Solvent-Driven Fractional Crystallization Applied to the Desalination of a Concentrated Wastewater by Reverse Osmosis

This paper reports the efficiency of the solvent-driven fractional crystallization (SDFC) process using ethanol, also known as antisolvent crystallization, in the treatment of a concentrated wastewater by reverse osmosis (RO). This experiment evaluated the effects of varying the volumetric mixing ratio of ethanol-to-RO concentrate, in conjunction with the incorporation of Ca(OH)2, on the efficiency of magnesium and boron removal. The incorporation of Ca(OH)2 resulted in an enhancement of the reduction of magnesium and boron concentrations at a mixing ratio of 85:15 (v/v) and a pH of 12. In these conditions, the removal efficiencies achieved for magnesium and boron were 98.64% and 90.82%, respectively. The findings indicate that Ca(OH)2 has a significant impact on enhancing the removal efficiencies of these elements. The RO concentrated wastewater used in this experiment exhibited a salinity of 50,497.200 ppm prior to the SDFC test. The experimental results also showed a 48.10% reduction in salinity and 28.10% salt precipitation at the maximum mixing ratio and pH level examined. The tested process demonstrated significant reduction of scaling ions including calcium, magnesium, and sulfate. Similar behavior was observed for arsenic and manganese. Moderate removal efficiencies were observed for monovalent ions such as chloride, sodium, and potassium. However, the process was no effective for iron and lithium, which showed low removal efficiencies. Based on the results obtained, SDFC technology is seen as a promising technological option for application in the treatment of complex mining wastewaters.