Vinasse processing by electrodialysis combined with nanofiltration: emphasis on process optimization and environmental sustainability

Abstract

Vinasse, due to its high organic load, low pH, high corrosivity, and high potassium levels, can cause salinization, acidification, loss of fertility, and leaching of constituents when applied to agricultural soils. In this context, electrodialysis (ED) was used to remove potassium from this effluent, to concentrate it in the cathode concentrate compartment. The cathode concentrate was subjected to nanofiltration (NF), allowing the electrolyte to be reconditioned and simultaneously generating a solution rich in potassium, making it an input for the fertilizer industry. The conditions of NF were optimized by the design of experiments. The optimal conditions obtained were 6 bar pressure, 1.8 L min−1 flow, and 1.6× feed dilution factor. Although the reconditioned electrolyte has been feasible, the raw vinasse (pre-ultrafiltered) was compared and proved to be a sustainable option. The NF permeate had a potassium concentration of 90% and magnesium of 84%, in addition to the annual reduction in magnesium sulfate demand (139,450,988 kg) and distilled water (5,019 m3). It was also possible to obtain an increase of approximately 400% in the rate of the application of vinasse in fertigation without compromising the needs of the plantation, the quality of the soil, and groundwater. HIGHLIGHTS The vinasse generated in the ethanol production process has a high concentration of chemical oxygen demand and K+.; Fertilizers with a high added value are essential for the economy of agricultural countries.; Nanofiltration was effective in recovering K from vinasse in accordance with the circular economy principle.; Vinasse can be effectively used as an electrolyte in the ED process and has allowed a reduction in the cost of the process.;

Keywords

• electrodialysis
• electrolyte reconditioning
• nanofiltration
• potassium
• vinasse