Synthesis of nickel–chromium–zinc ferrite powders from stainless steel pickling liquors

A low-temperature method was used to synthesize a nickel–chromium–zinc ferrite from stainless steel pickling liquor, a waste product of the steel industry, which is listed in most industrialized countries as a toxic and hazardous waste. This article reports the recovery (as a valuable ferric product) of the total metal content of this waste (namely, iron, chromium, nickel, and minor manganese), by coprecipitation of the multi-ionic solution and Zn²⁺ (provided by ZnO) with 1 M n-butylamine at room temperature. The spinel-type ferrite produced was characterized by x-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, and scanning electron microscopy. Its recorded magnetization of 2600 emu cm⁻³ allows its use in different magnetic applications. Furthermore, the synthesis method is a low-cost technology that yields a more environmentally friendly final effluent.