Iron removal process of aluminium sulfate

At present, the production method of aluminium sulfate mainly involves using bauxite for production, but due to the high iron content in bauxite, the iron content in the finished product will also be relatively high, which may affect its effectiveness when used, so the iron needs to be removed.

Generally speaking, this method is only suitable for ordinary iron removal. First, a certain amount of potassium permanganate solution is added to the hot solution, at which point a large amount of tan precipitate is generated. After filtration, the filtered liquid is concentrated and crystallised to obtain a product with lower iron content. The remaining iron is generally high-valent iron, resulting in a yellow product that appears poor in quality. During the concentration process, a small amount of aluminium flakes can be added to reduce the unclean iron to ferrous iron, causing the product to appear light green, which is more aesthetically pleasing, and after being left for 3 months, the colour has hardly changed.

The pH value of the solution also affects the iron removal process. The higher the pH of the solution, the better the iron removal. However, a higher pH also results in lower recovery of aluminium sulfate. Thus, after washing the filter residue, production losses can be significantly reduced. If the amount of potassium permanganate is insufficient, it may lead to poor iron removal or even failure in the iron removal process. Potassium permanganate first oxidises divalent iron ions to Fe, while manganese is reduced to Mn2+, at which point no Fe(OH)3 precipitation is formed. With the continuous addition of potassium permanganate, Mn2+ will gradually be oxidised to Mn+. A small amount of aluminium will be adsorbed together to form a precipitate. The higher the amount of H2O generated, the higher the iron removal rate.