Solute selectivity, separation mechanism and application performance of freezing wastewater treatment: Focus on air cooling and direct contact cooling

Freezing separation is a green and high efficient wastewater treatment technology. Considering the problems of freezing methods, treatment specificity and relative energy efficiency, an air cooling device and a direct contact cooling device were developed. The removal rates, ice-forming rates, and energy efficiency of different freezing methods were investigated with different concentrations of inorganic salt ions, small molecule organic matter, and organic polymer solutions. The results showed that there was solute selectivity in freezing separation, while the separation effects increased in decreasing solute concentration, with higher solute removal rates for inorganic salt solutions and small molecule organics and lower removal efficiency for high molecule organics, and there was the highest potential application value of copper contact column by comparing the removal rates and composition ratios. In addition, stirring enhanced the solute removal rate significantly, which affected the concentration gradient distribution and the microenvironment of the ice-forming interface. In the treatment of condensate wastewater from MVR(Mechanical Vapor Recompression) system and dye wastewater with high salt and high organic, the results showed that the removal rates reached 70% and 50% respectively, and it provided reference to the application of freezing separation in practical water treatment.

Automated summary

Freezing separation is a green and efficient wastewater treatment technology, with solute selectivity and improved separation effects at lower solute concentrations. Different types of substances have different removal efficiencies, and stirring can significantly enhance solute removal rates during the freezing process.