We successfully prepared the TiO2@Mn-Zn ferrite composite powder for magnetic photocatalyst. The core Mn-Zn ferrite powder was synthesized by using steel pickling liquor and used alkaline batteries as the starting materials. The shell TiO2 nanocrystal was prepared by sol-gel hydrolysis precipitation of titanium isopropoxide (Ti(OC3H7)(4)) on the Mn-Zn ferrite powder. The thickness of the titania shell was found to be approximately 2 nm. The core of Mn-Zn ferrite is of spherical or elliptical shape and the particle size of the core is in the range of 20-40 nm. The magnetic Mn-Zn ferrite nanopowder is uniformly encapsulated in a titania layer forming the core-shell structure of TiO2@Mn-Zn ferrite powder. The magnetic photocatalyst can be successfully used to treat dye waste waters. (C) 2013 Elsevier Ltd. All rights reserved.