Reclamation of sulfate-laden wastewater via a hybrid selective nanofiltration and electrodialysis metathesis process. Issue 6 (December 2022)

• Record Type: Journal Article
• Authors: Chen, Qing-Bai; Li, Peng-Fei; Wang, Jianyou; Xu, Yong; Zhao, Jinli
• Is Part Of: Journal of environmental chemical engineering. Volume 10:Issue 6(2022)
• Publication Date: 2022-12
• Subjects: Sulfate-laden wastewater -- Selective nanofiltration (SNF) -- Electrodialysis metathesis (EDM) -- Reclamation -- Potassium sulfate; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2022.108712
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: Electrodialysis metathesis (EDM) could be considered as a sustainable method for reclamation of SO4 2– from wastewater. However, its feasibility is limited by the coexisting Cl – . In this study, for the first time, an integrated process of selective nanofiltration and EDM (SNF/EDM) was proposed to prepare K2 SO4 from sulfate-laden wastewater. In SNF unit, concentration of Na2 SO4 accompanied by the efficient separation of Cl – and SO4 2– were realized in a diafiltration mode. A Na2 SO4 concentrate stream (53.0 g/L) of 96.7% purity was obtained employing 4/2 of preconcentration factor and 2.0 MPa of operating pressure. Then, the stream was further treated by EDM process to continuously convert Na2 SO4 into K2 SO4 using KCl as metathesis solution. Under the relatively optimized operating parameters of 0.5 V repeating unit voltage and 1.25 L/h replenishment flowrate, K2 SO4 solution (104.5 g/L) with purity of 92.6% was obtained during two-stage EDM with the energy consumption of 0.59 kWh/(kg·K2 SO4 ). Finally, K2 SO4 powder was obtained by evaporation process and the product purity met the standard of premium grade agricultural K2 SO4 based on XRD and composition analysis. This study thus identified an effective way to make high-valued reclamation of sulfate-laden wastewater which contained considerable amounts of Cl – . Graphical Abstract: ga1 Highlights: SNF/EDM integrated system for recycling SO4 2– from wastewater was proposed and examined. Concentration of Na2 SO4 accompanied by separation of SO4 2– and Cl – were realized via SNF diafiltration. Two-stage EDM were conducted to convert Na2 SO4 to K2 SO4 and promote closed cycle of residual brine. K2 SO4 solid with purity of 97.4% was obtained by evaporation and crystallization process.