High-quality and efficient zinc electrodeposition in a polyethylene glycol 20,000-assisted ammonia solution

Abstract

Ammonia system shows great potential in the treatment of zinc secondary resource, and electrodeposition has been confirmed as a vital process to extract zinc from the ammonia leachate. However, the ammonia system-based zinc electrodeposition is either inefficient or the zinc deposit in of undesired quality. This study proposes a polyethylene glycol 20,000 (PEG20000 polymer of formula H(OCH2CH2)nOH)-assisted ammonia system to conduct high-quality and efficient zinc electrodeposition. The practical operation achieved a low electrical energy consumption of 2391 kW h t−1 Zn and a high current efficiency of 99%, with a smooth and compact zinc deposit of fine (30.2 nm) grains. Further investigation of electrodeposition behavior revealed the following: (i) deposition principle, (ii) diffusion property, and (iii) three-dimensional (3D) instantaneous nucleation mode, and provided a useful reference for guiding the process design and conditions of the practical operation. In general, PEG20000-assisted ammonia system turns out to be a technically and economically viable option to electro-deposit zinc, for its high energy competitiveness and high-quality Zn products.