Reduction of oxides obtained from waste Ni-MH battery's positive electrode using waste plastics to produce nickel based alloy

摘要

Generation of electronic waste (e-waste) is a direct result of the world's dependence on electronics and daily use gadgets. Global consumption of e-waste was around 60 Mt in 2016 and is increasing each year in developed and developing countries. The waste accumulated not only affects the environment (soil and water) but also is detrimental to human health, thereby calling for sustainable recycling solutions. The current work details a novel approach to recover nickel alloy, using two waste streams: positive electrode materials of waste Ni-MH battery as Ni source in oxide form and e-waste plastics as a reductant. As an alternative to the use of conventional carbon, characterization studies, gas evolution kinetics, weight loss, fine black carbon generation were performed on e-waste plastics before carrying out the reduction of Nickel oxide at 1550 degrees C in an argon atmosphere in a high-temperature horizontal tube furnace. The selected temperature (1550 degrees C) favors the reduction without the addition of any additives and diminishes the formation of toxic compounds such as dioxins. FTIR gas spectra of the e-waste plastics confirmed the gradual decrease of functional groups, such as poly-methylene, phenol, and styrene as temperature increased from 400 degrees C to 850 degrees C. A mechanism of reduction starting from the cold zone of the furnace to hot zone was established which is observed to be predominantly gas based. High metal purity was confirmed by ICP-OES (Inductively coupled plasma optical emission spectros-copy) > 99% and XPS (X-ray photoelectron spectroscopy) 70-84 atomic %. XRD (X-ray powder diffraction) and EDS (Energy Dispersive X-ray spectroscopy) confirmed the formation of nickel alloy in the product phase and morphology was studied by SEM (scanning electron microscopy) which conveyed the uniformity of the product surface. This scientific study of using e-waste plastics as a reducing agent depicts a promising route to produce nickel alloy from the positive electrode of Ni-MH battery while reutilizing e-waste streams in a sustainable way. (C) 2019 Elsevier Ltd. All rights reserved.