Synthesis and properties of SrFe12O19 obtained by solid waste recycling of oily cold rolling mill sludge

Journal article, 2019

The aim of this study was to develop a new approach for the preparation of environmentally friendly, high-value products from oily cold rolling mill (CRM) sludge. Utilizing oily CRM sludge as a source of iron, strontium hexaferrite (SrFe12O19) powders were prepared by multi-step processes involving acid leaching, chemical conversion treatment, and synthesis by a citrate precursor. The influences of citric acid dosage and the pH of the sol system on the formation, crystallite size, and magnetic properties of the obtained SrFe12O19 powders were investigated. High saturation magnetization (74.8 mA-m(2)g(-1)) and intrinsic coercivities (614.46 mT) were achieved for pH 7.0 of the sol system, for which the molar ratio of citric acid dosage to the total dosage of Fe-3+ and Sr2+ was 1.5. This study presents a new approach to utilizing oily CRM sludge, and even refractory iron-containing solid waste.