Upcycling of waste sodium sulfate to sodium carbonate and sulfur.
basic_science · Level V
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- Record sourced from PubMed, PMID 42031791.
- Also identified by DOI 10.1038/s41467-026-72286-y.
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Abstract
Waste sodium sulfate (Na<sub>2</sub>SO<sub>4</sub>) is a common industrial byproduct that poses environmental risks and resource loss if improperly managed. Here, we report a thermochemical upcycling method to convert waste Na<sub>2</sub>SO<sub>4</sub> into value-added sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>) and sulfur (S<sub>x</sub>). In this process, Na<sub>2</sub>SO<sub>4</sub> is first reduced to sodium sulfide (Na<sub>2</sub>S) at 750 °C using charcoal. Subsequently, the generated Na<sub>2</sub>S is oxidized by CO<sub>2</sub> via carbonation at 300 °C to produce Na<sub>2</sub>CO<sub>3</sub> and S<sub>x</sub>. Temperature modulation shifts thermodynamic equilibrium to drive the conversion of SO<sub>4</sub><sup>2-</sup> to S<sub>x</sub>, achieving a carbonate yield of 95.35% with purity exceeding 99.53%. Life cycle assessment (LCA) indicates that this anhydrous route reduces the global warming potential by > 0.43 kg CO<sub>2</sub>-eq per kg Na<sub>2</sub>CO<sub>3</sub> compared with the conventional sodium sulfate-based ammonia-soda process (SSA-Process). By eliminating water-intensive steps and ammonia (NH<sub>3</sub>) usage, our method lowers the end-point environmental impact to 34.69 mPt per kg Na<sub>2</sub>CO<sub>3</sub> (vs. 48.81 mPt for conventional routes). Overall, this work provides a sustainable strategy for reclaiming waste salts and closing the sodium and sulfur cycles.