics of hydroxyl and carbonyl groups, without unsaturated bond and aromatic structure.

After the precipitation part of lignite in the alkaline acid extraction and precipitation process is treated by a specific process (no chemical reaction occurs in this process), the humic acid obtained from the precipitation after low temperature vacuum drying is crushed and pumped with boiling water. The insoluble matter after extraction is dried at a secondary low temperature and vacuum with a weight loss of about 10%. The extracted solution was adjusted to pH=1 with acid and then left to form without precipitation.

Therefore, the experiment shows that the solution after the precipitation of lignite alkali soluble acid is not the socalled mineral source fulvic acid or the content is very small and can be ignored; The precipitate of lignite after alkali soluble acid precipitation is humic acid, about 10% of which should be mineral source fulvic acid.