| With the rapid development of modern industry,industrial wastewater,especially high concentration and high salinity wastewater,has brought serious environmental pollution problems.The freezing crystallization method is a clean and promising treatment technology.During the formation and nucleation growth of inorganic salts and ice,understanding factors affecting the purity of salt and ice and control methods are key issues of this process.Sodium chloride simulated wastewater,high-salinity industrial wastewater,and wastewater containing specific organics were tested.The separation effect of freezing method on inorganic salts and organics was studied.In-depth study of the relationship between the strength of impurities(inorganic salts,organics)and water/ice molecules and the separation effect of impurities.In the freezing experiment,the different saturation sodium chloride solution,the saturated sodium chloride solution at low temperature and two kinds of high-salinity organic wastewater were taken as tests.The results found that:1,after treatment,the conductivity of simulated wastewater can be reduced by 68.5%,and the maximum salt precipitation rate can reach 26.5%;2,sodium chloride can easily grow larger at low temperatures,and excessive rotation speed can easily cause uneven sodium chloride size;3,the maximum COD and conductivity removal rate of high-salt organic fragrance industrial wastewater is 93.75%and 78.2%,respectively.The freezing method is applied to the high-concentration organic carvone industry wastewater,and the separation mechanism of impurities in the wastewater is discussed from quantum chemistry perspective.The experimental results and theoretical calculations show that during the freezing process,sodium phosphate is more likely to enter the ice than organics.It is inferred that hydrophilicity of impurities in the ice can affect the ice purity in the experiment.Four(hexane,hexanoic acid,hexanol,hexanal)simulated organic wastewater were used to study the relationship between organics hydrophilicity and ice purity.The experimental results show that the removal rates of hexane,hexanoic acid,hexanol and hexanal in wastewater can reach 67.07%,87.75%,94.71%and 95.32%,respectively.From the quantum chemistry perspective,the separation mechanism of organics during suspension crystallization of four organic simulation solutions is deeply studied.Hexanal has the smallest H-bond energy between the three polar organics and water molecules,and the highest removal rate.Hexane,as a non-polar organic,cannot form H-bonds with water molecules,so it is easy to precipitate and mix with suspended ice in the upper layer of the solution during,and has the lowest removal rate. |
