Direct generation of Zn metal using laser-induced ZnS to eradicate carbon emissions from electrolysis Zn production

Abstract

● An optical metallurgy is proposed to directly generate Zn⁰ from ZnS using laser.

● Zn⁰ and S₈ can be detected on the surface of ZnS at a high laser fluence.

● The generation mechanism of Zn⁰ and S₈ was explored.

● Providing a new way of producing high-purity metal without carbon emissions.

● A new method is proposed to promote the environmental goal of carbon neutrality.

In response to the goal of net-zero emissions proposed by Intergovernmental Panel on Climate Change, Chinese government has pledged that carbon emissions will peak by 2030, and achieve carbon neutrality by 2060. However, the high carbon energy structure of traditional industries has aggravated environmental problems, such as greenhouse effect and air pollution. The goal of carbon neutrality will be difficult to achieve without the development of disruptive theories and technologies. The electrolytic zinc industry requires high-temperature roasting at ~1000 °C, generating large amounts of greenhouse gases and SO₂. High concentrations of sulfuric acid (200 g/L) are subsequently used for electrolysis, and each ton of zinc produced generates 50 kg of anode slime with lead content of up to 16%, as well as 0.35 m³ of wastewater containing zinc and lead. To solve these problems, an optical metallurgy method is proposed in this study. The proposed method uses laser-induced photoreduction to decompose ZnS and reduce metal ions to metal. Results indicate that Zn⁰ and S₈ can be detected on the surface of ZnS at a specific wavelength and laser fluence. The generation mechanism of Zn⁰ is such that laser induces an electronic transition that breaks ionic bond in ZnS, resulting in its decomposition and photoreduction to Zn⁰ under an inert argon gas atmosphere. This method does not reduce other metals in the mineral since it does not use high-temperature roasting, providing a new way of producing high-purity metal without greenhouse gas emissions and heavy metal pollution caused by traditional zinc electrolysis.

Graphical abstract

Keywords

Laser metallurgy / ZnS / Photochemical reduction / Zinc

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The Author(s) 2024. This article is published with open access at link.springer.com and journal.hep. com.cn