Resource recovery from potash brine effluent: integrated chemical precipitation and evaporative crystallization for zero liquid discharge and sustainable brine management

The valorization of potash brine effluent (PBE) from carnallite processing offers a transformative opportunity to address environmental and economic challenges in the potash mining industry. This study presents a novel hydrometallurgical approach integrating chemical precipitation and evaporative crystallization to recover high-purity magnesium hydroxide (Mg(OH)₂) and potassium chloride (KCl) from PBE, achieving zero liquid discharge (ZLD). Chemical precipitation of magnesium using potassium hydroxide (KOH) was optimized via response surface methodology (RSM), achieving 88 % Mg recovery as Mg(OH)₂ with 95 % purity under optimal conditions (2.4 mol/L KOH, 60 °C, 40 min). Subsequent evaporative crystallization of the potassium-rich stream produced KCl crystals with 99.15 % purity, meeting commercial fertilizer standards. The process leverages fundamental aqueous chemistry principles, including pH control, supersaturation-driven nucleation, and selective crystallization, to maximize resource efficiency. Comprehensive characterization using XRD, SEM-EDS, and TGA confirmed the structural and compositional quality of the recovered products. By transforming PBE into marketable commodities, this integrated strategy not only mitigates environmental risks associated with brine disposal but also establishes a circular economy framework for the potash sector. The hybrid process achieves high-purity Mg(OH)₂ (95 %) and KCl (99.15 %) recovery from potash brine, fulfilling zero liquid discharge (ZLD) objectives. The methodology provides a foundation for sustainable brine management in mineral processing.