Potassium phosphate (K₃PO₄) is a common inorganic compound with broad applications in agriculture and industry. Although the traditional thermal method of preparing K₃PO₄ by reacting phosphoric acid with potassium hydroxide can obtain high-quality products, it consumes a lot of energy and has high costs. This study explores the process of preparing K₃PO₄ by Electrodialysis metathesis (EDM). This process uses sodium phosphate (Na₃PO₄) and potassium chloride (KCl) as raw materials and can prepare K₃PO₄ continuously. Under the optimized conditions (operating voltage of 8 V, 0.35 mol/L Na₃PO₄ and 1.05 mol/L KCl in raw flow with the rate of 30 mL/min), the product purity of K₃PO₄ reaches more than 97%, the energy consumption is 1191 kW·h/t, and the cost is about 8314 CNY/ton. Compared with traditional methods, EDM has the advantages of low cost, simple operation, and high utilization rate. This study shows that EDM technology has significant potential in preparing K₃PO₄.

In this study, the integrated process of reverse osmosis (RO) and electrodialysis (ED) is developed to concentrate the dilute solution of acetic acid (HAc). The key parameters, such as RO pressure, ED voltage, and ED volume ratio, were systematically evaluated and the operation conditions of the processes were optimized. Under an operating pressure of 5 MPa, RO can enrich low-concentration HAc from 1.5 wt.% to 6.5% wt.% and the energy consumption is 0.37 kW·h·kg⁻¹. Next, RO-concentrated water was used as the ED feed and the first ED with a volume ratio of the concentrated to dilute chamber of 1:4 was carried out under the conditions of a flow rate of 30 L/h and an operating voltage of 12 V; the HAc concentration reached 12.50 wt.%. The second ED with a volume ratio of 1:5 made the final HAc concentration reach 19.02 wt.%. This study shows that using RO-concentrated water instead of initial water for the ED process can reduce water energy consumption and cost markedly, and the RO–ED integrated process can efficiently pre-enrich low-concentration HAc aqueous solution, and the enriched HAc concentration meets the requirements for the further distillation of HAc.