The aim of this study is to develop a new method for the preparation of high-value, environmentally friendly products from spent pickling liquors. All ultrasound treatment was introduced into a chemical co-precipitation process to control the size of the particles produced. The particles were characterized by X-ray powder diffraction and transmission electron microscopy. The magnetic parameter was measured with a magnetic property measurement system. The product consisted of ferrous ferrite (Fe3O4) nanosized Cubic particles with a high level of crystallinity that exhibited super-paramagnetism. (C)2008 Elsevier B.V. All rights reserved.