To reduce cost and secondary pollution caused by complicated separation and purification in the recycling of spent batteries, an environmentally friendly process was proposed to treat and recycle a mixture of spent lithium-ion batteries (LIBs) and nickel-metal hydride (Ni-MH) batteries. In this novel process, spent LIBs and NiMH batteries were used as source materials to prepare magnetic nanoparticles of NiCo ferrite by sol-gel combustion. Characterization studies, such as XRD, FESEM and TEM, have been carried out to explore the particle size. The presence of functional group has been identified by Fourier transform infrared spectra. From TG-DSC studies, crystallization occurs at temperatures above 550 degrees C. The magnetic properties of final nanoparticles were found to be directly influenced by average size of products. The values of Ms, Mr, and Hc of NiCo ferrite increase with the increasing size of the final products. (C) 2015 Elsevier B.V. All rights reserved.