COAGULANTS ON THE BASIS OF WASTE FOR REMOVAL OF HEAVY AND COLORED METALS FROM SEWAGE WATER

The article discusses the development of waste-based coagulants for the removal of heavy and non-ferrous metals from waste water. The results of the developed new chemical reagentsorbent based on a modified phosphogypsum hydroxide suspension are presented. It has been found that modified aluminum hydroxide more effectively removes impurities from water having higher turbidity than that formed by aluminum sulfate. When sorbing fine crystalline hydroxide suspension on the surface of contaminants, the interaction occurs both between particles of the solid phase, with a shell consisting of hydroxide molecules, and sparingly soluble particles of the solid phase, which gradually contributes to the formation of a flocculent precipitate. The dose of coagulant increases with decreasing particle size, since large quantities are required for surrounding the particles with the hydroxide layer, as well as for the formation of the neutral phase necessary to create stable aggregate formations. It was noted that in the case of water with high turbidity, low color and a low content of organic suspensions, which is determined by its permanganate oxidation, it is justified when using small doses of modified coagulant, which has a larger number of hydroxyl groups. As a result, the modified aluminum hydroxide more effectively removes impurities from water having higher turbidity exceeding the turbidity of the solution with aluminum sulfate. The presence of phosphate ions, sulfate ions, chloride ions, hydrocarbonate ions in water leads to the formation of poorly soluble complexes that stimulate the coagulation process and reduce the consumption of aluminum sulfate reagent. But, with increased acidity of the medium, chloride ions exhibit a stabilizing effect and inhibit the formation of aluminum hydroxide until the cessation of this process, however, the process with modified aluminum hydroxide does not occur.