Electrodialysis-Based Recovery of Water and Chemicals in Recycled Polyethylene Terephthalate Industries: Energy, Environmental, and Economic Performance

Abstract

The increasing demand for recycled poly(ethylene terephthalate) (rPET) has raised concerns about the environmental impact of the production process, particularly regarding water consumption during the lye washing process. This study presents an integrated approach utilizing electrokinetic separation processes, specifically electrodialysis (ED) and electrodialysis with bipolar membranes (BMED), for on-site water reclamation and the circular regeneration of acid and base chemicals. Comprehensive treatment tests were performed on the actual effluent from the rPET process. Various performance indicators, including water reclamation efficiency, acid and base production, current efficiency, electricity consumption, and productivity, were systematically investigated. The results revealed that BMED, despite having higher energy consumption compared to ED, could recover 63.5 ± 8.8% of sulfate and 75.8 ± 7.3% of sodium from the wastewater. It produced sulfuric acid and sodium hydroxide solutions that could be reused in the process. Economic analysis demonstrated that integrating BMED into the rPET process resulted in lower operating costs (at least 10%) compared with traditional procedures, such as reverse osmosis and ED. Implementing BMED instead of direct effluent discharge in the rPET industry can significantly reduce the water footprint by 10-fold. Additionally, the carbon footprint can be further reduced by 5−17% with BMED deployment in the rPET industry. In conclusion, the integration of BMED has proven to be technically feasible and cost-effective for mitigating the environmental impact of rPET production. By recovering water and chemicals and achieving zero liquid discharge, this approach contributes to the sustainable production of rPET products.