Study On The Effect Of Organic Additives On The Crystallization Process Of Sodium Chloride

Zero discharge of wastewater is the ultimate goal of all kinds of wastewater treatment.The crystallization technology can separate the salts from the waste water to obtain the salt compound to achieve zero discharge.In the process of zero discharge of wastewater,the existence of organic matter has an adverse effect on crystallization of inorganic salt.Therefore,it is necessary to study the effect of organic additives on salt crystallization.The influence of three kinds of typical organic pollutants in industrial wastewater(peptone,phenol,heptane diacid)on thermodynamics,kinetics and particle size of sodium chloride crystallization were studied in this paper.It provides a reference for the treatment of high salinity organic wastewater and it is of great significance to realize the zero discharge of wastewater.The solubility of sodium chloride in pure water and aqueous solution that added peptone,phenol and heptane diacid were measured in this paper by static equilibrium method.The results show that the existence of the three kinds of organic matters decreases the solubility of sodium chloride.And the solubility decreases with the increase of organic concentration.The effect of heptane diacid is the largest.The supersolubility of sodium chloride in pure water and aqueous solution that added peptone,phenol and heptane diacid were measured in this paper by visual method.The results show that all the organic additives doped in sodium chloride will narrow the metastable zone width(MSZW),and the degrees of the organic additives are in the order as follows: phenol>heptane diacid>peptone.The faster the stir rate and the lower the cooling rate,the narrower the MSZW.In the presence of different organic matters,the order of the influence of stirring rate on the MSZW as follows: heptane diacid>peptone>phenol;the order of the influence of cooling rate on the MSZW as follows: peptone>phenol>heptane diacid.The nucleation orders are also calculated in the paper.The effects of different kinds and contents of organic matters on the average particle size of sodium chloride crystals were studied.The results show that the particle size decreased with the existence of three kinds of organic matter,and the size decreases with the increase of organic concentration,the degrees of the organic additives are in the order as follows: heptane diacid>phenol>peptone.At the same time,The influence of residence time and stirring rate on the average particle size and dispersion of sodium chloride crystals was investigated by the method of controlled variables.The crystallization kinetics of sodium chloride in the presence of different organic compouds were studied.The dynamic regression equation of sodium chloride under different conditions was simulated.The results showed that sodium chloride follow the law of ?L in the peptone,phenol and heptane aqueous solution with COD of 10000 mg/L.The nucleation activation energy of sodium chloride were reduced in the presence of three kinds of organic compounds.In the presence of different organic compounds,the influence rule of supersaturation,temperature and suspension density on the crystallization kinetics of sodium chloride were obtained.