Wastewater Purification by Solvent Induced Precipitation Using Freeze Technology to Recover Solvent

摘要

A method of treating strong aqueous hazardous wastewaters by combining solvent induced precipitation and freeze technology has been experimentally evaluated. The process involves the addition of a miscible organic solvent to an aqueous stream to lower the solubility of salts present in that stream. Precipitates are then separated from the solution, and the remaining brine is subjected to an indirect freeze system. The freeze process removes clean water as ice and concentrates the solvent laden brine for recycling to the system. Laboratory tests were performed on a mixture of synthetic wastewater and common solvents to determine freezing point depressions, solubilities, and effectiveness in inducing precipitation of salts. Precipitates formed were sulfates of sodium and calcium. Nitrates, chloride, and magnesium ions were not precipitable. From these tests, ethanol was selected for use in a full pilot plant simulation.