THERMOGRAPHIC EXAMINATION OF SLIMES FORMED DURING NEUTRALIZATION OF WASTE WATER FROM NON-FERROUS METALS PROCESSING PLANTS

摘要

When etching non-ferrous metal articles at non-ferrous metals processing plants, acidic effluents form which have to be treated with 5 percent milk of lime or a sodium hydroxide solution to neutralize them and remove their non-ferrous metal ions. The process is conducted at pH = 9, which - with neutralization of the effluents - leads to formation of low-soluble hydroxide metals (when treating waste water with alkali). When treated with milk of lime, basic non-ferrous metal carbonates will also form. In connection with the fact that technical lime is used to prepare milk of lime, the slimes of hydroxides and basic carbonates of metals, formed during the neutralization process, also contain the so-called "underroast" which remains after the limestone has been roasted.