Methods for reducing the iron content of iron-free aluminum sulfate

Methods for reducing the iron content of iron-free aluminum sulfate

Compared with ordinary aluminum sulfate, iron-free aluminum sulfate does not contain or contains less iron elements and is purer. Iron-free aluminum sulfate can be used in the production of high-grade paper, high-grade fabrics, food leavening agents, white rubber, white leather, etc.

Compared with ordinary aluminum sulfate, the production of iron-free aluminum sulfate requires an additional iron removal process, mainly the following methods:

1. Potassium permanganate iron removal method

The aluminum sulfate solution is adjusted to pH 3.0 with aluminum hydroxide. Under heating conditions, 5% (mass fraction) potassium permanganate solution is used to oxidize divalent iron to trivalent iron, generating iron hydroxide and manganese dioxide precipitation, cooling to 60°C and filtering, discarding the filter residue to achieve the iron removal effect, and the filtrate is concentrated and crystallized to obtain the finished product. After aluminum sulfate is oxidized and iron-removed by potassium permanganate, the iron mass fraction in aluminum sulfate can be reduced to below 0.01%, which can achieve the purpose of producing low-iron aluminum sulfate products.

2. Solution extraction method

Iron extraction is very complicated. It is affected by various conditions and factors such as various medium conditions, the structure of the extractant, and the composition of the extraction system. Therefore, the application of the extraction method must be studied in detail for specific situations, and it must be applied in industry after a certain scale of experiments.

After the aluminum sulfate solution is oxidized by H:O:, a 2608 sulfonated kerosene solution containing 20% (mass fraction) N1923 is added for extraction. The resulting aqueous phase is the aluminum sulfate solution, which is concentrated to obtain refined aluminum sulfate.

Add dilute sulfuric acid to the organic phase for 4-stage countercurrent extraction to recover the organic extractant. Taking primary amine extraction as an example, after primary amine N1923 and sulfonated kerosene organic solvent extraction and iron removal, the aluminum sulfate solid appearance is white fine crystals. The mass fraction of Fe:O in aluminum sulfate after iron removal can be reduced to 0.051%.