A novel technique was successfully developed for manufacturing Mn-Zn ferrite nano-particles by acid
dissolution and ferrite processes. The powders of waste dry batteries (PWDBs) were used as starting
raw materials because the Mn and Zn content inside the PWDBs is potentially high. Our data
showed that the most abundant elements inside PWDBs are manganese (41.0%), oxygen (40.6%), zinc
(15.3%), and carbon (3.1%). It was found that proper reductant was critical for dissolution where FeSO4
is essential for spinel ferrite formation. Synthesized Mn-Zn ferrite particles reached their saturation
magnetization at 63.8 emu/g and were successfully applied for As, Cd, and Pb removal in aqueous
solution. Under the conditions of Mn-Zn ferrite 0.005 g, volume 10 mL, temperature 27 ◦C, and contact
time 1 h, As, Cd, and Pb removal could reach 99.9, 99.7, and 99.8%, respectively. We demonstrate
a novel method that can be applied for transforming WDBs into resource materials. This not only
reduces the amount of WDBs, but also supports the concept of waste-battery reusable green-energy
policy.