Silicon, which is found in industrial wastewater in different forms, often ends up in sludge at the wastewater treatment plant. It can react with various chemicals in wastewater forming compounds that can interfere with the treatment process downstream. Hence it is necessary to isolate and filter it. In this article I discuss different chemical reactions that can take place in wastewater containing Silicon.

Silicon In Wastewater

If Ammonium Molybdate is present in the sample of wastewater being tested in the laboratory, then it can react with Silica to produce Heteropoly acids in the presence of Phosphate (PO4). Wastewater often contains Phosphates, a common industrial effluent often discharged in untreated wastewater.

These Heteropoly acids are composed of Oxygen, Hydrogen, Metals, certain non metals and different chemicals in wastewater. All of these can be found in wastewater and once these acids are formed they can act as a catalyst for other reactions. Under laboratory testing, these acids obtained are yellow in color.

If there is Oxalic acid in wastewater, then it can react with the Molybdophosphoric Acid. Under laboratory testing, the colorless Oxalic acid (C2O2(OH)2) is added to the sample containing the chemicals in wastewater to destroy the Molybdophosphoric Acid, which is obtained as a compound of yellow green color. This reaction does not affect the Molybdosilicic Acid which is obtained in a yellow colored solution.

But further action of this acid in a wastewater sample, for example with amino napthol sulphonic acid (H2NC10H5(OH)SO3H), causes a reduction reaction. The amino napthol sulphonic acid is normally white or gray colored crystals that easily dissolves in water. Under laboratory conditions, this reaction causes the color of the solution to turn to a shade of hetero poly blue.

A better understanding of these reactions can help in the treatment of wastewater.

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