Mechanism of Influence of Organic Impurity on Crystallization of Sodium Sulfate

Abstract

To promote the development of crystallization technology for recovering salt from high salinity wastewater, the effect of organic impurity on crystallization of sodium sulfate was investigated by using phenol as a representative organic impurity. The effect of phenol on crystallization thermodynamics of sodium sulfate was evaluated by measuring solubility data of sodium sulfate in water in the presence of phenol. It was found that the existence of phenol could suppress the solubility of sodium sulfate in water. The effect of organic impurity on crystal nucleation was performed by measuring the metastable zone width (MSZW) and induction time of sodium sulfate. Two models (self-consistent Nývlt-like equation and Classical 3D nucleation theory) were used to analyze the experimental data. It was found that Classical 3D nucleation theory (3D CNT) can better explain the effect of phenol on nucleation. From both MSZW data and induction time data, it was found that the existence of phenol will apparently increase the interfacial energy γ, which will result in higher nucleation Gibbs energy barrier and thus lower nucleation rate. Furthermore, the existence of phenol will increase the critical nucleus radius r* and the critical Gibbs energy ΔG*, which means that the formation of the nuclei will be more difficult in the presence of phenol. According to the above analysis, the possible mechanism of influence of organic impurity on crystallization of sodium sulfate was proposed.

Research Progress on Zero Discharge and Resource Utilization of Industrial High‐Salt Wastewater

“…The solubility on the side rich in sodium sulfate was significantly higher than that in pure water, as shown in Figure 6. Su et al [51] used phenol as a representative organic impurity to study the effect of organic impurities on the crystallization of sodium sulfate. The solubility data of sodium sulfate in water were measured in the presence of phenol to evaluate the effect of phenol on the thermodynamics of sodium sulfate crystals.…”

“…The increasing numbers of nucleation made the crystal particle size distributed at a smaller particle size, but the practical industrial crystals pursued a larger particle size, so primary nucleation should be avoided. Chew et al [52] first proposed the [51] Copyright 2018, American Chemical Society. concept of controlled cooling that was by controlling the temperature drop, the supersaturation of the solution during the crystallization process was maintained in the metastable zone, thereby avoiding the occurrence of the first nucleation, and improving the crystal product size distributed.…”

“…Nowadays, most studies focus on the induction period and metastable zone under the pure substance system and investigate the influence of certain impurity substances on the crystallization kinetics. Su et al [51] examined the effect of phenol on crystallization kinetics in high-salt wastewater systems. They measured the width of metastable zone of Na 2 SO 4 in water under different experimental conditions and the data of the induction period, investigated the effect of phenol on the metastable zone and the induction period of Na 2 SO 4 , and used the self-consistent Ny'vltlike equation and the classic 3D kernel theory to fit the data to obtain nucleation parameters.…”

“…Figure 8. Induction time graph under different supersaturation and different phenol concentration at 293.15 K. Reproduced with permission [51]. Copyright 2018, American Chemical Society.…”

Comparison of the Nucleation Parameters of Aqueous l-glycine Solutions in the Presence of l-arginine from Induction Time and Metastable-Zone-Width Data

“…The interfacial free energy is the energy required to create a new solid/liquid interface for the formation of crystals in liquid solutions, while the pre-exponential factor is related to the attachment rate of solute molecules to a cluster in the formation of crystals. The influences of impurities on the nucleation parameters have long been investigated using induction time or MSZW data with the addition of different impurities in solutions for a variety of compounds [4][5][6][7][8][9][10][11][12][13][14].…”