solventevaporation

Solvent evaporation is the removal of a volatile solvent from a liquid mixture or solution. It occurs when molecules escape from the liquid into the gas phase, driven by vapor pressure differences between the liquid and its surroundings. Evaporation can occur on exposed surfaces at ambient pressure, or be accelerated by heating or reduced pressure. Unlike distillation, evaporation concentrates solutes without necessarily separating them from the solvent, though at higher temperatures or with azeotropes separation can occur.

Common methods include open-air drying, oven or hot plate drying, rotary evaporation under reduced pressure, and spray drying. Vacuum evaporation lowers boiling points and minimizes thermal degradation, while increasing surface area speeds up the process. Freeze-drying is a related process based on sublimation rather than simple evaporation.

Key factors: solvent properties such as boiling point, vapor pressure, and azeotrope formation; ambient temperature, pressure, and airflow; solution properties; surface area and geometry; and the presence of inhibitors or surfactants. The rate is roughly proportional to surface area and to the driving force (vapor pressure difference), and inversely related to heat transfer limitations.

Applications include concentration of solutions, solvent exchange, crystallization, film casting, coating and drying of materials, solvent recycling, and sample preparation for analytical methods.

Safety and environmental considerations: evaporation involves volatile, often flammable solvents; adequate ventilation, explosion protection, and solvent recovery are important. Energy use and solvent loss are also considerations in industrial settings.