Treatment of Wastewater Resulting from the Mettallic Coatings Process

Abstract

The technological cleaning processes of steel strip surfaces used in metal coatings require organic or inorganic chemicals with a high risk of toxicity. To avoid pollution, the water resulting from these processes must be neutralized. During the degreasing process, alkaline solutions containing caustic soda (NaOH), tri-sodium phosphate (Na3PO4) and detergents are used and the pickling process is made in 15-20% HCl solution. Rinse waters resulting from these operations will have an alkaline pH respectively acid pH, with values depending on the duration of use or refresh solution. Neutralization was done with sulfuric acid solutions for alkaline water and sodium hydroxide solutions for acid water. The research aimed to establish the optimal conditions for neutralization and the optimal reagent consumptions.