Regular Article

Valuable metals recovery and vitrification of chromium-containing electroplating sludge

¹ State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China
² Beijing Key Laboratory of Green Recovery and Extraction of Rare and Precious Metals, University of Science and Technology Beijing, Beijing 100083, China

^* e-mail: ghzhang_ustb@163.com

Received: 5 December 2021
Accepted: 12 April 2022

Abstract

In this work, a two-stage process was developed to recover the valuable elements from chromium-containing electroplating sludge (CES). The low sulfur/carbon Fe-Si-Cr alloy containing 31.61%Fe, 31.78%Cr, 36.59%Si, 0.01%C and 0.01%S was produced, and the recovery extent of Cr reached 98.62%. The CES was pre-desulfurized at 1000–1200 ℃, and reaction between components CaSO₄ and Fe₂O₃ in the CES to produce CaFe₄O₇ was the main desulfurization mechanism. The desulfurized CES was then reduced by silicon at 1600 ℃ to prepare the Fe-Si-Cr alloy, and the SiO₂ generated from the silicothermic reduction helps the vitrification of the slag. The presence of silicon in alloys and the CaO in the slag are the key factors for the low content of sulfur in alloy. Adding CaO also helped to decrease the viscosity of slag, and thus reduced the metal loss by enhancing the slag-metal separation efficiency.