Physical separation, mechanical enrichment and recycling-oriented characterization of spent NiMH batteries

Burçak Ebin,Christian Ekberg,Martina Petranikova

doi:10.1007/s10163-018-0751-4

Burçak Ebin, Christian Ekberg + Show 1 more

Open Access

https://doi.org/10.1007/s10163-018-0751-4

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Abstract

Nickel–metal hydride (NiMH) batteries contain high amount of industrial metals, especially iron, nickel, cobalt and rare earth elements. Although the battery waste is a considerable secondary source for metal and chemical industries, a recycling process requires a suitable pretreatment method before proceeding with recovery step to reclaim all valuable elements. In this study, AA- and AAA-type spent NiMH batteries were ground and then sieved for size measurement and classification. Chemical composition of the ground battery black mass and sorted six different size fractions were determined by an analytical technique. Crystal structures of the samples were analyzed by X-ray diffraction. Results show that after mechanical treatment, almost 87 wt% of the spent NiMH batteries are suitable for further recycling steps. Size classification by sieving enriched the iron content of the samples in the coarse fraction which is bigger than 0.25 mm. On the other hand, the amounts of nickel and rare earth elements increased by decreasing sample size, and concentrated in the finer fractions. Anode and cathode active materials that are hydrogen storage alloy and nickel hydroxide were mainly collected in finer size fraction of the battery black mass.

Highlights

The importance of electrical energy storage systems have been increasing last two decades due to increasing amount of electrical and electronic equipment, hybrid electrical vehicles (HEV) and electrical vehicles (EV), and growing demand for renewable energy sources [1,2,3]
A spent nickel–metal hydride cylindrical type battery composes of about 36–42 wt% nickel (Ni), 22–25 wt% iron (Fe) 3–4 wt% cobalt (Co) and 8–10 wt% mischmetal consisting of rare earth elements [lanthanum (La), cerium (Ce), praseodymium (Pr) and neodymium (Nd)], 1–2 wt% potassium (K), 3–4 wt% plastics and < 1 wt% graphite [10, 11]
This study investigated the mechanical pretreatment of AA- and AAA-type cylindrical spent Nickel–metal hydride (NiMH) batteries, and enrichment possibility of the specific metallic contents according to size fractions, which is smaller than 4 mm

Summary

Introduction

The importance of electrical energy storage systems have been increasing last two decades due to increasing amount of electrical and electronic equipment, hybrid electrical vehicles (HEV) and electrical vehicles (EV), and growing demand for renewable energy sources [1,2,3]. Mechanical pretreatment reduces the material complexity of the spent batteries by the separation of plastics and papers, as well as enriching metal content in the fine fractions for further recycling step. Ruffino et al [30] studied the mechanical treatment of different types of spent alkaline, Zn–C and Ni–Cd batteries, and showed that particle size classification and chemical distribution change by battery type.

Results

Conclusion